Hobbies And Interests
Brain
The frog's nervous system, which consists of its brain, spinal cord, and nerves, is highly developed. A number of important parts of the frog's brain correspond to similar parts of the human brain. These include the medulla, which regulates respiration and digestion and the cerebrum, which regulates muscular coordination and body posture. When compared to that of humans, the cerebrum of a frog is proportionally very small.
Heart
The frog's heart consists of two upper chambers, termed the right and left atrium and a single lower chamber, which is termed a ventricle. A protective covering, called a pericardium, surrounds the heart. Both oxygen-rich blood and oxygen-poor blood, which contains waste gases, are present in the frog's ventricle at all times. The two types of blood are kept separate as oxygen-poor blood entering the right atrium, flows immediately to the bottom of the ventricle. Oxygen-rich blood that enters the left atrium also enters the single ventricle, but is held up by the oxygen-poor blood that lies at the bottom of the ventricle. There is both a solid and a liquid portion to the frog's blood. The red and white blood cells are transported in the liquid portion of the blood.
Lungs
Although the frog is able to breath through its skin, particularly when it is under water, these animals possess simple, sac-like lungs. Air that the frog takes in through two nostrils moves down the animal's windpipe and into its lungs. Frogs however, do not possess either a diaphragm or ribs, which in the case of humans, are used to assist breathing. Frogs breathe by opening their mouth to allow for air flow into their windpipe. Frogs can also breathe by closing their nostrils and lowering the floor of their mouth, which causes the animal's throat to expand. As the frog's nostrils open, air enters the enlarged mouth and is simply forced into the lungs by contraction of the floor of the mouth, as soon as the nostrils are closed again.
Stomach
Digestion begins in the frog's mouth, which contains small, ineffective teeth in the upper jaw. The mouth also contains a sticky tongue that the frog can flick out to capture prey, which is passed by way of the esophagus to the stomach. A small intestine, large digestive glands, gall bladder, pancreas and liver, make up the remainder of the digestive system. Both liquid and solid waste leaves the body through the cloacal vent.