Unit 3 Compilation
Table of contents
1) Chapter 5: The Skeletal System
Sections 5.1-Skeletal system consists of connective tissues
5.3-Mature bone undergoes remodeling and repair
5.4-Skeleton protects, supports and permits movement
5.5- Joint form connections between bones
2) Chapter 6: The Muscular System
Sections 6.1- Muscles produce movement or generate tension
6.2- Individual muscle cells contract and relax
6.4- Cardiac and smooth muscles have special features
3) Chapter 7: Blood
Sections 7.1- The components and functions of blood
7.2- Hemostasis: stopping blood loss
7.3- Human blood types
4) Chapter 8: Heart and Blood Vessels
Sections 8.1-Blood vessels transport blood
8.2- to page 173- The heart pumps through the vessels
5) Chapter 9: The Immune System and Mechanisms of Defense
Sections 9.1- Pathogens cause disease
9.2- The lymphatic system defends the body
9.3- Keeping pathogens out: The first line of defense
9.4- Nonspecific defenses: The second line of defense
9.5- Specific defense mechanisms: The third line of defense
9.6- Immune memory creates immunity
9.7- Medical assistance in the war against pathogens
9.9- Inappropriate immune system activity causes problems
6) Chapter 10: The Respiratory System: Exchange of Gases
Sections 10.1- Respiration takes place throughout the body
10.2- The respiratory system consists of upper and lower respiratory tracts
10.3- The process of breathing involves a pressure gradient
10.4- Gas exchange and transport occur passively
10.5- The nervous system regulates breathing
10.6- Disorders of the respiratory system
Chapter 5: The Skeletal System
Section 5.1- Skeletal system consists of connective tissue:
The human Body is capable of many physical activities. This is due in part of our Skeletal System. Just consider all the activities we do every day. Without our skeleton would we be able to something as simple as sit up when we wake in the morning? The skeletal system is made up of three types of connective tissue.
1) Bone – consists of nonliving extracellular crystals of calcium minerals. Bones are actually living, it consists of several types of living cells that are needed for the formation and remodeling. Also has nerves and blood vessels. Bone has five main important functions.
a) Support- allow for us to sit and stand upright.
b) Protection- keeps our internal organs safe from injury
c) Movement- allows us to walk, twist, and turn.
d) Blood Cell formation- cells from only certain bones allow for the formation of red/white blood cells and platelets.
e) Mineral storage- for calcium and phosphate stores for the needs of the bone.
The living cells of bone are osteoblast, osteocytes, osteoclasts.
1) Osteoblast- is a bone forming cell
2) Osteocytes- is mature bone cell
3) Osteoclast- a cell the resorbs or breaks down bone.
There are long bones , called this because they are longer than they are wide. They consist of a cylindrical shaft called diaphysis. These bones have an enlarged knob at the end of the shaft called epiphysis. Dense compact bone forms it’s shaft and covers each end. The central cavity in the shaft is filled with yellow bone marrow. The yellow bone marrow is made up of fat and can be used for energy. The outer layer of bone is covered by a tough connective tissue called periosteum. The periosteum contains bone forming cells . If a epiphysis of a long bone forms a joint with another bone that joint is covered by a layer of smooth cartilage to reduce friction. Inside the epiphysis is a spongy bone that is less dense and allow for bone to lightweight but strong. The spongy bone is the latticework for hard, relatively strong trabeculae, that are composed of calcium and living cells. In the long bones, such as humerus and femur, the spaces of the trabeculea are filled with red bone marrow, in this marrow are stem cells that are responsible for the production of the blood cells and platelets.
In compact bone, it is made up of extracellular deposits or calcium phosphate. This encloses and surrounds the living cells, osteocytes. These osteocytes are arranged in rings in cylindrical structures, osteons. The osteocytes nearest the center of osteons, receive nutrients by diffusion of the blood vessels that are in the central canal. As the bone develops and becomes hard the osteocytes become trapped in the hollow chambers of the lacunae. But the do remain in contact with other osteocytes through thin canals called canaliculi. This is through a gap junctions that permit movement of ions, water and other molecules between adjacent cells. The waste products from the osteocytes are exchanged in the opposite direction. The osteocytes in spongy bone do not have to rely on the central canal for nutrients or waste removal.
Ligaments are structures that hold bones together. They consist of dense, fibrous connective tissue made of collagen. That are all arranged in the same direction, and have few fibroblasts. They not only hold bone together but the permit movement of certain bones and also give strength.
Cartilage helps support. It is found where support is needed under the pressure of movement. Contains fibers of collagen and/or elastin, in a ground substance of water and other materials. Is smoother and more flexible than bone. There are three types of cartilage:
1) Fibrocartilage- primarily collagen fibers in thick bundles, withstands both pressure and tension. Examples are the disks between vertebrae and the support structure in the knee joint.
2) Hyaline cartilage- smooth , glassy cartilage of thin fibers. This cartilage forms an embryonic structure that will become the bones. Also at the end of mature bones at the joints to create a very smooth, low friction surface.
3) Elastic cartilage- made of mostly elastin fibers, very flexible and lends structure to parts of the body. Such as the outer ear and the epiglottis.
Section 5.3- Mature bone undergoes remodeling and repair:
Although our bones stop growing as we age, they are constantly undergoing remodeling and repair. These processes are due partly to the 3rd type of bone cell called osteoclast. Its job is to cut through the mature bone and dissolve hydroxyapatite and digest the osteoid matrix while doing so. In doing this they release calcium and phosphate ions to enter into the blood. The process attracts new ostioblasts to the area where the bone had been previously removed. The new osteoblasts put down the new osteoid matrix and the stimulates deposition of new hydroxyapatite crystals.
Over time bone changes in shape, size, ans strength. This is due to the constant remodeling of bone. Compression stress on a bone, causes tiny electrical currents. The electrical currents stimulate the bone forming from the osteoblasts activity. The current is strongest at the inside curvature of long bones that are undergoing the stress. And new bone is deposited in these areas and reabsorbed in the low impact areas.
Bone cells are regulated by hormones. The rates of the activity of the osteoblast and osteoclasts in and adult are regulated by the hormones, parathyroid hormone and calcitonin hormones. Theses hormones regulate hemostasis by making sure calcium and phosphorus levels remain in check.
Bone undergoes repair. If a bone is broken the blood vessels that supply the bone with blood, bleed into that area and form a hematoma. In the days following the break there are inflammation, swelling and pain. And the repair process begins, the firbroblasts move to the area of the break. Some of them become chondroblasts and produce a fibrocartilage bond called a callus, on either side of the broken areas. After this the osteoclast arrive and begin to break down the damaged areas of the break. And then the osteoblasts arrive and start to lay down osteo matrix and assist in the crystallization of minerals that convert the callus into bone. This process can take weeks to months. The rate is dependant on age and what bone was affected.
5.4- The skeleton protects, supports and permits movement:
Bones are classified in for type, that is based on shape:
Long Bone: Are longer than they are wide, include the bones of the limbs and fingers.
Short Bone: are about as wide as the are long. Such as the bones in the wrist.
Flat Bone: are thin flattened, sometimes curve, like those of the hip and skull.
There are 206 bones in a human body that make up the skeleton. There are different types of connective tissues, that hold the skeleton together. The three main functions of the skeleton are:
Structural : for the support of soft organs.
Protect: certain organs from injury.
Permit movement: allow the body to bend and twist.
The skeleton is made up of two parts/sections:
1) Axial skeleton: consists of the skull, sternum, ribs and vertebral column.
Skull/Craniuml: comprised of over 24 bones, protects the brain, and gives structure to the face. Are Flat bones.
Sternum/Ribs: protect the chest cavity, 12 rib bones, that are connected by cartilage to the sternum and wrap around the thorax region of the vertebral column. 2 of the ribs are “floating” because there is no attachment to the sternum. Sternum also called breast bone, is a flat blade bone, made up of three different bones that become fused at development.
Vertebral Column: is the main axis of the body, supports the cranium, protects the spinal cord, serves as the attachment point of all four limbs. Consists of 33 irregular bones called vertebrae, extends from the skull to the pelvis. There are five sections to the vertebral column:
a. Cervical- 7 vertebrae (neck)
b. Thoracic- 12 vertebrae (chest/thorax)
c. Lumbar- 5 vertebrae (lower back)
d. Sacral- 5 vertebrae that have become fused in the course of evolution (upper pelvic area)
e. Coccygeal- 4 fused vertebrae, the remnants of the tail after evolution (tail bone)
2) Appendicular skeleton: consists of the pectoral girdle, pelvic girdle and limbs.
Pectoral girdle: gives flexibility in the upper limbs, supportive frame, consists of the right/left clavicles, that extend the top of the chest and attach to the right/left scapulas, that are bones in the upper back that are also called shoulder blades. From the pectoral girdle stems the arm bones. The upper consists of the humerus. That is connected at the top of the scapula at the joint, and continues to the elbow joint, at the other side of that joint are the radius and ulna bones. These bones form the lower arm and stop at the wrist joints called carpal bones. They consist of eight small bones. Below these are the bones that make up the palm of the hand, called metacarpal bones. There are 5 of these bones in the hand. The finger bones are called phalanges. They consist of 14 bones.
