Digestion

Label the following:A:………………… B: …………………C:…………………D:…………………E:…………………F:…………………G:…………………H:…………………I:…………………J:…………………K:…………………

A

B

C

D

E

F

G

H

K J I

Mouth

Appendix

Stomach

RectumLarge intestine/ colonSmall intestinePancreas

Anus

LiverOesophagus

Salivary gland

Mouth Each Tooth has a special shape and role:

1. Incisors : sharp to cut and bite food.

2. Canines: Sharp and pointed to cut and tear.

3. Premolars: have cusps and grooves to grind , crush & chew the food.

4. Molars: same as premolars but larger in size

Salivary glands produce Saliva ; which contains:

5. Amylase enzyme

6. Mucin (slippery substance)

CanineIncisors

Premolars

Molars

crown

root

EnamelDentine

Pulp cavity

Gum

NervesBlood vessels

Jaw bone

Tooth decayDiscuss what brings about tooth decay and what could be done to prevent it.

A:………………… B: …………………C:…………………D:…………………E:…………………F:…………………G:…………………H:…………………

A B C

D

E

F

G

H

Label the following:

Duodenum

Pancreas

Pancreatic duct

Stomach

Oesophagus

Liver

Bile duct

Gall bladder

Stomach

Mechanical Digestion: muscles of stomach keep moving to churn up food just like a blender.

Chemical digestion: The gastric glands produce the gastric juice that contains:1. Pepsin enzyme2. HCl acid

Other glands produce mucus to protect the wall of the stomach from the corrosive acid.

Page 54 in BFU

Pancreas

Produces Pancreatic juice that contains1. Protease enzyme2. Amylase enzyme3. Lipase enzyme4. Sodium hydrogen

carbonate

The pancreatic juice travels through the pancreatic duct to mix with food in the duodenum.

Discuss the role of each of the four constituents of the pancreatic juice.

Liver and gall bladder

The liver produces the bile juice which is stored in the gall bladder and is released through the bile duct to mix with food in the duodenum.

The bile juice contains:1. Bile salts2. Bile pigments3. Sodium hydrogen

carbonate

Bile salts help to emulsify fat; change large drops of fat to small droplets of fat. How is emulsification useful?

Bile salts

Ileum

The ileum is lined with many finger-like projections called villi which help to increase the surface area of the ileum. The increased surface area helps to increase the rate of digestion and absorption.

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Villus

1. Each villus is covered with a one cell thick layer called the epithelium.

2. There is a network of blood capillaries that help to absorb glucose and amino acids.

3. A blind-ended lacteal absorbs the products of digestion of fat.

4. It contains muscles to move around; mixing food with enzymes.

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Features that increase the efficiency of the ileum.

Think of the following questions to find how villi are designed to maximize absorption.• Why so many villi?• Why a thin layer epithelium?• Why do epithelial cells have microvilli?• Why a dense network of capillaries?• Why does lacteal move?

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Large intestine (colon)

Most of the food has been digested and absorbed in the small intestine. In the large intestine some salts and water are absorbed. The rest of the food remains is mostly fibres that cannot be digested , they will be stored in the rectum and released through the anus. This is called egestion.

Liver and associated blood vessels

The liver is the only organ that has a blood supply from an organ other than the heart. The Hepatic portal vein carries blood rich in glucose and amino acids and other molecules that must be modified before circulating around the body.

Hepatic artery (from heart)

Hepatic vein (to heart)

Hepatic portal vein (from ileum)

Liver

Roles of liver1. It adjusts the blood glucose level. 2. Some of the glucose is used by liver cells in respiration. The pancreas

secretes insulin hormone when the blood glucose level rises above normal. The hormone stimulates the liver to change the glucose into glycogen to be stored in the liver cells.

3. Makes blood proteins e.g. fibrinogen using amino acids. 4. Performs deamination of excess amino acids to give two parts: Nitrogen-

containing part which become urea and is excreted by the kidney. Remainder that can be respired to release energy.

5. Stores iron from worn-out red blood cells, which it breaks down, excreting bile pigments.

6. Makes poisons harmless, this is called detoxification.7. Makes bile salts which emulsify the fats in the intestine8. Stores vitamins A & D.9. The heat produced by the many metabolic reactions help to keep the body

warm.

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Part of alimentary canal

Juices secreted from

Name of juice secreted

Juice contents

What is digested

Other points

Mouth

Stomach

Small intestine

Large intestine

Salivary glands

Saliva •Amylase•Mucin

Starch maltose

Mucin makes food slippery

Wall of stomach

Gastric juice

•HCl•Pepsin

Protein amino acids

Starch maltoseProtein amino acidsFats fatty acids + glycerol

Liver

Pancreas

Bile juice

Pancreatic juice

Bile saltsAlkaline sol amylaseproteaseLipaseAlkaline sol

HCl kills microbes

Bile salts emulsify fats

Absorption of water & digested food molecules

None None None NoneAbsorption of water and minerals