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Pearson Education 2011
Circulation System
Circulation System
The circulation system of each animal is vital for transporting nutrients, oxygen, and hormones throughout the body, and ridding the body of waste products, such as carbon dioxide.
Depending on the environment an animal lives in, their circulation system may look and function differently.
The Pump: The heart pumps blood through the body, each contraction controlled by electrical impulses from the Pacemaker. The pump is necessary in a closed system.
The Vessels: The veins and arteries transport fluid containing gases, nutrients, and waste around the body.
The Circulatory Fluid: Blood carries all of these molecules around the body, and deliveries the necessary nutrients and gases, and picks up waste to expel from the body.
Pearson Education 2011
All reptiles (except birds) have a three-chambered heart that contains two atria and one ventricle, which are separated partially by an incomplete septum. The right atrium receives deoxygenated blood, while the left atrium receives oxygenated blood. The one ventricle system allows for a small amount of mixing of this blood but still allows for efficient oxygen management. Muscular ridges that partly divide the ventricle and pressure differences of the outflow tracts maintains the separation of oxygenated and deoxygenated blood.
Reptiles have a double circulation system, meaning blood passes through the heart twice in one circuit. The first circulation is known as pulmonary circulation. Blood passes from the heart to the lungs for oxygenation. The second circulation is systemic circulation, where the heart pumps the body to the rest of the body.
The right ventricle pumps deoxygenated blood into the pulmonary trunk, where it eventually reaches the lungs. Then, via the paired aortae, pulmonary flow is restricted, and blood flow goes back towards the heart. The oxygenated blood then enters through the left atrium and is pumped into the left ventricular compartment.
Marine Iguanas
Marine Iguanas
As marine iguanas are the only known species of lizard that feed underwater, they have evolved a special physiological mechanism to survive underwater for long periods of time. Marine iguanas exhibit a condition known as bradycardia, where they significantly reduce their heart rate. This is a common adaption found in many diving animals, allowing for greater oxygen conservation and blood flow to vital, central organs.
Heart rate in marine iguanas can drop from 50-60 beats per minute on land to as low as 5-10 beats per minute underwater. Stimulation of the vagus nerve slows down the heart, and blood vessels in the extremities constrict to redirect blood flow. By slowing their heart rate, marine iguanas can increase their dive time and reduce energy/heat loss.
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