L18: intro to GI function

Question 1

what are the 3 sphincteres of the GI tract

Answer 1

• lower esophageal sphincter
• pylorus
• ileo-cecal sphincter

Question 2

what has failed to fuse in cleft palate

Answer 2

the opening between the oral and nasal cavity

Question 3

stenosis and atresia of the intestine is a _______ malformation; caused by what during embryonic development

Answer 3

congenital
inadquate blood supply - leads to atrophy of affected portion

Question 4

what layers make up the mucosa of the wall of the GI tract

Answer 4

epithelium
lamina propria
muscularis mucosa

Question 5

what are the muscle layers that are in the wall of the GI tract

Answer 5

inner circular muscle
outer longitudinal

Question 6

what plexuses make up the enteric NS of th GI tract

Answer 6

submucosal plexus + myenteric plexus

Question 7

what type of epithelium is in the esophagus

Answer 7

multilayered stratified squamous

Question 8

what type of epithelium is in the stomach, small and large intestine

Answer 8

columnar single layer

Question 9

the small and large intestine epithelium is arranged in what way and for what purpose

Answer 9

LI: crypts
SI: crypts + villi
arrangement is for surface amplification

Question 10

where do stem cells originate

Answer 10

neck area of crypts

Question 11

what is the benefit to the constant renewal of the GI tracts epithelial layer

Answer 11

helps prevent accumulation of defects

Question 12

neurons of the intrinsic nervous system (ENS) are located where

Answer 12

between an inner circular and outer longitudinal layer of muscularis externa (myenteric, Auerbach’s plexus) and within the submucosa (submucosal, Meissner’s plexus)

Question 13

what do the neurons within the Myenteric plexus innervate

Answer 13

the longitudinal and circular smooth muscle layers; primarily - control of gut movement

Question 14

what do the neurons of the submucosal plexus innervate

Answer 14

• glandular epithelium
• intestinal endocrine cells
• submucosal blood vessels
  primarily - control of intestinal secretion

Question 15

NTs of the enteric nervous system are released from ?

Answer 15

structures of the axons and axon collaterals called varicosites

Question 16

what is the advantage of varicosites in the ENS

Answer 16

they are able to innervate a larger area

Question 17

what are the excitatory NTs of the ENS

Answer 17

ACh and substance P

Question 18

what are the inhibitory NTs of the ENS

Answer 18

Nitric oxide
Vasoactive intestinal peptide (VIP)

Question 19

what is the function of the motor neurons on the ENS

Answer 19

innervate muscles and sphincters and cause contraction and or relaxation

Question 20

what do the sensory neurons of the ENS detect

Answer 20

detect luminal pH, temperature and pressure

Question 21

what are interstitial cells of Cajal (ICC)

Answer 21

specialized smooth muscle cells
- act as pacemakers to modulate contractile activity
- they have long processes that for gap junction with the longitudinal and circular sm cells
- self generating depolarizing rhythm that generate regular oscillations in the membrane potentia = slow waves

Question 22

what is resposible for generating the slow waves of the GI tract

Answer 22

Interstitial cells of Cajal

Question 23

what nerve is associated with the SNS of the GI

Answer 23

splanchnic

Question 24

what nerve is associated w/ the PNS of the GI

Answer 24

vagus

Question 25

what molecules are associated with **sympathetics** of the ENS and what effects do they have

Answer 25

**NO and VIP** they decrease motility and secretions and increase sphincters

Question 26

what molecules are associated with parasympathetics of the ENS and what effects do they have

Answer 26

Ach and substance P they increase motility and secretions and decrease sphincters

Question 27

what is the effect of NE on motility and secretions

Answer 27

decrease

Question 28

what is the effect of **Ach** on motility secretions and gut blood flow

Answer 28

increases

Question 29

what is a vagotomy

Answer 29

one of more branches of the vagus nerve are cut to **reduce the rate of gastric secretions nad motility**

Question 30

enteroendocrine cells release what from their **basal side** into circulation or interstitium

Answer 30

* hormones * neuroactive substances * paracrine * autocrines

Question 31

what does the apical side of enteroendocrine cells do

Answer 31

sense gut content

Question 32

endocrine secretions reach their target tissue via?

Answer 32

blood

Question 33

**paracrine** secretions reach their target tissue via?

Answer 33

diffusion through the interstitial space

Question 34

autocrine secretions of the paracrine cell modify the functions of ..?

Answer 34

the same cell hence auto

Question 35

enteric neurons secrete contents via _______ from _______

Answer 35

vesicles varicosites

Question 36

what hormones are produced by enteroendocrine cells

Answer 36

gastrin, secretin, CCK, GIP and motilin

Question 37

where are intrinsic endocrine neuroactive substances (NO, substance P, VIP, enkephalines) released

Answer 37

near afferent nerve terminals into the underlying lamina propria

Question 38

what does aldosterone do

Answer 38

stimulates water and sodium reabsorption in the colon by increases the amount of ENaC sodium channels also increases reabsorption in salivary glands

Question 39

what is the only hormone secreted outside of the GI tract that has controlling function

Answer 39

aldosterone

Question 40

what do glucocorticoids do

Answer 40

increase the activity of the Na/K ATPase