Digestive System - Mouth to Stomach

Question 1

Digestion

Answer 1

Food must be broken down into nutrients to be absorbed - involves interaction of many systems (circulatory, endocrine, nervous, muscuskeletal)

Question 2

Chemical Digestion

Answer 2

The breakdown of food through the actions of enzymes

Question 3

Mechanical Digestion

Answer 3

The physical breakdown of food by chewing, the muscular churning of the stomach, and emulsification of fats

Question 4

Digestion Steps

Answer 4

1. Ingestion - eating
2. Digestion - breakdown of food
3. Absorption - transfer of nutrients into the bloodstream
4. Egestion - removal of waste

Question 5

Physical Digestion in the Mouth

Answer 5

Food is broken into smaller pieces by teeth (incisors & canines cut and grab, molars crush & grind)

Question 6

Chemical Digestion in the Mouth

Answer 6

Food is mixed with saliva, containing:
- Enzymes (chemicals that increase the rate of reaction in living things) –> AMYLASE breaks down starch into sugar
- Water dissolves food particle to make it easier to taste
- Mucus as a lubricant and to help with swallowing

Question 7

Mouth to Stomach

Answer 7

3. Tongue pushes bolus (ball of food made with mixing saliva) to back of mouth where it’s swallowed
4. Flap called epiglottis pushes down to block the trachea opening and uvula pushes up to block nasal passages
5. Bolus travels from mouth to stomach through the esophagus, activating contractions by smooth muscles (PERISTALSIS)

Question 8

Lower Esophageal Sphincter

Answer 8

Muscular valve at top of stomach that prevents acid-soaked food from travelling up the esophagus

Question 9

Mechanical Digestion in the Stomach

Answer 9

Muscular contractions - peristalsis/churning

Question 10

Chemical Digestion in the Stomach
(release of gastric juices)

Answer 10

Nerves detect when food enters stomach –> triggers the release of hormone gastrin into bloodstream –> gastrin brought to gastric cells in the stomach –> stimulates release of gastric juices (contains mucus, acid HCl, digestive enzymes)

Acid = pH 2-3 meaning it kills microorganisms, stops amylase from working, and activates pepsinogen (pre-enzyme)

Question 11

Chemical Digestion in the Stomach
(pepsinogen)

Answer 11

Pepsinogen converts to pepsin which breaks down protein into amino acids (pepsinogen is a safety mechanism because the stomach would digest itself if cells produced pepsin)