1. Amphibians, reptiles ,mammals

2. Frogs and other amphibians have a three-chambered heart with two atria and one ventricle.
The ventricle pumps blood into a forked artery that splits the ventricle’s output into the pulmocutaneous and systemic circulations.
Separation aided by
spiral valve in arteriosus
Fig. 42.3b
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

3. The pulmocutaneous circulation leads to capillaries in the gas-exchange organs (the lungs and skin of a frog), where the blood picks up O2 and releases CO2 before returning to the heart’s left atrium.
Most of the returning blood is pumped into the systemic circulation, which supplies all body organs and then returns oxygen-poor blood to the right atrium via the veins.
This scheme, called double circulation, provides a vigorous flow of blood to the brain, muscles, and other organs because the blood is pumped a second time after it loses pressure in the capillary beds of the lung or skin.

4. In the ventricle of the frog, some oxygen-rich blood from the lungs mixes with oxygen-poor blood that has returned from the rest of the body.
However, a ridge within the ventricle diverts most of the oxygen-rich blood from the left atrium into the systemic circuit and most of the oxygen-poor blood from the right atrium into the pulmocutaneous circuit.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

8. Breathing lung , or skin
According to air breathing if pulmonary are breath its resistance will decrease … more blood directed to lung
If lung is collapse ….its resistance will be higher so blood flow to coetaneous increased

9. Amphibians in water, however, can obtain additional oxygen by diffusion through their skin.
This process, called cutaneous respiration, helps
to supplement the oxygenation of the blood in these
vertebrates.

10. Reptiles A- Non-crocodilian reptiles B- Crocodilian reptiles
A- Non-crocodilian Reptiles also have double circulation with pulmonary (lung) and systemic circuits.
However, there is even less mixing of oxygen-rich and oxygen-poor blood than in amphibians.
Although the reptilian heart is three-chambered, the ventricle is partially divided.

11. A- Turtle , lizard, …( non croco)
Its ventricle is partially divided by muscular ridge ( septum muskelleist)
Make separation between cavum pulmonar, cavum venosum, and cavum arteriosum
Aided by free horizontal limb

12. Left atrium receive oxygenated blood
Right atrium receive deoxygenated
Right atrium contract before left (slightly) and its blood ejected to cavum pulmonar over the free edge of horizontal septum.
Left atrium eject to cavum arteriosum
Cavum venosum mix

14. Ventricle contract ;
cavum venosum and cavum arteriosum eject to systemic arteries
Cavum pulmonar eject to pulmonary artery
Pulmonary artery has low BP so it receive before systemic

17. Diving or air breating
Blood pressure in pulmonary artery play a role in ventilation or diving.
No ventilation high resistance and higher blood pressure.
In ventilation low Blood pressure.

18. Blood flow pattern through the squamate reptile heart

19. B- In crocodilians, birds, and mammals, the ventricle is completely divided into separate right and left chambers.
In this arrangement, the left side of the heart receives and pumps only oxygen-rich blood, while the right side handles only oxygen-poor blood.
Double circulation restores pressure to the systemic circuit and prevents mixing of oxygen-rich and oxygen-poor blood.
Fig. 42.3c
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

20. Ventricle divided completely
Two systemic arch
- left ---from right ventricle
- right from left ventricle
Both are connected by foramen panizzae

21. Crocodilian Heart Mechanism for breathing and diving
Lungs not utilized
Blood not pumped to lungs
Foramen of Panizza
Valve between aortic trunks to divert blood
Allows left ventricle to pump to both arches when right ventricle closed
Underwater right ventricle helps pump systemic blood

22. The crocodile heart
Airbreathing

23. The crocodile heart
Diving

24. Diving Semilunar valve closed when above water
Semilunar valve forced open when submerged in water to divert pulmonary circulation
(b)
(a)
Figure 13.16: Crocodilian blood circulation when (a) diving and when (b) on the surface.

25. Lungfish and Amphibian vs Dogfish
Modifications of partial or complete partition in atrium
Left and right atria
Advent of lungs
Double circulation
Modification in conus arteriosus
Semi-lunar valve modified to shunt deoxygenated blood to lungs (spiral valve)

26. The evolution of a powerful four-chambered heart was an essential adaptation in support of the endothermic way of life characteristic of birds and mammals.
Endotherms use about ten times as much energy as ectotherms of the same size.
Therefore, the endotherm circulatory system needs to deliver about ten times as much fuel and O2 to their tissues and remove ten times as much wastes and CO2.

27. Adult Heart
Figure 13.19: Adult heart blood flow.

28. Fetal Circulation

31. Figure 13.35: Pre birth fetal circulation: liver (I), inferior vena cava (II), rt. atrium (III), lt. atrium (IV), ductus arteriosus into descending aorta.

32. Fetal Circulation (cont.)
Oxygenation at placenta
Umbilical veins supply fetus with oxy. blood
Vein passes through liver and unites with post cava
From right atrium, oxy. blood goes 2 directions
To right ventricle
To left atrium through foramen ovale
Figure 13.36: Foramen ovale in fetal circulation system.

33. Fetal Circulation (cont.)
In right ventricle, oxy. blood sent to pulmonary artery
Lungs nonfunctional
Ductus arteriosus diverts blood from lungs

34. Circulation At Birth Placenta shuts down
Umbilical vein collapses- near falciform ligament
Interatrial aperture closes (fossa ovalis)
Ductus arteriosus closes (ligamentum arteriosum)
Deoxygenated blood now enters right ventricle, pulmonary arteries, and continues to lungs
Ductus venosus collapses (ligamentum venosum)