The Circulatory and respiratory System of a Boa Constrictor

The boa constrictor’s respiratory system is quite interesting. Boa constrictors have a small opening just behind their tongue called the glottis, which opens into the trachea, or more commonly known as the windpipe. The glottis, unlike mammals, is always closed forming a vertical slit, unless the boa takes a breath. Inside the glottis a small piece of cartilage vibrates when the boa forcefully expels air from its lungs, producing the boa constrictor’s famous, loud hissing sound. Boa constrictors are capable of extending their glottis out the side of their mouths while they eat, which allows for respiration while they consume larger prey items. Supported by cartilaginous rings, the trachea is a long, straw like structure. These rings are incomplete they look more like a C shape then an O shape, inside the snake. A thin membrane completes the C shape of the rings. Just in front of the heart is where the trachea usually terminates, and at this point the trachea splits into the two primaries bronchi, airways that direct air into either the left or right lung. Boa constrictors breathe simply by contracting the muscles between their ribs. Boa constrictors, unlike mammals, do not have a diaphragm. A portion of a boa constrictors lung nearest to its head has a respiratory function; this is where oxygen exchange occurs. The portion of the lung that is closest to the tail is more of an air sac. The inside of this air sac looks more like an expanded balloon than actual lung. There is no exchange of breath in the air sac by the tail.

The circulatory system or more commonly known as the cardiovascular system. The boa constrictors heart is encased in a sac, called the pericardium, which is located at the bifurcation of the bronchi. Considering that a boa has no diaphragm, the heart is able to move around. This adjustment protects the heart from potential damage when large prey is ingested and passed through the esophagus. The spleen is attached to the pancreas and the gall bladder and filters the blood. The thymus gland of the boa is located in the fatty tissue above the heart and is responsible for the generation of immune cells in the blood. The cardiovascular system of a snake is different because of the presence of a renal portal system in which the blood from the snake’s tail passes through the kidneys before returning to the heart. As snakes tubular bodies require all of their organs to be long and thin the vestigial left lung is often small or nonexistent.