GI Physiology Flashcards by Marlon Turaja

Refers to movement of food from stomach to duodenum

Gastric emptying

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Basic GI layers

Mucosa, Submucosa, Muscularis, Serosa

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Function of the GI tract for secretion and absorption

Mucosa - Epithelium

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Part of the mucosa innervated by the Meissner’s plexus

Muscularis mucosa - smooth muscle cells controlling the eptihelium

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GI tract structure: composed of collagen, elastin, glands and blood vessels

Submucosa - composed of connective tissue

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GI tract structure: composed of muscle layer

Muscularis

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Muscle layer that causes decreases diameter of the lumen

Inner Circular Muscle layer

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GI muscle layer: shortens segment of the GI tract

Outer Longitudinal Muscle layer

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Muscle layer of the GI tract: refers to the actual peristalsis

Outer longitudinal muscle layer

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Serosa layer of the GI tract is also known as?

Adventitia or mesothelium

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GI plexus located between submucosal and inner circular muscle layer

Meissner’s plexus - also known as Submucosal plexus, for secretion, absorption and contraction of muscularis mucosae.

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GI plexus between inner circular and outer longitudinal muscle layer.

Auerbach’s plexus - also known as Myenteric plexus. For motility

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GI layer not seen in esophagus

Serosa

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Strongest layer of the Esophagus

Submucosa

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Muscle layer of the Stomach

Inner oblique, middle circular and outer longitudinal layer

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Myenteric plexus is mainly excitatory except in what region?

Pyloric sphincter and ileocecal valve - relaxation

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Extrinsic innervation of GI tract: excitatory of esophagus to upper large intestine

Vagus nerve

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Excitatory extrinsic innervation of Gi tract from lower large intestine to Anus

Pelvic nerves

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Refers to the alternate movement of inner circular and outer longitudinal muscle layers

Reciprocal innervation

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Three main function of VIP: Vasointestinal peptide

Relaxation of pyloric sphincter and ileocecal valves
Receptive relaxation of LES
Receptive relaxation of Stomach

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GI hormone: stimulated by gastric distention causes increase gastric H+ secretion and stimulates growth of gastric mucosa

Gastrin

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Main inhibitory of Gastrin

H+ and somatostatin

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GI hormone: stimulated during fasting.

Motilin

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From M cells, causes activation of migrating myoelectric complex or interdigestive myoelectric complex

Motilin

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GI hormone: increases pancreatic and biliary HCO3- secretion. And decreases effect of gastrin on gastric mucosa

Secretin - from S cells

Protective hormone for the duodenum against the acid of the stomach

Secretin

GI hormone: main trigger of release is Glucose. Increases insulin secretion and inhibits gastric emptying

Glucose dependent insulinotropic peptide - from K cells

Different Incretin hormones

GIP from K cells GLP from L cells Glucagon

GI hormone: produced by I cells in respond to all foods (FA: main trigger)

Cholecystokinin - CCK

Function of CCK

Gallbladder relaxation Sphincter of Oddi Relaxation Increaes pancreatic enzyme and HCO3- secretion Inhibits gastric emptying

Motilin has an action on GI tract except on what region?

Motilin act only on stomach and small intestine and not on Large intestine

Most potent stimuli for gastrin secretion

Protein - phenylalanine, tryptophan and methionine

Neurocrine from vagus nerve to G cells

GRP/ Bombesin

GI hormone: secreted in response to hypoglycemia thus resulting to glycogenolysis and gluconeogenesis

Enteroglucagon

Incretin hormone secreted by L cells of small intestines that stimulates insulin secretion

Glucagon like peptide 1 ( GLP-1)

GI hormone: that inhibits release of all GI hormones and gastric H+ secretion

Somatostatin

GI hormone: secreted by mast cells of gastric mucosa that increased H+ secretion, potentiates gastrin and Ach action

Histamine

GI hormone: that inhibits appetite, found at the ventromedial hypothalamus

Satiety center

Location of the Appetite/hunger center

Lateral hypothalamus - stimulates appetite

It sends signals to Satiety and Hunger Center

Arcuate nucleus pathway

It releases POMC to decrease appetite

Anorexigenic neurons

It releases Neuropeptide Y to increase appetite

Orexigenic neurons

It stimulates anorexigenic neurons and inhibits orexigenic neurons

Leptin (fat cells), insulin and GLP-1

It inhibits anorexigenic neurons

Ghrelin (gastric cells)

Inhibits Ghrelin

Peptide YY

It refers to constant level of contraction or tone without regular periods of relaxation

Tonic contractions - orad stomach, lower esophageal, ileocecal and internal anal sphincters

Tonic contractions are due to _ waves

Subthreshold slow waves - not true action potential but capable of irregular contractions

It refers to periodic contractions followed by relaxation for mixing and propulsion purposes.

