Vestigeal organs: During the process of evolution, they have lost their function in some organisms, while they are still functioning in others. Appendix, external ear muscles and tail muscles are few examples of vestigeal organs in humans.

Villi are finger-like projections in the walls of the small intestine. Due to the presence of villi, the surface area of the small intestine is tremendously increased. This aids in the process of absorption.

Saliva helps in lubricating food and thus helps in swallowing.

In the mouth cavity, food is churned and mixed with the saliva which contains digestive enzymes.

Peristaltic waves are the rings of contraction in the intestinal wall. They move forward resulting in propulsion of food.

Small intestine is a coiled muscular tube, divided into three parts : duodenum, jejunum and ileum. Rectum is a part of the large intestine.

Thyroid gland is not a part of the digestive system.

They are distributed through blood.

There are three pairs of salivary glands: parotid, sublingual and submaxillary. The gland shown in this diagram is the submaxillary gland.

It is known as the esophagus.

The gall bladder is a globular structure, which stores and concentrates bile. Whenever need for bile arises, it is discharged into the duodenum.

Bile is secreted in the liver.

Pancreas secretes pancreatic juice which contains digestive enzymes.

It is absorbed in the large intestine.

Most of the digested food is absorbed in the small intestine.