A smooth, shiny membrane called peritoneum can be seen lining the inside of the body wall. The visceral organs are suspended dorsally by a double membrane of peritoneum know as mesentery.
The liver is the largest organ lying within the body cavity. Its two main lobes, the right and left lobes, extend from the pectoral girdle posteriorly most of the length of the cavity. A third lobe much shorter lobe is located medially and contains the green gall bladder along its right edge.
The liver is rich in oil which stores energy for the shark. The oil's low specific gravity is also responsible for giving the shark a limited amount of buoyancy.
Esophagus
The esophagus is the cranial extension of the stomach and is short in length. It connects the pharynx and the stomach. The differentiation between the pharynx, the esophagus, and the stomach can be made by examining the mucosal surfaces of these organs.
Liver
The liver is divided into three lobes: the paired right and left lateral lobes and the singular median lobe. The lateral lobes extend caudally for the majority of the coelem’s largest of two fluid filled sacs. The liver is the largest organ and serves as a hydrostatic organ, helping the shark in buoyancy. The vast amount of oil created and stored in the shark’s liver, decreasing the weight of the shark and increasing its flotation.
Gall Bladder
The gall bladder is green in colour as it stores bile in its lumen. Bile is used to blend fats during digestion. The gall bladder is attached to the ventral surface of the median lobe of the liver. Bile is stored in the gall bladder until it is needed.
Bile Duct
Bile travels from the gall bladder to the first part of the intestine, the duodenal section, by means of the bile duct. It is light brown in colour and passes on the dorsal side of the duodenum for it goes through its wall.
Stomach
The shark’s stomach is J-shaped and is positioned ventral to the liver. The diameter of the stomach increases when traced distally. The part of the stomach between the esophagus and the sharp bend is known as the body. Following the bend, the stomach runs cranially for a short distance and is greatly reduced in diameter. When it bends again, it becomes parallel to the duodenal portion of the intestine.
Pancreas
The pancreas is divided into two lobes: the ventral lobe and the dorsal lobe. The ventral lobe is positioned on the ventral side of the duodenum and continues to the larger dorsal lobe of the pancreas, which is located dorsal to the stomach and duodenum. This exocrine gland is responsible for the bulk of the enzymes produced for digestion.
Spleen
Located at the bend of the stomach, the spleen is triangular in shape and dark in colour. It is connected to the stomach by the gastrosplenic ligament. The spleen’s function is the production, degradation, and storage of red blood cells and is integral to the shark’s immune system.
Small Intestine
Situated away from the duodenum, the intestine exhibits a large diameter. This section is called the spiral intestine and is so named because of its spiral fold. It makes up the majority of the intestine. Its many rungs are attached inside of the intestine and its spiral shape allows for an increase of internal surface area. With a greater surface area, the time food takes to digest is greatly reduced resulting in greater absorption of nutrients. The rungs of the intestine change direction near the middle of the intestine.
Rectum
The rectum is the part of the large intestine directly before the anus.
Papillae
The papillae are small projections located on the mucosal lining of the esophagus and contain the shark’s taste buds. The change between papillae of the esophagus and rugae of the stomach signifies the transition between these two organs.
Gastric Rugae
The gastric rugae line the stomach and function to increase the surface area of the stomach. When the stomach is empty, they protrude but when the stomach is full, they become flat.
Cloaca
The cloaca is where the digestive, urinary, and reproductive systems empty.
Rectal Gland
Also known as the digitiform gland and is a small cylindrical-shaped gland located dorsal to the colon. The Rectal Gland communicates with the colon via a small duct. The function of the rectal gland is to eliminate excess body salt by secreting it into the colon. Therefore, it plays an important role in osmoregulation.
Osmoregulation
Maintains control of the levels of water and mineral salts in the blood.This helps to maintain homeostasis, the maintenance of constant internal conditions, in the body.
Links/Resources:
http://www.pc.maricopa.edu/Biology/ppepe/BIO145/lab04_2.html
http://foggs.wikispaces.com/Shark+Digestion
http://en.wikipedia.org/wiki/Physical_characteristics_of_sharks
http://www.biology-online.org/articles/physical-characteristics-sharks/feeding-digestion.html
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