Pelvic girdle: supports the weight of the body, consists of the coxal bones and the sacrum and coccyx of the vertebral column. Coxal bones are attached to the sacral area of the vertebral column to the rear of the body. They curve forward and meet the pubic symphysis and are joined there by cartilage. Forms the pelvis. Theis area is broader and shallower in females than in males, to allow for childbirth. From the pelvic girdle extend the leg bones. The upper leg bone is called the femur. This is connected by a rounded upper part of the leg to the coxal joint. The femur run down and connects then to the knee joint. Connected below the knee joint or patella are the two bones that make the lower leg, called the tibia and fibula. These bones then connect to the ankle bones that are called tarsal bones. There are seven tarsal bones in the ankle/heel that form the foot. The tarsals are then connected to the phalanges of the foot. There are 14 phalanges, that form the toes .
5.5- Joints form connections between bones:
Joints are also called articulations. They are the contact points between bone. The joints have ligaments and tendons, that are connective tissues to stabilize many joints. The joints can either freely movable or immovable. There are three types of joints:
1) Fibrous joints: immovable, such as the fontanel of a baby’s skull. At the time of birth they were separated by spaces that allow for growth/development of the baby’s brain after birth. As the baby gets older and reaches adolescence the fibrous joints harden, the joint becomes fine lines or structures.
2) Cartilaginous joint: slightly movable and allow for some flexibility, where the joints are connected by hyaline cartilage, such as where vertebrae are connected to the backbone or where the ribs are connected to the sternum.
3) Synovial joints: most free moving joints of the body, joints are separated by a thin fluid filled cavity. The cavity is lined by the synovial membrane. The membrane secretes a fluid called synovial fluid, that acts as a lubricant for the joint. Found in hinge joints, such as the elbow and the knee. Also found in the ball and socket joints of the coxal and femurs. Also the pectoral girdle and the humerus. The ball at the end of the hur=erus and femur fit into the socket of the pectoral and coxal joint. These joints allow for movement in many different ways.
At joint connections are tendons, ligaments and the meeting of muscles. The function of these is to stabilize the joints. The synovial joint can withstand a lot of pounding and stress for many years. The reason for this is because of tendons, ligaments, and muscles and how the work together.
Chapter 6: The Muscular System
6.1- Muscles produce and generate tension.
Some of muscle movements are voluntary, meaning that we have control over them. Such as opening a door. Other movements are involuntary, meaning not having control over them. Such as the pumping beat of your heart. Other than producing movement the muscles also do other very important things, resist movement and produce heat. Resistance of movement is needed for our ability to be able to stand. The producing of heat assists in regulating body temperature.
The fundamental activity of muscle is to contract. All three groups of muscle cells have particular features in common. Theses features are:
1) They are excitable- this means they contract in a response to chemical or electrical signals from the other organ systems.
2) They have one mechanism of action- contract and relax.
Skeletal muscles work to act upon the skeleton and produce movement of the bones in the body. They can also prevent movement. There are more that 600 skeletal muscles in the human body. They are organized into groups. The muscles that work together are called synergistic muscles and the ones that work opposite of the other are called antagonistic muscles.
Most of our muscles are attached to the bone with tendons, but a few are attached to other muscles or to the skin. Theses attachments are important because of the many different ways the body can move.
Description of how the muscles are attached and lay:
1) The origin-the end of the muscle that joins to the bone a bone that remains fairly stationary.
2) The insertion- attached to another bone across a joint.
When a muscle contraction is produced, the insertion of a muscle is drawn toward the origin. The origin is almost always closer to the midline of the body, the insertion is further away from the midline.
Muscles are composed of many cells. In a single muscle is a group of individual cells, they have the same origin and insertion and have the same function. The muscle is arranged in fascicles that look like a bundle, and are surrounded with a thin membrane called fascia. The fascicles contain a range of cells, from a few dozen to thousands of muscle cells or fibers. There are more layers of fascia that join together at the end of the muscle to form the tendons, to attach to the bone. The individual muscle cells are tubed shaped and larger in size than that of other human cells. They range in size from 1 millimeter to as long as a centimeter in length. The muscle cell nuclei lay just under the membrane, and there are structures called myofibrils, that lay parallel and are cylindrical in appearance. A section of a myofibril form a Z line to the next one. This is called a sarcomere. Sacromeres consist of 2 protein filaments called myosin and actin. Muscle contraction is varied , depending on the actions between the myosin and the actin.
6.2- Individual muscle cells contract and relax.
While under contractual the sarcomere shortens some. Even though this is not a huge action it is powerful. The entire contraction of just one skeletal muscle relies on the sarcomeres. There are four keys to understanding how a muscle cell works:
1) The cell must be activated by a nerve.
2) The nerve activation increases the calcium in the area near the contractile proteins.
3) The presence of the calcium permits contraction. While its absence prevents the contraction.
4) When the nerve stops stimulating a cell the contraction stops.
There are nerves that stimulate the skeletal muscle to perform. They are called motor neurons. These secrete a chemical compound called acetylcholine, that is a neurotransmitter. This chemical substance can either have an exititory or an inhibitory effect on other cells. There is a junction between motor neuron on a skeletal muscle, it is called a neuromuscular junction. It is at this junction that the acetylchine is released from a nerve terminal and crosses the space between neuron and muscle. Then it binds to the receptors and causes the muscle cell membrane to generate an electrical impulse, and travels along the cell membrane in all different directions. There are extensions to the cell membrane that are called T tubules, that transmit the electrical impulse deep into the cell . This ensures the electrical current gets to all parts of the cell rapidly.
The activation of the T tubules releases calcium from the sarcoplasmic reticulum. The sarcoplasmic reticulum is similar to all other cell membranes except for the shape. The shape makes it possible to fit in small places in the cell that are not occupied by the myofibrils. When the calcium goes into the cell cytoplasm and comes into contact with the myofibrils there is a chain reaction or events that ultimately lead to the muscle contraction.
The calcium also starts the sliding filament mechanism contraction. This mechanism is the process of the sacromeres shortening and contracting the muscle, and the thick and thin filaments slide past each other. Each of the filament consists of two strands of actin molecules that spiral around each other. The thick filaments are made of many molecules of myosin. The contraction occurs when the myosin comes into contact with the filaments. This forms a crossbridge. The crossbridge causes the head of the myosin to bend relative to the shaft, and pull actin molecules to the sacromere. This process requires energy.
There are two molecules that are associated with actin, troponin and tropomyosin. Together that makes a protein complex. This complex requires calcium, so there is no interference with the myosin binding sites on an actin molecule.
The release of a muscle contraction occurs when the nerve activity ends. In this removal of nerve activity the calcium stops being released from the sarcoplasmic reticulum. If there is any interruption in the cycle of the nerve activation it could cause the muscle to malfunction. Such as in the disorder of myasthemia gravis. Where the persons own immune system attacks and destroys the acetylcholine receptors. This causes symptoms such as, weak muscle response to the nerve impulses, that causes drooping eyelids and double vision.
Muscles require energy from the ATP to contract. The myosin acts as an enzyme splitting ATP into ADP and inorganic phosphate that releases energy to do the work, in the presents of calcium. At the end of the nerve impulse cycle, the energy from ATP breakdown, is used to return the calcium back into the sarcoplasmic reticulum. At this point relaxation of the muscle occurs. There is a second requirement that must occur for the muscle to relax. This second action is that an intact molecule of ATP must bind to the myosin so that the myosin can detach from the actin. The muscle cells only store small amounts ATP for activity. Once it is used the cells must get more ATP from other energy sources. Such as creatine phosphate, glycogen, glucose and fatty acids.
Note that after exercising you breathe much heavier, this is due to the body’s need to reverse the oxygen debt that was created. The oxygen debt occurred because of the use of ATP early on by the muscles. Muscle fatigue is a decline of muscle performance. The most common cause is insufficient energy to meet the muscles needs. And the deletion of ATP, creatine phosphate and glycogen stores.
6.4- Cardiac and smooth muscles have special features.
The cardiac and smooth muscles are called involuntary muscles. Cardiac muscles are able able to beat on their own without the help of nerve signals. They also can regulate their own cycle of contraction and relaxation. The ones with the fastest rhythm are called pacemaker cells, because the rest of the cells follow the pace of these cells. The cardiac muscle is joined at the ends by structures called intercalated discs. The discs contain gap junctions to permit one cell to stimulate the next. The pacemaker cells dictate the rates of the contractions in the entire heart. The smooth muscle is joint also by gap junctions, it permits the cells to communicate the activation with other cells. This makes it so that the whole muscle contracts together. Although the cardiac and smooth muscles contract on their own, they can be stimulated by other nerve activity. The nerves of both muscle groups belong to the automatic nervous system. The effect of the heart rate increase can either by stimulatory or inhibitory.
Cardiac muscle cells contract and relax in rhythmic cycles. This is necessary, to allow for the heart muscle cells not to fatigue. Smooth muscles are partially contracted at all times. This makes them ideal for keeping the homeostatic regulation of blood pressure. The partial contraction is what allows for the constant diameter of blood vessels, and adjusting them as needed.
