BIOLOGY 206 CHAPTER 17: BLOOD: LAUREL SPRING 2007
I.Overview of Circulation
A.Blood exits the heart via arteries, which eventually become capillaries where diffusion to and from the tissues takes place. Oxygen and nutrients leave the blood and carbon dioxide and other wastes enter the blood. Veins return blood to the heart where it is sent to the lungs to remove the carbon dioxide and pick up fresh oxygen. Blood then returns to the heart to be pumped throughout the body again.
II.Composition and Functions of blood
A.Components
1.Only fluid tissue in body
2. Formed elements: cells and cell fragments
a.Erythrocytes= RBCs (5,000,000/ul) and function in the transportation of respiratory gases.
b.Leukocytes= WBC (4,000 - 11,000/ul) and function in defense
c.Platelets =cell fragments (300,000/ul) and function in clotting
3.RBCs = approximately 45% of whole blood.
- Hematocrit= % of RBCs present in total blood volume
Part/Whole X 100
a. = 45%
b.38-48% in women
c.44-54% in men
5.WBCs and platelets = <1% of whole blood and =buffy coat of the hematocrit.
6.Plasma= non-living fluid matrix of this connective tissue.
a.55% of whole blood
b.Lacks collagen and elastic fibers
B.Physical characteristics
1.Sticky, opaque, salty fluid w/ metallic taste
2.Heavier than water and 5 X more viscous
3.pH 7.35 - 7.45
4.8% of body weight
5.5-6 L/male (1.5 gallons)
4-5 L/female
C.Formation
1.all formed elements are produced in the red bone marrow
2.All fored elements develop from a common stem cell, the hemocytoblast
3.The hemocytoblast divides into cells committed to become red blood cells, white blood cells or platelets
D.Functions
1.Distribution:
a.Transport O2 and CO2 to and from lungs and cells
b.Transports nutrients from digestive system to all body cells
c.Transport metabolic wastes from cells to kidneys
d.Transport hormones from endocrine glands to target cells
2.Regulation:
a.Help regulate body temperature
b.Help regulate fluid and electrolyte balance
c.Maintenance of normal pH
3.Protection:
a.Prevention of infection: immune response and phagocytosis by WBC
b.Prevention of blood loss: clotting
III.Plasma
A.Appearance
1.Straw-colored and sticky fluid
2.Serum= plasma minus the clotting proteins
B.Composition
1.90% water to dissolve and suspend over 100 different solutes and distribute heat
2.8% Plasma proteinswhich remain in blood (not taken into cells) and made by liver
a.Albumin: important for maintaining osmotic pressure in blood which in turn maintains the correct water balance between blood and tissues. Also act as a buffer & a carrier
b.Globulins:
(1)alpha and beta bind to lipids and fat-soluble vitamins and transport them
(2)Gamma= antibodies released in immune response
c.Clotting proteins: Prothrombinfibrinogen
d.Enzymes: metabolic functions
e.Hormones: control and coordination of body functions.
3.Nitrogenous wastes: lactic acid, urea, uric acid, ammonium salts
4.Nutrients absorbed from GI tract
5.Electrolytes/salts/buffers: for osmotic pressure and pH
a. Na+, K+, Ca++
b.Cl-, HCO3-, PO-4 +
6.Respiratory gases
IV.Erythrocytes
A.Structural Characteristics
1.Biconcave & lack nucleus & other organelles
2.97% hemoglobin
3.Major contributor to blood viscosity
a.Males: 5.1 - 5.8 million/ul
b.Females: 4.3 - 5.2 million/ul
c.Higher values make blood flow more slowly and lower values make it flow more quickly
B.Function
1.Transport O2 from lungs to body tissues & transport CO2 from body tissues to lungs
2.Most O2 is transported by hemoglobin ( Hb)
3.Normal values of Hb (measured in grams/100 ml blood):
a.Infants: 14-20
b.Adult males: 13-18
c.Adult females: 12-16
4.Hb is a protein of 4 subunits each with a
a.polypeptide chain: globin part attached to a
b.Hemegroup which contains 1 Fe atom = red pigment
5.Each Fe can attach to 1 O2, so 1 Hb with 4 subunits has 4 Fe and carry 4 O2.
