Digestive System

In the previous lesson we discussed how the food enters the body, and how it is pushed along the gut. In this lesson we will discuss the organs that are followed by the oesophagus. To visit the first lesson on digestive system, click here.

1. Stomach:

Stomach is a muscular bag, with thick and well developed walls. The stomach has numerous pits which lead to gastric glands that secrete gastric juice. (The role of gastric juice will be further discussed in the upcoming lessons) The stomach is able to store food for few hours. There is a ring of muscle called the pyloric sphincter located where the stomach joins the small intestine. When this ring relaxes the entrance into the small intestine opens.

2.The Small Intestine:

The small intestine of a u-shaped duodenum, jejunum and the much coiled ileum. In humans the small intestine is 6 meters long. The walls of the small intestine contain glands which secrete digestive enzymes. The small intestine is also adapted to absorb broken molecules of food.

3.The Large Intestine:

The large intestine is 1.5 meters long. It is much broader than small intestine. The large intestine consists of colon and the rectum. At the junction between the colon and small intestine are the appendix (no specific function) and caecum (sac-like structure). These two, caecum and appendix have no specific function in humans. Faeces are stored in the rectum, when the rectum contracts the faeces are expelled from the anus. The main function of the colon is to absorb water and mineral salts from the undigested food material. No digestion occurs in large intestine.

Organs associated with the gut:

The liver: It is dark red and is made up of five lobes; three on the right and two on the left. The liver cells produce and secrete bile. Bile is greenish-yellow alkaline solution containing bile salts and bile pigments. Bile pigments give bile its color and are removed from the body through the faeces.

The Gall bladder: It is a greenish-yellow bag which temporarily stores bile in it. Bile flows into the duodenum via the bile duct.

The Pancreas: It is a gland connected to the duodenum via the pancreatic duct. The pancreas produce the pancreatic juice which contains digestive enzymes. The pancreas also secrete insulin and glucagon.

The role of these organs in digestion, will be discussed in detail in the upcoming lessons.

*All pictures are taken from google*