Shark Wallpapers | Top Shark Backgrounds

The shark is considered one of the largest known cartilaginous fishes lacking a gas-filled swim bladder to maintain buoyancy in deep water. In place of the swim bladder, sharks contain an organic compound known as squalene in their liver oil. Thirty percent of the body mass of a shark comprises the liver. Sharks obtain pure oxygen from seawater as it is transmitted from one-gill slit to another. The interesting thing about sharks’ gill slits is that they are not camouflaged by a protective covering. Instead, gill slits are present behind the head in a row. A spiracle is one large gill slit located behind the eyes of a bunch of shark species. Spiracles play a significant role in ram ventilation, during which water is passed from the oral cavity to the gills, and oxygen is extracted from it.

Sharks contain two-chambered hearts that play a significant role in converting deoxygenated blood into oxygenated blood in a cyclic manner. Most shark species are poikilothermic, which means that their internal body temperature equates to the external body temperature. Cold-blooded sharks contain a rectal gland at the terminals of small intestines, and the major objective of this rectal gland is to secrete enough chlorides as researchers have shown that urine excreted by sharks does not contain enough salts. Digestion is a long process in sharks, and it is reported that unpleasant or unwanted food items never make their way to the stomach. Instead, unwanted items are ejected.

Wanted items are moved from the oral cavity to a stomach that is J-shaped. The initial stages of digestion are completed in the stomach before the food is passed on to the intestine. In comparison to the digestive system of mammals, sharks have a system with shorter intestines. Some sharks, like swell sharks, appear fluorescent when subjected to sky blue light.