Circulation

1. Chapters 32 and 33 Circulation

2. Circulation and Circulatory Systems • heart • atria: receive blood • ventricles: pump blood • veins • vessels that transport blood back to heart • all veins carry deoxygenated blood (CO2-rich) , except those leaving the lungs • connective tissue  thin layer of smooth muscle  elastin  epithelial tissue • contain one-way valves  prevent backflow • venules • smallest veins in body  leave capillaries  join larger veins • arteries • vessels that transport blood away from heart • all arteries carry oxygenated blood (O2-rich) , except those bringing blood to lungs • connective tissue  thick layer of smooth muscle  elastin  epithelial tissue • arterioles • smallest arteries in body  merge into capillaries • capillaries • smallest blood vessels in body • thin layer of epithelial tissue • gas and nutrient exchange • capillary beds

3. blockages can be a problem in all vessels • especially arteries Fig. 32.3 Arteries, capillaries, and veins

4. Page 605 Coronary arteries and plaque

5. Some Animals Lack a Circulatory System • utilize diffusion, osmosis, or cell-to-cell transport • Invertebrate Circulatory Systems • open circulatory systems • blood enters and then leaves the vessels • after leaving, blood fills hemocoels (“blood cavities”) • saturates body tissues in blood  muscular contractions  blood returns to heart • closed circulatory systems • more efficient • blood remains in vessels • blood flows much more rapidly

6. Fig. 32.2 Open vs. closed circulatory systems

7. Vertebrate Circulatory Systems • all vertebrates have closed systems • blood • a connective tissue; 0.9% saline • formed elements (cell types) – 45% • erythrocytes (rbc’s) • transport O2 t0 body (hemoglobin) • concave shape and no nucleus • spleen • removes old rbc’sand stores wbc’s • leukocytes (wbc’s) • many different types  function in the immune system • thrombocytes (platelets) • cellular fragments that play a major role in blood clotting • all derive from hemocytoblasts in red bone marrow • plasma (a watery substance) – 55% • 92% H2O, 7% proteins, 1% other solids, gases, wastes • plasma proteins • albumins, globulins, fibrinogen, prothrombin, etc. • salts, fats, glucose, amino acids, hormones, vitamins, ions, etc. • gases: extra O2, CO2 • nitrogenous wastes: urea, uric acid Fig. 31.4 Formed elements

8. Fig. 32.13 Composition of blood

9. blood clotting • 7-10 steps; about 15 substances involved • some substances prevent accidental clotting • three major reactions • platelets form a “plug” at wound site  release thromboplastin • thromboplastin and Ca+ ions convert prothrombin to thrombin • thrombin converts fibrinogen to fibrin fibers  seal wound • the damaged cells, collagen, and other substances also help seal wound Fig. 32.14 Blood clotting

10. fish • two-chambered heart • 1 atrium, 1 ventricle • gas exchange across gill capillaries • amphibians and most reptiles • three-chambered heart • 2 atria, 1 ventricle • systemic vs. pulmonary circuit • pulmonary: blood flow to and from lungs • systemic: blood flow to and from rest of body • the two are not completely separate • deoxygenated vs. oxygenated blood • some mixing occurs in the single ventricle • birds, crocodilians, mammals, humans • four-chambered heart • 2 atria, 2 ventricles • systemic and pulmonary circuits completely separate • normally no mixing of deoxygenated and oxygenated blood

11. Fig. 32.5 Comparison of circulatory systems in vertebrates

12. Human Circulatory System • path of blood flow through body • 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 • blood makes a complete circuit with every beat

13. Fig. 32.6 External view of the heart

14. Fig. 32.7 Internal view of the heart Fig. 32.8 Heart valves

15. Fig. 32.10 Path of blood

16. control of heart contractions • unique nature of heart (cardiac) muscle • branching of muscle fibers • extrinsic control • external control outside of heart • nervous system and hormones (esp., epinephrine) • speeds up or slows down heart rate • intrinsic control • control within heart itself • sinoatrial (SA) and atrioventricular (AV) nodes • specialized regions of cells that can generate and carry electrical impulses • ventricular septum and Purkinje fibers • 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 • SA node initiates heartbeat; AV signals ventricles to contract

17. Fig. 32.9 Contraction system of the heart

18. the working heart • heart beat and activity • 1st sound: right and left AV valves closing • 2nd sound: aortic and pulmonary semilunar valves closing • all valves prevent backflow of blood • can be monitored with an EKG (electrocardiogram) • systole vs. diastole • stroke volume vs. cardiac volume • heart rate (pulse) – average = 72 beats/minute • blood pressure • sphygmomanometer • systolic vs. diastolic pressure (mm Hg) • normal measurements (120/80) • arterioles • vasoconstriction  muscle walls thicken  increases blood pressure • vasodilation muscle walls thin  decreases blood pressure • all gas and nutrient exchange takes place across capillaries • blood pressure lowest in veins (venous blood) • movement assisted by valves and smooth/skeletal muscle contraction

19. Fig. 32.12 Cross section of a valve in a vein

20. human circulatory circuits • circuit: a major pathway of blood flow and return • pulmonary • systemic • 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 • renal • cardiac • coronary arteries and veins • numerous ones in head and brain

21. Lymphatic System • series of small vessels that parallel circulatory system • transports lymph instead of blood • colorless, interstitial fluid that is derived from tissues • may be in tissue cells or between tissue layers • may be blood plasma that seeps into tissues • fluid moves in same fashion as venous blood  merges with circ. system • four essential functions • maintain fluid and ion balances in body • transports certain fatty acids • part of the immune system and cooperates with it • route by which interstitial fluids can return to the circ. system • structures • lymph capillaries  larger lymph vessels • lymph nodes • mass of lymphoid tissue located along the course of a lymph vessel • highly involved with immune system • lymph organs • other organs strongly associated with lymph • spleen, bone marrow, tonsils, thymus gland, etc.

22. Fig. 33.1 Lymphatic system

23. Fig. 33.2 Some lymphoid organs