Digestive System

Organs of the Digestive System and their Functions

The digestive system is responsible for breaking down food into smaller molecules that can be absorbed and used by the body.

1. Mouth:
   • Function: Ingestion of food. Mechanical digestion (chewing) and chemical digestion (saliva containing amylase begins carbohydrate digestion).
2. Pharynx:
   • Function: Passageway for food from the mouth to the esophagus.
3. Esophagus (Food Pipe):
   • Function: Transports food from the pharynx to the stomach through peristalsis (wave-like muscular contractions).
4. Stomach:
   • Function: Stores food, mixes it with gastric juices (containing hydrochloric acid and pepsin for protein digestion), and churns it into a semi-liquid paste called chyme.
5. Small Intestine:
   • Function: The primary site for the completion of digestion and absorption of nutrients. It receives digestive juices from the liver (bile) and pancreas (pancreatic enzymes).
6. Large Intestine:
   • Function: Absorbs water and electrolytes from the remaining indigestible food matter and transmits the useless waste material from the body.
7. Rectum:
   • Function: Stores feces before elimination.
8. Anus:
   • Function: The opening through which feces are expelled from the body.

Process of Digestion

Digestion involves the breakdown of complex food substances into simpler, absorbable forms.

Carbohydrates

• Mouth: Salivary amylase begins the digestion of complex carbohydrates (starch) into simpler sugars.
• Small Intestine: Pancreatic amylase and intestinal enzymes (e.g., maltase, sucrase, lactase) complete the breakdown of carbohydrates into monosaccharides (e.g., glucose), which are then absorbed.

Proteins

• Stomach: Pepsin (activated by hydrochloric acid) begins the digestion of proteins into smaller polypeptides.
• Small Intestine: Pancreatic proteases (e.g., trypsin) and intestinal peptidases break down polypeptides into amino acids, which are then absorbed.

Fats

• Small Intestine: Bile (produced by the liver, stored in the gallbladder) emulsifies fats (breaks large fat globules into smaller ones). Pancreatic lipase then breaks down emulsified fats into fatty acids and glycerol, which are absorbed.