Structure & Innervation of the GI Tract Flashcards
The function of the GI tract is _____ and ______ of nutrients.
digestion & absorption
List the general activities to accomplish digestion and absorption.
- motility
- secretions
- digestion
- nutrients absorbed
Tract the linear sequence of the GI tract.
mouth —> esophagus —> stomach —> small intestine —> large intestine —> anus
List the support structures of the GIT
- salivary glands
- pancreas
- liver
- gallbladder
What is the purpose of salivary glands?
lubrication, buffering, digestion of carbs, fat
What is the purpose of the pancreas?
buffering, digestion of carbs, lipids, proteins
What is the purpose of the liver? It is the _____ in metabolism.
receives all nutrients absorbed from gut (portal vein, fat and carb metabolism, bile)
“first-pass” metabolism
What is the purpose of the gallbladder?
store bile
What happens in the stomach?
protein breakdown, mix bolus —> chyme, decrease particle size
What happens in the small intestine?
digestion and absorption of carbs, lipids, proteins, absorption of vitamins and minerals
What happens in the large intestine?
water reabsorption, fermentation of fiber
What are the two surfaces of the GIT wall?
mucosal, serosal
What does the mucosal layer face?
the lumen
What does the serosal layer face?
the blood (basolateral)
List the main layers of the wall.
mucosal layer (lumen)
submucosal layer
smooth muscle
serosa
What are the 3 components of the mucosal layer?
epithelial cells
lamina propria
muscularis mucosae
What are the epithelial cells?
have absorptive and secretory functions
- sloughed and replaced after
part of the mucosal layer
What is the lamina propria?
contains CT, blood, & lymph tissue
part of the mucosal layer
What is the muscularis mucosae?
smooth muscle cells
- change shape and surface area of epithelial cell layer
part of mucosal layer
List the components of the submucosal layer.
collagen, elastin, glands, blood vessels
Which layer of smooth muscle is thinner with fewer nerves?
longitudinal muscle
The submucosal plexus, or _______ plexus, is between the _____ & ______.
Meissner’s
circular muscle & submucosa
The myenteric plexus, or ______ plexus, is between the ____ & ______.
Auerbach’s
longitudinal & circular layers
T/F: The enteric system is partially dependent on the brain and spinal cord.
FALSE - it can operate independent, functions even if vagus nerve is severed
The enteric system can control functions of the GIT in _________ via _________.
extrinsic system, via short reflex arcs
Where is the enteric nervous system located?
in ganglia of myenteric and submucosal plexuses
The ganglia in the myenteric & submucosal plexuses receive sensory information directly from ______ & sends motor information directly to _______
FROM receptors in mucosa
TO smooth muscle, secretory, and endocrine cells
What are the enteric neurons?
neurotransmitters, neuromodulators
Enteric plexuses communicate w/ things how?
interneurons and with CNS via vagal, pelvic, and splanchnic nerves
Most neurons of the ENS can secrete 2 or more _______.
neurotransmitters or neuromodulators
What does the vagus nerve innervate?
innervates upper GIT, striated muscle in upper 1/3rd of esophagus, wall of stomach, and ascending colon
Define pelvic nerve.
innervates lower GIT - striated muscle of external anal canal, walls of transverse, descending, and sigmoid colon
Where are PSNS ganglion located?
myenteric and submucosal plexuses within walls of GIT
- coordinated and relayed to smooth m., endocrine, secretory cells
List postganglionic neurons of PSNS
cholinergic (Ach) or peptidergic (substance P)
Afferent fibers in vagus nerve deliver sensory info from _________
periphery (receptors in wall of GIT) to CNS
Efferent fibers in vagus nerve deliver motor information from ________
CNS to target tissues (smooth muscle, secretory, endocrine cells)
T/F: SNS has short preganglionic fibers that synapse in ganglia inside the GIT.
FALSE - OUTSIDE
List the 4 sympathetic ganglia that serve the GIT.
celiac*
cranial mesenteric*
caudal mesenteric
hypogastric
* = celiacomesenterical
Postganglionic nerve fibers leave the sympathetic ganglia and synapse on ganglia in the ______ and ______ OR directly __________.
myenteric and submucosal plexuses
OR
directly innervate smooth muscle, endocrine, secretory cells
