Human Digestive System Explained: Processes & Organs

The Human Digestive System

The digestive system is responsible for processing food and transforming it so nutrients can be absorbed and distributed to every cell in the body.

The Respiratory System

The respiratory system captures the oxygen needed by cells and removes the carbon dioxide (CO2) produced during cellular metabolism.

The Circulatory System

The circulatory system transports nutrients and oxygen to cells and removes waste substances.

The Urinary System

The urinary system handles debris and waste products ejected from cell metabolism, which are carried by the circulatory system to be filtered and expelled.

Key Components of the Digestive System

• Digestive Tract: Measures about 8 meters and varies in diameter along its length. It begins in the mouth, continues through the pharynx, esophagus, stomach, small intestine, and large intestine, and ends at the anus.
• Accessory Glands: These organs discharge their secretions into the digestive tube. They include salivary glands (in the mouth), gastric glands (in the stomach), and intestinal glands (in the intestine). The liver and pancreas are also larger glands with significant digestive and hormonal functions.

Digestion Begins in the Mouth

Mastication: Mechanical Food Breakdown

Mastication is a process consisting of the mechanical crushing of food into smaller pieces to facilitate the digestive process. It is carried out by the teeth and helped by the tongue.

Types of Teeth and Their Functions:

• Incisors: Cut food.
• Canines: Tear food.
• Molars and Premolars: Grind food.

Insalivation: Food and Saliva Mixture

Insalivation consists of mixing the food with saliva produced by the salivary glands. The mixture of saliva with food is called the food bolus.

Key Functions of Saliva:

• Facilitates the passage of the bolus towards the pharynx and esophagus.
• Starts the digestion of certain food molecules, such as starch, thanks to the digestive enzyme called amylase.
• Destroys some bacteria present in food.

Swallowing: From Mouth to Esophagus

Swallowing is the passage of the food bolus towards the pharynx and esophagus.

Digestive Process in the Stomach

The stomach is an organ that communicates with the small intestine through a valve, normally closed, called the pylorus. The inlet valve, called the cardia, is always open.

The bolus in the stomach mixes with gastric juice and blends to form chyme, a more fluid substance than the original bolus.

Pepsin: A Key Digestive Enzyme

Pepsin is an enzyme responsible for protein digestion.

Hydrochloric Acid (HCl) in Digestion

Hydrochloric acid (HCl) activates pepsin and promotes its action, facilitating the breakdown of food and fibers. Additionally, it destroys bacteria that food may contain.