Introduction to GI Function & Regulation

Question 1

main functions of the GI system

Answer 1

conveys nutrients, water, and electrolytes into the body
boundary between external and internal environment

Question 2

oropharyngeal cavity function

Answer 2

prehension/initial intake
reduction (mechanical and enzyme)
mix with saliva
transport/swallow

Question 3

esophagus main function

Answer 3

transport

Question 4

stomach function

Answer 4

storage/delivery rate control
digestion

Question 5

small intestine function

Answer 5

digestion and absorption
monitor luminal content

Question 6

large intestine function

Answer 6

absorption
fermentation
storage

Question 7

what are the 5 main functions of the GI tract as a whole

Answer 7

motility, storage, secretion, digestion, absorption

Question 8

cleft palate renders ___ movement during suckling ineffective

Answer 8

oropharyngeal

Question 9

what occurs if the nasopharynx is not closed off (cleft palate)?

Answer 9

nasal regurgitation

Question 10

how does the palate normally form?

Answer 10

progressive fusion between lateral palatine processes

Question 11

what is atresia ani?

Answer 11

congenital abnormality where the anus is closed off (stenosis)

Question 12

describe the types of atresia ani/coli

Answer 12

Question 13

list the layers of the esophagus, stomach, SI, and large intestine

Answer 13

mucosa
submucosa
2 muscle layers
serosal layer

Question 14

what does the mucosa layer consist of?

Answer 14

epithelium, lamina propria, muscularis mucosa

Question 15

describe morphology of epithelium at different GI segments

Answer 15

esophagus = multilayer stratified squamous
stomach, SI, LI = columnar single layer

Question 16

how is accumulation of defects prevented in the GI tract?

Answer 16

constant and fast renewal of epithelium

Question 17

where do stem cells originate?

Answer 17

neck/crypt area to migrate up/down for differentiation

Question 18

what do stem cells differentiate into?

Answer 18

enterocytes, goblet cells, enteroendocrine, paneth cells

Question 19

GI functions are controlled by a ___ and ___ control system

Answer 19

intrinsic and extrinsic

Question 20

what is the ENS?

Answer 20

intrinsic nervous system

Question 21

where are ENS neurons located?

Answer 21

between inner circular and outer longitudinal layer of muscularis externa (myenteric)
AND
within submucosa (submucosal)

Question 22

myenteric plexus innervation

Answer 22

N to longitudinal and circular smooth muscle layers
mainly gut movement

Question 23

submucosal plexus innervation

Answer 23

N to glandular epithelium, intestinal endocrine cells, and submucosal blood vessels
mainly intestinal secretions

Question 24

what are circuits?

Answer 24

synaptically interconnected networks of neurons that connect receptors with target organs

Question 25

receptors of mucosa

Answer 25

mechano- chemo- temperature receptors

Question 26

gut wall receptors

Answer 26

mechanoreceptors

Question 27

muscosa target organs

Answer 27

glands, enteroendocrine cells

Question 28

gut wall target organs

Answer 28

muscle, blood vessels

Question 29

what are varicosities?

Answer 29

structures located on axons, release neurotransmitter

Question 30

what's an advantage of varicosities in ENS?

Answer 30

activates a broader area around axons vs focused at end of axon

Question 31

describe the motor function of ENS

Answer 31

N muscles and sphincters causes contract/relaxation, controlling motility through the system

Question 32

describe the sensory ENS function

Answer 32

detect lumen pH, temperature, pressure

Question 33

interstitial cells of cajal (ICC)

Answer 33

specialized smooth muscle cells act as pacemaker to modulate phasic contractile activity have gap junctions

Question 34

what are the "slow waves" of the GI tract?

Answer 34

regular oscillations in membrane potential due to ICC's self generating depolarizing rhythm

Question 35

what nervous system makes up the intrinsic system?

Answer 35

ENS

Question 36

what nerves make up the extrinsic system?

