The Blood.

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The Blood.

Terms And Definitions Regarding Blood.

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§The only fluid tissue in the human body -- Classified as a connective tissue -- Components of blood §Living cells §Formed elements §Non-living matrix §Plasma 
Components of blood
Living cells (formed elements) -- Non-Living Matrix (plasma)
Centrifuged Blood
§Erythrocytes sink to the bottom (45% of blood, a percentage known as the hematocrit) -- Buffy coat contains leukocytes and platelets (less than 1% of blood, a thin, whitish layer between the erythrocytes and plasma) -- Plasma rises to the top (55% of blood) 
Physical Characteristics of Blood
§Color range: oxygen-rich = scarlet red : oxygen-poor = dull red -- pH must remain between 7.35–7.45 -- Blood temperature is slightly higher than body temperature at 100.4°F -- In a healthy man, blood volume is about 5–6 liters or about 6 quarts -- Blood makes up 8% of body weight 
Blood Plasma
§Composed of approximately 90% water -- Includes many dissolved substances: Nutrients, Salts (electrolytes), Respiratory gases, Hormones, Plasma proteins, Waste products 
Plasma Proteins
§Most abundant solutes in plasma -- Most plasma proteins are made by liver -- Various plasma proteins include: Albumin & Clotting proteins & Antibodies
Albumin & Clotting proteins & Antibodies
-- regulates osmotic pressure -- help to stem blood loss when a blood vessel is injured -- help protect the body from pathogens
Acidosis & Alkalosis
§-- blood becomes too acidic -- blood becomes too basic -- In each scenario, the respiratory system and kidneys help restore blood pH to normal 
§Erythrocytes & Leukocytes
-- Red blood cells (RBCs) -- White blood cells (WBCs) -- biconcave disks; sacs of hemoglobin -- transport oxygen bound to hemoglobin molecule 
§Multilobed nucleus with fine granules -- Act as phagocytes at active sites of infection  
§Large brick-red cytoplasmic granules -- Found in response to allergies and parasitic worms 
§Have histamine-containing granules -- Initiate inflammation 
§Nucleus fills most of the cell -- Play an important role in the immune response 
§Largest of the white blood cells -- Function as macrophages -- Important in fighting chronic infection
§Derived from ruptured multinucleate cells (megakaryocytes) -- Needed for the clotting process -- Normal platelet count = 300,000/mm3
§Erythrocytes (red blood cells or RBCs) 
§Main function is to carry oxygen -- Anatomy of circulating erythrocytes: Biconcave disks, bags of hemoglobin, Anucleate (no nucleus), Contain very few organelles 
§Iron-containing protein -- Binds strongly, but reversibly, to oxygen -- Each molecule has four oxygen binding sites -- Each erythrocyte has 250 million -- Normal blood contains 12–18 g per 100 mL blood 
Homeostatic imbalance of RBCs
§Anemia -- Sickle cell anemia (SCA) -- Polycythemia 
§Anemia & Polycythemia
§-- a decrease in the oxygen-carrying ability of the blood -- an excessive or abnormal increase in the number of erythrocytes 
Hemorrhagic Anemia
-- sudden hemorrhage -- decrease in RBC number
Hemolytic Anemia
-- lysis of RBCs as a result of bacterial infections -- decrease in RBC number
Pernicious Anemia
-- lack of vitamin B12 -- decrease in RBC number
Aplastic Anemia
-- depression/deconstruction of bone marrow by cancer, radiation, of certain medications -- decrease in RBC number
Iron Deficiency Anemia
-- lack of iron in diet or prolonged bleeding which depletes iron reserves needed to make hemoglobin -- inadequate hemoglobin content in RBCs
Sickle Cell Anemia (SCA)
-- genetic defect leads to abnormal hemoglobin, which becomes sharp and sickle-shaped under conditions of increased oxygen use by body; Africans -- abnormal hemoglobin in RBCs
Leukocytes (white blood cells or WBCs)
§Crucial in the body’s defense against disease -- These are complete cells, with a nucleus and organelles -- Able to move into and out of blood vessels (diapedesis) -- Can move by ameboid motion -- Can respond to chemicals released by damaged tissues
§Leukocytosis §
WBC count above 11,000 leukocytes/mm -- generally indicates an infection 
§Abnormally low leukocyte level -- Commonly caused by certain drugs such as anticancer agents 
§Leukemia §
Bone marrow becomes cancerous, turns outexcess WBC 
§Granulocytes §
Granules in their cytoplasm can be stained -- Possess lobed nuclei -- Include neutrophils, eosinophils, and basophils 
§Agranulocytes §
Lack visible cytoplasmic granules -- Nuclei are spherical, oval, or kidney-shaped -- Include lymphocytes and monocytes