Phasic contractions - in esophagus, gastric antrum and small intestines

Phasic contractions are due to?

Spike potentials - true action potentials

Refers to GI pacemaker

Interstitial cells of Cajal

Depolarization during slow wave is due to?

Sodium influx

With slowest frequency

Stomach - 3waves/min

Fastest frequency

Duodenum - 12 waves/min

Spike potentials are due to?

Calcium influx - threshold of -40mV

What is the most common stimulus for Gi peristalsis?

Distention

It refers to muscles upstream contract, muscles downstream exhibit receptive relaxation

Myenteric reflex

What is the Law of the Gut?

Myenteric reflex + anal direction of peristalsis

How long does it take to transfer material from pylorus to ileocecal valve?

3-5 hours

How long does it take to transfer material from ileocecal valve to colon?

8-15 hours

Swallowing center?

Medulla

Three phases of swallowing?

Oral phase Pharyngeal phase Esophageal phase

Phase of swallowing that prevents aspiration of food contents

Pharyngeal phase - soft palate pulled upward, glottis covered, upper esophageal sphincter relaxes

Peristalsis that creates high pressure behind bolus of food propelling it towards the stomach

Primary peristaltic contraction - accelerated by Gravity

Relxation of the lower esophageal sphincter is vagally-mediated using?

VIP or vasoinstestinal peptide

Peristalsis that clears the esophagus of remaining food?

Secondary Peristaltic Contraction

Three muscle layers of the stomach

Inner oblique layer Middle circular layer Outer longitudinal layer

Three anatomic division of the stomach

Fundus, body and antrum

Two functional division of the stomach

Orad stomach ( thin-walled) and Caudad stomach ( thick-walled)

Refers to food propelled back to stomach for further reduction in particle size and mixing with gastric juice

Retropulsion - due to inner oblique muscle layer

Propelling of food from stomach to duodenum

Gastric emptying - 3 hours

Gastric emptying is inhibited by what?

Fat ( due to CCK) | H+ in duodenum (due to direct neural reflex)

Refers to the back-forth movement with no net forward motion.

Segmentation contraction - mixes chyme with pancreatic enzymes

It propels chyme towards the large intestines

Peristaltic contraction - actual peristalsis

What is reciprocally innervated means?

When one is contracted, the other is relaxed, and vice-versa. Prevent opposing each other

Sac-like segments due to segmental contractions of the large intestines

Haustra

It function merely for water absorption, to dry up feces

Proximal colon - 1.5L of water

Function as storage for feces

Distal colon

Refers to movement of colonic contents over long distances (from transverse colon to sigmoid colon)

Mass movement - occur 1-3x a day

Maneuver against closed glottis that assist defecation

Valsalva maneuver

Odor of the stool is due to what bacterial products?

Mercaptan, indole, skatole and hydrogen sulfide

Refers to increase peristalsis in ileum and relaxation of the ileocecal sphincter due to presence of food in the stomach

Gastroileal reflex

Food in the stomach increases peristalsis in the colon and frequency of mass movements

Gastrocolic reflex - mediated by parasympathetic NS, CCK and Gastrin

Refers to a reverse wave peristalsis that begins from the small intestines

Vomiting - preceded by Nausea

Vomiting center

Medulla

Incomplete vomiting

Retching

Gland with serous secretion only

Parotid gland

Gland with mixed secretion of mucus and serous

Submandibular and sublingual glands

Innervation of parotid gland

Cranial nerve 9

Innervation for submandibular and sublingual glands?

CN 9

Effect of sympathetic NS on salivation

Decreases salivation

Effect of parasympathetic NS on salivation

Increases salivation

Initial saliva is high in?

Sodium and Chloride ions

Final saliva is high in?

Bicarbonate and potassium ions

GI Physiology Flashcards

(93 cards)