6.1 RBC has 250 million Hb molecules and since each Hb has 4 Fe molecules = 1 billion O2 molecules/RBC!!!
7.Hb + O2 --> HbO2(oxyhemoglobin) = bright red
8.20% carbon dioxide also binds to Hb but it binds to globin, not heme portion
Hb + CO2 --> HbCO2(carbaminohemoglobin)
C.Regulation of RBC production
1.Homeostatic negative feedback mechanismskeep # of RBCs constant
a.production = 2 million/sec!!!
2.Mechanism requires
a.Hormones erythropoietin (EPO)
b.B vitamins (B12 and folic acid)
c.Fe
- Amino acids
3.Control is based on adequate O2 in blood in kidneys, not # RBCs
4.Increase in EPO --> increase RBC production
5.Mechanism:
a.decrease O2 to kidneys --> increase EPO --> increase RBC production --> increase O2 to kidneys -->decrease EPO--> decrease RBC production etc.
b.Decreased O2 may come from
(1) decreased RBCs,
(2)decreased availability of O2 to blood,
(3)increase tissue demand for O2
6.Erythropoietin increases RBC production by stimulating committed stem cells in marrow to mature faster.
7.Testosterone enhances erythropoietin-generating function of kidneys, and is partial cause for higher RBC/Hb values in males
D.Fate and Destruction of Erythrocytes
- Because RBCs are anucleate their life span = 120 days (4 mo.) and old are ones are phagocytized by macrophages, mostly in spleen but also in liver and bone marrow
- Hemolysis= destruction of RBC plasma membranes and subsequent release of Hb. This can occur as a result of old age and subsequent membrane destruction or by other factors such as
a.Snake venom
- Upsets in osmotic pressure (IV error)
3.Proteins (globins) in Hb are degraded to amino acids which are recycled in body
4.Fe is bound to a globulin protein, transferrin, and recycled in bone marrow
a.Excess Fe may be stored, primarily in liver, as ferritin or hemosiderin
11.Heme portion of Hb degraded to bilirubin(yellow pigment) in the organ of destruction, circulated in blood, picked up by the liver and excreted in bile and excreted in feces as brown pigment called stercobilin
V.Erythrocyte Disorders
A.Anemia
1.= a condition of reduced oxygen-carrying ability whatever the cause.
2.Symptoms: fatigue, paleness, shortness of breath, chilled
B.Polycythemia
1.Overabundance of RBCs
2.Increased viscosity --> impaired circulation
3.Polycythemia vera caused by bone marrow tumor and can produce hematocrits up to 80%
4.Secondary polycythemia occurs when less oxygen is available or EPO production increases.
a.Exposure to high altitudes is most common cause.
VI.Leukocytes
A. General features
- Nucleated, complete cells
2.Primary function is defense against disease and removal of dead cells and debris. All act as phagocytes in addition to special functions.
3.Move by pseudopods
a.RBCs stay in blood stream, but many WBCs move out of capillaries and into tissue fluid in process called diapedesis
b.Accumulate at site of infection, phagocytize microorganisms, die, and become a component of pus. (dead cells, bacteria, fluid)
4.Develop from uncommitted stem cells, the hemocytoblast, in red bone marrow in adults.
a.Life span varies from a few hours to months or years.
B.Granulocytes vs agranulocytes
1.Granulocytesare WBCs that have granules in their cytoplasm, and the 3 types stain differently
a.Have lobed nuclei and are larger than RBCs
b.Neutrophils, eosinophils, basophils
2.Agranulocyteslack granules in cytoplasm
a.Nuclei are spherical or kidney-shaped
b.Cytoplasm stains light blue in Wright Stain
c.Monocytes and lymphocytes.
3."Never Let Monkeys Eat Bananas" gives their order of abundance
C.Neutrophils
1.60% of WBCs (40-70)
- Complete development in marrow
- Circulate approximately. 10 hrs, spend 1-2 days in tissues and eliminated or excreted.
4.Function as phagocytes and fight against bacterial infections
5.Granules stain light lavender/pink vs red or blue
6.Nucleus is 3-5 lobed connected by thin strands = polymorphonucleate. (PMN/polymorphs)
D.Eosinophils
1.1-4% of WBCs
2.Granules stain bright red
3.Generally 2-lobed nucleus
4.Help control allergic reactions so increase in number during time of allergic reaction and during parasitic infection.
a.Granules release enzyme to inactive histamine which is released in allergic reaction and phagocytize antigen-antibody complexes
E.Basophils
1.< 1% of WBCs
2.Granule stain deep blue
3.Nucleus is S- or U-shaped; 2 or more indentations
4.Release
a.Heparin= anti-clotting chemical. (Also released by endothelial cells to prevent clotting)
b.Histamineto induce inflammation response by acting as a vasodilator to make capillaries leak and by attracting other WBCs to site
c.Mastcells are similar to basophils and are found in connective tissue
F.Lymphocytes
1.25-35% of WBCs (20-45)
2.Smallest = approximately size of RBC.
