Digestion and Peristalsis

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4 processes take place…

… ingestion,

ingestion,

absorption and

egestion …

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FOOD

Food is any substance absorbed into the body that supplies nutrients to the body cells for energy, growth and repair of tissues, regulation of life processes and staying healthy.

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The IMPORTANCE of FOOD

Food serves as a fuel, giving energy and heat to the body cells.

Food supplies the building material for growth and repair and replacement of damaged tissues

Food supplies important regulating substances that are essential for the correct functioning of cells and metabolic processes

Food is used by the body to stay healthy and protect it from diseases

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DIET

Diet refers to the daily food we eat and liquids we drink

A balanced diet contains all the nutrients in sufficient quantities and correct proportions needed for normal growth and good health

Malnutrition refers to the harmful effects on the body of eating to little or eating to much of the wrong kinds of food.

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Water in your dietWater is important in a healthy diet because:

Most of your body consists of water

All the chemical reactions in your body take place in water.

Water serves as a solvent for nutrients, wastes and gases

Water transports nutrients and waste products in the body

Water plays a role in digestion

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DEFICIENCY DISEASESResulting from not eating enough proteins or vitamins or minerals

Disease Cause Result

Beriberi Lack of vitamin B Nervous system affected

Scurvy Lack of vitamin C Gums bleed and teeth loosen

Pellagra Lack of nicotinic acid (part of vitamin B)

Dermatitis, dementia, diarrhoea

Rickets Lack of vitamin D Bones weaken and are malformed

Kwashiorkor Lack of protein, to much carbohydrates

Swollen stomach, skin appears red, hair loses colour and organs waste away

Marasmus General lack of food Thin, weak and stunted growth

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Kwashiorkor

Scurvy

Rickets

Beriberi

Marasmus

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EATING DISORDERS

This occurs when you have access to a healthy balanced diet and choose not to eat, or to eat too much

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Disorder Cause Result

Anorexia nervosa

Psychological illness that makes a person have an intense fear of gaining weight

Fatigue, muscle weakness, yellowish skin, brittle hair, osteoporosis and amenorrhea

Anorexia bulimia

Psychological illness that makes a person overeat and then cause themselves to vomit (Binge and Purge)

Fatigue, muscle weakness and rotting teeth

Obesity Overeating and lack of exercise

Cholesterol, high blood pressure and heart failure

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You are a tube inside a tube…

The tube starts

here:

And although

there are a few

twists and turns

along the way…

It comes out here:

Anything that goes

in the top hole

(mouth) does not

become part of the

body until it is

absorbed (taken in)

in a part called the

small intestine.

This tube is

called the

ALIMENTRY

CANAL or GUT.

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Fill in the labels

on this diagram

of the digestive

system

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Peristalsis

The contraction and relaxation of the muscles in the oesophagus to pass the food along

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http://www.lionden.com/peristalsis.htm17

The Mouth

Food is crushed and ground up by teeth

The salivary glands make saliva which makes the food moist and easy for swallowing

Amylase enzyme (in saliva) breaks the carbohydrate starch down into glucose.

Tongue keeps food between teeth when chewing, mixes food with saliva, moulds food into a bolus, assists with swallowing process

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Stomach

Stomach muscles contract and relax to mechanically break down the food

They also mix the food up with gastric juice and hydrochloric acid The acid kills germs in the food

Food spends about 3-4 hours in here.

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PANCREAS

Secretes enzymes which digest food

Also secretes hormones: Insulin and glucagon which control the blood sugar levels

If your insulin doesn’t work porperly you develop Diabetes

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The Duodenum (first section of small intestine – just out of the

stomach) The first part of the small intestine is

called the duodenum.

Food, still mixed with gastric juice is squirted into it from the stomach.

The food is now a semi liquid, highly acidic mush.

It needs to be neutralised and digestion needs to be continued…

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Liver

Gall bladder

Duodenum

Pancreas

Stomach

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Absorption

The food is then ABSORBED through the wall of the small intestine into the blood stream.

To do this effectively, the small intestine needs to have a large surface area.

This is achieved in the following ways:

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Absorption The tube is over 6 meters long

The inner wall of the tube has bends in it

The wall is covered in villi (small finger-like structures)

Outer wall

Inner wall

Pathway

for Food

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After absorption: The Liver

The liver produces bile which digests fatty foods

The gall bladder temporarily stores bile

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Egestion

Any indigestible food (e.g. fibre) passes into the large intestine (colon).

Water is absorbed back into the body.

The food becomes a solid waste called faeces.

Faeces are stored in the rectum and removed through the anus. This removal is called EGESTION.

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Ingestion• Intake of food

Digestion• Covert food into soluble nutrients

Absorption

• Soluble nutrients taken up by the blood stream

Egestion• Undigested food passes out of the body

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