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 Nutrients1. 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:agesex

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

http://www.innerbody.com/anim/mouth.html

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.