Process of Digestion: Mouth to Stomach

Question 1

Mechanical Digestion

Answer 1

-processes that mechanically tear, grind, crush, and mix food
-prepares food for chemical digestion
(I.e. Chewing in mouth, churning in stomach, and segmentation in the small intestine)

Question 2

Chemical digestion

Answer 2

• b/d polymers into monomers by chemical actions (mostly accomplished by enzymes)
• different kinds of enzymes break down different kinds of molecules

Question 3

Mouth

Answer 3

• ingestion, mechanical and chemical digestion, and propulsion
• b/d food
• forms bolus
• mixes food with saliva

Question 4

Saliva

Answer 4

• mixture of mucus and serous fluid
• helps moisten and binds good into bolus
• dissolves chemicals so they can be tasted
• chemical digestion

Question 5

Chemical digestion with saliva

Answer 5

• salivary amylase: b/d starch into maltose

- lysozymes and antibodies (not produced by salivary glands): inhibit bacteria

Question 6

Swallowing

Answer 6

• Bolus travels from mouth to stomach

- phases: buccal and pharyngeal-esophageal

Question 7

Buccal phase

Answer 7

• voluntary

- Bolus forced into pharynx by the tongue

Question 8

Pharyngeal-esophageal phase

Answer 8

• involuntary
• all passageways except esophagus are closed (tongue blocks mouth, uvula blocks nasopharynx, epiglottis blocks trachea)
• upper esophageal sphincter opens
• bolus travels by peristalsis down esophagus, as lower esophageal sphincter opens as food presses on it

Question 9

Pharynx and esophagus

Answer 9

• only digestive process which is propulsion

- Bolus actively moved by peristalsis to stomach

Question 10

Chemical digestion in stomach

Answer 10

• limits growth of microrganisms
• denatures proteins
• activates enzymes
• pH 2
• gastric juice is regulated by neural and hormonal factors
• food or rising pH causes the release of gastrin (hormone)

Question 11

Gastrin

Answer 11

• produces and releases:
• protein-digesting enzymes (chief cells),
• mucus (mucus neck cells)
• HCl acid (parietal cells)

Question 12

HCl

Answer 12

• activates enzymes
• denatures proteins
• provides a hostile environment for microbes

Question 13

Enzymes active in the stomach

Answer 13

-Pepsin (for peptide)
-secreted as inactive pepsinogen by chief cells
-activated by acid
-Renin
-digests milk proteins
(only present in infancy)

Question 14

Absorption in stomach

Answer 14

• happens very little

- only absorbs alcohol and acetylsalicylic acid (aspirin)

Question 15

Mechanical digestion and propulsion in stomach

Answer 15

• food is passed through the stomach, mixed, and slowly released into the duodenum
• propulsion: peristaltic wave move towards the duodenum
• grinding: waves become stronger towards pylorum, generates chyme
• retropulsion: small amount of chyme enters the duodenum (3 mL), rest is forced back in the stomach