1. Lymphatic system
Circulatory Systems - 1
January 2005

2. Lymphatic system Plays important role in fluid distribution
Important part of the immune system

3. Lymphatic system
Circulatory Systems - 1
January 2005

4. Edema Pulmonary edema Peripheral edema Circulatory Systems - 1
January 2005
Pulmonary edema
Peripheral edema

5. Skeletal muscle pump
Circulatory Systems - 1
January 2005

6. Moving Blood Back to the Heart
Blood in veins is under low pressure
Two major pumps assist in moving blood back to the heart
Skeletal muscle
Respiratory pumps
Inhalation: pressure in thoracic cage drops and draws blood into veins
Exhalation: pressure increases in the thoracic cage and pushes the blood towards the heart; blood does not move backwards because of valves
Figure 9.38

7. Veins – volume reservoir
Circulatory Systems - 1
Veins – volume reservoir
January 2005
Veins have thinner and more compliant walls
Small increases in blood pressure lead to large changes in volume
In mammals veins hold more than 60% of the blood

8. Regulation of circulatory systems
January 2005
Law of Bulk flow
Q = DP/R
For circulatory system
CO = MAP/ TPR
HR x SV = MAP/ TPR

9. Regulation of circulatory systems
January 2005

10. Regulation of circulatory systems
January 2005

11. Baroreceptor reflex Important mechanism for regulating blood pressure
Circulatory Systems - 1
Baroreceptor reflex
January 2005
Important mechanism for regulating blood pressure
“Pressure” (stretch) receptors located in carotid and aortic bodies

12. Circulatory Systems - 1
Baroreceptor reflex
January 2005
Baroreceptors are stretch-sensitive mechanoreceptors located in the walls of many major blood vessels
Most important of these are located in the carotid artery and aorta
Baroreceptor reflex regulates MAP
Rapid changes in blood pressure are possible through sympathetic changes in cardiac output & arteriolar tone

13. Baroreceptor discharges
Circulatory Systems - 1
Baroreceptor discharges
January 2005
Most sensitive in physiological range
More sensitive to pulsatile pressures

14. Arterial Pressure and blood volume
Blood volume regulation via kidneys
Simple filtration
Humoral controls Renin-angiotensin system (RAS) Antidiuretic hormone (ADH)

15. Effects of gravity on blood pressure
Circulatory Systems - 1
Effects of gravity on blood pressure
January 2005
Measured blood pressure when standing includes a hydrostatic (gravity) component
What happens when we change body positions?

16. Effects of gravity
Circulatory Systems - 1
January 2005

17. How Does Gravity Affect Blood Circulation?
Circulatory Systems - 1
January 2005
How Does Gravity Affect Blood Circulation?

18. How Does Gravity Affect Blood Circulation?
Very tall animals (e.g. giraffe) must be able to pump blood up to the head
They could also have difficulty with blood pooling in the feet, and peripheral edema

19. Circulatory Systems - 1
January 2005

20. Differences in central arterial blood pressures
systole/diastole
Human /80
Elephant /70
Pigeon /100
systole/diastole
Trout 45/33
systole/diastole
Turtle 31/25
gill
lung
ventral aorta
pulmonary artery
aorta
dorsal aorta

21. Primarily water containing ions and organic solutes Blood cells
Composition of Blood
Primarily water containing ions and organic solutes
Blood cells
Proteins

22. Invertebrates: primarily respiratory pigments
Blood Proteins
Invertebrates: primarily respiratory pigments
Vertebrates: carrier proteins such as albumin and globulins, and proteins involved in blood clotting

23. Blood Cells or Hemocytes
Functions: oxygen transport or storage, nutrient transport or storage, phagocytosis, immune defense, blood clotting
Figure 9.44

24. Contain high concentrations of respiratory pigments such as hemoglobin
Erythrocytes
Red blood cells are the most abundant cells in the blood of vertebrates
Contain high concentrations of respiratory pigments such as hemoglobin
Major function is the storage and transport of oxygen
Have evolved independently several times

25. Separates into three main components when centrifuged
Vertebrate Blood
Separates into three main components when centrifuged
Plasma
Erythrocytes
Other blood cells and clotting cells
Hematocrit – fraction of blood made up of erythrocytes
Figure 9.45

26. Mammalian erythrocytes are biconcave disks
Round or oval in shape
Mammalian erythrocytes are biconcave disks
This shape increases surface area, facilitating oxygen transfer

27. Function in the immune response All are nucleated
Leukocytes
White blood cells
Function in the immune response
All are nucleated
Found both in the blood and the interstitial fluid
Some are able to move across capillary walls
Five major types
Figure 9.46

