Lesson Three Blood and Immunity Outline II. Blood - Blood is composed of a cellular portion and a watery portion. It carries the essential life-sustaining nutrients, gases (oxygen) and wastes throughout the body. A. Plasma - A little more than half of your blood is a watery portion termed plasma. 1. Water makes up over 90% of plasma. 2. Proteins - Some very important proteins are present in plasma. Examples include antibodies (fighting infection proteins), clotting factors and albumin (which keeps water in the bloodstream - via osmosis). B. Cells - A bit less that half of your blood is made up of cells. Three types of cells are present 1. Erythrocytes = Red blood cells (RBC) a. Made in bone marrow, new erythrocytes are constantly made because each RBC only has a lifetime of a few months. RBCs are the most numerous of all of the blood cells. b. Hemoglobin - Hemoglobin is the pigment in RBCs that gives the RBCs their red color. The hemoglobin is the protein that actually carries oxygen. When oxygen is attached to hemoglobin, it turns a bright red color. When no oxygen is attached, the color is red/blue. Hemoglobin contains iron, and iron must be present to make hemoglobin and RBCs in the bone marrow. c. Function - RBCs (via hemoglobin) carry oxygen d. High altitudes - In an attempt to compensate for less oxygen at high altitudes, the body produces MORE RBCs. This improves their oxygen carrying capacity. Thought question: Why would athletes like to train at a higher altitude? e. Anemia - If you don't have enough RBCs, perhaps because you are losing blood through a bleeding ulcer, or perhaps you don't have enough iron to make RBCs, you are anemic. Therefore, you don't have enough oxygen
carrying capacity and will feel quite tired and weak. 2. Thrombocytes = Platelets - "Thromb-" means clot. These are your clotting cells. They are very tiny cells that are the second most numerous of your blood cells. a. Produced in the bone marrow b. Clotting pathway after an injury: 1. Smooth muscle contraction - A reflex occurs after blood vessel injury that causes the smooth muscle in the vessel wall to contract. This makes the blood vessel smaller, so that it won't bleed as much. 2. Platelet plug formation - Platelets passing by in the bloodstream automatically stick to any defect in the blood vessel wall. This alone, will stop the bleeding in small vessels. 3. Insoluble clot - If the injury is in a larger vessel, or more severe, the platelet plug needs to be more solid. It is converted into an insoluble clot. An analogy of what an insoluble clot is would be that the platelet plug is the consistency of a raw egg white. The insoluble clot is the consistency of a cooked egg white. a-clotting factors - Clotting factors, which are made in the liver, are responsible for converting the platelet plug into an insoluble clot. b-vitamin K is needed for making some of the clotting factors. c. Clot breakdown as injury is repaired - A couple of weeks later, as the injured blood vessel is repaired, the clot is broken down. d. Thrombus - Clotting must occur when you have an injured blood vessel, or else you would bleed to death. What happens if clotting occurs when there is NOT a broken blood vessel? If the blood vessel has a bumpy surface (such as a cholesterol plaque), it could elicit the clotting pathway and form an abnormal blood clot called a thrombus. This clot blocks blood from flowing along and the tissue served by that blood vessel does not get oxygen. This is what happens in coronary arteries going to the
heart and leads to a heart attack or in carotid arteries going to the brain and leads to a stroke. A stroke is when part of the brain loses blood supply and is damaged. e. Embolus/Embolism - If a thrombus becomes dislodged, it is an embolus. The embolus can then travel anywhere in the body, such as brain and lungs, and become lodged at another location. The new blockage, as a result of the embolus, blocks oxygen from going to tissue. f. Hemophilia - Hemophilia is a genetic disease in which one of the clotting factors is missing. Therefore, blood clotting is abnormal. It is treated with transfusions containing the missing clotting factor. 3. Leukocytes = White blood cells (WBCs) a. White blood cells are the fewest in number of all of the blood cells. They have a unique ability to migrate OUT of the bloodstream to go fight infection wherever it may be. b. Life span of WBC varies. It can be as short as 30 minutes if it dies in battle with a microorganism, or as long as a lifetime. New WBCs are made in many locations including the bone marrow, lymph nodes, tonsils and spleen. c. Function - WBCs fight off infections. III. Resistance to Disease A. Nonspecific Resistance to disease - These are protective mechanisms that you are born with to fight off ANY type of infection or damage. 1. Physical & Chemical barriers a. Skin, Mucous membranes - These barriers prevent microorganisms from entering the body. b. Hairs (nostril, cilia) - Hairs can sweep debris from entering your airways. c. Hydrochloric acid in the stomach is antimicrobial d. Enzyme in tears, saliva are antimicrobial. 2. Phagocytosis - WBCs can eat damaged cells and microorganisms. Once eaten, they are destroyed by the WBC's powerful lysosomal enzymes.
