Blood ---Ch 14 Circulating blood provides a vital function for survival: transports hormones to their destination, waste products to the kidneys for removal and transports ions / chemicals to various parts of the body. Blood: 5-6 liters in adult males, 4-5 liters in adult females on average ( this is a size thing) -makes up ~ 8 % of the total body weight -very viscous, 5x more than water ( thick ) -ph = 7.35 -- 7.45 (slightly basic) -venous blood = dark-red (blue), arterial blood = reddish Whole blood consists of a plasma and cellular component. Plasma - clear yellowish fluid - 55 % of whole blood ( 92 % of which is water, 7 % protein & 1 % ions and mineral ) - contains 3 major proteins * Fibrogen = involved with clotting * Albumin = involved in blood osmotic pressure by increasing viscosity * Globulins = important in antibody functioning and transporting hormones - major ions in the plasma include : Na+, Cl-, K+, Ca2+ Cellular - 45 % of whole blood ( 99 % of which is erythrocytes, < 1 % leukocytes & < 1 % platelets ) - consists of 3 major components: * Erythrocytes ( RBC ) = transport oxygen and carbon dioxide, 5 million/cubic mm of blood * Leukocytes (WBC ) = defend the body against pathogens, 5,000 to 11,000/ cubic mm of blood * Platelets = involved in blood clotting, 350,000 to 750,000 / cubic mm of blood
Red Blood Cells (RBC) -they are also called erythrocytes and are formed in the bone marrow -the hormone erythropoietin produced in the kidneys, targets the stem cells of the bone marrow (erythroblasts) and causes them to differentiate into erythrocytes. This process is called erythropoiesis. -erythroblasts have cell organelles as well as a nucleus, but as they undergo erythropoiesis, they lose their organelles and nucleus and begin to take in hemoglobin. Hemoglobin is made up of amino acids and heme. Heme is a molecule consisting of iron. Oxygen binds to the iron portion of heme, while carbon dioxide binds to the amino acid portion. -hemoglobin protein give blood it s red color in the presence of oxygen -erythrocytes have a life span of ~ 120 days because they don t have a nucleus or organelles so can t repair themselves if damaged. -anemia is a condition in which the number of RBC s are lower than normal or their ability to transport blood gases is reduced -RBC s are small, flexible, disc-shaped cells (look like Krispy creme donuts pushed in the middle). This shape is because they lose their nucleus during development. White Blood Cells (WBC) -they are also called leukocytes and are formed from stem cells in the bone marrow like RBC s -the production of leukocytes is called leukopoiesis - make up ~ 1 % of our total blood volume -important in controlling disease -all WBC s have a nucleus and can wander outside the circulatory system -the different WBC s differ in their cytoplasmic make up, size & size of nucleus -there are 5 major types : Neutrophils, Eosinophils, Basophils, Monocytes and Lymphocytes
* Neutrophils : 50 % -- 70 % of WBC s specialize in attacking and destroying bacteria * Eosinophils : 2 % -- 4 % of WBC s respond during an allergic reaction and parasite infection (like intestinal worm infestation) * Basophils : < 1 % of WBC s release histamine to promote inflammation for wound healing * Monocytes : 2 % -- 8 % of WBC s includes macrophages which are two fused monocyte cells that engulf foreign particles * Lymphocytes : 20 % -- 40 % of WBC s respond to bacterial and viral infections include T- cells and B- cells (beta) both which are important in immunity. B- cells produce antibodies Platelets -formerly known as thrombocytes (cytes = cells), but platelets are not really complete cells, but little fragments of cells. They look like shattered plates, hence the name platelets. -these little fragments are actually the smaller pieces of larger stem cells called megakaryoblasts which shrink and become platelets when they pass through the blood vessels of the lungs -platelets don t have nuclei -capable of ameboid movement -live ~ 10 days -130,000 -- 360,000 platelets per cubic mm -help repair damaged blood vessels by sticking to broken surfaces (important to blood clot formation) -the formation of platelets is called thrombopoiesis -when a blood vessel is cut, platelets stick to the jagged edges. The platelets pile on top of each other and eventually release a chemical called platelet thromboplastin factor (PTF). This factor starts the blood clotting process called hemostasis -Coagulation refers to a mechanism which causes the formation of a blood clot and it involves many clotting factors (takes ~ 5 min)
