UNIT 3: The Human Digestive System

Question 1

the digestive system

Answer 1

functions in nutrition.

long tube stretching the entire length of the body - called the alimentary canal

Question 2

herbivore

Answer 2

an animal that eats only plant material e.g. deer

Question 3

carnivore

Answer 3

an animal that eats only animal material e.g. hawk

Question 4

omnivore

Answer 4

an animals that eats both animal and plant material e.g pig

Question 5

nutrition

Answer 5

the way in which organisms obtain and use food

Question 6

ingestion

Answer 6

the taking in of food into the mouth

Question 7

digestion

Answer 7

the breakdown of food.

1. mechanical - the physical breakdown of large food particles into smaller ones.
2. chemical - the breakdown of food using enzymes.

Question 8

absorption

Answer 8

the passage of single biomolecules from the gut into the cells lining the gut.

Question 9

egestion

Answer 9

the getting rid of undigested material

Question 10

mouth

Answer 10

also known as the buccal or oral cavity.
it contains teeth and touth that both function in mechanical digestion.
saliva also acts in the mouth.

Question 11

teeth

Answer 11

there are 32 teeth in a fully formed healthy adult mouth: 8 incisors, 4 canines, 8 premolars, 12 molars.
the incisors function in cutting through food.
the canines function in tearing food.
the premolars and molars have cusps that function in grinding and crushing food.

Question 12

salivary glands

Answer 12

produce saliva which is a mixture of water, mucous and the enzyme amylase which digests starch into maltose.

Question 13

pharynx

Answer 13

involved in swallowing

Question 14

oesophagus

Answer 14

tube that is approx. 30cm long and carries food from the pharynx to the stomach by contraction of smooth muscle in its wall - peristalsis.

Question 15

peristalsis

Answer 15

rhythmical waves of contraction of smooth muscle pushing food along the alimentary canal in one direction only.

Question 16

stomach

Answer 16

muscular bag that receives food from the oesophagus. it stores food for approx. 2 hours and mixes it with gastric juice.

Question 17

gastric juice

Answer 17

produced by the gastric glands of the stomach wall (mucosa). it is composed of:

1. water- moistens the food and acts as a medium in which chemical digestion occurs. it also takes part in the hydolysis reactions that are important in chemical digestion.
2. mucous - protects the internal wall of the stomach from digesting itself.
3. hydrochloric acid - creates an acidic environment within the stomach (with a pH as low as 1). the acid helps to digest proteins by denaturing them and killing bacteria.
4. pepsin - released from the cells of the gastric glands in an inactive form called pepsinogen. this is so that the enzyme does not digest the cell before being released. once pepsinogen comes into contact with the acidic conditions of the stomach it is converted to the active pepsin which digests proteins into peptides.

Question 18

duodenum

Answer 18

30cm long tube that receives chyme from the stomach. it is also the section of the alimentary canal where most chemical digestion occurs.

Question 19

pancreas

Answer 19

organ that produces pancreatic juice.

Question 20

pancreatic juice contains

Answer 20

1. water - acts as the medium in which enzyme reactions occur and takes part in hydrolysis reactions.
2. mucous - protects the internal surface of the duodenum and ileum.
3. sodium bicarbonate - neutralises acidic chyme entering from the stomach.
4. lipase - digests lipids into fatty acids and glycerol.
5. amylase - digests starch into maltose.

Question 21

liver

Answer 21

largest internal organ of the human body. functions:

• breaks down old, worn out red blood cells and the haemoglobin.
• breaks down excess amino acids, in the process called deamination, into urea.
• produces bile, which contains water, mucous, salts (for emulsifying lipids), cholesterol and bile pigments (bilirubin and biliverdin)
• stores fat-soluble vitamins A,D,E &K.
• stores minerals, such as iron.
• produces plasma proteins
• stores glycogen - which is the storage form of carbohydrates in animals.
• detoxifies alcohol and other toxins present in the body.

Question 22

gall bladder

Answer 22

small, bag-like organ located underneath the liver. it stores bile produced by the liver before releasing it into the duodenum.

Question 23

bile duct

Answer 23

carries bile and pancreatic juice to the duodenum.

Question 24

ileum

Answer 24

6m long tube functioning in absorption of the products of digestion. The mucosa of the ileum has special adaptations that enable it to carry out absorption very efficiently:

• villi and microvilli - increase the surface area of the ileum available for absorption.
• a good blood supply - enable the products of digestion to be transported away quickly to where they are needed.
• a lymph supply (each villus has a lacteal) - responsible for the absorption of lipids.
• it is made of muscle - allows peristalsis.
• it is very long - increased surface area.
• villi have thin walls - improves absorption

Question 25

appendix

Answer 25

small, blind-ending tube attached to the caecum that is thought to function as part of the defence system.

Question 26

caecum

Answer 26

first part of the large intestine. functions in absorption of water. it contains a large amount of bacteria that function in producing vitamins and preventing the growth of pathogenic bacteria in the gut.

Question 27

colon

Answer 27

part of the large intestine. functions in absorption of water, vitamins and minerals. there are bacteria present in the colon that produce vitamins and prevent growth of pathogenic bacteria

Question 28

rectum

Answer 28

any undigested and unabsorbed material left at the end of the process is stored in the rectum as faeces before being released.

Question 29

anus

Answer 29

opening of the rectum. it is a sphincter that is consciously controlled

Question 30

balanced diet

Answer 30

one that contains all 7 nutrients in the correct proportions

1. proteins
2. lipids
3. carbohydrates
4. vitamins
5. minerals
6. fibre
7. water

Question 31

food pyramid

Answer 31

there are recommended daily amounts of different food types to have in the diet. an imbalance in any one of the nutrients or food types can lead to malnutrition

Question 32

Dental formula

Answer 32

2(I 2/2 C 1/1 P 2/2 M 3/3)