ZOO-ology: Giraffe heart spans 2 feet, weighs 25 pounds
Oct. 9, 2011 at 5:09 a.m.
By Judie Farnsworth
You probably don't spend sleepless nights pondering circulatory systems in the octopus, bat or giraffe, but the wide-awake facts are intriguing.
How an animal lives a certain way, filling a certain niche, can be astounding.
Sight, hearing, sense of touch - sure, they're important and noticeable, but what about less obvious systems like the circulatory system?
"How can bats hang upside-down - doesn't the blood rush to their heads?"
This is a question I've heard many times. It doesn't bother them a bit. A bat's circulatory system has unique valves that keep blood flowing smoothly and not pooling in the head.
There are lots of "wow" things with bat systems. Blood flow to the wings can be controlled. During times of torpor (inactivity), more blood may remain in the body, reducing heat loss at the wing surface.
Additional blood is circulated through the wings during flight. Some bat species' hearts beat 1,400 times per minute when active and some may slow to 20 beats per minute during torpor.
The giraffe is quite amazing. What kind of extra-strength apparatus does it take to pump blood up a 10-feet neck to the brain, then manage its flow below the heart, six feet to the hooves?
When a giraffe bends way down for a drink, why doesn't it faint from blood rushing to the brain? Why doesn't it stagger dizzily from a lack of blood to the brain when it stands back up?
A giraffe's super muscular heart is two feet long and weighs about 25 pounds. It pumps 16 gallons a minute. A remarkable network of veins and one-way valves prevent back-flow, keeping blood from rushing to the head. Blood vessels in the head are more elastic and may reserve some blood, which keeps the animal from fainting as it stands. Smaller red blood cells and capillaries all help make oxygen absorption quicker.
With gravity and a ton of weight sitting on four legs and hooves, why doesn't the giraffe have ballooning ankles?
NASA has studied this in developing gravity-suits for astronauts. Giraffes' legs have very strong, tight skin and tissue beneath. Rather like super compression stockings. Arteries are deep with thick, muscular walls.
A giraffe won't bleed heavily from a leg cut. It's interesting to note that while stroke and hardening of the arteries is seen in most mammals, it isn't a notable problem with the giraffe.
The octopus is an amazing creature with a lot of heart. Three hearts, to be exact. There is a systemic (main) heart. Two lesser hearts pump blood to the gills where waste is discarded and oxygen is received. They work like the right side of the human heart. The newly oxygenated blood is pumped back to the main heart and circulated through the body.
Did you know that an octopus is a true blue blood? Yes, its blood is blue. Our blood contains hemoglobin that helps absorb oxygen and gives a red color. The octopus has a protein called hemocyanin that causes a blue color.
There's always more than meets the eye. When you visit The Texas Zoo, let your curiosity guide you to learn more about our intriguing world.
Judie Farnsworth is a longtime volunteer at the Texas Zoo specializing in educational programs.