CH5: Human Digestive System

Question 1

Describe the process in which humans gain nutrition:

Answer 1

1. ingestion
2. digestion
3. absorption
4. assimilation

Question 2

What is the passage that leads from the mouth to the anus?

Answer 2

the alimentary canal

Question 3

Define ‘digestion’

Answer 3

The process that breaks down complex food substances into simple, soluble molecules that are small enough to be absorbed into the cells.

Question 4

Describe the physical process of digestion:

Answer 4

• MECHANICAL BREAK DOWN of food into SMALLER, SIMPLER, more SOLUBLE pieces
• increase SA-to-vol ratio for faster rate of chemical digestion by digestive enzymes

Question 5

Describe the chemical process of digestion:

Answer 5

• breakdown of large food molecules into small, simple, soluble molecules
• catalysed by digestive enzymes
• through hydrolytic reactions

Question 6

The act of taking food into the mouth is called?

Answer 6

ingestion

Question 7

How is food physically digested in the mouth?

Answer 7

CHEWING breaks down food pieces to increase SA-to-vol ratio for faster rate of chemical digestion by digestive enzymes

SALIVA produced by the salivary glands lubricate and soften food so it is easier to swallow

The chewed food is ROLLED into a bolus by the tongue before it is swallowed

Question 8

How is food chemically digested in the mouth?

Answer 8

SALIVA produced by the salivary glands contain AMYLASE which digests STARCH into MALTOSE

Question 9

What is the optimum pH in the mouth?

Answer 9

6.5 to 7.5 (close to neutral)

Question 10

Does starch continue to be digested in the oesophagas?

Answer 10

Yes

Question 11

How is food moved through the alimentary canal?

Answer 11

• through PERISTALSIS
• a rhythmic, wave-like muscular contraction of the wall
• to mix and propel food substances towards the stomach

Question 12

How does the stomach chemically digest food?

Answer 12

gastric glands secrete gastric juice
> consists HYDROCHLORIC ACID and PEPSIN (a protease)
> HCl provide acidic medium for enzymes to work by changing inactive forms of enzymes to active forms
> Pepsin digests proteins into polypeptides by hydrolysis

Question 13

Function of HCl in stomach

Answer 13

1. kill bacteria in food
2. provide acidic medium for enzymes to work
3. changes inactive forms of enzymes to active forms

Question 14

How is food physically digested in the stomach?

Answer 14

CHURNED and mixed with gastric juices by PERISTALTIC contractions of the stomach wall