3.Nucleus stains dark purple, is spherical or slightly indented and occupies most of the cell (very little cytoplasm).
4.Most exist in lymphoid tissue (lymph nodes/spleen) and play critical immune role
a.B-lymphocytes produce antibodies
b.T-lymphocytes destroy grafts, tumors, virus-infected cells and activate B-lymphocytes.
G.Monocytes
1.6% of WBCs (4-8)
2.Largest, can be 2 X size of a RBC (some are small)
3.Dark blue nucleus is kidney-shaped with abundant cytoplasm.
*4.Called macrophagesonce in tissue fluid and act as phagocytes
5.Increases in leukemia, TB, fungal infections: chronic infections
VII.Platelets
A.Structure and function
1.Cell fragments derived from hemocytoblast in red
2.No nucleus so lives < 10 days in circulation
3. = 300,000/ul
4.Function = hemostasis: stoppage of bleeding
B.3 stages of Hemostasis
1.Stage 1: Injury to vessel is immediately followed byvascular spasm in which vessel constricts to slow flow
2.Stage 2 = formation of platelet plug.
3.Stage 3 = Coagulation/clotting: formation of fibrin (note: clotting is not a synonym for hemostasis) which is a 3 step process
C.Platelet Plug Formation
1.Cut vessel --> exposed collagen fibers to which platelets adhere
2.Platelet degranulationoccurs, i.e., release numerous chemicals called clotting factors including prostaglandinswhich
(1)Serotonin is a clotting factor that enhances vascular spasm and
(2)Other factors attract more platelets which degranulate (+ feedback mechanism) = chemotaxis
3.Aspirin inhibits prostaglandin release by platelets --> increased bleeding
D.Coagulation
1.Step 1: formation of a complex of substances calledprothrombin activator.
a.Occurs via the intrinsicor extrinsicpathways
b.Both initiated by the same tissue damaging event such as a rough spot in a blood vessel
c.intrinsic pathway is slow
d.extrinsic pathway is faster
2.Step 2: Prothrombin activator catalyzes conversion of prothrombin(a plasma protein) to its active from, thrombin.
a.Vit K needed to form prothrombin
b.Ca ++ needed to catalyze the reaction
c.Note: Heparinis a natural anticoagulantwhich inhibits thrombin
3.Step 3: Thrombin catalyzes conversion of fibrinogen (another plasma protein) to fibrinwhich is an insoluble protein which forms sticky long threads to form clot and trap cells. (polymerized fibrin)
Intrinsic pathway Extrinsic pathway
Prothrombin Activator
(Vit K from liver) Prothrombin Thrombin
Fibrinogen Fibrin
- Clot retraction and Repair
1.Platelets contain actin and myosin (contractile proteins) that contract and pull on the surrounding fibrin strands, squeezing serum (plasma minus its clotting factors) from the mass. This pulls vessel ends together as clot gets hard and small
2.Meanwhile the walls of the vessel begin to repair themselves
a.Finally the clot dissolves = fibrinolysis
F.Fibrinolysis
1.Process by which the clot is dissolved as healing occurs
G.Thromboembolytic conditions
1.unwanted clots may form in intact vessels
2.Conditions which normally prevent unwanted clotting:
a.Smooth endothelium prevents platelets from piling up
- Positively charged endothelium also repels platelets
3.Thrombus= clot that forms and persists in unbroken vessel
a.May block vessel and cause death of that tissue as in heart attack = coronary thrombosis
4.Embolus= detached clot which may also eventuallycause blockage and lead to death (lungs, heart, brain)
- Common causes:
a.Roughened endothelium such as occurs in severe burns, inflammation, or atherosclerosis(lipid deposits form on endothelium) [a subset of arteriosclerosis which is any change in arteries that leads to their decreased elasticity such as loss of fiber elasticity in old age]
b.Slowly flowing blood as in immobilized patients
6.Common prescriptions are anticoagulants such as heparin or dicumerol or 1 aspirin every other day
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