The arrangement of cardiac muscle cells is like that of the skeletal muscle cells. It has thick and thin filaments in sacromeres, and is also called striated muscle. The filaments of smooth muscle are much different in arrangement. They are in bundles that attach in different directions to the cell membrane. And does not have the appearance of the striated cardiac and skeletal muscles.
Chapter 7: Blood
7-1- The components and functions of blood.
Blood is again a specialized connective tissue, and carries out three crucial tasks:
1) Transportation- of all substances needed to anywhere in the body, such as oxygen, nutrients, hormones and waste.
2) Regulation- of body temperature, volume of water in the body, and to regulate the pH of body fluids.
3) Defuse- contains special defense cells to protect from infections and illness, the ability to stop excessive blood loss.
On average and adult male can have as much as 5-6L of blood and adult female 4-5L in their body at one time. The amount is dependant on body size. Because the components of blood are denser that that of water, blood is thicker. Blood is approximately 5x more viscous that water. Even though the appearance of blood seems to be very uniform, it carries an array of components. The components fall into two categories:
Red blood cells- to transport oxygen into cells/tissues, and carbon dioxide away from the tissues.
White blood cells- Defender of the body from infection, invading organisms and abnormal cells.
Platelets- assist in blood clotting mechanism
Water- primary component of plasma.
Electrolytes- Sodium, potassium, chloride, bicarbonate, calcium, magnesium and others. Ions control cell function and volume, the electrical charge across cells, and the function of excitable cells. Must be at normal levels to maintain homeostasis.
Proteins- Albumins maintain and transport the electrolytes, hormones, and waste. Globulins act as antibodies and transport substances. Clotting proteins contribute to clotting of blood.
Hormones- Insulin, growth hormones, testosterone, estrogen and others. Are the chemical messengers of the molecules that supply information needed to regulate specific body functions.
Gases- Oxygen for metabolism, carbon dioxide is a waste, both are dissolved in plasma and carried by RBCs.
Nutrients/Waste- Includes glucose, urea and many others, the raw materials and wastes are transported by the blood all over the body.
When a blood sample is placed in a centrifuge and spun, it separates as such Plasma on top, WBCs and platelets in the middle and RBCs on the bottom.
Plasma consists of solutes, the largest are the plasma proteins. The plasma proteins are important and include: representing volume is about 55% of the total.
Albumins- serve to maintain proper water balance between blood and interstitial fluid.
Globulins-transport substances in the blood, such as cholesterol. When bound to a the molecule it creates lipoproteins . The lipoproteins that are important in the medical area are LDL and HDL. The LDL are at times called the bad proteins and the HDL the good proteins. Both are related to the cholesterol levels in the blood.
Clotting proteins- play an important role in the clotting of blood.
Red blood cell function is to transport oxygen and carbon dioxide. RBC represent about 45% of the total volume. Each cubic millimeter of blood carries 5 million RBCs. The RBC represents why structure serves a function. It is small, flattened, doughnut shaped disk that is thinner in the center and thicker at the edges. This is an unusual shape in the overall look of the cells in the body. But is shape lends to ease in function. They can bend/flex through blood vessels of and size, and at no point is the cytoplasm far from the surface. This facilitates the exchange of gases. Mature red blood cells have no nucleus and no real organelles they are primarily fluid filled bags. And are crammed with 300 million molecules of hemoglobin, that is an oxygen binding agent. The hemoglobins center contains a heme group. In the center of each heme group is an iron atom. This iron atom can bond with an oxygen molecule. In total an RBC can carry 1.2 billion molecules of oxygen. There is no mitochondria in RBCs , but RBC generates ATP by anaerobic pathways.
There are several factors in the binding of hemoglobin with oxygen, it binds easiest when the oxygen concentration is high and the pH is neutral. Which is the conditions of the lungs. In the lungs the oxygen diffuses first to the plasma then RBCs and attaches to iron atoms of the hemoglobin. By the binding of O2 to hemoglobin some of the O2 is removed. This makes room for more O2. Hemoglobin with four oxygen molecules is called oxyhemoglobin. Hemoglobin that has given up oxygen is called deoxyhemoglobin. The deoxyhemoglobin is purple in color. Blood that has both in it is maroon in color.
The hematocrit is the blood percentage that consists of RBCs. Also a relative measurement of oxygen carrying blood capacity. The normal ranges for men are 43-49% and for women 37-43%. If there is an unusual level of hematocrit it may be a cause for alarm. The low level may indicate a condition called anemia or other disorders of inadequate RBC production. Some of these changes are normal and temporary.
All of our blood cells and platelets come from stem cells. Stem cells come from the marrow of certain bones. Stem cells divide repeatedly through life. Producing new immature blood cells, that develop into platelets and other types of mature red and white blood cells.
The RBCs have a short life span. All new RBCs are generated from dividing stem cells, because they lack a nucleus and cannot perform many cellular activities, they wear out quickly. The life span for a RBC is about 120 days. During the 120 days it makes 3000 round trips a day in the human body. The old and damaged RBCs are removed from the blood system and destroyed by the liver and spleen, where there are large cells called macrophages. The macrophages are from monocytes, that are the largest WBC. The macrophages surround and digest the RBCs in a process called phangocytosis. The 4 peptide chain of the hemoglobin molecules is dismantled into amino acids. The amino acids are then returned to make new proteins. The iron atoms are then returned to the red bone marrow and used again to produce the new hemoglobin for RBCs. the groups of heme without the iron are then converted by the liver into a yellowish color that is called bilirubin. The actions that you see in a healing bruise, the purple, then blue, and to green then finally yellow are the chemical breakdown of the heme groups. If the liver is working properly the hemoglobin broke down and the bilirubin then is secreted into the bile and digested then passes to the intestine. If the liver is not working properly and does not filter the bilirubin, then it accumulates in the blood plasma and makes the skin, eye and mucous membranes turn yellow. The condition for this is called jaundice. Jaundice can also be caused by a increase in the rate of the breakdown of RBCs.
The regulation of RBCs is a negative feedback control loop. RBC regulation is not of numbers, but by their effect or ability to do their job. If the oxygen level drops for any reason, cells cause the kidney to secrete a hormone called erythropoietin. The erythropoietin it moved through the blood to the red blood marrow. It then stimulates the stem cells to make more of the RBCs. When the oxygenated blood returns to the proper level , the cells are then cut back on production. There has been abuse of erythropoietin by athletes. They have used it to increase the RBCs in their blood stream, which rises the oxygen carrying ability. This practice is known as blood doping. The consequences of blood doping can be severe, the excess blood cell makes it more viscous, which makes the heart have to work much harder, the dehydration that follows blood doping and strenuous exercise can increase the chances of blood clots.
The WBCs are protectors of the body. WBCs are approximately 1% of the whole blood. They are also called leukocytes. WBCs are larger that the RBCs, and are more structurally diverse along with function. They do have a nucleus but no hemoglobin, this makes them translucent and difficult to see under a microscope unless a stain is added to them. Every millimeter of blood contains 7,000 WBCs. The WBCs also comes from the stem cells, where they develop from immature blood cells and turn into various WBCs. There are two categories of WBCs: Granulocytes and Agranulocytes. The both are granular but not able to be stained for being seen under a microscope. They are filled with proteins and enzymes to assist in the defensive work of the WBCs. The WBCs have a relatively short life span, ranging from a few hours to as long as 9 days. This may be caused by the fighting of invaders and the injuries it may cause. Monocytes may live for several months, lymphocytes several days to many years. The dead or injured WBcs are constantly removed from the blood stream by the spleen and liver.
WBCs rise whenever the body is under threat of viruses, bacteria and other challenges to our health. The RBCs almost always remain in the blood system, unless there is tissue damage. However the WBCs may at some point leave the system. They circulate in other places in the body, such as the lymphatic system and other tissues.
Granular leukocytes: Neutrophils, Eosinophils and Basophils
Nuetrophils- make up to 60% of WBCs, the first to combat infection, surround and engulf foreign cells. Target bacteria and some fungi, their numbers rise rapidly during acute bacterial infection.
Eosinophils- make up only 2-4% of WBCs, two important functions; defend the body against large parasites and to release chemicals that control the severity of an allergic reaction.
Basophils- The Rarest of the WBCs, only about 0.5%, contain a histamine, that causes tissues around an injury to release plasma into the area, they bring in nutrients, cells, and chemicals that start the healing process.
Agranular leukocytes: Monocytes and Lymphocytes
Monocytes- the largest of the WBCs, make up about 5% of the WBCs, can go out of the blood stream and go to other body tissues, differentiate with the macrophages, engulf invaders and dead cell debris, stimulate the lymphocytes, more active during active time of infection.
Lymphocytes- make up 30% of WBCs, found in blood stream, tonsils, spleen, lymph nodes and thymus gland. Classified in two types; B lymphocytes that give rise to plasma cell to produce antibodies and T lymphocytes target and destroy specific threats.
There is a key to forming of clots, that is platelets. They make up less than 1% of whole blood. They come from megakaryocytes, that are large cells from stem cells. The megakaryocytes do not migrate but remain in the bone marrow. The platelets are small fragments of the megakaryocytes cell membrane and cytoplasm. Due to the fact that platelets are not living , they only remain for about 5-9 days. When there is an injury or leak to vessels the platelets aid in the clotting, and also in the repair process. They do so by releasing proteins that cause blood vessel growth and repair.
