Composition of blood

1. Connective tissue – with liquid matrix (plasma) and formed elements (cells)

2. Hematocrit – when blood is spun in a centrifuge heavier RBC (bottom)

3. Erythrocytes (RBC) – take up 45% volume in a normal hematocrit

4. Plasma – takes up 55% volume in normal hematocrit

5. Buffy Coat – whitish layer at RBC plasma border; WBCs and platelets

Function of blood

1. Distribution – nutrients, waste, oxygen, carbon dioxide, hormones

2. Thermoregulation – capillaries in skin; cool body off or retain heat

3. Clotting – prevents blood loss

4. Infection protection – antibodies, cellular defenses

5. Fluid volume – salts and albumin prevent fluid loss; maintain vascular volume

Composition of plasma

1. Proteins - include

-a. Albumin – 60%; osmotic pressure to keep fluid in blood

-b. Antibodies – or gamma globulins; immunity

-c. Clotting proteins – prothrobin and fibrinogen

2. Others - include

-a. Nutrients – such as blood glucose

-b. Electrolytes – most notably sodium ion

Erythrocytes

1. Structure – related to function

-a. Anucleate – lack nucleus and other cellular organelles; bags of hemoglobin

-b. Biconcave – concave on both sides; optimum increase in surface area

2. Hemoglobin – red pigment; carries oxygen

-a. Globin – 4 polypeptide chains; 2 alpha; 2 beta

-b. Heme – iron containing compound; one associated with each globin

3. Function - of red blood cell and hemoglobin

-a. Oxyhemoglobin – one molecule of oxygen binds to the iron in each heme

-b. Carbaminohemoglobin – carbon dioxide binds with amino acid of globin

Hematopoiesis

1. Defined – general term for blood cell formation

2. Red bone marrow – where it takes place; axial; girdles

3. Hematopoetic stem cell (hemocytoblast) – all formed elements come from

Erythropoiesis

1. Defined – formation of erythrocytes

2. Hemocytoblast – forms all formed elements

3. Proerythroblast – rabid dividing; all decedents are erythrocytes

4. Erythroblast – ribosomes to produce hemoglobin

5. Normoblast – much hemoglobin; later nucleus degenerates and ejected

6. Reticulocytes – still some ribosomes; enter blood stream like this

7. Erythrocytes – ribosomes degraded after about 2 days

Regulation and requirements of erythropoesis

1. Negative feedback mechanism – in homeostasis; acts against the stimulus

2. Hypoxia – low blood oxygen level; stimulates kidney

3. Erythropoietin – hormone released by kidney targets red bone marrow

4. Red bone marrow – erythrocyte production is stimulated; blood oxygen increases

5. Requirements – iron, B complex vitamins, and amino acids

Fate of erythrocytes

1. Life span – up to 120 days; no nucleus, no long term maintenance

2. Spleen – in small capillaries RBCs consumed by macrophages

3. Bilirubin – yellow pigment; remnant of heme; released in bile

4. Globulin – broken down to amino acids; recycled to blood

Erythrocyte disorders: anemias

1. Anemia – low RBCs or hemoglobin

2. Hemorrhagic anemia – low number of RBCs resulting from blood loss

3. Hemolytic anemia – RBCs prematurely destroyed; transfusion mismatch

4. Aplastic anemia – hemopoietic components destroyed; radiation; other problems

5. Iron deficiency anemia – decreased hemoglobin due to lack of iron

6. Athlete’s anemia – exercise caused increased blood supply; dilutes blood

7. Pernicious anemia – vitamin B-12 deficiency; rarely result of diet

-a. Intrinsic factor – produced by stomach; B-12 absorption; less in old age

8. Thalassemias –genetic; Mediterranean; deficient hemoglobin in RBCs

9. Sickle cell anemia – genetic; West Africa; crescent RBCs rupture; dam vessels

Erythrocyte disorders: polycythemias

1. Polycythemia – high RBCs

2. Polycythemia vera – usually bone marrow cancer; 80% RBCs

3. Secondary polycythemia – usually from high altitudes; high erythropoietin

Leukocytes

1. True cells – have nucleus and other cellular organelles

2. Protection – both nonspecific and immune response to pathogens

3. Leukocytosis – over 11,000; hours after bacteria or viral infection

4. NLMEB - neutrophils, lymphocytes, monocytes, eosinophils, and basophils

5. Classification – two main groups

-a. Granulocytes – membrane bound granules; lobed nuclei

-b. Agranulocytes – membrane bound granules not apparent

Granulocytes

1. Neutrophils

-a. Cytoplasm – pale lilac; both acidic and basic stains

-b. Nucleus – 3 to 6 lobes; polymorphonuclear leukocytes

-c. Function – phygocytosis (mostly bacteria)

