Describe the various digestive glands associated with alimentary canal.

The digestive glands associated with the alimentary canal include the salivary glands, liver and pancreas. 

1. Salivary Glands: 

• There are three pairs of salivary glands which open in buccal cavity.
• Parotid glands are present in front of the ear. 
• The submandibular glands are present below the lower jaw.
• The glands present below the tongue are called sublingual. 
• Salivary glands are made up of two types of cells. 
• Serous cells secrete a fluid containing digestive enzyme called salivary amylase. 
• Mucous cells produce mucus that lubricates food and helps swallowing. 

2. Liver:

• Liver is dark reddish-brown coloured largest gland of the body, weighing 1.2 to 1.5 kg, in adults. 
• Situated in right upper portion of the abdominal cavity, below the diaphragm.
• Divided into 2 lobes, right and left. 
• A thin connective tissue sheath called Glisson’s capsule covers the liver and invaginates inside to divide the liver into cord like structures called hepatic lobules which are functional units of liver containing hepatic cells (hepatocytes).
• Each hepatic lobule is polygonal in shape. At the junction of adjacent lobules, a triangular portal area is present. 
• In this portal area a branch of each of hepatic artery, hepatic portal vein and bile duct are present. Lobule consist of cords of hepatic cells which are arranged around a central vein. 
• In between the cords of hepatic cells, spaces called sinusoids are present through which the blood flows. In the sinusoids, phagocytic cells called Kupffer cells are present. 
• Hepatic cells secrete bile. Bile is carried by hepatic ducts in a thin muscular sac called gall bladder. The duct of the gall bladder and hepatic duct together form common bile duct.
• Liver synthesizes vitamins A, D, K and B , blood proteins. 

3. Pancreas: 

• Pancreas is a leaf shaped heterocrine gland present in the gap formed by bend of duodenum under the stomach. 
• Exocrine part of pancreas is made up of acini, the acinar cells secrete alkaline pancreatic juice that contains various digestive enzymes.
• Pancreatic juice is collected and carried to duodenum by pancreatic duct. 
• The common bile duct joins pancreatic duct to form hepatopancreatic duct. It opens into duodenum. Opening of hepato-pancreatic duct is guarded by sphincter of Oddi. Endocrine part of pancreas is made up of islets of Langerhans situated between the acini.
• It contains three types of cells acells which secrete glucagon, P-cells which secretes insulin and 5 cells secrete somatostatin hormone.
• Glucagon and insulin together control the blood-sugar level.
• Somatostatin hormone inhibits glucagon and insulin secretion.