CIRCULATION AND GAS EXCHANGE

1. CIRCULATION AND GAS EXCHANGE

2. Circulation in Animals • Transport systems functionally connect the organs of exchange with body cells. • Diffusion is too slow. • By rapidly transporting fluid in bulk it connects the aqueous environment of cells to organs of gas exchange. • Nutrients are absorbed and wastes are taken away.

3. Invertebrate Nutrient and Gas Exchange • Gastrovascular Cavities • Simple organisms with few layers absorb nutrients through pockets in their bodies. • Extra-cellular digestion occurs to break down larger particles. • Cnidarians, Planarians, and Porifera • Circulation unnecessary because all cells are exposed to the environment.

4. Cnidarians

5. Open Circulatory Systems • Open circulatory system • Blood bathes organs directly • Arthropods and most mollusks • No distinction between blood and interstitial fluid. • Body fluid called hemolymph. • Sinuses are spaces around organs. • One or more hearts pull blood in through ostia. • Blood squeezed around the body through movement.

7. Closed Circulatory System • Blood is confined to vessel and distinct from interstitial fluid. • Earth worms and higher animals. • Vertebrates have a cardiovascular system. • Atrium – top chamber of the heart • Ventricle- lower chamber of the heart. • Arteries – direct blood away from the heart. • Veins direct blood to the heart. • Capillary beds infiltrate each tissue.

10. Route of Blood Through the Body • Systemic circuit – delivers blood to the body. • Pulmonary circuit – picks up blood from pulmonary organs and delivers it back to the heart.

11. Fish Heart • Fish • Two chambers • Single circulation which means blood must travel through two capillary beds before it returns to the heart. • Because pressure drops in the capillary bed, blood flow is much slower than in other organisms.

12. AmphibianHeart • Three chambers • Two atria and one ventricle • A ridge separates most of the oxygenated from the deoxygenated blood, however some mixing does occur. • Double circulation • Blood returns to the heart after picking up oxygen. Sustains a higher pressure. • Pulmocutaneous circuit. • Pulmonary organs are the lungs and skin. • Reptiles • Three chambers clearly divided • Have a pulmonary circuit

13. Mammalian Heart • Two atria and two ventricles • Distinct separation of oxygen and deoxygenated blood. • Double circulation with a pulmonary circuit.

14. Mammalian Cardiac Cycle • Cardiac Cycle - One complete pumping and filling. • Systole – contraction phase of the cycle • Diastole – relaxation phase of the cycle. • Cardiac Output – the volume of blood that the left ventricle pumps into the systemic circuit per minute. • Depends on two factors: • Heart rate - rate of heart beat. • Stroke volume – blood pumped from left ventricle per contraction.

15. Average stroke volume for humans is 75 ml with a cardiac output of about 5.25 L/min. and an average pulse of 70 beats per minute. • Exercising increases stroke volume because the heart beats more efficiently. • More blood pumped to the systemic circuit per contraction.

16. The “Lub Dub” • Atrioventricular valves • Separate atria from ventricles. • Semilunar valves • Present at both exits of the heart. • Heart Murmur • Defect in the valves. • “Lub” • Recoil of blood against closed atrioventricular valves. • “Dub” • Recoil of blood against closed semilunar valves

17. Maintaining the Beat • Sinoatrial Node • Located in the right atrium near the Superior Vena Cava. • Sets the tempo for contraction. • Stimulates atrium to contract in unison. • Orchestration of muscle cells accomplished through intercalated discs. • Perkunji Fibers • Transmit electrical signal. • 0.1 second delay allows atria to completely empty before the ventricles contract

18. Maintaining the Beat • Atriovenricular Node • Causes the ventricles to contract. • Factors That Affect Heart Rate • Body temperature • 1o F increase increases heart rate by 10 beats/min. • Exercise • Hormonal stimulation. • Epinephrine –speeds up heart rate.

