alimentary canal

DIGESTION ??

alimentary canal

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Comic version of the Alimentary Canal

Brief intro:

Tube through which food passes in animals – it extends from the mouth to the anus and forms a large part of the digestive system. In human adults, it is about 9 m/30 ft long, consisting of the mouth cavity, pharynx, oesophagus, stomach, and the small and large intestines. It is also known as the gut. It is a complex organ, specifically adapted for digestion and the absorption of food. Enzymes from the wall of the canal and from other associated organs, such as the pancreas, speed up the digestive process.

The muscles in the wall of the alimentary canal contract, mixing food with the enzymes and slowly pushing it along in the direction of the anus in a process known as peristalsis. Dietary fibre encourages this movement. The constant stream of enzymes from the canal wall and from the pancreas assists the breakdown of food molecules into smaller, soluble nutrient molecules, which are absorbed through the canal wall into the bloodstream and carried to individual cells. The wall of the canal receives an excellent supply of blood and is folded so as to increase its surface area. These two adaptations ensure efficient absorption of nutrient molecules.

MOUTH

The mouth, or oral cavity, contains the salivary glands, which release saliva to aid in the break down and decontamination of food entering the body. When food enters the mouth, the tongue mixes it with saliva during chewing and initiates swallowing

OESOPHAGUS

The esophagus is sometimes referred to as a gullet. It transports food by peristalsis from the pharynx, through the thoracic cavity, through the diaphragm to the stomach.

STOMACH

The stomach is a C-shaped digestive organ located on the left side of the abdominal cavity. It acts as the body's temporary storage tank and is where food is physically broken down. It has circular and longitudinal muscles. It also has an obliquely arranged layer of muscle that helps it to churn and mix food.

The mucosa, or inner lining, of the stomach is dotted with gastric pits which lead to gastric glands that secrete gastric juice. Gastric juice is used to break down food.

The Chief cells produce protein-digesting enzymes called pepsinogens. Some parietal cells produce corrosive hydrochloric acid, making the stomach acidic, which activates enzymes.

SMALL INTESTINE

This is the body's major digestive organ. It is here that usable food is prepared for the journey into the cells of the body.

Chemical digestion of food takes place in the small intestines.

Enzymes produced by the intestinal cells and pancreas are ducted into the duodenum through the pancreatic duct to complete the chemical break down of foods.Through the same area, bile enters through the bile duct.

All food absorption occurs in the small intestine.

Villi are the fingerlike projections of the mucosa that give it a velvety appearance. Within each villi is a rich capillary bed and a modified lymphatic capillary called a lacteal. Digested foods are absorbed through the mucosa cells into both the capillaries and the lateal.

LARGE INTESTINE

The job of the large intestine is to dry out the indigestible food residue by absorbing water. It is also responsible for eliminating these residues from the body as feces.

The large intestine also consists of the colon, the anal canal, and the rectum.

The large intestine has no villi, but instead has goblet cells that produce mucus for lubrication to remove the faeces to the rectum to be passed out.

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