DIGESTION SYSTEM

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DIGESTION SYSTEM

Food is our fuel, and its nutrients give our bodies' cells the energy and substances they need to operate. But before food can do that, it must be digested into small pieces, so the body can absorb and use.

At its simplest, the digestive system is a tube running from mouth to anus. It’s chief goal is to break down huge macromolecules (proteins, fats and starch), which cannot be absorbed intact, into smaller molecules (amino acids, fatty acids and glucose) that can be absorbed across the wall of the tube. The alimentary tract of the digestive system is composed of :

· mouth

· pharynx

· esophagus

· stomach

· small intestine

· large intestine

· anus

The tongue and teeth are accessory structures located in the mouth. The salivary glands, liver, gallbladder, and pancreas are major accessory organs that have a role in digestion. These organs secrete fluids into the digestive tract.
Food undergoes three types of processes in the body:

· digestion

· absorption

· elimination

After the nutrients are absorbed, they are available to all cells in the body and are utilized by the body cells in metabolism.

Alimentary Tract

1. MOUTH

The MOUTH contains the tongue and tooth. That is the salivary glands which secrete saliva and the teeth, 32 in number of which 8 are called incisors, 4 canines, 8 premolars, and 12 molars. Once food is in the mouth, the tastebuds begin determining the chemicals within the food via their nerve endings, in order to give you the taste sensations of salt, sweet, sour or bitter. As your teeth chew and grind the food, breaking it down, it's mixed with saliva. Saliva also contains enzymes, which moistens the food so it can pass easily through the digestive tract.

2. PHARYNX

The pharynx is a fibromuscular passageway that connects the nasal and oral cavities to the larynx and esophagus. It serves both the respiratory and digestive systems as a channel for air and food.

3. ESOPHAGUS

After the food has been swallowed, food passes down the throat to the esophagus, the first of a succession of hollow organs that transport their contents through muscular contractions known as peristalsis. The oesophagus can contract and relax in order to propel the food onwards, and each mouthful of food takes about six seconds to reach the stomach once swallowed.

4. STOMACH

The stomach, which receives food from the esophagus. The stomach serves as a temporary store for food, then dissolved food.

5. SMALL INTESTINE

Digestion and absorption of fats, protein and carbohydrates occurs in the small intestine.

6. LARGE INTESTINE

From the small intestine, undigested food (and some water) travels to the large intestine. By the time food reaches the large intestine, the work of absorbing nutrients is nearly finished. The large intestine's main function is to remove water from the undigested matter and form solid waste that can be excreted.

7. ANUS

Anus is where the discharge of waste from the digestive process.