Animal Digestion

Question 1

Ex) Structural variation in GI tract (diet)

Answer 1

Carnivores - large incisors to kill prey/rip away flesh.

Herbivores - broad surfaced molars with ridged surfaces, grind fibrous plant material.

Question 2

Ex) Variations in GI tract (Fox & Koala

Answer 2

Fox: short digestive tract sufficient, easy to digest and absorb nutrients from meat.

Koala: nutrients + water from protein poor Eucalyptus leaves
–> large alimentary canals (hard to digest cellulose/cell walls)

Question 3

Ex) Variations in Gut Microbiome (Humans)

Answer 3

–> community of beneficial microbes

(constantly changing during life cycle: diet, age, stress, genetics, environment)

Question 4

What is simplified anatomy of human alimentary canal?

Answer 4

Mouth (mastication)
food –> bolus

Pharynx (swallowing)
peristalsis (bolus –> stomach)

Esophagus (sphincters)
upper+lower (air/acid reflux)

Stomach
bolus –> fluid chyme

Small intestine (digestion + nutrient absorption)

Large intestine (fluid absorption, feces formation)

Question 5

Purpose of chewing in digestion/nutrient absorption

Answer 5

1) Maximise enzymatic attack (^SA, v particle size)

2) Lubricate for swallowing
(food+saliva –> softer, warmer)

3) Stimulates/Preps GI tract
(digestive juices secretes in stomach, prep for next stage save E)

Question 6

What does Pharynx do?

Answer 6

Swallowing:

Primary peristalsis (bolus –> stomach 2-3s)

Secondary peristalsis (swallowing induced by distension)

Question 7

Purpose of esophageal sphincters (2)

Answer 7

Upper/pharyngo-esophageal
-keeps air out of eso

Lower/gastro-esophageal
-keeps acid reflux from entering eso

Question 8

Oxyntic glands (where, what)
4 cell types

Answer 8

Stomach (mucosa - epithelial cells)

1) ECL cell (secretes Histamine, stimulates parietal cells to produce HCl)

2) Parietal (secretes HCl creates acidic environment
(pH 1-2) does most of digestion, kills pathogen + intrinsic factor)

3) Mucous neck cells (secrete mucus + bicarb to protect stomach lining from acidic conditions)

4) Cheif cells secrete pepsinogen (inactive precursor of pepsin, activated by HCl breaks down proteins into amino acids)

Question 9

Small Intestine parts + purpose (3)

Answer 9

Digestion & Nutrient Absorption

1. Duodenum (mixing and prep for digestion)
   –> neutralize acids in chyme (bicarb mucus)
   –> mix chyme with bile from pancreas/liver
2. Jejunum (villi absorb main products into bloodstream)
   –> sugars, amino acids, fatty acids
3. Ileum (villi absorb remaining nutrients)
   –> Vit B12, remaining acids

Question 10

Large Intestine major function

Answer 10

Fluid absorption + feces formation

–> recover water from alimentary canal
–> feces (undigested food, mucus, bacteria)
–> no digestive enzymes, some water, salt Vit B12 absorption