Lecture #11: Blood and Blood Clotting

I. GENERAL PROPERTIES OF BLOOD

1. The average human body contains 5 L of whole blood.

2. Plasma is whole blood minus the formed elements (i.e., the cells) = 55%. (Fig. 42.14)

3. Serum is plasma minus the blood-clotting protein fibrinogen.

4. About 10% of plasma is a variety of dissolved solutes:

a. electrolytes (inorganic salts) are important for osmotic balance, pH, membrane potentials, and membrane permeability.

b. plasma proteins carry out a variety of important functions:

(1) albumin affects osmotic balance and pH, and transports steroids and other lipids.

(2) fibrinogens are precursors to clotting fibers.

(3) immunoglobulins are antibodies that combat microbes (viruses).

(4) plasma also contains nutrients, metabolic wastes, gases, and proteinaceous hormones.

II. BLOOD CELLS (Fig. 42.15)

1. Red blood cells: (erythrocytes) (for gas transport)

a. form from stem cells in marrow of ribs, vertebrae, breastbone, and pelvis.

b. each mm³ contains about 5,000,000 RBCs, with 250 million hemoglobins each.

c. if tissues have insufficient O₂, then kidney secretes erythropoietin.

d. they lack nuclei and mitochondria (for aerobic respiration) to maximize transport.

e. after 3-4 months of circulation, they are destroyed by phagocytic cells in liver.

2. White blood cells: (leukocytes) (serve to fight infection)

a. they arise from same stem cells in marrow as the RBC's.

b. each mm³ contains about 5,000 -- 10,000 WBC's (but number goes up with infection).

c. leukocytes spend most of time outside the blood in interstitial fluid for fight.

d. types of WBC's

(1) monocytes squeeze thru capillary walls and ingest foreign particles.

(2) neutrophils also squeeze thru capillary walls and ingest foreign particles.

(3) eosinophils are rarer, and increase in infections (parasitic infections).

(4) basophils leave blood and develop into histamine-producing mast cells.

(5) lymphocytes combat disease by producing antibodies.

3. Platelets are fragments of thrombocytes. (for blood clotting) (250,000 -- 400,000).

III. BLOOD CLOTTING (Fig 42.16)

1. When a blood vessel is injured (torn, etc.) collagen fibers are exposed.

2. Exposed collagen fibers cause platelets to adhere (aggregate).

3. This platelet aggregation causes platelets to release thromboplastin.

4. Thromboplastin, in the presence of calcium and vitamin K, activates prothombin.

5. Thrombin converts fibrinogen into fibrin, which is strong fibrous protein.

IV. CARDIOVASCULAR DISEASE

1. An embolus is a moving clot (which may clog anywhere--heart, brain, lung).

2. Cholesterol travels in blood mainly as part of low-density lipoproteins (LDL's).

3. Cells (in liver) have LDL receptors to remove blood cholesterol by endocytosis.

4. High-density lipoproteins more readily undergo endocytosis, and remove cholesterol.

5. Cholesterol infiltrates vascular smooth muscle and promotes plaque growth.

6. Atherosclerosis is the vascular disease that arises from such plaque formation.

7. Arteriosclerosis is the more hardened state when calcium is deposited (inelastic).

8. Hypertension (high blood pressure) damages the endothelium and promotes plaquing.

9. Exercise improves the LDL/HDL ratio by increasing HDL's.

10. Smoking has the opposite effect on this ratio.