Examples of clotting factors include: *Fibrinogen (factor I) = which converts to fibrin *Prothrombin (factor II) = assists the above mentioned conversion *Antihemophiliac factor (factor VIII) = people who lack the gene for this factor have the disease hemophilia Certain drugs / chemicals inhibit blood clotting and are referred to as blood thinners. Two common ones are Heparin and Coumadin. As we age (eat poorly too), plaque can build-up on our arteries. Because the plaque has jagged edges, platelets stick to it. So this sets up the scenario for a blood clot. Thrombus is a clot in a vessel Embolus is when the clot breaks away and travels in the circulatory system. If the clot continues till it reaches narrow vessels like those of the brain, an embolism (blockage) results. An embolism is also called a stroke. This is why many doctors suggest taking low dose aspirin to reduce the chance of a brain clot. The aspirin acts like an anticlotting agent because it reduces the stickiness of the platelets. Leukocyte Response If the body gets an infection, the leukocytes will reproduce and increase in numbers. They will try to eat (phagocytize) the invaders or release other substances / chemicals to destroy the invaders. Doctors look at a person s WBC count if they believe their patient is sick and not in homeostasis. Normal WBC count is 5,000 --- 11,000 WBC/mm3. If the count is > 11,000 this would indicate infection. The technologist and / or doctor would then determine which of the 5 WBC types was high so the correct drug therapy could be prescribed.
Blood Groups In the 1800 s it was thought that all blood was the same, doctors would use any blood for their patients. Most often the patient die. By 1933 it was found that different people had different proteins on the surface of their RBCs. Antigens ( agglutinogens ) = surface proteins on RBCs--like a name tag ex. A, B, AB, O & C, D (Rh factor) Antibodies ( agglutinins ) = proteins in blood plasma The reaction of blood antigens and antibodies determines if blood will clump or agglutinate. Blood Typing involves identifying the antigens present on the RBCs. There are many systems of blood typing, the two most common being : ABO system & the Rh system. ABO System This system contains only two antigens : A & B. Type AB blood has both antigens, type A blood has A antigen, type B blood has B and type O blood has no antigen on it s surface (zero). The antibodies that react may be either anti-a or anti-b. Refer to the following below. IA = Type A -- has A antigen, antibodies against B IB = Type B -- has B antigen, antibodies against A io = Type O -- has no antigens, has both A & B antibodies IAIB = Type AB -- has both A & B antigens but, no antibodies Therefore, Type AB = Universal Recipient Type O = Universal Donor I = immunogen or antigen
Phenotype Genotype Blood can Receive A I A I A, I A i O A, O B I B I B, I B i O B, O AB I A I B A, B, AB, O O i O i O O Rh System This system identifies a class of antigens called Rh. It was 1st discovered in the Rhesus monkey (D agglutinogen). People that have this antigen are said to have positive blood. People who don t are said to have negative blood. This Rh factor is of particular importance during pregnancy. Incompatible mixing may occur if Rh-negative blood is exposed to Rh-positive blood more than once. For example, in consecutive pregnancies of a Rhnegative mother and Rh-positive baby, agglutination does not occur the first time because the Rh-negative blood has not been stimulated to produce anti-rh antibodies. But, her baby s blood at the time of birth enters into the mother s blood stream and causes her to produce Rh antibodies. Now mom has the Rh antibodies in her plasma. During her second pregnancy if she has a Rh-positive baby, some of the Rhantibodies could enter the baby s circulatory system and cause death to the child. This condition is called erythroblastosis fetalis or hemolytic disease. But, today this is not a problem. Since 1970, the development of a drug RhoGam is given to an expectant mom with negative blood. RhoGam covers (masks) the Rh aggluttinins so they will not bind to anything, so the baby remains protected.