2. Eosinophils

-a. Cytoplasm – brick red; acidic dyes; lysosome like digestive enzymes

-b. Nucleus – two lobed; like old telephone receivers

-c. Function – parasitic worms; allergy

3. Basophils

-a. Cytoplasm – blue purple; basic dyes; histamine

-b. Nucleus – S or U shaped

-c. Function – release histamine; this brings about inflammation

Agranulocytes

1. Lymphocyte – immune response; found in lymphoid tissue

-a. Nucleus – large and spherical; takes up most of cell

-b. T lymphocytes – act directly against viral infected and tumor cells

-c. B lymphocytes – some become plasma cells which produce antibodies

2. Monocytes

-a. Size – largest of all leukocytes

-b. Macrophages – once in tissue they become theses

-c. Phagocytosis – of viruses and intercellular bacteria

Leukopoiesis

1. Cytokines – glycoprotein hormones stimulate production.

2. Hemocytoblast – parent of all formed elements

3. Lymphoid stem cell – ultimately become lymphocytes

4. Myeloid stem cell – all other formed elements

-a. Monoblast – become monocytes which become macrophages

-b. Myeloblast – become granulocytes

Leukocyte disorders

1. Leukopenia – abnormally low WBC; anticancer drugs; glucocorticoids

2. Leukemia – cancerous; high number unspecialized precursor cells

3. Infectious mononucleosis – Epstein-Barr virus; many atypical granulocytes

Platelets

1. Appearance – blue staining cellular fragments

2. Function – hemostasis

3. Granules – in platelets contain procoagulants

4. Formation

-a. megakaryoblast – from myeloid stem cell; mitosis without cytokinesis

-b. promegakaryocyte

-c. megakaryocyte – divided by cell membrane; peel off like stamps

Hemostasis

1. Vascular spasm – constriction decreases blood loss

2. Platelet plug formation

-a. Collagen – exposed when damaged; platelets stick to it

-b. Degranulation – release chemicals; draw platelets; clotting

3. Blood clotting

Blood clotting

1. Procoagulants – promote coagulation; made in liver and platelets

2. Calcium ion – important in many stages in blood clotting

3. Two pathways – to prothrombin activator

-a. Extrinsic pathway – faster; depend on factors from tissue

-b. Intrinsic pathway – slower; all procoagulants found in blood

4. Prothrombin activator – acts on

5. Prothrombin – which is converted into

6. Thrombin – an enzyme which acts on

7. Fibrinogen – which is soluble; converted to

8. Fibrin – insoluble fibers; form mesh; catches formed elements

9. Clot retraction – contractile proteins in platelets; compact clot

Fibrinolysis

1. Defined – removal of unneeded clots

2. Plasminogen – inactive enzyme; activated by chemicals from endothelium

3. Plasmin – enzyme which digest fibrin

Disorders of hemostasis

1. Thrombus – clot which occurs and persist in unbroken blood vessel

2. Embolus – clot which breaks free and floats in bloodstream

3. Thrombocytopenia – low platelets; small blood vessel bleeding

4. Impaired liver function – procoagulants not produced; vitamin K poor absorbed

5. Hemophilia – hereditary disorder; can’t synthesis a procoagulant

Blood groups

1. Agglutinogen – antigen found on a RBC; glycoprotein

2. Agglutinin – antibodies against agglutionogens

3. ABO blood groups – agglutinins are preformed; not until 2 months old

-a. AB – A and B agglutinogens; no agglutinins

-b. A – A agglutinogen; B agglutinins

-c. B – B agglutinogen; A agglutinins

-d. O – no agglutinogens; A and B agglutinins

-e. mismatched blood – results in agglutination and lysis

4. Rh blood groups – agglutinins are not preformed

-a. Rh positive – Rh agglutinogen; will not form agglutinin against

-b. Rh negative – no Rh agglutinogen; will form agglutinin against

-c. Erythroblatosis fetalis – hemolytic disease of newborn; RBCs are destroyed