Nutrients in Food and How the Digestive System Works

Food Composition and Nutrients

Simple and Compound Foods

• Simple: These consist of a single type of substance. Examples include oil and table sugar.
• Compounds: These are composed of different substances. Examples include bread and milk.

Inorganic Substances

These are not unique to living matter.

• Water: The most abundant compound in living things and the medium in which life develops within cells.
• Minerals: Chlorides, carbonates, and phosphates, along with sodium, potassium, and calcium, are found in bones and teeth, providing hardness. They are also dissolved in all body fluids, such as blood, tears, and sweat.

Organic Substances

Carbohydrates

The simplest carbohydrates, such as glucose and maltose, have a sweet taste. Glucose is a sugar that cannot be decomposed into simpler ones. Maltose is formed by the joining of two glucose molecules.

Lipids

These include fats and cholesterol. They are generally insoluble in water. Vegetable or unsaturated fats are liquid at room temperature and are called oils. Animal or saturated fats, such as butter and tallow, are solid at room temperature.

Proteins

Examples include hemoglobin and gluten. They are macromolecules formed by the union of hundreds or thousands of simple molecules called amino acids.

Vitamins

Required in small amounts, vitamins are essential for the body to function properly. They are obtained through foods that contain them.

The Human Digestive System

• Mouth: The opening containing the teeth and tongue. The teeth are made of a material similar to bone called dentin, which is covered by enamel. The inner pulp contains nerve endings and blood vessels. The tongue consists of powerful muscles and contains taste buds.
• Pharynx: It passes food from the mouth to the esophagus.
• Esophagus: The tube where food moves from the pharynx to the stomach.
• Stomach: A widening of the digestive tract. Its walls have very powerful muscles. Food enters through the cardia, and the pylorus connects the stomach to the small intestine.
• Small Intestine: A long tube, folded many times, that connects the stomach to the large intestine. The first section immediately after the stomach is the duodenum.
• Large Intestine: A thicker duct than the small intestine, which it surrounds. Its most important, U-shaped part is called the colon. At the junction of the colon with the small intestine is the cecum, whose closed end has a thin extension called the appendix. The colon communicates with the outside through the rectum, which ends at the anus.