anatomy 2 ch 18 blood, hemostasis, blood groups

blood typing

-determination of the blood group of a person -when serum containing anti-A or anti-B agglutinins is added to blood, agglutination will occur b/t the agglutinin & corresponding agglutinogens -positive reactions indicate agglutination

Rh blood groups

-45 different agglutinogens (Rh factors) -C, D, and E are most common -Rh+ indicates presence of D -anti-Rh antibodies are not spontaneously formed in Rh- individuals -anti-Rh antibodies form if an Rh- individual receives Rh+ blood -a second exposure to Rh+ blood will results in a typical transfusion reaction

blood plasma

-90% water -proteins are the most common solutes by weight, mostly produced by liver ---60% albumin (colloid osmotic pressure) ---36% globulins (functional proteins, like enzymes or antibodies) ---4% fibrinogen (most important blood clotting factor) -other solutes are nutrients (glucose, carbohydrates, amino acids), electrolytes (Na+, Ca2+, Cl-, HCO3-), respiratory gases (o2, Co2), hormones, & metabolic waste products (lactic acid, urea, creatinine)

coagulation

-a set of reactions in which blood is transformed from a liquid to gel -reinforces the platelet plug w/ fibrin threads three phases of coagulation: 1. prothrombin activator is formed (intrinsic & extrinsic pathways) 2. prothrombin is converted into thrombin 3. thrombin catalyzes the joining of fibrinogen to form a fibrin mesh

ABO blood groups

-based on the presence or absence of two agglutinogens (A and B) on the surface of the RBC's -types A (has A), B (has B), AB (has A and B), and O (lacks A and B) -blood may contain anti-A or anti-B antibodies (agglutinins) that act against transfused RBC's w/ ABO antigens not normally present -anti-A or anti-B form in the blood at about 2 months of age

hematopoiesis (hemopoiesis)

-blood cell formation occurs in red bone marrow of axial skeleton, girdles & proximal epiphyses of humerus & femur -hemocytoblasts (hematopoietic stem cells) ---give rise to all formed elements ---hormones & growth factors push cells toward specific pathway of blood cell development -new blood cells enter blood sinusoids

erythrocytes

-by far most numerous cells w/ approx. 5 million per uL of blood -biconcave discs, anucleate, no mitochondria; ATP production is anaerobic; no o2 is used in generation of ATP -biconcave shape = huge surface area relative to volume -filled w/ hemoglobin (Hb) for gas transport -are the major factor contributing to blood viscosity

coagulation phase 3

-common pathway to the fibrin mesh ---thrombin converts soluble fibrinogen into fibrin ---fibrin strands form the structural basis of a clot ---fibrin causes plasma to become a gel-like trap for formed elements ---thrombin (w/ Ca2+) activates factor XIII which: cross links fibrin, strengthens & stabilizes the clot

erythrocyte function

-dedicated to respiratory gas transport -hemoglobin binds reversibly w/ oxygen hemoglobin structure: ---protein globin: two alpha & two beta chains ---heme pigment bonded to each globing chain -iron atom in each heme can bind to one o2 molecule -each Hb molecule can transport four o2

erythropoietin (EPO)

-direct stimulus for erythropoiesis -released by kidneys (and liver 10%) in response to hypoxia causes of hypoxia: -hemorrhage or increases RBC destruction reduces RBC numbers -insufficient hemoglobin (iron deficiency) -reduced availability of o2 (high altitudes)

hemostasis

-fast series of reactions for stoppage of bleeding three steps: 1. vascular spasm 2. platelet plug formation 3. coagulation (blood clotting)

blood groups

-humans have 30 varieties of naturally occurring RBC antigens -antigens of the ABO & Rh blood groups cause vigorous transfusion reactions -other blood groups (MNS, Duffy, Kell, & Lewis) are usually weak agglutinogens

agranulocytes

-lack visible cytoplasmic granules ---have spherical or kidney-shaped nuclei

fate & destruction of erythrocytes

-life span: 100-120 days, every day approx. 1% of RBC's have to be replaced = reticulocyte index (RI) is 1 -old or damaged RBC's are destroyed by macrophages in spleen & liver: ---heme & globin are separated ---iron is salvaged for reuse -heme is degraded to yellow the pigment bilirubin ---liver secretes bilirubin (in bile) into the intestines ---degraded pigment leaves the body in feces are stercobilin -globin is metabolized into amino acids

