CIRCULATION

Chapters 32 and 33

I. Circulation and Circulatory SystemsA. heart

1. atria: receive blood 2. ventricles: pump blood

B. veins1. vessels that transport blood back to heart2. all veins carry deoxygenated blood (CO2-rich) , except those leaving

the lungs3. connective tissue thin layer of smooth muscle elastin epithelial

tissue4. contain one-way valves prevent backflow 5. venules• smallest veins in body leave capillaries join larger veins

C. arteries1. vessels that transport blood away from heart2. all arteries carry oxygenated blood (O2-rich) , except those bringing

blood to lungs3. connective tissue thick layer of smooth muscle elastin epithelial

tissue4. arterioles• smallest arteries in body merge into capillaries

D. capillaries1. smallest blood vessels in body• thin layer of epithelial tissue

2. gas and nutrient exchange3. capillary beds

E. blockages can be a problem in all vessels

• especially arteries

Fig. 32.3 Arteries, capillaries, and veins

Page 605 Coronary arteries and plaque

II. Some Animals Lack a Circulatory System• utilize diffusion, osmosis, or cell-to-cell

transport

III.Invertebrate Circulatory SystemsA. open circulatory systems

1. blood enters and then leaves the vessels2. after leaving, blood fills hemocoels (“blood

cavities”) • saturates body tissues in blood muscular

contractions blood returns to heart

B. closed circulatory systems1. more efficient2. blood remains in vessels 3. blood flows much more rapidly

Fig. 32.2 Open vs. closed circulatory systems

IV. Vertebrate Circulatory SystemsA. all vertebrates have closed systemsB. blood

1. a connective tissue; 0.9% saline2. formed elements (cell types) – 45%

a. erythrocytes (rbc’s)i. transport O2 t0 body (hemoglobin)

ii. concave shape and no nucleusiii. spleen• removes old rbc’s and stores wbc’s

b. leukocytes (wbc’s)• many different types function in the immune system

c. thrombocytes (platelets)• cellular fragments that play a major role in blood

clotting

d. all derive from hemocytoblasts in red bone marrow3. plasma (a watery substance) – 55%

1. 92% H2O, 7% proteins, 1% other solids, gases, wastes

2. plasma proteins• albumins, globulins, fibrinogen, prothrombin, etc.

3. salts, fats, glucose, amino acids, hormones, vitamins, ions, etc.

4. gases: extra O2, CO2

5. nitrogenous wastes: urea, uric acid

Fig. 31.4 Formed elements

Fig. 32.13 Composition of blood

C. blood clotting1. 7-10 steps; about 15 substances involved2. some substances prevent accidental clotting3. three major reactions

a. platelets form a “plug” at wound site release thromboplastin

b. thromboplastin and Ca+ ions convert prothrombin to thrombinc. thrombin converts fibrinogen to fibrin fibers seal woundd. the damaged cells, collagen, and other substances also help

seal wound

Fig. 32.14 Blood clotting

D. fish1. two-chambered heart • 1 atrium, 1 ventricle

2. gas exchange across gill capillariesE. amphibians and most reptiles

1. three-chambered heart • 2 atria, 1 ventricle

2. systemic vs. pulmonary circuita. pulmonary: blood flow to and from lungsb. systemic: blood flow to and from rest of bodyc. the two are not completely separate

3. deoxygenated vs. oxygenated blood• some mixing occurs in the single ventricle

F. birds, crocodilians, mammals, humansa. four-chambered heart • 2 atria, 2 ventricles

b. systemic and pulmonary circuits completely separate

c. normally no mixing of deoxygenated and oxygenated blood

Fig. 32.5 Comparison of circulatory systems in vertebrates

V. Human Circulatory SystemA. path of blood flow through body

1. deoxy. blood in body capillaries body venules body veins superior/inferior vena cavas right atrium right AV valve right ventricle pulmonary semilunar valve pulmonary artery lung arterioles lung capillaries (gas exchange; blood now oxy.) lung venules pulmonary veins left atrium left AV valve left ventricle aortic semilunar valve aorta body arteries body arterioles body capillary beds (gas & nutrient exch.; blood now deoxy.) REPEAT

2. blood makes a complete circuit with every beat

Fig. 32.6 External view of the heart

Fig. 32.7 Internal view of the heart

Fig. 32.8 Heart valves

Fig. 32.10 Path of blood

B. control of heart contractions1. unique nature of heart (cardiac) muscle• branching of muscle fibers

2. extrinsic controla. external control outside of heartb. nervous system and hormones (esp., epinephrine) c. speeds up or slows down heart rate

3. intrinsic controla. control within heart itselfb. sinoatrial (SA) and atrioventricular (AV) nodes• specialized regions of cells that can generate and carry

electrical impulsesc. ventricular septum and Purkinje fibersd. SA node creates impulse walls of atria atria contract

signal travels to AV node signal routed down ventricular septum in two paths Purkinje fibers walls of ventricles ventricles contract

e. SA node initiates heartbeat; AV signals ventricles to contract

Fig. 32.9 Contraction system of the heart

C. the working heart1. heart beat and activity

a. 1st sound: right and left AV valves closingb. 2nd sound: aortic and pulmonary semilunar valves closing

c. all valves prevent backflow of bloodd. can be monitored with an EKG (electrocardiogram)

2. systole vs. diastole3. stroke volume vs. cardiac volume4. heart rate (pulse) – average = 72 beats/minute5. blood pressure

a. sphygmomanometerb. systolic vs. diastolic pressure (mm Hg)c. normal measurements (120/80)

6. arteriolesa. vasoconstriction muscle walls thicken increases blood

pressure b. vasodilation muscle walls thin decreases blood pressure

7. all gas and nutrient exchange takes place across capillaries8. blood pressure lowest in veins (venous blood)• movement assisted by valves and smooth/skeletal muscle

contraction

Fig. 32.12 Cross section of a valve in a vein

D. human circulatory circuits1. circuit: a major pathway of blood flow and return2. pulmonary3. systemic4. hepatic portal• nutrients absorbed by small intestine travel in hepatic portal

vein to liver liver monitors blood content and stores extra nutrients blood enters general circulation

5. renal6. cardiac • coronary arteries and veins

7. numerous ones in head and brain

VI.Lymphatic SystemA. series of small vessels that parallel circulatory systemB. transports lymph instead of blood

1. colorless, interstitial fluid that is derived from tissues• may be in tissue cells or between tissue layers

2. may be blood plasma that seeps into tissues3. fluid moves in same fashion as venous blood merges with

circ. systemC. four essential functions

1. maintain fluid and ion balances in body2. transports certain fatty acids3. part of the immune system and cooperates with it4. route by which interstitial fluids can return to the circ.

systemD. structures

1. lymph capillaries larger lymph vessels2. lymph nodes

a. mass of lymphoid tissue located along the course of a lymph vessel

b. highly involved with immune system3. lymph organs

a. other organs strongly associated with lymphb. spleen, bone marrow, tonsils, thymus gland, etc.

Fig. 33.1 Lymphatic system

Fig. 33.2 Some lymphoid organs