7-2 Hemostasis: stopping blood loss.
The circulatory system has a very important ability. That ability is to limit the loss of blood after and injury. The natural process of stopping loss and flow of the blood is called hemostasis. There are 3 stages to hemostasis:
1) Vascular spasm- the intense contraction of the blood vessels in the area of injury or blood loss. Depending on the severity of the injury the constrictions could last 30min to an hour. If the vessels affected are medium to large in size, the spasms will reduce the immediate blood flow, minimizing the damage. This is to prepare the area for the later stages of hemostasis.
2) Formation- of a platelet plug, the platelets stick together and form a seal to the injured vessel. This is caused by the vessel rupturing and the platelets swelling and developing spike like extensions. Depending on the area or size involved the platelet plug can stop the flow and close the area in seconds.
3) Blood clotting- forms around the platelet plug, the blood changes from a liquid to a gel, caused by chemical reactions. That produces a mesh of protein fibers. There are at least 12 substances that make up the clot. Three of them are:
A) Prothrombin activator- activates the conversion of prothrombin into an enzyme called thrombin. Prothrombin is a protein of the plasma. This process requires calcium ions.
B) Thrombin- makes it so the soluble plasma protein can convert to fibrogin into the threads of a protein called fibrin.
C) Fibrin- for an interlocking mess around the clot at the wound, that traps the platelets, blood cells and other molecules.
The fibrin clot can form in less than a minute. After the clot is formed, the platelets start to contract, this tightens the clot and pulls the vessel together. The entire process of clot formation generally takes less than an hour. However, if any step is blocked in the clotting process, even a minor cut could become life threatening. Such as the condition hemophilia, this condition is a deficiency of one or more clotting factor. In one type, the person is lacking a clotting protean and the blood may clot slowly or not at all. Even if the injury is under the skin, the bruising could spread to other areas. Also certain medications can interfere with clotting.
7-3 Human blood types.
To understand blood types we must first the understand antigens and antibodies. Our body can recognize self and nonself.
1) Antigen- the body recognizes as notself, this is a notself cell protein. It stimulates the immune system to defend the organism.
2) Antibody- in result of the immune system recognizing the notself or antigen, the immune system produces an opposing protein, the antibody.
Antibodies are produced by lymphocytes, and belong to plasma proteins that are called gamma globulins. These proteins counter attack the antigens. There are many antibodies, individual antibodies specialize in attacking one specific antigen. The move freely in the blood and lymph system until they come in contact with its specific antigen. They then bind to the antigen, forming a antigen-antibody complex. In some cases the antibodies do not allow the antigen to enter human cells. The reactions between antibodies and antigens are what cause blood transfusions to not be successful.
Blood Typing- based on A B antigens. RBCs have surface proteins that allow them to be identified by the body as self. The RBCs are classified in a ABO grouping system. All humans belong to one of theses blood types:
1) A blood type- has A antigen, B plasma antibodies.
2) B blood type- has B antigen, A plasma antibodies
3) AB blood type- has AB antigens and neither A or B antibodies
4) O blood type- has neither A or B antigens and has both A and B antibodies
The antibodies attack the RBCs with foreign antigens and cause them to agglutinate or clump. If the agglutination is severe then the clumps could cause blockages in vessels and cause organ damage and even death. The hemoglobin that is released by the damaged blood cells could block the kidneys and cause them to fail. Because of the possibilities of the reactions to transfusions, blood must be screened carefully to match the donor blood to the recipient.
If a person has A blood they are to get A or O blood, because neither has the B antigen but not AB because of the B antigens. If a person has B type blood they can not receive A blood or AB blood, but can receive B and O types. People with AB can receive from all three A B and O. AB can only donate to other AB types. O type persons can donate to all types. This is because they carry neither A or B antigens. O blood type is then called a universal donor.
Along with making sure the blood type is correct for transfusion, there is one other factor. The other factor is, Rh+; meaning that they carry the Rh antigen and an Rh-; meaning they do not carry the antigen. The Rh factor comes from a reaction seen in rhesus monkeys. There is about 85% Rh+ and 15%- Americans. The factor that is important is the Rh- women. If she becomes pregnant by and Rh+ man, the fetus could be Rh+, and the antigens from the fetus could leak back into the mothers blood stream. If this happens the mother’s body will start to produce anti-Rh antibodies. These antibodies may then cross the placenta and attack the babies RBCs. It can result in a disease called hemolytic disease of newborns, characterized by the reduced numbers of RBCs and toxic hemoglobin breakdown. This disease can lead to mental retardation and even death. The risk of this disease is higher in the second and consecutive pregnancies. Because of the duration that it takes for the antibodies to be produced in the first pregnancy. The highest risk of exposure is at childbirth. To prevent the reaction, an Rh- woman who may be carrying a + baby, is given an injection of anti-Rh antibodies at 28 weeks. If the baby is positive at birth then the mother is given a second injection.
Chapter 8: Heart and Blood vessels
8-1 Blood vessels transport blood.
The blood vessels are a branching network. This network transports blood to all parts of the body. If out blood vessels were stretched out end to end, they would be 60,00 miles long. The blood vessels and heart are called the cardiovascular system. The blood vessels are classified in three types:
1) Arteries- large muscular thick walled, transport blood away from the heart, must withstand pressure, they have very muscular walls to do so. As the arteries branch repeatedly and get further from the heart, the smaller the diameter they are. There are three layers of the vessel walls:
A) Endothelium- the inner layer, thin. This layer is made of squamous epithelial cells. The cells fit closely together and are slick, to prevent friction and promote smooth blood flow.
B) Elastic connective tissue- primarily smooth muscle, it’s the thickest layer, this makes the medium arteries stretchy but strong enough to withstand the pressure of the blood at each heart beat.
C) Collagen layer- The outermost layer of large and medium arteries, anchors vessels to the tissue and protects from injury.
If the endothelium of the vessel wall weakens or is injured, the area could split and an aneurysm may occur. An aneurysm may cause a buldge inward and cause a narrowing large enough to slow blood flow to either and organ or area of the body. Some may cause symptoms like chest pain, but others may not have symptoms until they rupture. They can take years to develop, and can be surgically repaired if caught in time. Aneurysms can be found with a special CT scan, but some can be picked up by a doctor with a stethoscope, if the aneurysm is an inward bulging type. This is because of the tale tell sound they make.
The blood will eventually reach the arterioles and precapillary sphincters. Arterioles are the smallest of the arteries. By the time blood reaches here the pressure has dropped quite a bit. They are simpler in structure, usually lack the outer connective layer and smooth layer is not as thick. They help regulate the amount of blood that flows to capillaries. They contract and relax the smooth muscle to do so.
2) Capillaries- this is where the blood transfers substances with tissues. the capillaries are connected to and are smaller than the arterioles. The network of capillaries is called the capillary bed and can be found in all areas of the body. This is why you bleed no matter the size of the cut or where you cut yourself. Because they are thin and porous they exchange oxygen, carbon dioxide, nutrients and waste rather easily. The holes in capillaries are small enough to keep RBCs and most plasmas in them but allow for exchange of materials and other fluids with the interstitial fluids and blood. They are the only vessels that can do this. The fluids are reabsorbed through diffusion in the last part of the capillary before it joins with the veins. Because not all fluids can be reabsorbed some of the fluid and some remains in the interstitial fluid, there is a need to regulate the volume of the blood. The lymphatic system is what helps maintain the volume. Lymphatic capillaries pick up the excess fluid. Then transports it to the veins near the heart. While doing so the lymphatic system intercepts microorganisms. Even though this system is not really part of the cardiovascular system it does play a big role in keeping volumes in control.
3) Veins- the blood flows back to the heart through venules and veins. There are three walls in the vein. The outer two layers are much thinner than the ones in arteries. Pressure in veins is far less than that of arteries. The veins are able to stretch easily to promote movement of of large amount of blood a relatively low pressure. The veins serve also as a reservoir for the cardiovascular system. But the distendibility of veins can cause problems, such as the return of blood to the heart while having to pump against gravity. This makes it so blood could pool in the legs, happens most often in people that stand long periods of time. This can cause varicose veins, the drying and hardening of the veins because they are not receiving the proper amount of blood. There are three things that assure the proper return of blood to the heart:
A) Contractions of skeletal muscles- as we move the movement of our muscle assists the blood in moving properly.
B) One-way valves- are the small folds of the inner layer of the vein, protrude and make it so the blood cannot flow backwards.
The skeletal muscles and the one-way valves together male the skeletal muscle pump.
C) Breathing pressure- the in and outward breathing causes pressure changes in the thoracic cavity and abdominal cavity, the veins get squeezed in the abdominal cavity as you breath in, at the same time the thoracic cavity pressure decreases and allow the blood to be pushed from the abdomen to the chest toward the heart.
8-2 The heart pumps blood through the vessels.
In the thoracic cavity, behind the sternum, between the lungs lies the heart. The heart is slightly larger than a fist and in cone shaped. It is made of muscle. Comprised of a special type of muscle called cardiac muscle. The heart pumps continuously in a squeezing motion that pushes the blood through all of the vessels in your body.