leukocytes

-make up <1% of total blood volume (4,500 to 11,000 cells per uL) -leukocytosis: WBC count over 11,000/mm3 ---normal response to bacterial or viral invasion -complete cells w/ a nucleus & cell organelles -can leave capillaries via diapedesis -move through tissue spaces by ameboid motion & positive chemotaxis

effects of EPO

-more rapid maturation of committed bone marrow cells -increased circulating reticulocyte count in 1-2 days dietary requirements: -nutrients: amino acids, lipids, carbohydrates -iron -vitamin B12 & folic acid: necessary for DNA synthesis for cell division *testosterone also enhances EPO production, resulting in higher RBC counts in men

neutrophils

-most numerous = 50-70% of WBC's (3,000-7,000 per uL) -polymorphonuclear leukocytes (PMNs) -fine granules take up both acidic & basic dyes -give cytoplasm a lilac color -granules contain hydrolytic enzymes or defensins -very phagocytic = 'bacteria slayers'

hemoglobin (Hb)

-o2 loading in the lungs produces bright red oxygenated Hb or oxyhemoglobin -o2 unloading in the tissues produces dark red deoxygenated Hb or deoxyhemoglobin -Co2 loading in the tissues produces carbaminohemoglobin (carries 20% of Co2 in the blood)

transfusion reactions

-occur if mismatched blood is infused -donor cells: ---are attacked by the recipient's plasm agglutinins ---agglutinate & clog small vessels ---rupture & release free hemoglobin into the bloodstream result in: ---diminished oxygen-carrying capacity ---hemoglobin in kidney tubules & renal failure

formed elements

-only leukocytes are complete cells -erythrocytes have no nuclei or organelles -platelets are cell fragments -most blood cells originate from bone marrow & do not divide

coagulation phase 2

-pathway to thrombin -prothrombin activator catalyzes the transformation of prothrombin to the active enzyme thrombin

basophils

-rarest WBC's = 20-50 in 1 uL (0.5-1% of WBC's) -large, purplish-black (basophilic) granules contain: ---histamine & heparin: an inflammatory chemical that acts as a vasodilator & attracts other WBC's to inflamed sites

eosinophils

-red-staining, bilobed nuclei -100-400 in 1 uL (2-4% of WBCs) -red to crimson (acidophilic) coarse, lysosome-like granules -digest parasitic worms that are too large to be phagocytized -modulators of the immune response

platelets (thrombocytes)

-small fragments of megakaryocytes -formation is regulated by thrombopoietin -blue-staining outer region, purple granules -granules contain serotonin, Ca2+ enzymes, ADP, & platelet-derived growth factor (PDGF) -form a temporary platelet plug that helps seal breaks in blood vessels -circulating platelets are kept inactive & mobile by NO & prostacyclin from endothelial cells of blood vessels

factors limiting clot growth or formation

-swift removal & dilution of clotting factors -inhibition of activated clotting factors fibrinolysis begins w/ in two days: ---plasminogen in clot is converted to plasmin by tissue plasminogen activator (tPA), factor XII & thrombin ---plasmin is a fibrin-digesting enzyme

erythropoiesis

-the last stage of the development before the mature red blood cells is the reticulocyte, which can already transport oxygen -after being released into the blood it will develop into a mature erythrocyte

viscosity of blood

-thickness of blood, mainly determined by amount of red blood cells -hematocrit = percent of blood volume that is RBCs -47% +- 5% for males -42% +- 5% for females

regulation of erythropoiesis

-too few RBCs leads to oxygen deficiency or hypoxia in the tissues -too many RBCs increases blood viscosity -balance b/t RBC production & destruction depends on --hormonal controls --adequate supplies of iron, amino acids, & B vitamins

coagulation phase 1

-two pathways to prothrombin activator -initiated by either the intrinsic or extrinsic pathway (usually both) ---triggered by tissue-damaging events ---involves a series of procoagulants ---each pathway cascades toward factor X -factor x complexes w/ Ca2+, PF3, & factor V to form prothrombin activator

vascular spasm

-vasoconstriction of damaged blood vessel triggered by: -direct injury -chemicals released by endothelial cells & platelets -pain reflexes *cannot stop the bleeding but will slow down the loss of blood

