Harmony of giraffe and tree snakes
1986/06/01 Elhuyar Zientzia Iturria: Elhuyar aldizkaria
What can giraffes and tree snakes have in common? The answer is that both have problems with blood circulation. The discomfort caused by gravity in the circulation of blood through the body seems to have been resolved in the same way by mammals and reptiles.
An average giraffe measures 5 m and is 2.5 m above the heart. Blood comes out at high pressures from the giraffe's heart. So far it was thought that such high pressure was necessary to carry blood to the head, counteracting the force of gravity. However, according to recent studies by Professor Badeer of Omaha University, this interpretation may be wrong.
Badeer indicates that the blood supply of the brain is like a siphon: it goes through the heart, crosses the brain and falls to the heart closing the cycle.
Although gravity prevents upward flow, it helps downward and does not completely affect blood flow resistance. The only resistance is friction on the tube wall.
Why does giraffe maintain such high blood pressure? Badeer suggests that high pressure prevents the collapse of the brain ducts. Due to the low hydrostatic pressure so far from the heart, the tube walls could fall down. However, when the animal lowers its head to drink water, blood pressure in the head rises from 100-150 mmHg to 250-350 mmHg. This increased pressure would have to cause giraffe problems.
Badeer points out that brain circulation is protected from increased blood pressure a few meters from cerebrospinal fluid. Thus, the pressure on both sides of the walls of the head tubes remains the same regardless of the head position. In addition, there is another adptation; the jugulare vein has a series of valves that prevent blood from pouring back when the head is lowered.
On the other hand, another study on climbing tree snakes (Pitnophis melanolenais) has shown that snakes have giraffe adaptations to rule out the effects of gravity on the blood.
Finally, and summarizing, the cases show us that nature finds similar solutions to solve similar problems.