3. Inflammation - This isolates and prevents spread of damage or infection. B. Specific Resistance to Disease = Immunity - This is a response that you develop over time and provides a specifically-tailored response for each and every microorganism that you may encounter in a lifetime. The essence of immunity is that it has memory, so that the second or thousandth time you encounter a microorganism invader that you've already "met", you will fight it off bigger and faster so that you won't even get sick. 1. Antigen - Substance capable of eliciting immune response. Examples include microorganisms and poisons made by the microorganisms. a. Cellular Immunity 1. Lymphocytes - Lymphocytes are a type of WBC. They are the cell involved in this type of immunity. There are two different types of lymphocytes - T cells and B cells. The T cells function in cellular immunity. 2. T cells specifically recognize antigens, such as viruses, fungi, bacteria residing inside of our cells, and parasites, and destroy them. Stimulated T cells can release powerful chemicals that destroy the antigen. 3. Some of the activated T cells become memory T cells. These cells can launch a bigger and quicker attack upon subsequent exposure to the same antigen. b. Antibody Response 1. B lymphocytes are involved with this type of immunity. 2. Antibodies are made by descendants of B lymphocytes. Antibodies are tiny proteins that latch onto the antigen and result in the demise of the antigen. 3. B cells have memory, so that subsequent encounters with the antigen will result in huge amounts of antibodies produced very quickly. c. Vaccination - Vaccination works because of the memory involved in immunity. When you get a flu shot, you are exposed to inactivated flu virus. Your immune system attacks it & stores the information in memory. Therefore, when someone coughs on you and exposes you to the real
flu virus, you launch such a huge and quick attack, that you do not even get sick. C. Immune Disorders - AIDS 1. AIDS = Acquired Immune Deficiency Syndrome 2. Occurrence - Estimates are that there are 10 million people with the virus worldwide. About 1.5 million in the U.S. carry the virus. 3. Cause a. Human Immunodeficiency Virus b. HIV selectively infects & replicates in T (helper) Cells (which are lymphocytes, a type of WBC) c. Consequences of T Cell destruction - This cripples the immune system. 4. Course of disease a. HIV+ This means that you have been exposed to the virus. However, you may or may not be sick. b. Symptomatic Stages - These are the stages when you are sick due to failing of your immune system. Signs and symptoms can be vague flu-like symptoms, night sweats, weight loss. c. Full blown AIDS - At this point, which may take years to develop, if at all, your immune system is so crippled that your T cell counts are very low and/or you have an opportunistic infection. Opportunistic infections are infections that occur because you do NOT have a functional immune system. 5. Transmission of HIV a. Blood b. Sexual 1. Transfusions 2. Contaminated IV needles c. Across placenta (mom to baby) d. Very fragile outside of body - HIV cannot be transmitted by casual contact such as shaking hands or sharing a drinking cup.
6. Prevention of HIV infection a. Abstinence from sexual contact, or proper usage of latex condoms to protect from infected sexual fluids. b. Use sterile needles for all injections c. Blood supplies are checked for HIV in the U.S. This case is not always true in poorer countries. 7. Treatment options a. Anti-viral drugs do not kill HIV, but slow down or even prevent its replication. b. Antibiotics to prevent the common opportunistic infections. c. Vaccines and new anti-viral drugs are being researched d. Treatments are VERY expensive. Do you suppose that third-world countries can afford treatments for the infected population?