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Digestion
Sharks swallow their food whole, or in large pieces. Very little physical digestion occurs in the mouth. Food then travels down a short, and wide esophagus, which is hard to distinguish from the stomach, and then into the stomach. A sharks stomach contains very strong stomach acids and enzymes to dissolve most of what they swallow. Contents that can't be digested, are vomited. The stomach contents then enter the intestines (spiral valve) which is short with a large surface are, due to the unfolding of the inner surface. The spiral valve then leads to the rectum, and then the cloaca. Cloaca is a common opening for the urinary, digestive, and reproductive systems.
Respiration
Most species of shark can be motionless and still breath by gulping water. This form of breathing is called buccal pumping. Pelagic group of sharks that must constantly swim in order to breath or they will drowned, are called obligate ram ventilators. This group includes the great hammer head shark. Ram ventilation is moving through water letting the water run into their mouth, and move over their gills.
Nervous System
The hammerhead's nervous system is made up of the brain, spinal column, and a network of branching nerves. They have an astonishing since of smell. they are capable of detecting one part, per million of blood in sea water. Their eyesight is like ours, with the ability to dilate, increasing visibility in water.
Circulatory System
In the vicinity of the sharks head is their heart. The heart has two chambers, an atrium, and a ventricle. The heart is an S shaped tube that pumps blood through afferent branchial artery's (paired dorsal aorta), through the tissue of the body, and then back to the heart through veins.
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