Digestive System

Question 1

6 Steps of digestion

Answer 1

1. Ingestion
   - Intake of food through MOUTH
   >involves mechanical (teeth) and chemical (saliva) digestion
2. Propulsion
   - Involuntary, propulsive muscles perform peristalsis to move bolus down alimentary canal (PHARYNX and ESOPHAGUS)
   > mechanical
3. Mechanical Digestion
   - STOMACH muscles churn to turn food into chyme
4. Chemical digestion
   - Enzymatic breakdown into chemical constituents in STOMACH
5. Absorption
   - Uptake of nutrients into the bloodstream through he mucosal epithelial cells, daily in small intestine
6. Defecation
   There are undigested materials from the food that is eliminated from the bod through the faeces.

Question 2

Order of organs involved in digestion

Answer 2

Mouth
Pharynx
Oesophagus
Stomach
Pyloric Sphincter
- Liver produces bile which is stored in gallbladder and released into small intestine
Duodenum
Small intestine
Caecum
Large intestine
Rectum
Anus

Question 3

alimentary canal

Answer 3

mouth, pharynx, oesophagus, stomach, small intestine, large intestine

Question 4

Accessory organs

Answer 4

Teeth, tongue, salivary glands, liver, gall bladder, pancreas

Question 5

Mucosa tissue (alimentary canal)

Answer 5

Innermost layer
Functions:
- secreting mucous, enzymes, hormones
- Absorption of nutrients
- Protection from pathogens

Question 6

Muscularis tissue (alimentary canal)

Answer 6

Layers of muscle extending in two directions

• circular
• longitudinal

Question 7

Submucosa tissue (alimentary canal)

Answer 7

Contains glands, nerve fibres and blood vessels

Question 8

Serosa tissue (visceral peritoneum) (alimentary canal)

Answer 8

Membrane secretes slippery, watery fluid

reduces friction as digestive organs contract and move

Question 9

Name the different teeth and description 🦷

Answer 9

Incisors - Cutting pieces of food
Canines (cuspids) - Tear and pierce
Premolars (bicuspids) - Crushing
Molars (tricuspids) - Grinding

Question 10

Hard and soft palate

Answer 10

hard- Bony roof of mouth

soft - rest of mouth

Question 11

Processes from mouth to oesophagus

Answer 11

mastication 
bolus
deglutition
pharynx
oesophagus

Question 12

Rugae

Answer 12

Soft wrinkles in stomach that stretch when stomach becomes full

Question 13

Intestinal juice

Answer 13

Breakdown sugar:
- Maltase
- Sucrase
- Lactase
Breakdown protein:
- Peptidase
- Enterokinase

Question 14

Why is bile important?

Answer 14

Bile does not contain any digestive enzymes, but bile salts are very important in the digestion of fats/lipids. They emulsify the fat, breaking it into tiny droplets. This is a form of mechanical digestion, increasing SA on which lipase can act.

Question 15

Pancreatic juice

Answer 15

The pancreas produces pancreatic juice, which contains enzymes including:
- pancreatic amylase
helps breakdown starch
-Pancreatic amylase
breaks down proteins into small chains of amino acids
- Ribonuclease and deoxyribonuclease
digest DNA and RNA
- Pancreatic lipases
break down fats into fatty acids and glycerol

Question 16

Appendix

Answer 16

Small tube attached to the caecum (large intestine) and has no function in humans.

Question 17

Constipation

Answer 17

As water is absorbed, the faeces become drier and harder than usual. Caused by a lack of fibre in diet.

Question 18

Diarrhoea

Answer 18

Frequent defecation of watery faeces. Caused by irritation in small/large intestine which increases peristalsis so that the contents of the intestines moves through faster with less absorption. Caused by bacteria or infection.

Question 19

Explain:

Pepsinogen -> Pepsin

Answer 19

The stomach wall secreted the inactive substance pepsinogen, and the HCl in gastric juice converts the substance into the active substance pepsin. The enzyme pepsin breaks the bonds between certain amino acids that make up protein molecules.