HRR: GI secretions and motility I

Question 1

What is considered the foregut?

Answer 1

Esophagus to proximal duodenum

Question 2

What is considered the midgut?

Answer 2

Distal duodenum to proximal 2/3 of transverse colon

Question 3

What is considered the hindgut?

Answer 3

Distal third of the transverse colon to the anal canal

Question 4

What vessel supplies the foregut?

Answer 4

Celiac artery

Question 5

What vessel supplies the midgut?

Answer 5

Superior mesenteric artery

Question 6

What vessel supplies the hindgut?

Answer 6

Inferior mesenteric artery

Question 7

What are the accessory organs of the GI tract?

Answer 7

Salivary glands, pancreas, liver, gallbladder

Question 8

What is the arterial/venous supply of the GI tract?

Answer 8

Splanchnic circulation

Question 9

What are the histological layers of the GI tract?

Answer 9

Mucosa, submucosa, muscularis externa, serosa/adventitia

Question 10

In which layer is the myenteric plexus?

Answer 10

In the muscularis externa between the two muscle layers

Question 11

What are the control mechanisms of GI function?

Answer 11

Endocrine, paracrine, Neurocrine

Question 12

Briefly describe endocrine signaling.

Answer 12

Sensing cell in the GI tract secretes a regulatory hormone or peptide that travels in the bloodstream to target cells at a different location

Question 13

What are the main sensing cells in the GI tract?

Answer 13

Enteroendocrine cells

Question 14

Give the basic structure of an enteroendocrine cell.

Answer 14

Apical surface contacts the lumen and secretory granules are at the basolateral end. The apical end will sense, and cause release from secretory granules into the blood for endocrine signaling

Question 15

What are G cells?

Answer 15

Enteroendocrine cells that sense partially digested proteins in the GI tract, and lead to the release of gastrin into the bloodstream to increase digestive function

Question 16

Gastrin binds to which receptor?

Answer 16

CCK2

Question 17

Briefly describe paracrine regulation.

Answer 17

Chemical messenger or peptide is released by a sensing cell and acts of a nearby cell via diffusion through the interstitial space; doesn’t necessarily involve travel via blood

Question 18

What are enterochromaffin cells?

Answer 18

They are cells in the stomach that receive a signal and secrete histamine. They use this histamine for paracellular regulation, stimulating neighboring parietal cells that will them secrete H+ into the gastric lumen

Question 19

Describe neural regulation of the gut.

Answer 19

The enteric and extrinsic nervous systems work together to control functioning of the GI tract. The enteric nervous system is within the gut, and the extrinsic is the autonomic nervous system

Question 20

What are the two parts of the enteric nervous system?

Answer 20

Submucosal plexus and myenteric plexus

Question 21

Which division of the enteric nervous system is involved in motility?

Answer 21

Myenteric plexus; has ascending and descending fibers to do this!

Question 22

What are the main neurotransmitters involved in gut signaling for contraction?

Answer 22

Ach and substance P

Question 23

What are the main neurotransmitters involved in gut signaling for relaxation?

Answer 23

VIP and NO

Question 24

Describe impact of PSNS on the gut.

Answer 24

Increases motility, secretions, and digestive function

Question 25

What is the main PSNS nerve for the GI tract?

Answer 25

Vagus nerve

Question 26

PSNS preganglionic nerves are in the ___ and postganglionic neurons are found in the ___?

Answer 26

Brainstem, GI tract

Question 27

What is the vagovagal reflex?

Answer 27

Vagus nerve afferent fibers bring sensory input and synapse with an interneuron, which then stimulates a motor neuron

Question 28

Cell bodies for vagal afferents are in the…

Answer 28

Nodose ganglion

Question 29

What is the effect of the SNS on the GI tract?

Answer 29

Decreases secretions, motility, and overall GI function

Question 30

Sympathetic preganglionic neurons are in the ___, and postganglionic neurons ___?

Answer 30

Spinal cord; synapse in ENS or directly innervate effector cells

Question 31

Where do SNS preganglionic fibers terminate?

Answer 31

Prevertebral ganglia

Question 32

What sections of prevertebral ganglia are relevant to the GI tract?

Answer 32

Celiac (T5-9), superior mesenteric (T10-12), inferior mesenteric (L1-2)

Question 33

What is peristalsis?

Answer 33

Coordinated propulsion of food forward

Question 34

What is the most potent stimulator of peristalsis?

Answer 34

Distension/stretch

Question 35

In which segments of the GI tract does peristalsis occur?

Answer 35

Pharynx, esophagus, gastric antrum, small/large intestine

Question 36

Where does segmentation occur?

Answer 36

Small/large intestines

Question 37

Where do tonic contractions occur?

Answer 37

Sphincters

Question 38

What is the migratory motor complex?

Answer 38

Rhythmic phase peristaltic contractions that occur in the fasting state; a basal rate of motility that helps clear the GI tract

Question 39

What are pathologic patterns of motility?

Answer 39

Spasms (maximal contractile activity) or ileus (absent contractile activity)

Question 40

What are interstitial cells of cajal?

Answer 40

They form gap junctions with smooth muscle cells to help the cells work together as one; they’re pacemakers and highly associated with the myenteric plexus

Question 41

Smooth muscle contraction in the gut results from…

Answer 41

Temporal summation of AP’s

Question 42

GI tone is influenced by…

Answer 42

Neurotransmitters, hormones, paracrine substances, drugs