It is enclosed in a special fibrous sac, the pericardium. This protects the heart and also anchors it to the structures and keeps it from becoming too full. Inside the pericardium is a pericardium cavity, that holds a lubricating film/fluid, to prevent friction.
In the cross section of the heart consists of three layers:
1) Epicardium- the outer most layer, a thin epithelial and connective tissue.
2) Myocardium- mainly cardiac muscle and forms the bulk of the heart, is the layer that contracts with every heartbeat. Squeezes each chamber of the heart and pushes the blood outward to the arteries.
3) Endocardium- thin endothelial layer that rests on the layer of connective tissue, is consistent with the endothelium that lines blood vessels.
There are four chambers in the heart:
1) Atria- two chambers at the top of the heart, make up the left and right atrium.
2) Ventricles- more muscular, make up the left and right ventricle.
There is a partition between the left and right side of the heart called the septum.
The blood returning to the heart comes in through the right atrium, then goes to through the right ventricle. The blood returning from the lungs goes first to the left atrium and then through a third valve to the left ventricle, then through the fourth valve to the largest artery , the aorta. From the aorta the blood then goes through the arteries and arterioles to the systemic capillaries, venules then to the veins and back to the right atrium. the most muscular of the chambers is the left ventricle, this is because it must perform the most work. It has to generate pressures greater that the aortic blood pressure. The right ventricle has a thinner wall and does less work, because the pressure in the arteries that feed the lungs is less than that of the aorta.
There are valves that ensure that the flow of blood in the heart go correctly, in a one-way pattern and prevent. In total there are four:
Atrioventricular- (AV) Right and left, between the atria and their ventricles, prevent back flow into the atria at the time of ventricular contractions. They are membranes made of thin connective tissue flaps. The right one is the tricuspid valve, because it has 3 flexible flaps. The left has 2 flaps and called bicuspids/mitral valves. There are bands of connective tissue that help support the valves. These are called chordae tendineae. They then connect to papillary muscles that are attached to the ventricle walls. Together theses prevent the valves from opening backward, into the atria in ventricular contraction. There are two other valves called semilunar valves, that prevent the backflow of blood into the ventricles from the arteries that leave the heart, when the heart is relaxed. They have 3 pocket like flaps.
The pattern/flow of the blood through the body:
1) Blood returns to the heart from the veins, it enters the right atrium, and is deoxygenated.
2) From the right atrium, it passes through the right AV into the right ventricle.
3) in the right ventricle the blood is pumped through the pulmonary semilunar valve to the pulmonary trunk, that divides into 2 trunks, the right and left pulmonary arteries, that supply the lungs.
4) At the pulmonary capillaries the blood gives up carbon dioxide and picks up oxygen, from the air we breath in. The blood is now oxygenated.
5) After the blood is oxygenated it goes into the pulmonary veins that lead to the heart. Through the left atrium then to the left AV into the left ventricle.
There is never a time when the deoxygenated blood on the right side of the heart will ever mix with the oxygenated blood of the left side. The blood must first past the pulmonary circuit to pick up oxygen, before it enters the left side of the heart.
When the blood enters the left ventricle the heart , it enters what is called the systemic circuit, that then takes to the rest of the body.
1) Left ventricle then pumps the blood through the aortic semilunar valve into the aorta. Which is the largest of the arteries.
2) After going through the aorta the blood then travels through the branching arteries and arterioles then to the capillaries, this is the point that the oxygen and nutrients are delivered to the bodies many tissues and organs and where the wastes are removed.
3) The blood then moves from the capillaries to the venules and the veins, then back to the right atrium again.
The heart requires a lot of oxygen, this is because of all the work that it does. Not only does it require oxygen, but also nutrients. Even though the heart is only 1\200 of our body weight it requires 1/20 of our flow of blood at rest to do its job. Even though the heart is full of nutrient rich blood most of the time, it can not absorb through the myocardium. The heart must have its own set of blood vessels, called the coronary arteries. The coronary arteries branch off of the aorta right above the aortic semilunar valve and encircle the heart’s surface, then they branch inward to supply the myocardium. The cardiac veins collect the blood from the heart muscle and feed it to the right atrium again. These arteries are small in diameter, so if they become blocked, even only partially, serious health problems could arise.
Chapter 9: The Immune System and Mechanisms of Defense
9-1 Pathogens cause disease
The immune system is a group of cells, proteins and structures of the lymphatic/circulatory systems. Even though the immune system is complex, it is not perfect. It can only kill or neutralize the pathogens or abnormal cells that is can recognize.
Pathogens: bacteria, viruses, fungi, and a few protozoa, even possibly prions.
Bacteria- a single celled living organism, without nucleus or membrane-bound organelles, DNA in bacteria contain just one chromosome most of the time. The ribosomes are smaller than ours and float freely in the cytoplasm, the outer surface is covered with a cell wall that is stiff and gives the bacteria its shape. Because of their large numbers we can say that they are the most successful organisms on earth. Bacteria utilize ATP for energy also, and amino acids to make proteins, storage of energy is in the form of fats and carbohydrates. To get theses materials to survive, they draw from the raw sewage breakdown and decomposition of dead or dying animals, plants, soil and air. Humans have learned to be able to harness bacteria to produce commercial products like, antibiotics, hormones, vaccines and some foods. Bacteria Live in our digestive tract, drawing the energy from the foods we ingest, and control the population of good bacteria vs harmful bacteria. There are a few bacteria that are pathogens, that rely on living cells to get the energy they need to survive. In the process of trying to survive the bacteria damage and kill human cells. However most bacteria are harmless and many are beneficial.
Viruses- extremely small infectious agents, 100th the size of bacterium and 1000th the size of eukaryotic cell. The virus structure is simple, it is just one piece of genetic material, surrounded by a protein. They can not reproduce or grown on their own. This is because they have no organelles. Viruses have many ways of getting into a host with living cells:
1) Through the cytoplasm via endocytosis; once they are inside they dissolve the the protein coating and the genetic material of the virus is released, this causes the copying of the viruses genetic material.
2) By merging the outer protein coat with that of the cell membrane then inject the genetic material, this causes the cell to begin copying the genetic material.
Some of the material is released from the cell while it is still alive, in other cases the cell becomes over full and simply bursts and spreads the material.
The infections from viruses affect differently in each person, some can be minor, others life threatening. Viruses tend to be minor in healthy persons, but if the person is young/old or in poor health it may be more serious. The best way to cure viral infections is to prevent them, antibiotics do not work on viruses.
Prion- a miss folded piece of brain cell protein, can trigger the miss folding of other forms of proteins also. Once in the nerve cells it becomes self propagating and keeps producing other prions. Eventually the prions produce so much, that they infect the brain cells, and the cells burst and die. This releases prions to infect other brain cells. The death of the nerve cells account for the symptoms, neurological and degeneration that produces the characteristics seen in mad cow disease and human vCID. Prions are found in beef that we ingest, and prions are very resistant to cooking of, freezing of, and even drying of the infected meat. The best prevention of prions is to control the spread of mad cow disease in the cattle we produce.
There are some pathogens that are more dangerous to human health than others. The factors that determine this are:
Transmissibility- how easy is the pathogen past from one to another person.
Mode of transmission- how it is passed from one to another.
Virulence- how much damage is done by the resulting disease.
The fact is that pathogens challenge the human defenses continually.
9-2 The lymphatic system defends the body
Most all of the immune system cells are kept in the lymphatic system, but can circulate in the blood and enter the interstitial fluids. There are basic components of the lymphatic system:
Lymphatic vessels- starts with blind-ended lymphatic capillaries, near the cells and blood capillaries. There are wide spaces of overlapping material in the lymph capillaries, this allows them to take in substances that are too large to enter the blood capillaries. The fluid of the lymphatic capillaries is a fluid that contains, WBCs, proteins, fats and sometimes bacteria and or viruses. This fluid is called lymph. The capillaries of the lymph then then merge with the lymphatic vessels, the walls of the vessels contain 3 thin layers and one way valves, the flow is assisted by the skeletal muscles and pressure changes in the thoracic cavity. They merge to form larger and larger vessels, eventually creating two lymphatic ducts; right lymphatic duct and thoracic duct. Theses ducts join the subclavian veins near the shoulders and then return the lymph to the cardiovascular system.
Lymph nodes- remove microorganisms, cellular debris, and abnormal cells from the lymph before returning to the cardiovascular system. They are located along the lymphatic vessels, and are clustered along different areas of the body. They are of different sizes, from 1 millimeter to 2.5 centimeters. The lymph nodes are encased in a capsule of connective tissue and WBCs called macrophages and lymphocytes and is pieced by lymphatic vessels that carry lymph in and out of the node. To ensure that the lymph does flow in only one direction there are valves. The two WBCs do two specific things, macrophages destroy the foreign cells by phagocytosis and the lymphocytes activate other defenses. The now clean lymph can now flow out of the node and continue the path to the veins.
