Essential Nutrients and the Human Digestive Process

Nutritional Components: Organic and Inorganic

Nutrients are chemical compounds found in foods that all cells need to live. They are classified according to their origin:

Organic Nutrients

Carbohydrates

Carbohydrates (or carbs) are primary sources of energy and are consumed frequently. Examples include the sugar found in fruits, pasta, etc.

Proteins

Proteins are essential in the human diet, found in meat, dairy, legumes, eggs, and cereals. They serve several critical functions:

• Structural: Necessary for growth, tissue repair, etc.
• Contractile: Involved in muscle contraction.
• Transportation: Enables the transport of oxygen.
• Catalytic: The enzymes that regulate chemical reactions of metabolism are proteins.

Lipids (Fats)

Lipids are found in vegetable oils, animal fats, seeds, etc. They fulfill structural and energy functions, and excess is stored in the body.

Inorganic Nutrients

Minerals

Inorganic Minerals play key roles, regulating many metabolic processes. They are categorized by required levels:

• Macronutrients: Required in higher levels (e.g., calcium).
• Micronutrients: Required in smaller levels (e.g., iodine, copper).

Water

Water is the essential component for life and the most abundant component in food. Water is lost daily through sweat, urine, and feces, and recovered through drinks, milk, and foods such as fruits and vegetables.

The Digestive System and Nutrient Processing

In the context of nutrition, the digestive system is responsible for the ingestion of food, digestion, and egestion.

Stages of Digestion

1. Ingestion: The incorporation of food by mouth.
2. Digestion: The key process for nutrition, based on the incorporation of food and its transformation into simple molecules that are sent to the body's cells to be used as a source of energy or nutrients.
3. Egestion: The elimination of food waste through the anus.

Ingestion and Initial Processing

Food enters the digestive tract through the mouth. Each type of tooth has its role (cutting, tearing, and grinding food). While chewing, saliva moistens the food and provides the first digestive enzyme. The tongue mixes the food and allows the swallowing of the bolus, which passes into the pharynx.

Swallowing and Passage to the Stomach

The pharynx is a muscular organ that communicates with the nostrils at the top and the esophagus at the bottom. The esophagus is a cylindrical tube that connects the pharynx to the stomach. Swallowing is the process that allows the progress of the bolus into the esophagus first and then the stomach.

The Stomach

At the junction of the esophagus to the stomach is a muscular ring called the cardia that contracts and relaxes, preventing the acidic juices of the stomach from entering the esophagus. The stomach is a flexible, pouch-like organ that communicates with the esophagus through the cardia and the small intestine through another valve called the pylorus. It contains cells specialized in secretion and produces enzymes that make up the juice.