Human Digestion & Human Nutrition

Nutrition All the activities by which an organism obtains and uses food for growth and repair of cells.

Nutrients The substances in food that an organism needs and uses for its life functions.

Function of Nutrients 1.They act as a fuel to provide energy for the life activities of cells. 2.They supply chemicals needed for growth and repair of cells. 3.They regulate the metabolic processes needed for the proper functioning of the cell.

Nutritional requirements vary with an individuals: age sex activities

Six Types of Nutrients 1. Carbohydrates 2. Proteins 3. Lipids 4. Vitamins 5. Minerals 6. Water

Carbohydrates Main source of energy for body functions. Ex: bread, pasta, and fruits

Lipids Supply of energy Part of cell membrane Storage form of excess food in the body. Ex: butter, bacon, and nuts

Proteins Used for growth and repair of body tissue. Ex: meat, milk, eggs, and fish

Water Solvent in which chemical reactions take place. Aids in the transport of materials in the body.

Minerals Make up the body structures. Ex: calcium- make up bone and teeth iron- part of hemoglobin (red blood cells)

Vitamins Needed for normal metabolism. Ex: vegetables, fruits, and meats

Carbohydrates, proteins, and lipids need to be digested by the body in order to be absorbed into the blood. Vitamins, minerals, and water do not need to be digested and are easily absorbed into the blood.

Digestive Tract Also known as the GI tract Consists of a one-way digestive tract. Food is moved through the tract by slow, rhythmic muscular contractions called peristalsis.

Organs of the Digestive System 1. pharynx (throat) 2. mouth (teeth) 3. tongue 4. stomach 5. pancreas 6. small intestine 7. rectum 8. salivary glands 9. esophagus 10. liver 11. gall bladder 12. large intestine 13. appendix 14. anus

(II) Sequence (way food travels) oral cavity (mouth)  esophagus  stomach  small intestine  large intestine  rectum  anus  toilet

1. Oral Cavity Ingestion of food Teeth are used in the mechanical breakdown of food which serves to increase surface area for enzyme action. Carbohydrate digestion begins in the mouth by enzymes secreted from the salivary glands. Ex: amylase

2. Esophagus Connects mouth to stomach. Peristaltic action of the esophagus moves food to the stomach.

3. Stomach Lining of the stomach contains gastric glands that secrete gastric juice. This gastric juice contains enzymes and hydrochloric acid. Protein digestion begins here.

4. Small Intestine Carbohydrate, protein, and lipid digestion is completed here. Nutrient absorption occurs in the small intestine. Structures like the gall bladder and pancreas secrete enzymes into the small intestine for digestion.

Gall Bladder Bile is produced in the liver and stored in the gall bladder. Bile is secreted by the gall bladder into the small intestine for emulsification. Emulsification- the breakdown of fats.

Pancreas Located near the stomach For digestive purposes, the pancreas secretes: protease- breakdown of proteins lipase- breakdown of lipids (fats)

5. Large Intestine Water absorption only NO nutrient absorption occurs here. Undigested material is known as feces. The large intestine passes the feces into the rectum.

6. Rectum Temporarily stores the feces.

7. Anus Opening through which feces passes out of the body. (Egestion)

(III) Nutrient Absorption Takes place in the small intestine. Chemical digestion in humans is accomplished by Hydrolysis and the use of enzymes.

End Products of Digestion Proteins  amino acids Carbohydrates  glucose Lipids  3 fatty acids + glycerol

The end products of digestion are absorbed in the small intestine by finger-like projections called villi.

Villus Lacteal- absorption of fatty acids and glycerol. Capillary network- absorption of glucose and amino acids.

Roughage Is an indigestible material in food that provides bulk, which stimulates the muscles of the digestive tube and thus keeps food moving through it. sources: fruits, vegetables, and grains. Lack of roughage in the diet is one cause of constipation.

Disorders of the Digestive Tract

Anorexia Nervosa A condition in which there is a severe loss of weight accompanied by symptoms of nutritional deficiencies. Psychological condition where a person is unable to take or retain food due to an excessive concern about obesity.

Ulcers * An erosion of the surface of the digestive tract associated with pain, nausea, and vomiting.

Constipation * Too much water is absorbed in the large intestine. *Also can exist due to lack of roughage.

Diarrhea * Decreased water absorption and increased peristaltic activity of large intestine. * Results in an increased, multiple, watery feces.

Appendicitis *An inflammation of the appendix. *Usually feces that infects the appendix.

Gallstones * An accumulation of hardened cholesterol deposits in the gall bladder.