transfusions

-whole-blood transfusions are used when blood loss is substantial -packed red cells (plasma removed) are used to restore oxygen-carrying capacity -transfusion of incompatible blood can be fatal

monocytes

100-700 in 1 uL (3-8% of WBC's) -the largest leukocytes -abundant pale-blue cytoplasm -dark purple staining, U or kidney-shaped nuclei -leave circulation, enter tissues, & differentiate into macrophages ---actively phagocytic cells; crucial against viruses, intracellular bacterial parasites, chronic infections ---activate lymphocytes to mount an immune response

lymphocytes

1500-3000 in 1 uL; 25-40% of WBC's -large, dark-purple, circular nuclei w/ a thin rim of blue cytoplasm -mostly in lymphoid tissue; few circulate in the blood -crucial to immunity: ---t lymphocytes act against virus-infected cells & tumor cells ---B lymphocytes give rise to plasma cells, which produce antibodies

human blood groups

RBC membranes bear 30 types of glycoprotein antigens that are: -perceived as foreign if transfused blood is mismatched -unique to each individual -promotes of agglutination & are called agglutinogens *presence or absence of each antigen is used to classify blood cells into different groups

blood composition

a connective tissue composed of: --plasma --formed elements: erythrocytes (RBC's), leukocytes (WBC's), thrombocytes (platelets) -color Scarlett to dark red depending on oxygenation -pH 7.35-7.45 -100.4 degrees F (38 degrees C) -8% of body weight, avg. volume 5-6 L (1.5 gallons) for males, 4-5 L for females

leukocytes subdivided

based on the presence or absence of granules in the cytoplasm into: -granulocytes: contain granules ---neutrophils, eosinophils, basophils -agranulocytes: no visible granules ---lymphocytes & monocytes

hemostasis clot retraction & repair

clot retraction: -actin & myosin in platelets contract w/ in 30-60 minutes -platelets pull on the fibrin strands, squeezing serum from the clot clot repair: -platelet-derived growth factor (PDGF) stimulates division of smooth muscle cells & fibroblasts to rebuild blood vessel wall -vascular endothelial growth factor (VEGF) stimulates endothelial cells to multiply & restore the endothelial lining

functions of blood

distribution of: -o2 & nutrients to body cells -metabolic wastes to lungs & kidneys for elimination -hormones from endocrine organs to target organs regulation of: -body temp. by absorbing & distributing heat -normal pH using buffers -adequate fluid volume in circulatory system protection against: -blood loss & infection

homeostatic imbalance

hemolytic disease of the newborn -also called erythroblastosis fetalis -Rh- mother becomes sensitized when exposure to Rh+ blood causes her body to synthesize anti-Rh antibodies -anti-Rh antibodies cross the placenta & destroy the RBC's of an Rh+ baby -the baby can be treated w/ prebirth transfusions & exchange transfusions after birth -rhoGAM serum containing anti-Rh can prevent the Rh- mother from becoming sensitized

coagulation phase 1 pathways

intrinsic pathway: -is triggered by negatively charged surfaces (activated platelets, collagen, glass) -uses factors present w/ in the blood (intrinsic) extrinsic pathway: -is triggered by exposure to tissue factor (TF) or factor III (an extrinsic factor) -bypasses several steps of the intrinsic pathway, so is faster

granulocytes

neutrophils, eosinophils, basophils -cytoplasmic granules -larger than RBC's -lobed nuclei -phagocytic

factors preventing undesirable clotting

platelet adhesion is prevented by: -smooth endothelial lining of blood vessels -antithrombic substances nitric oxide & prostacyclin secreted by endothelial cells

platelet plug formation

positive feedback cycle: -platelets stick to exposed collagen fibers at the site of vessel injury -swell, become spiked & sticky, & release chemical messengers ---ADP causes more platelets to stick & release their contents ---serotonin & thromboxane A2 enhance vascular spasm & more platelet aggregation *platelet plug temporarily plugs damage to the vessel wall

leukopoiesis

production of WBC's is stimulated by chemical messengers from bone marrow & mature WBC's -interleukins (IL-1, IL-2) -colony-stimulating factors (CSF's) named for the WBC type the stimulate (granulocyte - CSF stimulates granulocytes) -all leukocytes originate from hemocytoblasts