Spleen- is the largest lymphatic organ. Is a soft, fist sized mass that is located in the upper left area of the abdominal cavity, and has a dense layer of connective tissue that is mixed with smooth muscle cells around it. The inside of the spleen consists of red pulp and white pulp. The spleen has 2 main functions; controlling the quality of RBCs as they circulate by removing damaged and old RBCs, and to help fight invading infection. The red pulp has macrophages also. The cleaned RBCs are then stored in the red pulp, where is can be held for use in cases of blood loss or a drop in blood pressure. The white pulp is primarily lymphocytes that are in search of foreign pathogens and does not store any blood. If you get a blow to that abdomen there is a possibility that the spleen could rupture, thus causing internal bleeding, removal of the spleen via surgery may be necessary to stop a fatal hemorrhage. It is possible to live without a spleen because of the mixed functions it shares with the lymph gland, liver, and red bone marrow. A person may be more vulnerable to infection after the spleen is removed.
Thymus Glan- located in the lower neck, just above the heart and behind the sternum. Contains epithelial cells and lymphocytes and is enclosed in connective tissue. The thymus secretes two hormones called thymosin and thymopietin. They cause the T lymphocytes to become mature and take the active role in specific defenses. The thymus gland is not the same size throughout life, size is depending on age. In childhood the thymus gland is most active and largest, during adolescence is stops growing and shrinks, in older age the gland may disappear all together.
Tonsils- are lymphatic tissue at the entrance to the throat. There are lymphocytes on them that gather and filter out many of the microorganisms that enter via air or food. There are more tonsils throughout the body and are not readily seen, the ones in our throats are the largest and most often infected. There are other lymphatic tissues that lay in the nasal passages called adenoids. They are more affected by swelling in childhood, but most often start to shrink around age 5, and may disappear completely. However they may continue to be a problem into adulthood and cause obstruction to the airways of the nose and throat, and may cause snoring, mouth breathing and a nasal voice.
9-3 Keeping pathogens out: The first line of defense.
Skin- is the most important barrier to stop pathogens from entering the body. The four key attributes are: structure, constant replacement, acidic pH and production of antibiotics in the sweat glands. the dry skin on the outside of your body is dried epithelial cells, that have a fibrous protein call keratin. Keratin forms a dry protective barrier that is somewhat elastic, to aid in stopping microorganisms from gaining entry. Because the skin dies and is constantly being replaced over our lives, any pathogens that deposit there are removed when the dry dead skin comes off. Because healthy skin has a pH of 5-6it is a hostile environment for microorganisms. Finally the sweat glands produce an antibiotic peptide called dermicidin, that can kill a large range of harmful bacteria.
If the pathogens bypass the skin and attempt to gain entry through other areas, our bodies have other mechanisms to launch a counter attack:
Tears/Saliva/Earwax- If we look beyond theses substances as in liberation, then we can see that tears and saliva both contain lysozyme, an enzyme that kills bacteria. Saliva keeps the tissue moist so that they don’t crack and open, which would allow for entry. Earwax traps impeding microorganisms and particles.
Mucus- a gel like material that is secreted by the cells in various areas of the mouth, digestive tract, and airway openings. Microorganisms that come into contact with saliva are unable to gain entry to the cells under it. The airways also have hair like projections called cilia, that move in a wavelike motion to move the mucus out of the airways and into the throat, where they are gotten rid of by coughing, sneezing and the blowing of the nose.
Digestive/vaginal acids- the undiluted digestive acid can kill almost all pathogens that enter the digestive tract on an empty stomach. However one can survive, the Helicobacter pylori, that is known to cause ulcers of the stomach. The vaginal secretions are slightly acidic but not as acidic as the digestive tract.
Vomiting/Urination/Defication- Even though the thought of vomiting is not a nice thought, it is a most effective way of ridding the body of a pathogen, that is in the digestive tract. There is not a population of bacteria in the urinary system, this is because urine is slightly acidic and the flushing action of the urinary tract assists in keeping bacteria out. The movement of feces and the act of defecation, also aid in the removal of microorganisms. When we do get sick from a pathogen, the walls of the intestine contract intensely and they secrete additional fluid to flush the pathogen out.
Resident bacteria- some of the bacteria that are in our bodies are beneficial, they assist in keeping populations of bad bacteria under control, and they aid in the digestion of the food we ingest.
9-4 Nonspecific defenses: The second line of defense.
The second line in defense includes: phagocytes, natural killer cells, inflammatory response, complement system and fever.
Phagocytes- WBCs, called neutrophils, destroy foreign cells, and is done by a process called phagocytosis. In this process the bacterium is captured, surrounded, enclosed, fused with a vesicle, lysosomes digest it and waste/debris are discarded. If the invaders are too large the eosinophils take action, they cluster around the larger invaders, bombarding them with digestive enzymes, they can also digest some foreign proteins. Other WBCs called monocytes can leave the vascular system and enter other tissues and develop into macrophages, that can engulf and digest large numbers of foreign cells, like bacterial parasites. The macrophages serve as cleaners, they scavenge on the old cells, dead tissues, and cellular debris. When they leave the blood they are no longer considered WBCs. When the body is actively fighting an infection there is a high mortality rate of WBCs. the fluid, dead phagocytes and microorganisms, cellular debris, accumulate in the area and from the discharge we know as pus. If the pus is unable to drain from the infection site then the result is an abscess. Some abscesses can be simply drained, others require the use of antibiotic or to be removed surgically.
Inflammation- is redness, warmth, swelling and pain. Theses are present at any trauma to any type of tissue. It is called an inflammatory response. There are chemicals that are responsible for this response. The chemical stimulates mast cells, that are connective tissue, that release histamines to promote vasodilation of close together blood cells vessels, The WBCs called basophils also release histamines as well. However the endothelial cells in the vessel wall pull the cells slightly apart, the cells become more permeable, to allow for more phagocytes to get through the capillaries and into the interstitial fluid, where they attack the foreign organisms and any damaged cells. After doing this the phagocytes return to the lymphatic system and they activate lymphocytes, to start a specific defense. The vasodilation causes the redness and warmth, by bringing more blood to the site of injury. Because of the increases temperature the phagocyte activity raises and the capillary walls allow for fluid to seep, causing the swelling of the area. This then starts the clot formation. When the swelling occurs tissues push together and press the nerve endings, and creates the pain sensation. This sensation can be a good thing, it may limit the activity in that area and promote healing.
Natural killer cells (NK) – Lymphocytes that destroy tumor cells and the cells infected with viruses. They recognize specific changes in plasma membrane of tumor cells and virus-infected cells. NK are nonspecific killers. They are not phagocytes, but are chemicals used to break down the cell membrane of their intended target and the membrane of that cell develops holes, this makes the cell nucleus degenerate. NK cells create a inflammatory response by secreting substances.
Complement system- is made up of at least 20 plasma proteins that flow in the blood. They complement or assist the other defense mechanisms. Proteins usually circulate in an inactive state, but are activated in the presents of infection and become strong defense forces. The activation is a cascade effect on other proteins. They can join together and create larger protein complexes, to create the holes in bacterial cell walls. The fluids and salts can then leak through the holes until the bacterium swells and ultimately bursts. Some of the complement proteins bind with a bacterial membrane and mark them for destruction by phagocytes or they can stimulate others to release histamines. They can also act as attractants for phagocytes.
Interferons- Cells that are infected by a virus release this group of proteins, they then diffuse to other healthy cells, bind to the membranes, and stimulate the healthy cells to produce proteins. Theses proteins then interfere with the synthesis of viral proteins, and make it harder for viruses to infect those cells. Interferons can be produced in pharmaceutical laboratories to assist in the fight against viruses.
Fever- is the rise in body temperature, the normal body temperature is 98.6 degrees F, but can range from 97-99 degrees. During the attack on the virus or bacteria chemicals release by the macrophages, called pyrogens. The pyrogens cause the brain to reset the body’s thermostat to a high temperature. We have a strong need to try and treat even a slight temperature, however this is not a wise idea. A low grade temperature can aid the body in the fight to relieve its self of the invader. Because the fever increases the metabolic rate of the body cells, it speeds up the defense mechanisms. Which can speed up the process of ridding the body of the invader. But high fevers can be dangerous, so it is wise to keep a close eye on them.
9-5 Specific defense mechanisms: The third line of defense.
Even if foreign cells get past the first 2 defense mechanisms, they still have to fight against this sophisticated line of defense. The activities of the immune system are called an immune response. Because the immune system targets specific invaders, we refer to the operations as specific defense mechanisms. There are three important characteristics of the these mechanisms: recognition of the intended target, memories of the past exposure to target, protect the body as a whole.
The immune system targets antigens, antigens are any substance that mobilizes the immune system or and immune response is activated by. Antigens are large protein or polysaccharide molecules. Each antigen has a unique shape, each bacterium or virus has a different one. Each different uniquely shaped antigen is acted upon by the immune system, by the producing of specific antibodies. Theses antibodies attack and inactivate the antigen. Because all antigens are located on the outside of a cell or virus, the immune system cannot detect the once they get inside a living human cell. But human cells have proteins that can act as antigens if the circumstances are just right. Each persons cell has a unique set of proteins on their surface, your immune system uses these proteins to be able to recognize cells that are “you”. They are called self markers and are known as major histocompatibility complex (MHC) proteins. They are as unique to you as genes are. MCH proteins signal your immune system to bypass your own cells, under normal circumstances. But if MCH proteins of your body were put into another person they would be antigens in the other person. Cancerous and abnormal cells in your body have nonself markers on them.
