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Julia Breedh

circulation (anatomy and physiology) :: Birds -- Britannica Online Encyclopedia - 3 views

www.britannica.com/...Birds

bird circulatory system reptiles sinus venosus ventricle

shared by Julia Breedh on 20 Jan 10 - Cached
  • Mammals also evolved from reptiles, but not from the same group as did birds, and must have developed their double circulation independently from early reptiles. Nevertheless, several parallel changes occurred, such as the common incorporation of the sinus venosus into the right auricle. The most striking manifestation of different origins is seen in the mammalian aorta, which leaves the left ventricle and curves to the left. The aorta corresponds to the left half of the systemic arch, while the right is missing. The carotid arteries arise from the left systemic arch (aorta), though their precise position varies among mammals. The arterial system is asymmetric, as in birds, but in the opposite way.
  • The heart of both mammals and birds is a double pump, powering two systems of vessels with different characteristics. The left ventricle has a thicker layer of muscle around it, a necessary adaptation for powering its beat against the high resistance of the extensive systemic circulation throughout the body. The right ventricle has a thinner wall, consistent with its role in pumping blood to the lungs against a much lower resistance.
  • Hearts
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  • Birds
  • Mammals
  • Bird circulatory systems have many similarities to those of reptiles, from which they evolved. The changes that have occurred are more of degree than of kind. The heart is completely divided into right and left sides. The sinus venosus is incorporated into the right auricle and becomes the sinoauricular node. It is from this point that the heartbeat is initiated. There is no conus, and only two vessels leave the divided ventricle. These are the pulmonary artery from the right side and the systemic arch from the left. The systemic arch is asymmetrical—the main difference in this area between birds and lizards. Only the right part of the systemic arch is present, the left being suppressed. The arterial arches are no longer bilaterally symmetrical. Another difference between birds and lizards is found in the venous circulation: the renal portal system is reduced in birds.
  • Julia Breedh on 20 Jan 10
     
    Massor med superbra information om hjärtat och dess evolution i bl.a. Verbrater.
ene05sah

ANIMAL KINGDOM :: BIRDS :: BIRD :: ANATOMY OF A BIRD image - Visual Dictionary Online - 0 views

visual.merriam-webster.com/...anatomy-bird.php

shared by ene05sah on 25 Nov 09 - Cached
  • anatomy of a bird
  • ene05sah on 25 Nov 09
     
    heart, crop, liver, lung, kidney, gizzard, ureter, rectum
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