Birds and mammals that regularly immerse their limbs in cold or icy water have particularly well developed counter-current blood flow systems to their limbs, allowing prolonged exposure of the extremities to the cold without significant loss of body heat, even when the limbs are as thin as the lower legs, or tarsi, of a bird, for instance.

The over-all effect is that of a countercurrent exchange barrier insulating the bird's warm body from its own cold feet (Fig. 3, A). Similar mechanisms have been identified in the mammal. 62 Countercurrent exchangers may, therefore, equilibrate as in the placenta or separate as in the rete mirabile of the bird.

Birds have the ability to produce urine that is much more concentrated than their own blood plasma. This is achieved through a process called countercurrent multiplication, where the nephrons actively reabsorb water from the urine back into the bloodstream.

The capacity to conserve urinary water by producing a concentrated urine is directly related to the number of Henle's loops in the kidneys of three terrestrial birds. This suggests that a Henle's loop countercurrent multiplier is responsible for urine concentration in these birds.

The capacity to conserve urinary water by producing a concentrated urine is directly related to the number of Henle's loops in the kidneys of three terrestrial birds. This suggests that a Henle's...

2003年6月1日 · Theories have predicted that countercurrent exchanger efficiency is favored by high permeability to solute. In contrast to the conceptualization of vasa recta as simple "U-tube" diffusive...

The capacity to conserve urinary water by producing a concentrated urine is directly related to the number of Henle's loops in the kidneys of three terrestrial birds. This suggests that a Henle's loop countercurrent multiplier is responsible for urine concentration in these birds.

2014年3月8日 · This is referred to as the countercurrent exchange mechanism. In the presence of ADH (secreted in response to hypovolemia and hyperosmolality in peripheral blood), water is absorbed (without NaCl) in the collecting tubule into the medulla.

Countercurrent heat exchange is a common mechanism among marine animals, facilitating the maintenance of warm body temperature in cold environments. For example, arteries and veins in...

Countercurrent exchange is a mechanism for avoiding heat loss in the legs of birds, especially those swimming or standing in water or on ice or snow. See left. 1. Warm arterial blood from the body's center moves down the leg. 2. Arterial blood transfers heat to venous blood returning from the foot to the heart. 3.