PTE 754: exam 3

name the organs that make up the GI system.

mouth, pharynx, esophagus, stomach, small intestine (duodenum, jejunum, ileum), large intestine (cecum, colon, rectum), and anus

name the organs that act as the “support” group for the GI system via controlling secretions.

liver, gallbladder, and pancreas

the GI system is known to have a “little brain.” what does that mean?

little brain = the enteric nervous system (ENS) a vast, independent network of over 100 million nerve cells lining the GI tract; it regulates digestion, including motility, enzyme secretion, and nutrient absorption

while the GI system has a “little brain,” it still works through the autonomic nervous system. describe that nervous system’s role on the GI system.

parasympathetic: rest and digest → facilitate GI

sympathetic: fight or flight → inhibit GI

GI organ overview

what are the GI’s functions?

• portal for food

• mixes food with secretions

• absorption of nutrients

• expels residue and debris

• innate and adaptive immunological function

list the cellular layers of the GI tract from inside to outside.

microvilla → epithelium → basement membrane → lamina propria → muscularis mucosa → submucosa → circular muscle → myenteric plexus → longitudinal muscle → mesothelium

functions of the GI cellular layers

what are the four phase of digestion?

1. oral

2. gastric

3. intestinal

4. defecation

the oral phase of digestion is within the mouth. what are the two components of this phase?

1. chewing

2. swallowing

what occurs during the chewing component of the oral phase?

lubricates food through saliva, amylase breaks down starch (carbs), and mechanical chewing chops food in smaller pieces

the secretion of saliva needed for chewing is controlled by the autonomic nervous system. what are the two types of saliva produced in response to the ANS?

PSNS: watery saliva

SNS: viscous saliva

what occurs during the swallowing component of the oral phase?

its a reflexive response that transmits sensory impulses to an area at the medulla-pons and then motor impulses of various cranial nerves contracts various muscles (CN 5, 7, 9, 10, 12)

functions of the CNs within the oral phase