A4 Digestive System

Question 1

What is the function of the digestive system?

Answer 1

To break down large, insoluble food molecules into smaller, soluble molecules that can be absorbed into the blood stream or lymphatic system

Question 2

What are the three main parts of the digestive system?

Answer 2

The gastrointestinal tract, liver, gallbladder, pancreas, digestive enzymes (amylase)

Question 3

What is the duodenum and what happens in there?

Answer 3

• The first part of the small intestine
• Food mixed with stomach acid enters here
• Bile enters from gall bladder
• Digestive enzymes from pancreas enter

Question 4

What is the function of villi and how is it specialised to do its role?

Answer 4

Absorbs nutrients into blood due to large surface area, therefore increasing the rate of absorption

Question 5

What is villi and microvilli?

Answer 5

Villi - folds in wall of the intestine
Microvilli - folds of the cell membrane of individual cells

Question 6

Describe cotransport of glucose and sodium

Answer 6

1) Sodium potassium pump brings in potassium and pumps sodium out of villi using active transport (low concentration of sodium in villi)
2) Sodium diffuses from high concentration to low concentration into the villi and brings glucose with it
3) Glucose will diffuse from a high concentration to a low concentration into the blood

Question 7

What is the ileum and what happens in there?

Answer 7

• The final section of the small intestine
• This is where nutrients are absorbed into the blood stream
• Lined with villi and microvilli
• Begins to absorb water

Question 8

What happens in the colon?

Answer 8

• Absorbs water from undigested food
• Forms the faeces

Question 9

What is coeliac disease?

Answer 9

An autoimmune disease that is triggered by eating gluten

Question 10

Which vessels are the breakdown products of proteins and carbohydrates absorbed into?

Answer 10

Capillaries
Amino acids (from proteins) and sugars (from carbohydrates) are absorbed by diffusion from the small intestine into the capillaries

Question 11

Which vessels are the breakdown products of lipids (fatty acids and glycerol) absorbed into?

Answer 11

Fatty acids and glycerol are absorbed into the lymphatic vessels called lacteal and later filtered into venous (vein) circulation

Question 12

How does diffusion play an important role in digestion

Answer 12

Small food molecules move passively down their concentration gradient
- Food molecules are at high concentrations in the small intestine into
- Food molecules are at low concentration in the blood capillaries and lineal vessels

Question 13

What are the organs in the gastrointestinal tract?

Answer 13

Mouth, oesophagus, stomach, duodenum, jejunum, ileum, large intestine, anus, rectum

Question 14

What happens in the mouth?

Answer 14

Ingested food is broken down by the teeth and mixed with saliva
Saliva contains amylase which begins the chemical digestion of starch

Question 15

What happens in the oesophagus?

Answer 15

It connects the throat to the stomach allowing food to pass down once it has been swallowed
There are four layers:
mucous membrane to secrete mucus for smoother movement of food
submucosa which holds the mucous membrane in its position
a thick layer of muscle that causes peristalsis
an outer protective coating

Question 16

What happens in the stomach?

Answer 16

Food is churned and mixed with stomach acid and enzymes

Question 17

What happens in the duodenum?

Answer 17

Food passes in small quantities from the stomach into the duodenum. Further digestion takes place.
Input of pancreatic juices with hydrolytic enzymes and bile from liver
Lipids are broken down into fatty acids.
Protein is broken down into amino acids.

Question 18

What happens in the jejunum and ileum?

Answer 18

From the jejunum, food passes into the last part of the small intestine the ileum
The products of digestion are absorbed across the walls of the ileum and into the bloodstream or lymphatic system

Question 19

What happens in the anus?

Answer 19

Stretching of the rectum wall initiates a defaecation reflex and forces faeces into the anal canal
Impulses reach the brain and we make a decision as to whether to open the external anal sphincter

Question 20

What happens in the large intestine?

Answer 20

The large intestine absorbs water (by osmosis), minerals and vitamins

Question 21

What happens in the rectum?

Answer 21

Any undigested food passes into the rectum where it is stored as faeces

Question 22

What is the main function of the kidney?

Answer 22

The kidney is involved in filtering waste and excess water from the blood.

Question 23

What does the ureter do?

Answer 23

Carries urine from the kidneys to the bladder

Question 24

What does the bladder do?

Answer 24

It stores urine

Question 25

What is the function of the renal veins?

Answer 25

Carries blood that has been cleaned back to the body

Question 26

What is the function of the renal arteries?

Answer 26

Carries blood that contains waste from the body back to the kidneys

Question 27

What does urine flow through to leave the body?

Answer 27

The urethra

Question 28

What are the waste products released from the body?

Answer 28

CO2 and urea

Question 29

What are the three outlets in the urinary system?

Answer 29

Renal artery, renal vein and the ureter

Question 30

How is urea formed?

Answer 30

By the breaking down of ‘excess’ amino acids in the liver

Question 31

Where are the kidneys located in the body?

Answer 31

On the back wall partially protected by the ribcage

Question 32

When blood is filtered, what is left behind?

Answer 32

Proteins and blood cells are never filtered as they are too big to fit through the filter

Question 33

What molecules should be found in the urine?

Answer 33

Water and sodium molecules and glucose

Question 34

What is found in the cortex?

Answer 34

Bowmans capsule, Glomerulus