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Dig system review

Dig system review

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THE DIGESTIVE SYSTEM

Miller & Levine BIOLOGY (pp 875-881; 889-890) Page 1

FUNCTIONS OF THE DIGESTIVE SYSTEM: What are the functions of the digestive system?

General:

• The conversion of foods into useful molecules both in human and in animals is the job of the digestive system.

• The digestive system converts food into small molecules that can be used by the cells of the body.

• Food is processed by the digestive system in 4 phases:

o Ingestion – process of putting food into your mouth – the

opening to the digestive tract.

o Digestion – as food passes through the digestive system, it is

broken down in 2 ways:

▪ Mechanical digestion - physical breakdown of large

pieces of food into smaller pieces. These smaller pieces

can be swallowed and accessed by digestive enzymes.

▪ Chemical digestion – the enzymes break down food into

the small molecules that the body can use.

o Absorption – once food has been broken into small molecules,

it can be absorbed by cells in the small intestine. From the small

intestine, the molecules enter the circulatory system which

transports them throughout the body.

o Elimination – the digestive system cannot digest and absorb all

the substances in food that enter the body. Some materials, such

as cellulose, travel through the large intestine and are eliminated

from the body as feces.

THE PROCESS OF DIGESTION: What occurs during digestion?

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THE DIGESTIVE SYSTEM

Miller & Levine BIOLOGY (pp 875-881; 889-890) Page 2

General:

• The human digestive system, like those of other chordates, is built around an alimentary canal – a one-way tube that passes

through the body.

• During digestion, food travels through the mouth, esophagus, stomach and small intestine.

• Mechanical digestion and chemical digestion are the two processes by which food is reduced to molecules that can be

absorbed.

• Both mechanical digestion and chemical digestion start in the mouth.

The Mouth:

• As one takes food in the mouth, the work of the digestive system begins.

• Teeth and saliva start to work on your food first.

• Chewing begins the process of mechanical digestion.

• Chemical digestion begins as digestive enzymes in saliva start the breakdown of complex carbohydrates into smaller

molecules.

Teeth

✓ Anchored in the bones of the jaw.

✓ The surfaces of the teeth are protected by a coating of mineralized enamel.

✓ The teeth do much of the mechanical work of digestion.

✓ The incisors, cuspids and bicuspids cut into and tear at food.

✓ The molars grind and crush food into a fine paste that can be swallowed.

✓ The tongue moves food around so that it comes in contact with your teeth.

Saliva

✓ As the teeth cut and grind the food, the salivary glands secrete saliva, which helps to

moisten the food and make it easier to chew.

✓ The release of saliva is under the control of the nervous system and can be triggered by the scent of food.

✓ Not only eases the passage of food through the digestive system but also begins the process of chemical digestion.

✓ Saliva contains an enzyme called amylase that begins to break the chemical bonds in starches, forming sugar.

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THE DIGESTIVE SYSTEM FUNCTIONS OF THE DIGESTIVE SYSTEM: What are the functions of the digestive system? General: • • • 1 5 2 4 3 The conversion of foods into useful molecules both in human and in animals is the job of the digestive system. The digestive system converts food into small molecules that can be used by the cells of the body. Food is processed by the digestive system in 4 phases: o Ingestion – process of putting food into your mouth – the opening to the digestive tract. o Digestion – as food passes through the digestive system, it is broken down in 2 ways: ▪ Mechanical digestion - physical breakdown of large pieces of food into smaller pieces. These smaller pieces can be swallowed and accessed by digestive enzymes. ▪ Chemical digestion – the enzymes break down food into the small molecules that the body can use. o Absorption – once food has been broken into small molecules, it can be absorbed by cells in the small intestine. From the small intestine, the molecules enter the circulatory system which transports them throughout the body. o Elimination – the digestive system cannot digest and absorb all the substances in food that enter the body. Some materials, such as cellulose, travel through the large intestine and are eliminated from the body as feces. THE PROCESS OF DIGESTION: What occurs during digestion? Miller & Levine BIOLOGY (pp 875-881; 889-890) Page 1 THE DIGESTIVE SYSTEM General: • • • • The human digestive system, l ...
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