Atelectasis is composed of 78% nitrogen and 21% oxygen. Since oxygen is exchanged at the alveoli-capillary membrane, nitrogen is a major component for the alveoli's state of inflation. If a large volume of nitrogen in the lungs is replaced with oxygen, the oxygen may subsequently be absorbed into the blood, reducing the volume of the alveoli, resulting in a form of alveolar collapse known as absorption atelectasis. It is usually associated with accumulation of blood, fluid, or air within the pleural cavity, which mechanically collapses the lung. This is a frequent occurrence with pleural effusion, caused by congestive heart failure (CHF).
Neoteny in humans while relinquishing others. For example, the high leg-to-body ratio (long legs) of adult humans as opposed to human infants shows that there is not a holistic trend in humans towards neoteny when compared to the other great apes. Andrew Arthur Abbie agrees, citing the gerontomorphic fleshy human nose and long human legs as contradicting the neoteny hominid evolution hypothesis, although he does believe humans are generally neotenous. Brian K. Hall also cites the long legs of humans as a peramorphic trait, which is in sharp contrast to neoteny. On the balance, an all or nothing approach could be regarded as