lecture 32 Flashcards
1
Q
upper esophageal sphincter
A
- separates pharynx of the throat and top of esophagus
- will relax when swallowing so food can reach esophagus
1
Q
sphincters of GI tracts
A
- are rings of smooth muscle that are tonically constricted to adjacent organs unless there is a stimulus for them to relax
- serve as one way valves
2
Q
lower esophageal sphincter
A
- separates esophagus from stomach
- can spontaneously relax allowing acid stomach contents to splash back up into esophagus and burn esophageal wall resulting in heart burn or adic reflux
3
Q
pyloric sphincter
A
- separates stomach from small intestine
- contents will remain in stomach till its done with them
- contents leave in the form of chyme through pyloric sphincter into the duodenum of the small intestine where chemical digestion will continue and absorption of most substances will begin
4
Q
Ileocecal sphincter
A
- separates small intestine and large intestine
- found at the start of the large intestine
5
Q
Internal and external anal sphincters
A
- have voluntary conscious control over the external anal sphincter but not the internal
6
Q
Name the structures that a carbohydrate would pass through from beginning to end of GI tract
A
- oral cavity
- esophagus
- stomach
- small intestine
- large intestine
- rectum
7
Q
The GI tract
A
- main role is to transfer nutrients and water from food into body
- 4.5m continuous hollow tube from mouth to anus
- anything a part of your GI tract or anything in the lumen is considered external environment. To become internal we need to cross the wall of the GI tract through the process of absorption happening in the small intestine
- accessory glands and organs are functionally associated with the GI tract, but material does not pass through them (salivary glands, liver, gallbladder, pancreas)
8
Q
what are the 4 tissues that make up the wall of GI tract in the stomach and small intestine (inside to outside)
A
- mucosa
- submucosa
- muscularis externa (longitudinal muscle and circular muscle)
- serosa
9
Q
mucosa
A
- the innermost layer
10
Q
what is the mucosal layer comprised of?
A
- epithelium that lines the GI tract
- transporting epithelium cells (absorption of glucose)
- secreting epithelium cells (secrete carbohydrates, mucous (HCO3- to neutralize stomach acids)
- stem cells because cells turn over quick because they’re facing a harsh environment
- lamina propria that epithelium cells adhere too contain glands, lymph vessels, blood supply and nerve fibers
- muscularis mucosae is a thin layer of smooth muscle that separates mucosa from submucosa and can contract to alter SA of mucosa for absorption
11
Q
what is the submucosa comprised of
A
- loose connective tissue that contains nerve trunks, lymph vessels and blood supply
- in this layer the small intestine also has the submucosal plexus
12
Q
Muscularis externa
A
- has 2 layers of smooth muscle which are circular muscle (constrict lumen) and longitudinal muscle (shorten tract)
- alternating contraction of these 2 muscle give rise to type of contraction that occurs in small intestine called segmental
- stomach has extra layer called oblique layer (runs diagonal)
- myenteric plexus is located just in between these 2 muscle layers
13
Q
serosa
A
- outer layer covering the entire GI tract
- largely connective tissue
- comprised of secretory epithelium that allows for lubrication so we don’t get friction when all these different types of muscle contractions are happening
- protects and suspends GI tract within abdominal cavity
14
Q
The 4 basic GI processes
A
- secretion: movement of material from cells to lumen (saliva, gastric juice, pancreatic enzymes
- digestion: mechanical or chemical digestion of food into absorbable bits
- absorption: movement of material from GI lumen to ECF
- motility: movement throughout GI tract as a result of muscle contractions
