Gastrointestinal Physiology Flashcards by Butch Cabatu

Use to locate the appendix

TAEnia Colin

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ANTRUM

G cells

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Parietal cells (IF, HCL)

Fundus

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Vitamin C & iron are absorbed

Duodenum

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All nutrients are absorbed

Jejunum

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Vitamin B12, IF, ADEK, Bile salt, Bile acids are absorbed

Ileum

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Folate

Jejunum

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Vagus nerve found

Transverse colon

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Absorption of water

Proximal colon

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Storage of feces

Rectum

Distal Colon

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Basic GI Layers

Mucosa
Submucosal
Muscularis
Serosa

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Smooth muscle cells controlling the epithelium

Muscularis Mucosa

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Collagen, elastin, glands and blood vessels

Submucosa

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Decreases diameter of the lumen

Inner Circular Muscle Layer

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Shortens segment of the GIT

Outer Longitudinal Muscle Layer

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Aka adventitia or mesothelium

Serosa

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between inner circular &amp; outer longitudinal muscle layers
For motility (inner circular &amp; outer longitudinal muscle layers)

Myenteric Plexus / Auerbach Plexus

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Which layer is NOT seen in the esophagus?

Serosa

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Strongest layer of the esophagus?

Submucosa

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3 muscle layers are found in the stomach instead of two. What are these muscle layers?

Inner Oblique
Middle Circular
Outer Longitudinal

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The Myenteric Plexus is mainly excitatory EXCEPT for which regions?

Pyloric Sphincter & Ileocecal Valve

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Esophageal to upper large intestines

vagus nerve

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Lower large intestines to anus

Pelvic nerves

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Secretion & absorption

Meisner plexus/ Submucosal Plexus

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Motility

Auerbach plexus/ Myenteric Plexus

For retropulsion of food

Inner oblique

G cells, stomach, Antrim

Gastrin

Stimulus: small peptides, stomach Distention, vagus nerve via GRP; inhibited by H & somatostatin

Gastrin

Increases gastric H secretion | Stimulates growth of gastric mucosa

Gastrin

S cells | Duodenum

Secretin

Stimulus: H in duodenum | Fatty acids in duodenum

Secretin

Increases Pancreatic HCO3 secretions Increases Biliary HCO3 secretion Decreases effect of gastric on gastric mucosa

Secretin

I cells | Duodenum & Jejunum

CCK | Cholecystokinin

Monoglycerides, FA, small peptides and AA

CCK | Cholecystokinin

Stimulates GB contraction, sphincter of Oddi Relaxation Increases Pancreatic enzyme & HCO3 secretion Increases growth of exocrine pancreas and gallbladder Inhibits gastric emptying

CCK | Cholecystokinin

K cells | Duodenum

Glucose - dependent Insulinotropic Peptide

Stimulus: Oral glucose, fat, AA

Glucose - dependent Insulinotropic Peptide

Increases Insulin secretion | Inhibits Gastric Emptying (only above normal physiologic levels)

Glucose - dependent Insulinotropic Peptide (GDIP)

M cells Duodenum Jejunum

Motilin

stimulus: Fasting

Motilin

Stimulates

Motilin

Most potent stimuli for gastric secretion

phenylalanine Tryptophan Methionine

Neurocrine from vagus nerve to G cells

GRP/Bombesin

GI hormone classifies as an INCRETIN

GIP | GLP 1

GI hormone responsible for the interdigestive myoelectric complex

Motilin

Secreted by pancreas in response to CHO, CHON, lipids

Pancreatic Polypeptide

Inhibits pancreatic HCO3 and enzymes

Pancreatic Polypeptide

Secreted by intestinal cells in response to hypoglycemia

Enteroglucagon

Stimulates glycogenolysis and gluconeogenesis

Enteroglucagon

Secreted by L-cells of small intestines

Glucagon-Like Peptide 1 (GLP-1)

Stimulates insulin secretion

Glucagon-Like Peptide 1 (GLP-1)

