Structure & Innervation of the GI Tract

Question 1

The function of the GI tract is _____ and ______ of nutrients.

Answer 1

digestion & absorption

Question 2

List the general activities to accomplish digestion and absorption.

Answer 2

• motility
• secretions
• digestion
• nutrients absorbed

Question 3

Tract the linear sequence of the GI tract.

Answer 3

mouth —> esophagus —> stomach —> small intestine —> large intestine —> anus

Question 4

List the support structures of the GIT

Answer 4

• salivary glands
• pancreas
• liver
• gallbladder

Question 5

What is the purpose of salivary glands?

Answer 5

lubrication, buffering, digestion of carbs, fat

Question 6

What is the purpose of the pancreas?

Answer 6

buffering, digestion of carbs, lipids, proteins

Question 7

What is the purpose of the liver? It is the _____ in metabolism.

Answer 7

receives all nutrients absorbed from gut (portal vein, fat and carb metabolism, bile)
“first-pass” metabolism

Question 8

What is the purpose of the gallbladder?

Answer 8

store bile

Question 9

What happens in the stomach?

Answer 9

protein breakdown, mix bolus —> chyme, decrease particle size

Question 10

What happens in the small intestine?

Answer 10

digestion and absorption of carbs, lipids, proteins, absorption of vitamins and minerals

Question 11

What happens in the large intestine?

Answer 11

water reabsorption, fermentation of fiber

Question 12

What are the two surfaces of the GIT wall?

Answer 12

mucosal, serosal

Question 13

What does the mucosal layer face?

Answer 13

the lumen

Question 14

What does the serosal layer face?

Answer 14

the blood (basolateral)

Question 15

List the main layers of the wall.

Answer 15

mucosal layer (lumen)
submucosal layer
smooth muscle
serosa

Question 16

What are the 3 components of the mucosal layer?

Answer 16

epithelial cells
lamina propria
muscularis mucosae

Question 17

What are the epithelial cells?

Answer 17

have absorptive and secretory functions
- sloughed and replaced after
part of the mucosal layer

Question 18

What is the lamina propria?

Answer 18

contains CT, blood, & lymph tissue
part of the mucosal layer

Question 19

What is the muscularis mucosae?

Answer 19

smooth muscle cells
- change shape and surface area of epithelial cell layer
part of mucosal layer

Question 20

List the components of the submucosal layer.

Answer 20

collagen, elastin, glands, blood vessels

Question 21

Which layer of smooth muscle is thinner with fewer nerves?

Answer 21

longitudinal muscle

Question 22

The submucosal plexus, or _______ plexus, is between the _____ & ______.

Answer 22

Meissner’s
circular muscle & submucosa

Question 23

The myenteric plexus, or ______ plexus, is between the ____ & ______.

Answer 23

Auerbach’s
longitudinal & circular layers

Question 24

T/F: The enteric system is partially dependent on the brain and spinal cord.

Answer 24

FALSE - it can operate independent, functions even if vagus nerve is severed

Question 25

The enteric system can control functions of the GIT in _________ via _________.

Answer 25

extrinsic system, via short reflex arcs

Question 26

Where is the enteric nervous system located?

Answer 26

in ganglia of myenteric and submucosal plexuses

Question 27

The ganglia in the myenteric & submucosal plexuses receive sensory information directly from ______ & sends motor information directly to _______

Answer 27

FROM receptors in mucosa TO smooth muscle, secretory, and endocrine cells

Question 28

What are the enteric neurons?

Answer 28

neurotransmitters, neuromodulators

Question 29

Enteric plexuses communicate w/ things how?

Answer 29

interneurons and with CNS via vagal, pelvic, and splanchnic nerves

Question 30

Most neurons of the ENS can secrete 2 or more _______.

Answer 30

neurotransmitters or neuromodulators

Question 31

What does the vagus nerve innervate?

Answer 31

innervates upper GIT, striated muscle in upper 1/3rd of esophagus, wall of stomach, and ascending colon

Question 32

Define pelvic nerve.

Answer 32

innervates lower GIT - striated muscle of external anal canal, walls of transverse, descending, and sigmoid colon

Question 33

Where are PSNS ganglion located?

Answer 33

myenteric and submucosal plexuses within walls of GIT - coordinated and relayed to smooth m., endocrine, secretory cells

Question 34

List postganglionic neurons of PSNS

Answer 34

cholinergic (Ach) or peptidergic (substance P)

Question 35

Afferent fibers in vagus nerve deliver sensory info from _________

Answer 35

periphery (receptors in wall of GIT) to CNS

Question 36

Efferent fibers in vagus nerve deliver motor information from ________

Answer 36

CNS to target tissues (smooth muscle, secretory, endocrine cells)

Question 37

T/F: SNS has short preganglionic fibers that synapse in ganglia inside the GIT.

Answer 37

FALSE - OUTSIDE

Question 38

List the 4 sympathetic ganglia that serve the GIT.

Answer 38

celiac* cranial mesenteric* caudal mesenteric hypogastric * = celiacomesenterical

Question 39

Postganglionic nerve fibers leave the sympathetic ganglia and synapse on ganglia in the ______ and ______ OR directly __________.

Answer 39

myenteric and submucosal plexuses OR directly innervate smooth muscle, endocrine, secretory cells