Answer 36

vagus and splanchnic nerves

Question 37

sympathetic nervous system effect on GI

Answer 37

NOR = decrease motility, increase sphincters, decrease secretions NO and VIP (vasoactive intestinal peptide)

Question 38

parasympathetic nervous system effect on GI

Answer 38

N secretory cells in glands, smooth muscle of blood vessels, myenteric plexus VAGUS NERVE ACh increases motility, decreases sphincters, increase secretions

Question 39

what's involved in the sympathetic NS for GI?

Answer 39

NO VIP (vasoactive intestinal peptide) splanchnic nerve

Question 40

what's involved in the parasympathetic NS for GI?

Answer 40

ACh substance P vagus nerve

Question 41

the splanchnic nerve contains sympathetic ___ and spinal ___

Answer 41

sympathetic efferent spinal afferent

Question 42

what do splanchnic afferents carry?

Answer 42

info about distension of gut wall, presence of noxious chemicals, inflammation

Question 43

splanchnic efferents are ___ in nature

Answer 43

INHIBITORY

Question 44

what hormone decreases motility and glandular secretions?

Answer 44

norepinephrine

Question 45

what does the vagus nerve contain?

Answer 45

sensory afferents motor efferents

Question 46

what does vagus innervate?

Answer 46

abdominal viscera and pharyngeal mucosa

Question 47

vagus/parasympathetic control is typically ___ in nature

Answer 47

STIMULATORY

Question 48

what hormone increases gut blood flow, motility, and gland secretions>

Answer 48

ACh

Question 49

what is a vagotomy?

Answer 49

Sx where one or more branches of the vagus nerve are cut

Question 50

vagotomy usually ___ rate of gastric secretion and motility

Answer 50

reduces

Question 51

vagotomy can reduce problems related to ___ gastric acid production in ___ animals

Answer 51

excessive monogastric

Question 52

damage to the vagus causes malfermentation in ___

Answer 52

ruminants

Question 53

what are the endocrine secretions of the intrinsic system?

Answer 53

CCK, gastrin, secretin, GIP, motilin

Question 54

enteroendocrine cells sense ___ on their ___ side

Answer 54

sense gut content on their apical side

Question 55

what do enteroendocrine cells release from their basal side?

Answer 55

hormones, neuroactive substances (neurocrines), paracrines, autocrines

Question 56

what are the four routes of intrinsic endocrine control of the GI tract?

Answer 56

endocrine neurocrine paracrine autocrine

Question 57

which intrinsic endocrine route is this?

Answer 57

endocrine

Question 58

which intrinsic endocrine route is this?

Answer 58

neurocrine

Question 59

which intrinsic endocrine route is this?

Answer 59

paracrine

Question 60

which intrinsic endocrine route is this?

Answer 60

autocrine

Question 61

enteroendocrine cells of the stomach and SI produce which hormones?

Answer 61

gastrin, secretin, CCK, GIP, motilin

Question 62

which endocrine cell produces gastrin?

Answer 62

G cell

Question 63

which endocrine cell produces CCK?

Answer 63

I cells

Question 64

which endocrine cell produces secretin?

Answer 64

S cells

Question 65

which endocrine cell produces motiliin?

Answer 65

M cells

Question 66

which endocrine cell produces GIP?

Answer 66

K cells

Question 67

what are some examples of neuroactive substances?

Answer 67

NO substance P VIP enkephalines

Question 68

where are neuroactive substances released?

Answer 68

near afferent nerve terminals into lamina propria

Question 69

which endocrine secretions are part of extrinsic system?

Answer 69

aldosterone

Question 70

what does aldosterone do regarding GI?

Answer 70

stimulates Na and water reabsorption in colon via ENac sodium channels increases reabsorption in salivary glands

Question 71

aldosterone ___ Na absorption in the colon and salivary duct

Answer 71

increases

Question 72

glucocorticoids ___ activity of Na/K ATPase

Answer 72

increase