Food is an important source for human beings to derive nutritional energy. Carbohydrates, proteins, and fats are the major components of food. Human beings cannot utilize these major components in their complex form or in the natural form. So, the digestive system in the human beings helps to convert these complex biomolecules into the simpler substances. The alimentary canal and digestive glands are the parts of the digestive system. Let us take an overview of the digestive glands like salivary gland, liver and pancreas and their role in digestion.
The alimentary canal is associated with the digestive glands in the human digestive system. Three major glands play an important role in the digestion. These are as follows:
- Salivary gland.
The salivary glands are one of the important exocrine glands. The main function of the salivary gland is to produce saliva. Saliva has many functions in the digestion process as follows:
- It is used to lubricate the mouth.
- It helps to swallow the food.
- It helps to protect the teeth from bacterial infections.
- It aids in the food digestion.
Salivary glands consist of the following three pairs.
- Parotid glands: These are located on the inside of the cheeks.
- Submandibular glands: These are located under the lower jaw bone of the mouth.
- Sublingual glands: These are located in the mouth below the area of the front end of the tongue.
The liver is one of the digestive glands and plays an important role in the digestive system. It is the largest gland of the human body. It is located in the abdominal cavity. The liver is connected to the two following large blood vessels.
- Hepatic vein – It is used to carry the blood, which is rich in oxygen.
- Portal vein – It is used to carry the blood, which is rich in digested nutrients.
The liver consists of two hepatic lobules which are made up of hepatic cells. Lobules are the structural and functional unit of the liver. Each lobule is overlaid by the Glisson’s capsule which is a thin connective tissue. Hepatic cells secrete the bile and pass into the gallbladder through the hepatic ducts. The hepatic duct from the liver and cystic duct from the gallbladder forms the common bile duct.
The pancreas is a gland which has two functional units to secrete both endocrine and exocrine enzymes. It is located between the duodenum limbs. Pancreas consists of two portions as follows:
- Endocrine portion – It is used to secrete the hormones, insulin, and glucagon which circulate into the bloodstream.
- Exocrine portion – It is used to secrete the digestive enzymes into the small intestine which are called as pancreatic juice.
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