3The 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.
8Breathing lung , or skinAccording to air breathing if pulmonary are breath its resistance will decrease … more blood directed to lungIf lung is collapse ….its resistance will be higher so blood flow to coetaneous increased
9Amphibians in water, however, can obtain additional oxygen by diffusion through their skin. This process, called cutaneous respiration, helpsto supplement the oxygenation of the blood in thesevertebrates.
10Reptiles 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.
11A- Turtle , lizard, …( non croco) Its ventricle is partially divided by muscular ridge ( septum muskelleist)Make separation between cavum pulmonar, cavum venosum, and cavum arteriosumAided by free horizontal limb
12Left atrium receive oxygenated blood Right atrium receive deoxygenatedRight atrium contract before left (slightly) and its blood ejected to cavum pulmonar over the free edge of horizontal septum.Left atrium eject to cavum arteriosumCavum venosum mix
20Ventricle divided completely Two systemic arch- left ---from right ventricle- right from left ventricleBoth are connected by foramen panizzae
21Crocodilian Heart Mechanism for breathing and diving Lungs not utilizedBlood not pumped to lungsForamen of PanizzaValve between aortic trunks to divert bloodAllows left ventricle to pump to both arches when right ventricle closedUnderwater right ventricle helps pump systemic blood
24Diving 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.
25Lungfish and Amphibian vs Dogfish Modifications of partial or complete partition in atriumLeft and right atriaAdvent of lungsDouble circulationModification in conus arteriosusSemi-lunar valve modified to shunt deoxygenated blood to lungs (spiral valve)
26The 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.
32Fetal Circulation (cont.) Oxygenation at placentaUmbilical veins supply fetus with oxy. bloodVein passes through liver and unites with post cavaFrom right atrium, oxy. blood goes 2 directionsTo right ventricleTo left atrium through foramen ovaleFigure 13.36: Foramen ovale in fetal circulation system.
33Fetal Circulation (cont.) In right ventricle, oxy. blood sent to pulmonary arteryLungs nonfunctionalDuctus arteriosus diverts blood from lungs
34Circulation At Birth Placenta shuts down Umbilical vein collapses- near falciform ligamentInteratrial aperture closes (fossa ovalis)Ductus arteriosus closes (ligamentum arteriosum)Deoxygenated blood now enters right ventricle, pulmonary arteries, and continues to lungsDuctus venosus collapses (ligamentum venosum)