chapter 9: digestive system

Question 1

describe the parts and functions of the mouth.

Answer 1

-mouth=buccal cavity
-contains teeth, tongue, lips

-functions: prehension, mastication, deglutination

Question 2

what are the 4 different types of teeth and their function?

Answer 2

1. incisors (I): front teeth; ruminants=dental pad
2. canine (C): caudal to incisors; ruminants=none
3. premolars (P): cheek teeth; slice and grind
4. molars (M): cheek teeth; grind and sheer

Question 3

how is saliva secreted?

Answer 3

mastication stimulates salivation

Question 4

what is the function of saliva?

Answer 4

chemical digestion; moistens food

Question 5

what is the function of the esophagus?

Answer 5

move food in one direction (toward stomach) through peristalsis

Question 6

what are the compartments of the monogastric stomach?

Answer 6

1. cardia: site where esophagus enters from
2. fundus: upper middle region; lined with rugae
3. body; main/largest compartment
4. pyloric antrum: grinds food
5. pylorus: leads to duodenum of small intestine; regulates amount of food that flows into SI

Question 7

what are the three cells within the pyloric antrum?

Answer 7

1. G-cells: produce gastrin
2. D-cells: produce somatostatin (inhibits acid secretion once food is in SI)
3. ECL cells: produce histamine (acid secretion)

Question 8

what are the 4 compartments/chambers of the ruminant stomach?

Answer 8

1. rumen: main site of fermentation; mixes contents
   -lined w/ papillae=> increase SA for microbial digestion
2. reticulum: smallest region
   -honeycomb interior
   -foreign objects sit in reticulum
3. omasum: muscular chamber w/ folds
   -water absorption
   -removes bicarbonate buffer
4. abomasum: “true stomach”
   -lined w/ glandular epithelium=> mucus and enzymes (glandular digestion)

Question 9

what are the three sections of the small intestine?

Answer 9

1. duodenum
2. jejunum
3. ileum

Question 10

what are the main functions of the small intestine?

Answer 10

-digestion of starch, protein, fat
-absorbed nutrients move into blood across mesentery and into portal circulation between gut and liver

*Brunner’s gland: secretes digestive juices
*lined with villi and microvilli for increased absorption

Question 11

what are the 2 parts of the large intestine?

Answer 11

1. cecum
2. colon (ascending, transverse, descending)

Question 12

what is the function of the cecum?

Answer 12

microbial fermentation

Question 13

what is the function of the colon?

Answer 13

-digestion of plant fibers (cellulose,hemicellulose)
-water absorption
-secretion of mucus via goblet cells

Question 14

what is the function of the rectum?

Answer 14

-storage site for feces before reaching the anus

Question 15

what is the function of the anus?

Answer 15

defecation

Question 16

describe the enteric nervous system within the stomach.

Answer 16

1. parasympathetic system stimulates enteric nervous system when animal is preparing to eat

2.cephalic phase (before food enters stomach):
-Ach is released
-Ach binds to receptors that cause the release of HCl and pepsinogen (gastric juices)
-Ach triggers histamine release which furthers the production of gastric juices/acid

3. gastric phase (food enters stomach):
   -stretch receptors in stomach trigger gastric phase
   -peptides form and trigger the vagal nerve
   -stimulation of G-cells triggers the production of gastrin
   -gastrin triggers more histamine and HCl (gastric acid) to be produced
   -stomach acidity lowers for enhanced digestion

Question 17

describe the enteric nervous system within the small intestine.

Answer 17

1. intestinal phase:
   -triggered by amino acids and fatty acids entering the intestine
   -Ach triggers vagal nerve stimulation
   -CCK and secretin production increase
   -CCK and secretin stimulate bicarbonate and bile secretion
   -acid production in the stomach decrease and pancreatic and biliary secretion increase for digestion within the SI