Lymphocytes play an important role in the specific defense mechanisms. There are two types:
B cells- (B lymphocytes) – mature in the bone marrow, go about recognizing and targeting antigen bearing cells, by antibody-mediated immunity. These cells produce antibodies, that they release into the blood stream, lymph, and tissue fluid, and the antibodies flow freely throughout the body. The antibodies of B cells work best against viruses, bacteria, and foreign molecules that are soluble in blood and lymph.
T cells- (T lymphocytes) – mature in the thymus gland, recognize by the cell-mediated immunity. This requires the actions of several types of T cells. They directly attack the cells carrying the antigens while other T cells release proteins to help coordinate aspects of the immune response. This includes the actions of both T cells and B cells and also macrophages. Cell-mediated immunity protects against parasites, bacteria, viruses, fungi, cancerous cells and the cells perceived as foreign. They attack and kill the infected human cells before the cells can even release a new bacteria or virus in the blood. In order for the T cells do their job, there must be an antigen present that they can recognize. This is because T cells do not recognize fragments of an antigen. There are cells that help fulfill this need, they are called antigen presenting cells (APCs). They engulf with macrophages, partially digest with lysosomes, a vesicle containing MHC molecule binds to the digestive vesicle, the MCH molecules and a fragment of the antigen of the antigen-MCH complex, the complex is now displayed on the surface of the cell when the vesicle fuses with its membrane then releases the digestive products. The cell now is able to represent to the T cell as something it recognizes. As T cells mature they also develop they one of two surface proteins, CD4 or CD8. They determine what type a T cell will become. CD4 become helper T cells. Hepler T cells stimulate other immune cells. When a helper T cell comes across an APC fragment it differentiates and undergoes mitosis, which produces identical helper cells. Because the new helper cell has the same receptors they are recognized as same antigen. A majority of the helper T cells in the clone now begins to secrete signaling molecules called cytokines. The cytokines stimulate actions in the T cells, macrophages and substances promote other immune cells, like the natural killer cells and phagocytes. They also attract other blood cells to the area, and activate the B cells. With out the helper T cells and the cytokines the activities of the other immune cells, there would not be an immune response at all. When a mature T cell with C8 receptors meets a APC that has the antigen fragment, the T cell will produce a clone of the cytotoxic T cells. These T cells are the only cells to make a direct attack and destroy other cells.
Antibodies are in a class of blood plasma proteins called gamma globulins. Because they are so important in the immunity that are often called immunoglobulin. There are five classes of immunoglobulins:
1) IgG- make up 75% of the immunoglobulins, found in blood, lymph, intestines ans tissue fluid. They activate the complement system and have long lives. They are the only antibodies to cross the placenta, and pass the mother’s immunity.
2) IgM- make up 5-10% of the immunoglobulins, the first released during immune responses. Found in blood and lymph, and activate the complement system and cause foreign cells to agglutinate. ABO antibodies belong to this class.
3) IgA- make up 15% of the immunoglobulins, enter the areas of the human body that are covered by mucous membranes, and are in mother milk. The neutralize infectious pathogens.
4) IgD- make up less than 1% of immunoglobulins, are found in the blood, lymph and B cells. There specific function is not clear, they may in the activation of B cells.
5) IgE- make up approximately 0.1%, these are the rarest of the immunoglobulins. In B cells, mast cells and basophils. Active the inflammatory response, by triggering the release of histamine, and are behind allergic responses.
9-6 Immune memory creates immunity.
At the first exposure to an antigen, the immune system protects with plenty of defenses. This first exposure creates a primary immune response. This response has a time laps of 3-6 days after the antigen is presented. While in this time frame the B cells that are to that antigen multiply and develop into plasma cells. The concentrations of antibodies rise and reach a peak over 10-12 days of first contact, then tapers off. The B cells and T cells have created memory cells. The memory cells are the base for the immunity from a disease. The later contact with a disease then initiates a secondary immune response, this response is quicker, lasts longer and more effective that the primary immune response. Memory cells have long lives and can generate that secondary response over a life time. This does not mean that you don’t get repeated colds or flu, you may get one that acts or feels like the last. This new cold/flu is not the same because there are over 100 different viruses that cause these ailments. Also the viruses that cause colds and flu, evolve very fast, that they are different every year.
9-7 Medical assistance in the war against pathogens.
Even though our natural defenses against pathogens work quite well, we as humans have tried to take it into our own hands. We have been able to take the concept and produce an every effective arsenal against pathogens. One of the largest and important development, immunizations. The immunizations aid the human body to be resistant to specific pathogens. Active immunization uses the body’s own immune system, in administering an antigen containing mixture called a vaccine. Most vaccines are from either dead or weakened pathogens. Others are made from organisms that have been genetically produced. The vaccines made from dead or weakened pathogens have limitations, such as safety, time used and expense of making. the weakened pathogens do have the potential to cause a disease, but do elicit a stronger immune response. Because a vaccine to a pathogen only protects for one pathogen, multiple vaccines are needed for multiple pathogens. Vaccinations are not very effective if given after a pathogen has entered the body. Because the cost of producing vaccines is very costly, it is hard to acquire them in some countries. Vaccines are highly used by Americans for their children, however the vaccine usage in adults has slipped off and the result is that nearly 50,000 adults die each year due to pathogens that could be prevented by vaccinating.
There is also Passive immunization, where a human can be given antibodies that are prepared in advance from either a human donor or an animal donor that has immunity to an illness. This usually comes in the form of a gamma globulin injection. Passive immunization works effectively on existing infections. It only protects for a short period of time, and cannot give long-term immunity to a second exposure, due to the fact that the persons own B cells are not activated, therefore no memory cells develop.
There is also another aid in immunity called monoclonal antibodies. These are antibodies that are produced in a laboratory from cloned descendants of a single hybrid B cell. Theses antibodies are useful in testing, research and cancer treatments, this is because they are pure and not costly to produce.
Antibiotics combat bacteria. They kill and inhibit growth of bacteria, derived from mold and fungi extracts. Even though there are hundreds of antibiotics available today they all used the differences between human and bacterial cells to work. Some antibiotics work on only specific bacteria, other called broad-spectrum antibiotics work on a several groups.
9-9 Inappropriate immune system activities cause problems.
Allergies: hypersensitivity in the immune system, creations can be from relatively minor to severe that would cause hospitalization, can be caused by anything from foods to drugs. Immunoglobulins IgE, are the ones responsible for these reactions. Exposure to an allergen triggers the B cells to produce the IgE antibodies, that then bind to mast cells and the circulating basophils. Upon the second entry into the body the allergen then binds to the antibodies on mast cells and basophils and causes them to release histamine, that results in the inflammatory response. Some allergens only affect a certain area and others are absorbed into the blood stream and spread.
When the immune system fails to recognize self, it may trigger cytotoxic T cells to target its own cells. the conditions are called autoimmune disorders. It is unknown how this disorder comes about, but in certain cases antigens never exposed to the immune system as it undergoes the fetal development, and the antigens are never seen as self. When the damaged tissue exposes them, mature immune system responds like they were not of self. Other cases may be that the antibodies produce to fight a foreign antigen, cross-react with the body’s own tissues. At this time there are no cures for auto-immune disorders. But there are treatment that help with the symptoms. The diseases range from, Type 1 diabetes, Lupus and Rheumatoid Arthritis.
Chapter 10: The Respiratory System: The exchange of gases
10-1 Respiration takes place throughout the body.
Respiration is in four processes:
1) Breathing, the moving of air in and out of the lungs.
2) External respiration, the exchange of gases from inhaled air and blood.
3) Internal respiration, the exchange of gases from blood to tissue fluids.
4) Cellular respiration, the use of oxygen to produce ATP, generates carbon dioxide as a waste.
Not only does the respiratory system exchange gases it also aid in the vocalization process.
10-2 The respiratory system consists of and upper and lower tract.
Upper: Filters, warms and humidifies the air we breath
Components of the upper respiratory tract:
External nose- the visible portion. Made up of cartilage, in front of two nasal bones, lined on the inside with hairs.
Nasal cavity- internal portion of the nose, separated into two portions of the septum. Lined with moist epithelial tissue that helps humidify the air, and supplied with plenty of blood vessels that help warm the incoming air. On the epithelial tissue is mucus that helps trap dust and pathogens. There are cilia in the nasal cavity also, they trap and move foreign products to the produce a sneeze or cough to remove them.
Sinuses- air spaces in our skull, lined also with epithelial tissue and mucus. They drain into tear ducts and the nasal cavity.
Pharynx- connects the mouth and nasal cavity to the larynx, extends from the nasal cavity to the roof of the mouth. The auditory tubes are located open into the nasal cavity from the ears, to allow for drainage. The lower pharynx is the common passageway for food and air.
Larynx- extends for 5cm from the pharynx. Has 2 important structures; the epiglottis, a flexible flap of cartilage at the opening of the larynx, and remains open when you inhale. And the vocal cords, two flexible pieces of connective tissue that surround the airway called the glottis. Produces sound when air is forced over them..
