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2.2 The Digestive and Excretory Systems

• Nutrients are substances the body requires for energy, growth, development, repair, or maintenance.

• We get nutrients from what we eat and drink.

See pages 64 - 65

•Four Food Groups•Grain products•Vegetables and fruit•Milk products•Meat and alternatives

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Types of Nutrients

• Carbohydrates The bodies quickest source of

energy Examples include: rice,

vegetables, cereal, and bread

• Proteins Used to build parts of your bodies

muscles, skin, hair, and nails Examples include: fish, meat,

eggs, nuts, soy products

See pages 66 - 69

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Types of Nutrients

• Fats Used to build cell membranes and

can be stored for future energy. Examples include: butter, vegetable

oil, and meat

• Minerals and Vitamins Needed in small amounts to perform

various body functions Two common minerals and vitamins

are calcium and vitamin D

See pages 66 - 69

Water is not a nutrient but is necessary for life!

Types of Nutrients

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(c) McGraw Hill Ryerson 2007

The Four Stages of Digestion

See page 70

• The process in which food is broken down, nutrients are absorbed, and wastes eliminated is called digestion and occurs in the digestive system.

• The fours stages of digestion are: Ingesting Digesting Absorbing Eliminating

(c) McGraw Hill Ryerson 2007

(c) McGraw Hill Ryerson 2007

Stage 1: Ingesting

See page 71

• Ingesting, or ingestion, means to bring food into the body. This is the starting point of the digestive process.

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Stage 2: Digesting

See page 71

• Mechanical digestion occurs when your teeth and tongue break food into small enough pieces to swallow.

• Each small piece of food is called bolus.

• Chemical digestion occurs when saliva begins to break down the bolus.

• An enzyme in your saliva begins to break down simple and complex carbohydrates.

The Mouth

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Stage 2: Digesting

See page 72

• When you swallow, your food enters the esophagus.

• The esophagus is a long muscular tube that carries food to your stomach.

• The bolus is pushed through the esophagus in a process called peristalsis.

The Esophagus

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Stage 2: Digesting

See page 73

• Inside the stomach is gastric juice, which is very acidic.

• The stomach walls are lined with mucus to protect the tissue from being damaged by the acid.

• An enzyme called pepsin, present in gastric juice, breaks down protein.

• The bolus that enters your stomach breaks down into a liquid called chyme.

The Stomach

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Stage 2: Digesting

See page 74

• The first metre of the small intestine is called the duodenum.

• The pancreas adds enzymes that help break down the carbohydrates, protein, and fat in the chyme.

• The liver produces bile which is stored in the gall bladder.

• Bile breaks the globs of fat into smaller droplets.

The Small Intestine

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(c) McGraw Hill Ryerson 2007

Stage 3: Absorbing

See page 75

• Absorption is the process in which nutrients and water are absorbed by the small and large intestine.

• The small intestine is covered with villi to help increase the rate at which nutrients are absorbed.

• The large intestine absorbs water and some minerals.

The Small and Large Intestine

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Stage 4: Eliminating

See page 76

• Any solid material, undigested by the end of the large intestine is called feces.

• Feces are stored in the rectum until they are eliminated through the anus.

• Liquid and gas wastes are removed by your excretory system. The main organs in your excretory

system are your kidneys and your bladder.

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(c) McGraw Hill Ryerson 2007

Kidney: filters the blood and removes waste

KIDNEY

Ureter: Moves the urine to the bladder via peristalsis

KIDNEY

URETER

Bladder: stores the urine

KIDNEY

URETER

BLADDER

Urethra: when the sphincter relaxes, the urethra carries the urine outside the body.

20 cm in males

4 cm in females

KIDNEY

URETER

BLADDER

URETHRA

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Eating Disorders

• Anorexia nervosa is a disorder when a person severely restricts what they eat.

• Bulimia nervosa is a disorder when a person eats large amounts of food and then vomits or takes laxatives to get rid of the food before it is completely digested.

See page 77

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Take the Section 2.2 Quiz