ch. 11.1: steps of digestion part 1

what are the 9 steps of digestion in order

1) prehension

2) mastication

3) salivation

4) swallowing/deglutition

5) stomach

6) small intestine

7) large intestine

8) defecation

9) urination** (technically waste from metabolism & not digestion)

define prehension

• first step of digestion

• seizing and conveying of food to the mouth

what are the means of prehension in bipeds vs quadraupeds

bipeds: use upper limbs

quadrupeds: use mouth, teeth, or lips

what are the means of prehension in carnivores?

canine teeth for ripping and tearing, strong jaws, and strong upper & lower molars

what are the means of prehension in cows?

use mobile tongue to seize grass

have a dental pad (no upper incisors)

have lower and upper molars for mastication

what are the means of prehension in sheep?

cleft lip (mobile lip, allows to nibble closer and more selectively)

dental pad (no upper incisors)

what are the means of prehension in horses?

have mobile lips for nibbling & grazing closer than a cow canwhat are the means of prehension in

have upper & lower incisors

what are the means of prehension in avians?

no lips, no teeth

very diverse

define mastication

vertical movements of the jaw which crush the food particles between teeth

how does mastication vary between carnivores, omnivores, herbivores, and ruminants?

• carnivores: not much chewing bc of competition (eat as much as possible as quickly as possible)

• omnivores: depends on species

  • pigs: not much chewing

  • avian: no teeth = no chewing

  • humans: some chew more than others?

• herbivores: thorough mastication

• ruminants (herbivores): regurgitate bolus, extensive chewing

what part of mastication is special in horses?

i think they chew more horizontally, more of a grind

define salivation

the secretion and mixing of saliva with food

what are the 3 main salivary glands and where are they located?

1) parotid: beneath ear

2) submandibular (submaxillary): either side of jaw

3) sublingual: underneath tongue

how does the amount of saliva produced vary across species?

carnivores: not much bc they eat wet feed

omnivores: depends on how much they chew (more chewing = more saliva)

herbivores: generally high amounts bc chew a lot

what are the 4 components of saliva?

1) mostly water

2) mucin

3) electrolytes - Na/K

4) salivary amylase

• an enzyme that breaks down starch

• not present in all animals

what animals is salivary amylase PRESENT in?

apes, avian (some), man, pigs, rats,

what animals is salivary amylase NOT present in?

cattle, cats, dogs and horses

what are the 7 functions of saliva?

1) food lubrication

2) solvent (dissolves food into solution and allows food to mix w taste buds)

3) cleans oral cavity (inhibits growth of bacteria)

4) washes dental cavity

5) buffer in ruminants (NaCO3)

• necessary to prevent acidosis bc fermentation produces VFAs

6) nitrogen recycling in ruminants (urea)

• urea is in the saliva so each time they swallow their saliva, that urea goes back to the rumen to provide nitrogen for microbial rumination

7) phosphorus source for ruminants

• same mechanism as urea

define deglutition

swallowing; the reflex of passing material from the mouth to the stomach through the esophagus

what are the 3 steps of deglutition?

1) neural reflex

• first 1/3 of swallowing process: voluntary

• last 2/3 of swallowing process: involuntary

2) bolus moves down esophagus via peristaltic wave

3) bolus moves thru cardia sphincter

• the end of the esophagus

• function: prevent reflux and vomiting

• horses have a particularly strong sphincter