Digestive glands

a) The Liver:

• It is the site of glycogen storage, it produces a variety of substances, including enzymes that help with digestion and it is a major chemical factory producing various hormones as well as numerous other important molecules.
• The liver has no specific shape in fish and generally molds itself into the space around the stomach and the heart.
• Bile is secreted from the liver and poured into the duodenum region of the intestine and the cardiac part of the intestinal bulb.
• The liver usually has two separate lobes, but it may have only one (some members of the Salmonidae) or even three as in the Mackeral (Scomber Scomber).
• The gall bladder is usually found somewhere within the liver, it secretes substances that attack fats and help them to be broken down.
• The liver always has at least one, and sometimes as many as eight ducts leading into the first part of the intestines.

b) The Pancreas:

• The pancreas which is an exocrine and endocrine organ may be a discrete organ or it may be diffused in the liver or the alimentary canal.
• The Pancreas is well developed in lungfish, sharks, rays, and most juvenile fish, however, in many teleosts it becomes quite reduced and diffused in adults.
• In sharks and rays, it is quite distinct from the liver, but in those teleosts wherein it is found, it is often partially embedded in the liver. It is also diffused in the alimentary canal ina few fishes.
• The pancreas secretes enzymes such as trypsin (attacks proteins), amylases (attack carbohydrates), and lipases (attack fats) into the intestines either through sharing one of the hepatic ducts (those belonging to the liver) or through its pancreatic duct.
• The exocrine cells are found in periphery places. The endocrine cells are also called the Islet of Langerhans that secrete insulin.
• But exocrine secretion is called pancreatic juice which mostly amylase enzymes.