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in the evolution of the heart and arteries, amphibians loose branchial circulation at _____.
In the evolution of heart and arteries, reptiles never show _____.
What are the modifications of aortic arches in amphibians and reptiles?
- Reduced in number
- 3rd pair remains as part of internal carotids to the head.
- 4th and somtimes 5th are systemic arches to the dorsal aorta and body.
- 6th arch provides pulmonary arches to lungs.
What are the heart modifications in amphibians and reptiles?
- Blood returning from the body is seperated from that returning from the lungs by a completely divided atrium (Thus a three chambered heart).
- Level of division of ventricle, conus arteriosus, and ventral aorta is variable (crocodilians have divided ventricles thus a four chambered heart)
- Generally, venous and arterial blood are separated.
Describe the aortic arches in birds and mammals.
- Both retain third aortic arches as part of carotids.
- 6th aortic arches form part of the pulmonary arteries.
- Right fourth aortic arch becomes the systemic arch (Aorta) in birds, so the aorta of birds curves to the right.
- Left fourth aortic arch becomes the systemic arch in mammals, so the aorta in mammals curves to the left.
Both birds and mammals have completely divided hearts with _____ , but they evolved these independently.
Describe the left and right side of the heart in birds and mammals.
- Right side of the heart receives venous blood from the body and sends it to the lungs.
- Left side receives blood from the lungs and sends it to the body.