§Blood cell formation -- Occurs in red bone marrow -- All blood cells are derived from a common stem cell (hemocytoblast) 
§Hemocytoblast Differentiation 
§Lymphoid stem cell produces lymphocytes -- Myeloid stem cell produces all other formed elements 
Formation of Erythrocytes
§Unable to divide, grow, or synthesize proteins - Wear out in 100 to 120 days - When worn out, RBCs are eliminated by phagocytes in the spleen or liver - Lost cells are replaced by division of hemocytoblasts in the red bone marrow
Control of Erythrocyte Production
§Rate is controlled by a hormone (erythropoietin) - Kidneys produce most erythropoietin as a response to reduced oxygen levels in the blood - Homeostasis is maintained by negative feedback from blood oxygen levels 
Formation of White Blood Cells & Platelets
§Controlled by hormones: colony stimulating factors (CSFs) & interleukins prompt bone marrow to generate leukocytes - thrombopoietin stimulates production of platelets 
§Stoppage of bleeding resulting from a break in a blood vessel -- involves three phases: Vascular spasms, Platelet plug formation, Coagulation (blood clotting) 
§Vascular spasms §
Vasoconstriction causes blood vessel to spasm -- Spasms narrow the blood vessel, decreasing bloodloss 
Platelet plug formation
§Collagen fibers are exposed by a break in a blood vessel -- Platelets become “sticky” and cling to fibers -- Anchored platelets release chemicals to attract more platelets -- Platelets pile up to form a platelet plug 
§Injured tissues release tissue factor (TF) -- PF3 (a phospholipid) interacts with TF, blood protein clotting factors, and calcium ions to trigger a clotting cascade -- Prothrombin activator converts prothrombin to thrombin (an enzyme) -- Thrombin joins fibrinogen proteins into hair-like molecules of insoluble fibrin -- Fibrin forms a meshwork (the basis for a clot)
Blood Clotting
§Blood usually clots within 3 to 6 minutes -- The clot remains as endothelium regenerates -- The clot is broken down after tissue repair 
§A clot in an unbroken blood vessel -- Can be deadly in areas like the heart
§A thrombus that breaks away and floats freely in the bloodstream -- Can later clog vessels in critical areas such as the brain 
§Platelet deficiency -- Even normal movements can cause bleeding from small blood vessels that require platelets for clotting 
§Hereditary bleeding disorder -- Normal clotting factors are missing
§The only way to replace blood quickly -- Blood must be of the same blood group 
Blood Loss
§Loss of 15–30% causes weakness -- Loss of over 30% causes shock, which can be fatal 
Human Blood Groups
§Blood contains genetically determined proteins -- Blood is “typed” by using antibodies that will cause blood with certain proteins to clump (agglutination) 
Antigens & Antibodies 
A substance the body recognizes as foreign, may be attacked by the immune system, over 30 -- the “recognizers”
Type O
§ §the lack of both antigens -- can receive type O blood -- Universal donor
Type AB
the presence of both antigens A & B -- can receive A, B, AB, and O blood -- Universal recipient 
Type B
The presence of antigen B -- can receive type B & O blood
Type A
The presence of antigen A -- can receive type A & O blood
Rh Blood Groups
§Named because of the presence or absence of one of eight Rh antigens (agglutinogen D) that was originally defined in Rhesus monkeys -- Most Americans are Rh+ (Rh positive) -- Problems can occur in mixing Rh+ blood into a body with Rh– (Rh negative) blood 
Rh Dangers During Pregnancy
§Danger occurs only when the mother is Rh– and the father is Rh+, and the child inherits the Rh+  factor -- RhoGAM shot can prevent buildup of anti-Rh+ antibodies in mother’s blood
Rh Dangers During Pregnancy cont.
§The mismatch of an Rh– mother carrying an Rh+ baby can cause problems for the unborn child -- The first pregnancy usually proceeds without problems -- The immune system is sensitized after the first pregnancy -- In a second pregnancy, the mother’s immune system produces antibodies to attack the Rh+ blood (hemolytic disease of the newborn) 
Blood Typing
§Blood samples are mixed with anti-A and anti-B serum -- Coagulation or no coagulation leads to determining blood type -- Typing for ABO and Rh factors is done in the same manner
Sites of blood cell formation
§The fetal liver and spleen are early sites of blood cell formation -- Bone marrow takes over hematopoiesis by the seventh month 
§Fetal hemoglobin differs from hemoglobin produced after birth 
§Physiologic jaundice results in infants in which the liver cannot rid the body of hemoglobin breakdown products fast enough