mam,pls explain about the digestive system in human beings in detail.

Asked by deepa1973 | 8th Jun, 2015, 04:28: PM

Expert Answer:

Human digestive system consists of following parts:

Mouth

  • The space where the food is chewed and mixed with saliva is called the mouth or mouth cavity.
  • The mouth is bound in the front by upper and lower lips and laterally by the jaws.
  • The mouth opens into the buccal cavity which has teeth, a tongue and three pairs of salivary glands.
  • During ingestion, food is taken in through the mouth.
Tongue
  • The tongue is a fleshy muscular organ attached to the floor of the buccal cavity at the back region of the mouth.
  • The upper surface of the tongue contains several papillae or sensory buds.
  • The tongue helps in mixing of saliva with the food while chewing.
  • It also helps in mastication and swallowing of food.
  • The tongue has several taste buds at its tip which detect different tastes of food.
Teeth
  • The upper and lower jaws are embedded with teeth.
  • Teeth help to cut food into small pieces, to chew and to grind it.

Salivary Glands

  • There are three pairs of salivary glands in the wall of the buccal cavity which open into the mouth. They are the parotid glands, submaxillary glands and sublingual glands.
  • Salivary glands secrete saliva which converts starch into maltose and dextrose sugars.

Pharynx

  • The pharynx is the common passage for food and air leading to the oesophagus and the larynx, respectively.
  • Food passes through the pharynx to the oesophagus.

Oesophagus

  • The oesophagus, also known as the food pipe, is a narrow tube that connects the pharynx to the stomach.
  • The oesophagus pushes the chewed food down to the stomach. It takes only about seven seconds for food to pass through the oesophagus to the stomach for digestion to occur.

Stomach:

  • The stomach is a J-shaped muscular, bag-like organ. It consists of four conspicuous regions—cardiac, fundus, body and pyloric.
  • The stomach is lined internally by a mucous membrane. It contains a number of glands known as gastric glands. Gastric glands are responsible for the secretion of gastric juices and mucin.
  • The gastric glands release three gastric juices—hydrochloric acid, enzyme pepsin and mucus.
  • Hydrochloric acid gets mixed with food and kills the bacteria present in food.
  • Pepsin breaks down proteins into peptones and proteases.
  • Lipase converts fats into fatty acids and glycerol.
  • Mucus is a slimy fluid. It is secreted by all regions of the gut.

Small Intestine:

  • The small intestine is a very long tube found in the abdomen. It is about 6–7 metre in length and about 2.5–3 cm wide.
  • The small intestine is divisible into three regions—duodenum, jejunum and ileum.
  • The small intestine serves both for digestion and absorption. It receives two digestive juices—the bile and the pancreatic juice in the duodenum. The bile and the pancreatic juice enter the duodenum through a common duct called the pancreatic duct.
  • Intestinal glands are present in the walls of the ileum which secrete the intestinal juice. The intestinal juice contains peptidase, maltase, sucrase, lactase and lipase. These enzymes complete the process of converting proteins to amino acids, complex carbohydrates to glucose and fats to fatty acids.
  • The digested food is absorbed by the blood vessels in the small intestine.

Large Intestine:

  • The large intestine extends from the ileum to the anus and is about 1.5 metre in length. It is divided into the caecum, colon and rectum.
  • The large intestine does not contain any digestive gland or secretes any enzyme.
  • It is the place for temporary storage of undigested food. It helps in absorbing water and salts from undigested food.

Liver and pancreas are the glands associated with the digestive system

Liver:

  • The liver is a reddish-brown gland situated in the upper part of the abdomen on the right side.
  • It secretes bile.
  • Bile juice helps in digestion of fats. It breaks down large fat globules into smaller ones. Bile salts reduce the surface tension of fats and break them into tiny droplets. This is called emulsification. Emulsification helps lipase to act on fats by providing greater surface area for the action of enzyme.

Pancreas:

  • The pancreas is a long, leaf-like transparent gland, about 15-20 cm long. It is a yellowish-grey gland present on the left side of the duodenum below the stomach.
  • The pancreas secretes pancreatic juice. It has digestive enzymes trypsin, enterokinase, steapsin and pancreatic amylase, which partly digest proteins, fats and carbohydrates. Pancreatic juice has a large amount of sodium bicarbonate, which neutralises the acid present in chyme and makes it alkaline.

Answered by Hemangi Binny | 8th Jun, 2015, 05:50: PM