EXAM 1- JONES

PRACTICE:

Which of the following is considered a part of the Muscularis Externa?

a. basement membrane

b. muscularis mucosal

c. serosa

d. longitudinal smooth muscle

d

PRACTICE:

What part of the GI tract is the arrow pointing towards?

esophagus

What are the 2 main parts to circulation in the GI tract?

• spleenic side—> blood comes FROM the heart to the organs

• portal side—> blood comes FROM the organs to the liver than back to the heart

What organ receives all the blood from the portal vein and then sorts/stores blood before returning it to the heart?

a. spleen

b. stomach

c. small intestine

d. pancreas

e. liver

e. LIVER

What are the 4 layers to the GI wall?

1. Mucosal

2. Submucosal

3. Muscularis Externa

4. Serosa

What are the 4 parts of the mucosal layer of the GI wall?

• epithelial cells

• basement membrane

• lamina propia

• muscularis mucosal

What is the job of the muscularis mucosal?

• move villi in/out to CONTROL SURFACE AREA

What layer of the GI wall is “space” and contains glands, ducts, etc.?

submucosa

What layer of the GI wall has the function of “holding things in place” and is like an outer protective layer?

Serosa

What 2 muscles make up the muscularis externa? Are they smooth or skeletal muscle?

1. Inner circular muscle

2. outer longitudinal muscle

both are SMOOTH muscle

For smooth muscle, what causes contraction? What causes relaxation?

contraction—> Ca++ (from SR, transporters, or Ach)

relaxation—> increase cGMP, inhibiting cAMP

What cells have a pacemaker ability in the GI tract?

ICC (Interstitial cells of Cajal)

What are slow waves? What are spike potentials?

slow waves- local depolarizing events generated by ICC, set BER

spike potentials- generated by increased slow wave potentials- lead to contractions

What are plexus? What are their names and where are they found in the GI wall?

• plexus- nerve cell bodies

• submucosal plexus—> found under the submucosa layer

• myenteric plexus—> found between circular and longitudinal muscle

How does the wall of the stomach compare to the small intestine?

• THE MUCOSA LAYER!!!!

  • in stomach—> invaginate and make pits

  • in small intestine—> have villi and crypts (small invaginations)

In the GI tract muscles move by segmentation or peristalsis…describe both.

• segmentation- “mixing”, moves food back AND forth to break it up

• PERISTALSIS- forward movement (HOW OUR FOOD GOES DOWN OUR INTESTINES)

  • basically we contract behind, and send inhibitory signals ahead to relax ahead. this propels food forward

What is the name of the neural control of the GI tract?

ENTERIC

Because we have plexxi in the GI tract, does that mean we don’t use our CNS or any outside innervation?

no—> enteric but can be controlled by ANS

Short reflexes only use the ____________ neural system. Long reflexes also use the _____.

a. central, enteric

b. vasovagel, enteric

c. enteric, central

d. enteric, somatic

c. enteric, CNS

Does the following example describe long or short reflexes:

internal stimuli—> chemoreceptor—> myenteric plexus—>smooth muscle—> contraction

short (does not involve the CNS)

What is a combination of mucous, electrolytes, lysozyme, IgA and is secreted by the parotid, submandibular, and sublingual glands?

saliva

What salivary gland is stimulated the most when eating?

parotid

What are the 2 cells of the salivary glands? What are their functions?

1. acinar cells- secretors (serous and mucous)

2. ductal cells- modifiers (absorption and secretion)

Does the parasympathetic or sympathetic system mainly control salivation?

Parasympathetic (doesn’t mean SNS has no effect)

SALIVA IS ALWAYS _____________________ to PLASMA.

a. isotonic

b. hypertonic

c. hypotonic

c

How does a fast and slow flow rate effect the tonicity of saliva?

fast—> less hypotonic

slow—> more hypotonic

In the ductile cells of the salivary glands, what electrolytes go out of the saliva and which come in?

out—> Na+, Cl-

in—> K+, HCO3-

Why is saliva hypotonic?

more NaCl is removed than K+, HCO3 is brought in

Answer the following about Sjogren syndrome:

• Cause

• Sym

• Tx

• Cause- autoimmune destruction of salivary gland

• Sym- DRY MOUTH (xerostomia), DRY EYES (keratoconjunctivitis sicca), mouth ulcer

• Tx- fluids, stimulants, steroids

Describe the voluntary phase of swallowing/deglutition:

• chew and push food to back of throat

• mechanoreceptors are activated—> begins involuntary phase

Describe the involuntary phase of swallowing/deglutition:

several muscle events occur:

1. upper esophageal sphincter opens

2. peristalsis

3. lower esophageal sphincter opens

4. receptive relaxation ( NO and VIP)

What is secondary peristalsis?

if food gets stuck in your throat, your enteric system activates a super strong push

The Upper esophageal area is covered in ___________ muscle. The lower esophageal area is covered in _________________ muscle.

skeletal, smooth

The _________ relaxes to allow food to enter the stomach because of NO and VIP.

LES (lower esophageal sphincter)

When does the LES relax?

AS SOON AS YOU SWALLOW (not when the food reaches it)

What is Achalasia?