Trachea- transports air to the left and right bronchi, consists of C-shaped rings, made of cartilage and held together by connective tissues and muscles. Is lined with cilia and epithelial tissues. There is mucus present here also.
Bronchi- branches from the trachea, is two airways called left and right bronchi and enters the lung cavity. They divide into multiple smaller bronchi. The walls consist of fibrous connective tissue, smooth muscle and are enforced with cartilage. As it branches and gets smaller the bronchus lack cartilage and are called bronchioles. Not only do they transport air but they also cleanse it, warm it, and saturate with water vapor before it reaches the delicate gas exchanging surfaces of the lungs. The smallest bronchi have ciliated epithelial cells along with some mucus cells, that trap dust, bacteria and other small particles.
Lungs- are the organs of exchanging gases, consists of supportive tissue that encloses the bronchi, the bronchioles and the blood vessels along with the area where gas exchange occurs. There are two lungs, left and right, they take up the majority of the thoracic cavity. They are separated by the heart. The shape fits and runs along the thoracic cavity with them being broader at the bottom, and stop at the diaphragm. The lungs are enclosed in two layers of epithelial membranes called pleural membrane. The two layers are separated by a small space called the plueral cavity, and it contains a watery fluid that reduces friction in the motion of breathing. In the lungs are several lobes, three in the right and two in the left, that can function independently of each other.
Alveoli- located at the end of the branching airways are 300million air-filled sacks. They are a thin bubble of living squamous epithelial cells. This is where the exchange of gases happens. In them is epithelial cells that secret lipoproteins called surfactant, that reduces surface tension, Without it the surface tension could cause the alveoli to collapse.
Pulmonary capillaries- as the blood from the right ventricle pumps the deoxygenated blood to the pulmonary trunk and it splits into the left and right pulmonary arteries, the the arteries divide smaller and smaller arterioles and terminating in the pulmonary bed, the blood comes very close to the air of the alveoli, a series of veneules and veins collect the oxygen from them. Because of this close proximity of blood and gases this could prove to be a alternative way of delivering medications into the bloodstream.
10-3 The process of breathing involves a pressure gradient.
the lings do not have bones so, ribs, intercostal muscles, and diaphragm are the mechanisms of breathing. The air we breath move in and out of the lungs in a cyclic manner. As the bones surrounding the lungs move. The way gas pressure change and how it moves follows 3 basic principles:
1) The pressure of gas causes the molecule of gas to collide.
2) In a closed space and high volume the gas molecules are further apart, as the pressure decreases the gas pressure increases.
3) Gases of a high pressure flow to areas of lower pressure.
Inspiration- pulls air into the respiratory system, lung volume then expands.
Expiration- pushes air out of the system and volume declines.
If we are relaxed the breathing of inspiration is active and expiration is passive. If we in increase the need for air flow both may be active. To breath in more deeply we can do so because the diaphragm and rib cage can expand. If we need to exhale deeply the abdominal muscle push the diaphragm up higher. At times of coughing/sneezing the sudden rising of the abdominal pressure pushes the diaphragm upward and against the plural cavity and forces the air out.
Lung volume- at rest you breathe about 12 breaths per minute, each breath represents tidal volume of air, 500 milliliters, of that only 350 reach the alveoli. The remainder remains in the airways, and do not participate in gas exchange, thus referred to as dead airway space.
Vital capacity- the maximum volume of air you exhale after a maximal inhalation, vital capacity is about 4800ml and 10 times that of tidal volume at rest.
The maximum amount that can be inhaled past tidal volume is 3100ml and is called inspiratory reserve volume. The amount we can forcefully exhale is 1200ml, and is called expiratory reserve volume. However no matter how hard you force the air out 1200ml remains, this is called residual volume.
10-4 Gas exchange and transport occur passively.
Although we are surrounded by gases, and they have greater atmospheric pressure, we do not feel the pressure, because the pressure in our lung is the same as the atmospheric pressure, while we are at rest. On the earth there are nitrogen (78%), oxygen (21%) and trace amounts of carbon dioxide (0.04%), each gas exerts a partial pressure, proportional to the percentage of the total composition of the gas. The fact that we know the percentages of each gas in our atmosphere, we can find the partial pressure for each, by taking the 760mm (millimeters of mercury) Hg and multiplying it by the percent of the gas represented (example 760mm Hg x .78 (the percent of nitrogen) =592. 8mm Hg). The partial pressure in a gas mixture is proportional to concentration, gases diffuse down the partial pressure gradient. This does not take energy from ATP, it is done slowly by partial pressure.
External respiration- In the lungs, oxygen will diffuse into de-oxygenated blood (oxygen was removed from the blood in the body) and carbon dioxide will diffuse out of the blood into the lungs and expelled from your body when you breathe out.
Internal respiration- the metabolic processes whereby certain organisms obtain energy from organic molecules; processes that take place in the cells and tissues during which energy is released and carbon dioxide is produced and absorbed by the blood to be transported to the lungs
Both external and internal respiration occurs entirely by diffusion, the maintenance of partial pressure gradients that permit diffusion is done by breathing, blood transport and cellular respiration.
Hemoglobin and the transport of oxygen molecules- transport of oxygen in blood is undertaken by hemoglobin. This protein collects oxygen in respiratory organs, mainly in the lungs, and releases it in tissues in order to generate the energy necessary for cell survival. The oxygen that we breath in is processed one of two ways, either by binding to hemoglobin or dissolved in blood plasma. 98% of the oxygen is processed by the hemoglobin after it is taken out of the alveoli. Without processing through hemoglobin the tissues would not receive sufficient amount of oxygen to sustain life. Each hemoglobin can bind to 4 oxygen molecules, and represents a oxyhemoglobin. The reaction is reversible and depend on partial pressure of the oxygen.
Carbon dioxide produced in the tissue cells diffuses into the blood plasma. The largest fraction of carbon dioxide diffuses into the red blood cells. The carbon dioxide in the red blood cells is transported as: dissolved CO2, combined with hemoglobin, or as bicarbonate. Bicarbonate diffuses out of the red blood cells into the plasma in venous blood and in arterial blood. Chloride ion always diffuses in an opposite direction of bicarbonate ion in order to maintain a charge balance. At the lungs the CO2 diffuses from the blood and goes into the alveolar air. This loss of CO2 from the plasma causes a drop in the PCO2, and causes a chemical reaction that had formed the bicarbonate, to reverse.
10-5 The nervous system regulates breathing.
The medulla oblongata, located near the base of the brain, is responsible for the inspiration and expiration, also the rate that of breathing. Inside this area is the respiratory center. It is a group of nerves that generates and automatic cycle of electrical impulses. The impulses travel to the nerves of the diaphragm and the intercostal muscles. The impulses stimulate contraction in theses muscles. When inhalation happens the respiratory center receives another set of impulses that monitor the amount of inflation and limit inhalation then initiate exhalation. At the point where the impulses end, the muscle and rib cage relax, then we exhale. There are chemical receptors to monitor the CO2, H+ and O2 levels. When the levels of gases rise, such as that of the H+ the medulla oblongata can detect it. When the levels rise so do the the PCO2 levels of the arterial blood, in turn the receptor cell signal the respiratory cent t to speed up breathing, we breathe more deeply and frequently and lower the levels of CO2 and return the blood gas levels to normal.
There is some conscious control that we can have over breathing. This control resides in the cortex of the brain. This makes it so we have the ability to hold our breath.
10-6 Disorders of the respiratory system.
There are many factors that lead to the disorders of the respiratory system. Such as, air flow or gas exchange, infections, cancer, and diseases of other organs.
Reduced air flow or gas exchange- such as Asthma; the spasmodic contractions of the bronchi. Also Emphysema; the alveoli become permanently impaired. Bronchitis; simply inflammation of the bronchi. Cystic Fibrosis; inherited condition, mucus cells of the lungs produce a thick, sticky mucus.
Microorganisms- the lungs are very prone to infections, because they present a warm, moist environment for the reproduction microorganisms. Besides the common cold and flu, there are other more serious diseases caused by microorganisms. Pneumonia; infection in the lungs, caused by either virus or bacteria. Tuberculosis; a bacterial infection that scares the lungs, infectious disease, past through coughing or sneezing. Botulism; poisoning via bacterial toxin, found in improperly cooked or preserved food.
Lung Cancer- Caused by the uncontrolled growth of abnormal cells, can impede the exchange of air gases and movement of the air you breathe. Closely related to smoking, 90% of cases.
Pneumothorax and Atalectasis- Pneumothorax is the collapse of one or more of the lung lobes, caused most often by an injury to the chest. But can also happen due to disease or spontaneously. Can be life threatening. A Atalectasis, the lack of gas exchange, due to alveolar collapse or build up of fluid. Is sometimes a result of surgery, but also when the surfactant is deficient.
Congestive Heart failure- when a person has this heart failure the heart does not beat sufficiently, and blood backs up in the pulmonary blood vessels, the result is a rise in blood pressure of the pulmonary blood vessels, as a result blood then builds up in the interstitial spaces between the capillaries and the alveoli. Increases diffusional distance and diffusion of gases.