1. Transport & Maintenance
Circulatory Systems
Transport & Maintenance

2. Circulatory Systems transport to & from tissues
nutrients, O2; waste, CO2
hormones
maintain electrolyte balance of intercellular fluid
transport to/from homeostatic organs
small intestine delivers nutrients
liver removes wastes, controls nutrients
kidney controls electrolytes, dumps wastes

3. Circulatory Systems some animals lack circulatory systems
aquatic environment fulfills same functions
some animals have open circulatory systems
the heart pumps interstitial fluid
vessels deliver interstitial fluid to tissues
interstitial fluids leave the vessels & bathe the cells of the tissues
interstitial fluids return to the heart
other animals have closed circulatory systems

4. open circulatory systems Figure 49.1

5. closed circulatory system of earthworm Figure 49.2

6. Closed Circulatory Systems
components of closed circulatory systems
heart(s) - pump
vessels - transport conduits
blood -
transport medium
distinct from interstitial fluid
advantages over open system
speed
control of blood flow
cellular elements of blood remain in vessels

7. Circulatory Systems hearts vertebrates have chambered hearts
valves impose one-way flow
number of chambers varies with phylogeny
blood circulates through one or two circuits
H => G.E.M. => B
H => G.E.M. => H => B
pulmonary systemic
circuit circuit

8. Closed Circulatory Systems
vessels
arteries
transport blood away from heart
veins
transport blood toward heart
arterioles/venules
small arteries/veins
capillaries
connect arterioles to venules

9. Closed Circulatory Systems
systems with two-chambered hearts - fish
one circuit
atrium =>ventricle =>gills =>aorta =>body =>atrium
ventricular pressure is dissipated in gill capillaries

10. fish circulation schematic p. 943

11. Closed Circulatory Systems
systems with two-chambered hearts - lungfish
modified for breathing air or water
out-pocketing of gut acts as a lung
some gill arteries supply blood to lung
some gill arteries deliver blood to aorta
gills exchange gases with water
partially separated atrium
right side => oxygenated blood => body
left side => deoxygenated blood => gills/lungs

12. lungfish circulation schematic p. 943
* one pair of gill arteries delivers blood to lung
* two gill arches deliver blood directly to aorta
* “gilled” gill arches exchange gases with blood

13. Closed Circulatory Systems
systems with three-chambered hearts - amphibians
two atria
left atrium receives pulmonary blood
right atrium receives systemic blood
ventricle anatomy limits mixing
deoxygenated blood travels to lung
oxygenated blood travels to body

14. amphibian circulation schematic p. 943

15. Closed Circulatory Systems
reptilian hearts provide further control
two atria receive blood from pulmonary & systemic circuits
partially separated ventricle supplies three vessels
pulmonary artery & two aortas
when breathing, the right aorta carries deoxygenated blood to the pulmonary circuit
when not breathing, both aortas carry blood to the systemic circuit

16. reptilian circulation schematic p. 944

17. Closed Circulatory Systems
crocodilian hearts have four chambers
two atria, two ventricles, two aortas
two aortas are bridged near their origins
when breathing, the left ventricle (& aorta) pressure is higher
deoxygenated blood goes to lungs
when not breathing, right aorta pressure is higher
pulmonary circuit is bypassed

18. crocodilian schematic p. 944

19. Closed Circulatory Systems
endotherm hearts have four chambers and one aorta
systemic/pulmonary circuits are separated
tissues receive highest possible [O2] (P1) under high pressure
lungs receive lowest possible [O2] (P2) under lower pressure

20. endotherm schematic p. 945

21. human circulatory system Figure 49.3

22. Human Circulatory System
circulation
deoxygenated blood arrives at right atrium from inferior & superior vena cava
atrium pumps blood to right ventricle
ventricle pumps blood to pulmonary artery
backflow is prevented by atrioventricular valve
ventricle relaxes
backflow is prevented by pulmonary valve