• loss of inhibitory neurons

• causes LES to not be able to RELAX

Answer the following about GERD:

• cause

• symptom

• tx

• cause- LES issues, hernia, can’t empty stomach

• symptom- esophagitis

• tx- antacids, h2 blockers, PPIs, motility drugs, lifestyle changes

What are the functions of the stomach?

1. storage

2. mixing (break up food)

3. digestion

4. antibacterial secretions

What the 3 main regions of the stomach? (top to bottom)

1. fundus

2. body

3. pylorus

Does the mucosa in the stomach form pits, crypts, or villi?

pits

The ________ is a region in the fundus in the upper stomach.

cardia

What is the name of the sphincter between the esophagus and the stomach? What is the name of the sphincter between the stomach and intestine?

• eso-stomach: lower esophageal sphincter

• stomach-intestine: pyloric sphincter

When does the pyloric sphincter fully relax?

NEVER—> always contracted and is only slightly opened when food needs to exit

What are the 2 types of pits in the stomach? Where are they found? What cell types are found in each?

1. oxyntic pits (body)- mucous, parietal, ECL cells, and Chief cells

2. pyloric pits (pylorus)- Mucous, D cells, G cells

For each of the following cell types, describe the substance secreted by the cell and the substance’s function.

mucous neck cell, parietal cells, ECL cells, chief cells, D cells, G cells

Cell type	Substance secreted	Function
Mucous neck cell	Mucous and Bicarb	Mucous- protects Bicarb- gets in mucus layer and helps neutralize acid
Parietal cells	HCl and IF	HCl- digestive acid IF- B12
ECL cells	Histamine	Blocks parietal not ECL cells--> paracrine local signaling
Chief Cells	Pepsinogen	Pepsinogen interacts w/ HCl to form pepsin which degrades proteins
D cells	Somatostatin	Inhibits G-cells/ acid secretion in general
G cells	Gastrin	HORMONE- stimulates acid secretion, promotes contraction (main idea--supports digestion of food)

What 3 hormones regulate the release of HCl? (3 mediators)

1. gastrin

2. ACh

3. Histamine

Describe how we secreting acid:

• what kind of pumps?

• when were not digesting where are the pumps?

• where are the pumps when were digesting?

• Increasing what 2 things make the pump move intra to extra cellular?

• What are those 3 stimulus?

• What is the end result?

• PROTON pumps

• at rest= vesicles w/pumps are inside the cell

• during digestion- at surface of parietal cell

• increasing Ca++ or cAMP

• 3 stimuli- Ach, Gastrin, Histamine

• end result- HCl secretion

How do we get the proton (H+) for HCl?

carbonic anhydrase takes water and carbon dioxide and forms H+ and bicarb

How do we get the Cl- for HCl?

on basolateral side we exchange bicarb for Cl-

What happens to H+ and bicarb after its formed?

H+ moves into lumen through H+/K+ ATPase

bicarb moves into the blood

Describe gastric motility/ the contractions and relaxation in the stomach:

1. receptive relaxation- when LES opens bc of VIP/NO also opens up the stomach

2. peristaltic contractions- once food is in stomach we contract down the stomach… contractions get stronger as you move down

3. pylorus contractions intensify and cause retropulsion- when it hits bottom of stomach it doesn’t just all go into intestine it goes back up stomach and contracts down again

4. slow emptying

Can slow waves in the stomach cause contraction?

YES!!!!!!

A diet that consists of proteins and lipids will empty _______ than an all liquid diet.

slower

What stimulates the release of ACh, gastrin, and histamine?

ACh- parasympathetic post ganglion

Histamine- Ach and Gastrin activate ECL cell

Gastrin- distention of stomach or enteric nervous system releases GRP

What inhibits the release of somatostatin from D cells?

Ach

What activates the release of somatostatin from D cells?

• low pH (H+)

• entero gastric reflex—> CCK and secretin are intestinal hormones that turn on D cells

• GIP and VIP

Describe the cephalic phase of gastric secretion

• Think: before eating

• we want to prepare stomach for food

• mainly stimulate stomach to secrete acid thru vagus nerves

  • stimulate Mucous cells, chief cells, parietal cells, g cells all to prepare for the food incoming

• 20% of acid secretion

Describe the gastric phase of gastric secretion:

• Think: eating phase

• STRETCH STOMACH—> mechanoreceptors detect stretch tell enteric neural system to secrete acid

• our enteric system stimulates mucous cells, chief cells, parietal cells, and g cells all to help break down our food

• 70% of acid secretion

Describe the intestinal phase of gastric secretion:

• Stimulatory effect: g cells in intestine= increase acid secretion

  • 10% of acid secretion

• Inhibitory effect: entero-gastric reflex and intestinal hormones

Describe how gastric secretion is inhibited:

• ENTERO-GASTRIC REFLEX

• turns off the stomach

• Hormones: CCK, secretin, VIP, GIP

How is an ulcer formed? What are some not-natural things that can damage the mucosal defenses?

• ulcer is formed when acid breaks thru epi layer and degrades

• some things that can damage- H. pylori, NSAIDs, aspirin, cigs, alcohol, i