The Human Digestive System: Processes and Organs

Digestive System Processes

Ingestion

Seizure of food by the digestive system through the mouth.

Chewing

Spraying of food through chewing movements and mixing with saliva.

Swallowing

Movement of food from the mouth to the stomach.

Digestion

Mechanical and chemical breakdown of food into absorbable molecules.

Absorption

Passage of monomers of food molecules through the mucous membranes of the intestine into the bloodstream.

Peristalsis

Waves of rhythmic contractions that propel food along the digestive tract.

Elimination (Clarification)

Discarding of indigestible waste, called feces, which contains water, dead cells, dead bacteria, mucus, and gas.

Digestive System Phases

• Propulsion: Movement of food along the digestive tract.
• Secretion: Release of digestive juices.
• Absorption: Uptake of food, water, and electrolytes.

Digestive Organs

Mouth

Seizure, grinding (mechanical and chemical), and formation of the bolus; produces saliva.

Esophagus

Tube for the passage of food from the mouth to the stomach.

Stomach

Food storage, mechanical and chemical digestion; produces hydrochloric acid, enzymes (like pepsin, which digests protein), mucus, etc.

Small Intestine

Mechanical and chemical digestion. It has functions in the production of mucus, enzymes, and hormones that regulate digestion. It is the main site of food digestion and the primary site of absorption of the end products of digestion, electrolytes, vitamins, and water.

Colon

Does not have a mechanical or chemical function. It is the local storage of fecal products and has a great capacity to absorb water.

Related Functions and Substances

Secretion

The process of releasing digestive juices, enzymes, hormones, and mucus into the digestive tract.

Excretion

The process by which unnecessary or excessive substances are eliminated from the body.

Functions of Saliva

• Protecting the oral cavity and the epithelium of the oropharynx.
• Moistening the hard and soft tissues of the oral cavity.
• Indicates hydration levels.

Mucus

A protective substance lining the digestive tract. It helps lubricate food passage and protects the lining from digestive enzymes and acids. It helps bind indigestible material and is a component of stool.

Hydrochloric Acid

Produced in the stomach. It does not digest food itself but favors the action of pepsin. It has the function of maintaining an ideal pH in the stomach and transforms pepsinogen into pepsin.

Enzymes and the Pancreas

The pancreas produces digestive enzymes, such as trypsin, which are crucial for chemical digestion in the small intestine. While essential for digestion, the pancreas is considered an accessory organ rather than part of the digestive tract.