28. Play a key role in blood clotting
Thrombocytes
Play a key role in blood clotting
Spindle-shaped cells in nonmammals and classified as leukocytes
Anucleated cell fragments in mammals called platelets
Three steps in blood clotting
Vasoconstriction
Platelet plug formation
Clot formation through coagulation cascade

29. Process is called hematopoiesis Location of stem cells
Blood Cell Formation
Process is called hematopoiesis
Location of stem cells
Adult mammals: only in bone marrow
Fishes: kidney
Amphibians, reptiles, birds: spleen, liver, kidney, bone marrow
Specific signaling factors are involved, e.g., erythropoietin is a hormone released by the kidney in response to low blood oxygen

30. Blood flow distribution & circulatory patterns
Evolution of air breathing: Plumbing & pressures
Separation of respiratory & systemic circulations Air-breathing fishes Lungfishes Amphibians Reptiles
Mammalian fetal circulation
In-series circuits
1 atrium + 1 ventricle
Single pump
In-parallel circuits
2 atria + 1 ventricle
Single pump or a functional double pump
In-series circuits
2 atria + 2 ventricles
Double pump

31. Heart has four chambers arranged in series
Fish
Heart has four chambers arranged in series

32. Air-Breathing Fishes Air-breathing evolved several times in fishes
Air-breathing organs are arranged in parallel; oxygenated and deoxygenated blood mix
Lungfish are the most specialized air-breathing fishes and have only limited mixing of the oxygenated and deoxygenated blood
Various organs serve as ABOs in fish
Can use: Swimbladder, mouth, gut, gills, skin, etc.
Common problems: O2 blood enters venous system  mixed venous blood Single atrium receives mixed venous blood

33. Lungfish Lungfish: true lung (developmentally)
Largely solved the problem of mixed venous blood
Atrium has a partial septum: oxygenated on one side; deoxygenated on the other
Ventricle has partial septum: separation maintained
Outflow vessel has a partial septum: separation is maintained

34. Amphibians and Reptiles
Like lungfish, the heart is only partially divided; two atria and one ventricle
Oxygenated and deoxygenated blood can mix
Two streams of blood are kept fairly separate although the mechanism is not completely understood
Crocodilians have a completely divided ventricle

35. Amphibians Anatomically undivided heart, in-parallel circulations
pulmonary capillaries
heart
systemic capillaries
Two atria
Separate pulmonary & systemic venous return
Single ventricle
Blood mixing
Single outflow vessel
High lung pressure
The beauty
vagal vasoconstriction can close off lung circulation during breath-hold or diving
Solutions
Trabecular heart
Spiral valve
Lymph hearts

36. Amphibian heart
Spongy myocardium & spiral valve in conus help separate oxygenated & deoxygenated blood within the single ventricle
Three chambered heart: two atria and one ventricle
Trabeculae within the ventricle and a spiral fold within the conus arteriosus help to keep oxygenated and deoxygenated blood separate

37. Reptilian hearts: 3 major strategies
1. Anatomically undivided heart, in-parallel circulations
Squamate lizards, turtles, tortoises & most snakes
Spongy myocardium & ventricular septa (creating cava) helps separate oxygenated & deoxygenated blood within the single ventricle
Right atrium largely to cavum pulmonale
Two outflow vessels: pulmonary & systemic arteries
Blood pressures in cavum venosum, cavum pulmonale & cavum arteriosum are identical during ventricular contraction
Pulmonary capillaries protected by outflow resistance site (vagal constriction)

38. Reptilian hearts: 3 major strategies
2. Functionally divided heart, in-parallel circulations
Varanid lizards & pythons
Highly developed ventricular muscular ridge
Systolic pressure in cavum pulmonale is lower than cavum arteriosum, but no difference during diastole: low pulmonary pressure
= functional, but not anatomical separation

39. Crocodilian heart: best of both worlds:
3. Anatomically divided heart, double circulation with a by-pass
heart  pulmonary capillaries  heart  systemic capillaries
Right ventricle has pulmonary artery
& a right systemic aorta
Left ventricle has a “left” systemic aorta
Foramen of Panizza provides a pressure connection between “left” & “right” aortae
Cog valve
Can close off lung circulation (vagal vasoconstriction)
Powered by 2 atria & 2 ventricles with same wall thickness

40. Can shunt blood to bypass either the pulmonary or systemic circuit
Reptiles
Can shunt blood to bypass either the pulmonary or systemic circuit
Right-to-left shunt: deoxygenated blood bypasses the pulmonary circuit and reenters the systemic circuit
Left-to-right shunt: some pulmonary blood reenters the pulmonary circuit
Figure 9.16a

41. Mammalian fetal circulation
No air ventilation of lungs
O2 comes from placenta
placenta
In-series circuits
2 atria + 2 ventricles
Double pump
Low pulmonary pressure