Reptlia Heart 1.pptx

zoology

1. REPTALIA HEART CIRCULATORY SYSTEM Dr. G.D. HANDE

2. Reptilian hearts differ significantly from those of mammals. Most reptiles possess three chambered hearts, with the exception of crocodilians. The anatomy of the great vessels is quite different from that of mammals and can be confusing to uninitiated. Adequate knowledge of normal anatomy and function is paramount in assessing health and performing certain clinical procedures.

3. Reptile cardiovascular physiology is also significantly different from that of mammals. Reptiles are much less susceptible to the adverse effects of hypoxia and changes in blood pH, and therefore capable of enduring much wider fluctuations in heart rate, blood pressure, and oxygenation.

4. Most reptiles have three chambered hearts with two  atria  and one common ventricle. The  right atrium  receives blood returning from the systemic circulation via the sinus venosus , which is formed by the confluence of the right and left precaval veins and the single postcaval vein.

5. The reptilian  heart  has a partial septum between the ventricles. This allows better separation of oxygenated and deoxygenated blood. The separation increases the efficiency of transporting oxygenated blood to the body.

6. Reptiles have  a  three - chambered heart   – Two atria and one partially divided ventricle. There is a mixing of oxygenated and deoxygenated blood because the ventricle is not split completely. The crocodile  has  a four- chambered heart  similar to mammals and birds where the ventricles are split completely.

7. Anatomy and function The location of the heart within the body cavity varies according to species. In most chelonians the heart lies on midline just caudal to the thoracic girdle, ventral to the lungs. The heart of some chelonians such as soft-shelled turtles is pushed to the side of the body cavity in order to accommodate the retracted neck.

8. The heart of most lizards lies within the thoracic girdle, with the exception of some species such as monitors and crocodilians in which the heart lies farther back in the coelomic cavity. Cardiac location varies in snakes according to species, but usually is found at the junction of the first and second quarter of the animal's body length. Typically arboreal snakes' hearts are found more cranially in the body than in terrestrial animals. Snake's hearts are fairly mobile within the coelomic cavity helping to facilitate the ingestion of large prey items.

9. The cardiac structure of reptiles is significantly different from that of mammals. Please note that the following descriptions are very general, and that significant variation exists between species. Most reptiles have three chambered hearts with two atria and one common ventricle. The right atrium receives blood returning from the systemic circulation via the sinus venosus , which is formed by the confluence of the right and left precaval veins and the single postcaval vein.

10. The walls of the sinus venosus contain cardiac muscle and the pacemaker of the heart. The left atrium receives oxygenated blood from the lungs via the pulmonary vein(s). The atrioventricular valves are bicuspid, membranous structures. Under normal conditions the three chambered heart functions much like a four chambered structure, therefore relatively little mixing of oxygenated and de-oxygenated blood occurs.  

11. The cardiac structure of reptiles is significantly different from that of mammals. Please note that the following descriptions are very general, and that significant variation exists between species. Most reptiles have three chambered hearts with two atria and one common ventricle. The right atrium receives blood returning from the systemic circulation via the sinus venosus , which is formed by the confluence of the right and left precaval veins and the single postcaval vein.

12. The walls of the sinus venosus contain cardiac muscle and the pacemaker of the heart. The left atrium receives oxygenated blood from the lungs via the pulmonary vein(s). The atrioventricular valves are bicuspid, membranous structures. Under normal conditions the three chambered heart functions much like a four chambered structure, therefore relatively little mixing of oxygenated and de-oxygenated blood occurs. 

13. Crocodilians are the only reptiles which possess four chambered hearts comparable to mammals. Even so, crocodilian cardiac anatomy is quite different from what is seen in birds and mammals. Crocodilians possess two aortas; the right arising from the left ventricle and the left from the right ventricle. Both aortas route blood to the systemic circulation.