22. Arteries • Thicker walls • Outer wall connective tissue with elastic fibers • Middle layer smooth muscle – peristalsis • Inner wall – Endothelium , composed of smooth flat cells to reduce resistance to blood flow.

23. Veins • Thinner than arteries. • Valves to prevent back flow. • Blood moves through by muscle contractions. • Virtually all pressure from ventricular contraction is gone.

24. Capillaries • Lack outer and middle layers. • Basement membrane with endothelial layer. • Designed for gas and nutrient exchange between blood and interstitial fluid. • Blood flows 1000 times slower than in arteries and veins due to a large surface area. • Facilitates gas exchange. • Pressure drops dramatically in capillary beds

28. Blood Pressure • Hydrostatic pressure pushes blood through blood vessels. • Systole – pressure due to ventricular contraction. • Arteries stretch because blood flows out much more quickly than it can leave the artery. • Diastole – pressure due to the arterial wall ”snapping back”. • Next contraction occurs before all blood has left the artery and maintains pressure flow.

29. Blood pressure determined by: • Cardiac output • Peripheral resistance • Contraction of atrioles creates peripheral resistance. • Contractions triggered by stress, hormones, and nicotine. • Exercise increases cardiac output and dilates atrioles to supply blood to the muscles. • Giraffes and probably dinosaurs have valves and sinuses in their brain and neck to prevent a stroke while bending down for a drink.

31. Gas Exchange in the Capillaries • O2 and CO2 diffuse down their gradient. • Hydrostatic pressure on the atriole end forces 80% of the fluid out into the tissues. • Large proteins and blood cells left behind increases the osmolarity of the blood. • Causes fluid to move back into the capillaries at the venule end. • Fluid that doesn’t make it back into the cappilarie(15%) is returned to the blood through the lymphatic system.

34. Lymph Vessels • Lymph fluid composition about the same as interstitial fluid. • Moves through the body by squeezing of skeletal muscles and peristalsis. • Valves prevent back flow. • Lymph returns fluid that has leaked out in capillary beds to the circulatory system near the right atrium. • Lymph contains white cells that attack bacteria and viruses.

35. Plasma • Composition of Plasma • 90% H2O, inorganic salts (electrolytes) • PH about 7.4 • Plasma proteins • Buffers • Fibrinogen (clotting) • Proteins that escort lipids which are insoluble in water. • Hormones • Viscosity proteins • Kidneys maintain electrolytes.

36. Erythrocytes • Biconcave for more surface area. • Lack mitochondria and nuclei – more room for hemoglobin. • molecules of hemoglobin per cell. • Generate ATP through anaerobic metabolism. • Kidneys produce erythropoietin to stimulate the function of Red blood cells. • Hemoglobin also binds NO to relax capillaries.

38. RBC’S, Neutrophils

42. Blood Pressure • Hydrostatic pressure pushes blood through blood vessels. • Highest during ventricular contraction. • During systole blood is pushed out into the artery faster than it can leave the artery. • During diastole artery “snaps back” and creates residual pressure in the arteries to continue pushing blood through. • Blood pressure is determined by cardiac output and peripheral resistance. • Stress contracts blood vessels and raises blood pressure. • Exercise causes atrioles to dilate causing more blood to flow in. A drop in pressure occurs and the cardiac output increases to compensate.

43. Cardiovascular Disease • Thrombus – blood clot. • Embolus – when clot breaks off and moves elsewhere in the body. • When a clot blocks a coronary artery – myocardial infarction. • Atherosclerosis – plaques form on the inner wall of the artery. • Arteriosclerosis – when plaques harden through calcification. • Angina Pectoris – heart pain that signals that the heart is not getting enough oxygen.

44. Hypertension • High Blood Pressure • Causes chronic abuse of the endothelium and encourages plaque formation. • Narrows the lumen of the blood vessels and reduces elasticity of blood vessels. • Can compromise arterial walls and increase risk for embolisms and aneurisms.

45. Plaque Build-Up in Blood Vessels