The Digestive System and Nutrition: A Comprehensive Guide

Posted on Nov 9, 2024 in Biology

Feeding and Nutrition

Feeding

Feeding is the ingestion of food from our environment. Our diet consists of the food we select.

Nutrients

Nutrients are substances in food that provide us with the matter and energy necessary for our vital functions.

Characteristics of Food

Quantity

The amount of nutrients varies depending on the food. Bread and pasta are rich in carbohydrates, meat provides proteins, and lettuce and other green vegetables are good sources of vitamins.

Quality

Higher quality foods provide nutrients that our body cannot manufacture by itself.

Nutritive Value

The nutritive value of food is determined by the types and amounts of nutrients it contains.

Classification of Food

Food is varied and classified into seven groups according to their origin and nutrient content:

  1. G-1: Milk and dairy products.
  2. G-2: Meat, fish, and eggs.
  3. G-3: Legumes, potatoes, and nuts.
  4. G-4: Vegetables.
  5. G-5: Fruits.
  6. G-6: Cereals, cereal products, sugar, and sweets.
  7. G-7: Fats, oils, and butter.

Nutrition

Nutrition is an involuntary process by which our body extracts, transforms, and incorporates the nutrients it needs from food.

Types of Nutrients

Essential Nutrients

These are nutrients the body cannot produce.

Nonessential Nutrients

These are nutrients the body can synthesize from others during metabolic processes.

Roles of Nutrients

Energy

Nutrients provide the energy necessary for vital functions and heat.

Structural/Plastic

Nutrients provide the materials we use to build and repair our own tissues.

Regulator

Nutrients, like vitamins and minerals, control the numerous chemical reactions that occur in the body.

Classification of Nutrients

Carbohydrates

Carbohydrates are the primary energy source. The simplest forms are sugars like glucose and sucrose, which are the main energy components of cells.

Lipids

Lipids, such as fats, form the structure of cell membranes.

Proteins

Proteins are made up of amino acids. They are involved in all biological functions, such as carrying oxygen to tissues and enabling muscle contraction.

Vitamins

Vitamins are essential nutrients. Deficiencies can cause diseases. There are water-soluble vitamins (B and C) and fat-soluble vitamins (A, D, E, and K).

Minerals

Minerals are essential nutrients. Some, like phosphorus and calcium, are crucial for bone structure.

Water

Water is the major component of the body, making up 60% of adult weight.

Basal Metabolic Rate (BMR)

BMR is the amount of energy needed to maintain vital functions at rest.

The Digestive System

The digestive system provides nutrients to cells by digesting food.

Components of the Digestive System

The Gut

The gut consists of the mouth, pharynx, esophagus, stomach, small intestine, and large intestine.

Attached Glands

These glands secrete substances that aid in digestion:

  • Salivary Glands: Three pairs of glands (parotid, submandibular, and sublingual) that release saliva into the mouth.
  • Pancreas: Has gastrointestinal (secretes pancreatic juice) and endocrine (releases substances into the blood) functions.
  • Liver: Secretes bile, which is stored in the gallbladder. The liver also stores glucose and removes toxins from the blood.

Anatomy of the Digestive Tract

Parts

  • Mouth: The roof of the mouth is called the palate. It separates the mouth from the nostrils. The uvula hangs at the back. Food is crushed by the teeth.
  • Pharynx: Connects the mouth to the esophagus. The epiglottis covers the airway during swallowing.
  • Esophagus: A tube behind the trachea that carries the food bolus from the pharynx to the stomach.
  • Stomach: A muscular sac that expands when filled with food.
  • Small Intestine: A long tube with loops. Its walls contain glands that secrete intestinal juice.
  • Large Intestine: U-shaped with three areas: cecum, colon, and rectum, ending at the anus. The cecum contains the vermiform appendix.

Digestion

Digestion is the process of extracting and absorbing nutrients from food. There are three types:

  • Mechanical Digestion: Involves chewing and the movement of food through the digestive tract.
  • Chemical Digestion: Digestive juices containing enzymes break down food into nutrients.
  • Absorption of Nutrients: Occurs mainly in the small intestine.

Chewing and Swallowing

Chewing

Chewing fragments food and mixes it with saliva from the salivary glands.

Swallowing

Swallowing moves the chewed and moistened food from the mouth to the esophagus.

Chemical Digestion Processes

Mouth

Saliva contains mucus, which lubricates food, and amylase, an enzyme that begins carbohydrate digestion.

Stomach

Gastric juices contain hydrochloric acid and pepsin.

Small Intestine

Bile from the liver aids in lipid digestion. Pancreatic juice and intestinal juice are also released here.

Healthy Digestive Habits

  • Wash hands before eating.
  • Wash fruits and vegetables.
  • Avoid very hot or very cold foods.
  • Chew food thoroughly.
  • Maintain good oral hygiene.