Anatomy (4&5)
Mouth-Since sharks swallow food as a whole or as large pieces, very little physical digestion happens in the mouth. Therefore, there is no report on secretion of digestive juices in the mouth.
Esophagus-Connects the oral cavity and pharynx with the stomach. It has "finger-like extensions", which prevents food from going out of the mouth. There are striated muscles, so esophagus can stretch when swallowing.
Stomach- Food is stored in stomach and digestion starts here. It secrets strong acids and enzymes (gastric acids and pepsinogen), which helps to digest what is eaten and turns food into liquid mush.
Pyloric Valve- The valve between stomach and the small intestine. Mush goes into intestine through this valve. The valve is small in size, so only liquid mush can enter the intestine.
Small Intestine- It consists of duodenum and valvular intestine (ileum). Duodenum is a short portion of the small intestine, which connects the stomach with the small intestine. Valvular intestine is the larger portion of small intestine. Compared to herbivores, the intestine is relatively short because meat is easier to digest than plants. There is "spiral valve" in the intestine, which is "screw-like and symmetrical shaped". The spiral valve adds surface area to enhance digestion and absorption.
Colon- Continuation of the small intestine.
Rectum and Cloaca-Collects waste products from colon and leads to excretion.