Table of Contents
Digestive Glands in Scoliodon:
Digestive glands associated with the alimentary canal of Scoliodon are the liver, pancreas, rectal glands, spleen and all of them have a major function in the complete process of digestion but the function of the rectal gland or caecal gland is not completely known to us.
Liver:
The digestive system of Scoliodon has a bilobed liver, the liver is yellowish and has a large size in Scoliodon. Two lobes of the liver are connected to the septum transversum by a ligament, on the posterior region, the two lobes remain freely in the abdominal body cavity.
The gall bladder is V-shaped and is embedded in the right lobe of the liver, the bile is temporarily stored in the gall bladder. A small-sized bile duct connected to the anterior part of the intestine, the bile juice reaches into the intestine from the gall bladder through the bile duct.
The liver destroys the old erythrocytes of the blood, store glycogen and fat, the bile is secreted by the liver collected by two ducts each from one liver lobe and open into the bile duct.
Pancreas:
The pancreas is bilobed and whitish, a small duct collects the pancreatic juice and pours it into the intestine, the pancreatic duct opens into the intestine just opposite to the opening of the bile duct into the intestine.
Among the two-lobe of the pancreas, the dorsal lobe is much longer than the ventral lobe of the pancreas.
Caecal or Rectal Gland:
On the dorsal side of the rectum, a finger-like gland is presently known as the rectal gland or caecal gland, the rectal gland opens into the rectum by a small duct. The rectal gland secret a special fluid into the intestine, the inner wall of the rectal gland is lined by cuboidal epithelium, the rectal gland is highly vascularized and has lymphoid tissue.
Spleen:
In the cardiac stomach and pyloric stomach, we can see a fringe-like large gland which is actually the spleen. Through the spleen attached to the stomach but the spleen has no direct role in digestion, the spleen is actually a part of the circulatory system, the spleen is a lymphoid organ and it takes part in the production of lymphocytes.
Feeding Mechanism in Scoliodon:
The food of Scoliodon is generally the smaller-sized fish, Scoliodon is a predator and obviously, they are carnivorous. But along with fishes Scoliodon also feeds on other animals in ocean-like crabs, lobster, worms. The teeth present in Scoliodon are not for chewing, they are used for capturing the prey, Scoliodon just swallows their prey without chewing.
Digestion in Scoliodon:
They swallow their prey and the food inside the buccal cavity does not digest, in the buccal cavity of Scoliodon there is no digestive gland so the digestion in Scoliodon does not start from the buccal cavity.
Then the food passes from the buccal cavity to the stomach through the pharynx and the esophagus. But in the pharynx and esophagus, no digestion occurs because there is no digestive gland present in the pharynx and esophagus, the first digestion starts in the stomach.
The stomach secret gastric juice in which hydrochloric acid and pepsin are present, the pepsin breaks down the protein into syntonin, peptones, and protease. Then the semi-digested acidic foods reach the intestine, the bile juice makes the acidic foods alkaline.
The pancreatic juice contains trypsinogen, amylopsin, and lipase, the trypsinogen work on protein, the amylopsin work on starches, and the lipase work on fat but Scoliodon is unable to digest chitin. In the intestine of Scoliodon, a longitudinal spiral-like fold is present, it is known as the spiral valve or scroll valve.
In Scoliodon the spiral valve help in the proper absorption of food, the spiral path of the scroll valve retard the movement of food inside the intestine. The spiral valve also increases the absorption surface of the intestine, when food move inside the spiral valve slowly then the intestine gets much time for absorption of food.
Detailed Study On
Coelom and Viscera in Scoliodon
Placoid Scales In Scoliodon (Exoskeleton)
Skin of Scoliodon (Integument)
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