23. human heart anatomy Figure 49.3

24. Human Circulatory System
circulation
oxygenated blood arrives at left atrium through pulmonary veins
atrium pumps blood into left ventricle
ventricle pumps blood to aorta
backflow is prevented by atrioventricular valve
ventricle relaxes
backflow is prevented by aortic valve

25. human heart anatomy Figure 49.3

26. Human Circulatory System
cardiac cycle
systole - contraction of ventricles
maximum pressure generated
major electrical event
diastole - relaxation of ventricles
minimum pressure
characteristic electrical signatures

27. ventricular pressures & volumes Figure 49.4

28. measuring blood pressure Figure 49.5

29. Human Circulatory System
heartbeat is myogenic
pacemaker cells occur at sinoatrial node
resting membrane potential depolarizes
at threshold, voltage gated Ca2+ channels open
K+ channels open to repolarize cells
K+ channels close slowly, allow gradual depolarization
autonomic nervous system regulates the rate of depolarization

30. autonomic control of heart rate Figure 49.6 Figure 49.8 Figure 44. 9
norepinephrine
acetylcholine
autonomic control of heart rate Figure 49.6 Figure 49.8 Figure 44. 9

31. Human Circulatory System
contraction
the pacemaker action potential spreads across the atrial walls
atria contract
action potential is transmitted to ventricles through the atrioventricular node and the bundle of His
the action potential spreads to Purkinje fibers in ventricular muscle
ventricles contract

32. origin and spread of cardiac contraction Figure 49.7

33. Human Circulatory System
vascular system
arteries carry blood from heart
elastic tissues absorb pressure of heart contractions
smooth muscle allows control of blood flow by neural and hormonal signals

34. artery structure Figure 49.10

35. Human Circulatory System
vascular system
capillaries
fed by arterioles; drained by venules
exchange materials between blood & intercellular fluids
high total capacity; slow flow
thin walls

36. capillary bed Figure 49.10

37. Human Circulatory System
vascular system
capillaries
exchange materials by filtration, osmosis & diffusion
water & solutes move through capillary walls under pressure on the arteriole side
remaining solutes & diffusing CO2 produce a low osmotic potential
water returns to capillaries on the venule side

38. water movement balanced between blood pressure & osmotic potential Figure 49.12

39. Human Circulatory System
[lymphatics
lymph vessels return excess tissue fluid to blood
lymphatic capillaries collect lymph
capillaries merge into larger vessels
vessels contain one-way valves
the major lymph vessel, the thoracic duct, empties into the superior vena cava
lymph nodes participate in lymphocyte production & phagocyte activity]

40. vein structure Figure 49.10

41. Human Circulatory System
veins
receive blood from capillaries under low pressure
contain one-way valves
blood is propelled by skeletal muscle contraction or gravity

42. venous return by skeletal muscle contraction and one-way valves

43. Human Circulatory System
blood - a fluid connective tissue
fluid matrix - plasma
dissolved gases, ions, proteins, nutrients, hormones, etc.
many components found in tissue fluid
cellular elements
red blood cells (erythrocytes)
white blood cells (leukocytes)
platelets

44. blood components Figure 49.15

45. human blood samples before and after centrifugation to separate red blood cells from serum

46. Human Circulatory System
control & regulation of circulation
capillaries are subject to auto-regulation
pre-capillary sphincters and arterial smooth muscle are sensitive to
O2 & CO2 concentrations
accumulated waste materials

47. local control of blood flow Figure 49.17

48. Human Circulatory System
control & regulation of circulation
simultaneous auto-regulation of capillary beds produces systemic responses
changes in breathing, heart rate
changes in blood distribution
systemic control is neural or hormonal
sympathetic stimulation contracts most arteries; dilates skeletal muscle arteries
hormones constrict arteries in targeted tissues

49. circulatory regulation at two levels Figure 49.18

50. Human Circulatory System
control & regulation of circulation
autonomic control of circulation originates in medulla of brain stem
inputs arrive from
stretch receptors
chemosensors
higher brain centers
responses may be
direct - artery relaxation or contraction
indirect - release of epinephrine

51. neural control of circulation is centered in the medulla Figure 49.19