This is the first sound a fetus makes when it is delivered outside the mother's body. In the womb, the fetus receives oxygen from the mother's arterial blood through the umbilical vein, and the umbilical arterial blood containing carbon dioxide and waste products is returned to the mother's venous blood. Therefore, gas exchange does not take place through the lungs, but when oxygen supply from the mother is no longer available at birth, carbon dioxide accumulates in the newborn's blood, stimulating the respiratory center, causing the first inspiration, followed by expiration. This expiration is the first cry. Therefore, the absence of a first cry is a sign of asphyxia and indicates the risk of brain damage due to oxygen deficiency. Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information |
胎児が母体外に出たときに最初に出す声。子宮内では,胎児は臍静脈を通じて母体の動脈血中の酸素の供給を受け,炭酸ガスや老廃物を含んだ臍動脈血を再び母体の静脈血中に戻している。そのため肺によるガス交換は行われていないが,出生により母体から酸素供給が受けられなくなると新生児の血液内に炭酸ガスがたまり,これが呼吸中枢を刺激して最初の吸気が起り続いて呼気が起る。この呼気が産声となる。したがって産声が聞かれないことは仮死の兆候であり,酸素欠乏による脳損傷の危険性を意味する。
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