Secreted by cells throughout the GIT in response to H

Somatostatin

Inhibits release of ALL GI hormones

Somatostatin

Inhibits gastric H secretion

Somatostatin

Secreted by mast cells of gastric mucosa

Histamine

Increases H secretion; potentials gastric and Ach action

Histamine

Action of Ach

``` Contraction of smooth muscle in wall Relaxation of sphincter a Inc salivary secretion Inc gastric secretion Inc pancreatic secretion ```

Source of Ach

Cholinergic neurons

Action of NE

Relaxation of smooth much in wall Contraction of sphincters Inc salivary secretion

Source of NE

Adrenergic Neurons

Actions of VIP Vasoactive intestinal Peptide

Relaxation of smooth muscle Inc intestinal secretion Inc pancreatic secretion

Source of VIP

Neurons of mucosa and smooth muscle

Action of Gastrin-Releasing (GRP) or Bombesin

Inc gastric secretion

Source of GRP or Bombesin

Neurons of gastric mucosa

Actions of Enkephalins (Opiates)

Contraction of smooth muscle | Dec intestinal secretion

Source of Enkephalins

Neurons of mucosa and smooth muscle

Actions of neuropeptide Y

Relaxation of smooth muscle | Dec intestinal secretion

Source of Neuropeptide Y

Neurons of mucosa and smooth muscle

Action of substance P

Contraction of smooth muscle | Inc salivary secretion

Source of Substance P

Consecrated with Ach

Inhibits appetite | Found at the Ventromedial Hypothalamus

Satiety Center

Stimulates appetite | Found at the Lateral Hypothalamic Area

Appetite/Hunger Center

Sends signals to Satiety & Hunger Centers

Arcuate Nucleus

Releases POMC to decrease appetite

Anorexigenic Neurons

Releases Neuropeptide Y to increase appetite

Orexigenic Neurons

Stimulates Anorexigenic neurons, inhibits orexigenic neurons

leptin (fats cells), Insulin, GLP-1

Inhibits Anorexigenic neurons

Gherkin (gastric cells)

Inhibits gherkin

Peptide Y

Constant level of contraction or tone without regular periods of relaxation

Tonic contractions

Due to subthreshold slow waves

Tonic contractions

Orad (upper) region of the stomach and in the lower esophageal, Ileocecal and internal anal sphincter so

Tonic contractions

Periodic contractions followed by relaxation

Phasic Contractions

for mixing and propulsion | Due to spike potentials

Phasic Contractions

Seen in the esophagus, gastric Antrum, small intestines

Phasic Contractions

Not true action potential

Slow waves

Due to GI pacemaker Intertitial cell of cajal

Slow waves

Slowest frequency

Stomach

Fastest frequency

Small intestines

True action potential

Spike potential

What is the most common stimulus for GI peristalsis?

Distention

What is the Myenteric Reflex

Muscles Upstream contract, muscles downstream exhibit receptive relaxation

What is the Law of the GUT?

Myenteric Reflux + anal direction of peristalsis

How long does it take to transfer material from pyloric to Ilecocecal valve, and ileocecal valve to colon, respectively?

3-5 hours, 8-15 hours

The law of the gut is due to what phenomenon?

Peristaltic reflex | Receptive relaxation

Begins CHO digestion

Amylase

Swallowing center

Medulla

Triggers reflex when food is at the pharynx

Oral phase

Soft palate pulled upward (closes nasopharyngeal), glottis covered (prevents aspiration), upper esophageal sphincter a relaxes

Pharyngeal Phase

UES close, primary and secondary esophageal peristalsis occurs

Esophageal Phase

Capacity of stomach for food Amount of water absorb in proximal colon Amount of gastric secretion

1.5 L

Able to bypass the pyloric sphincter

Water

Who of the following is a possible effect of bago tony on gastric emptying?

Decreased emptying of solids

Back and forth movement with no net forward motion

Segmentation Contraction

Mixes chyme with pancreatic enzymes

Segmentation Contraction

Propels chyme towards large intestines

Peristaltic contraction

Mouth and stomach

Bonus

Small intestine

Chyme

Large ins testiness

Feces

Saclike segments due to segmental contractions of the large intestines

Haustra

For absorption of water

Proximal colon

For storage of feces

Distal colon

Occurs 1-3x a day to move colonic contents over long distances (from transverse colon to sigmoid colon)

Mass movement

Color of feces is due to

Stercobilin

Food in the stomach increases peristalsis in the ileum and relaxation of the Ileocecal sphincter

Gastroileal Reflex

Food in the stomach increases peristalsis in the colon and frequency of mass movement mediated by the Parasympathetic NS, CCK, gastrin

Gastrocolic Reflex

Vomiting center

Medulla

Incomplete vomiting | Closed UES

Retching

Submucosal of duodenum

Brunner's gland

Produce initial saliva | High Na, Low K

Acinar Cells

Reabsorption Na K Stimulated by aldosterone HCO3, K

Ductal Cells

Serous secretion

Parotid gland

Mixed secretion

Submandibular gland | Sublingual gland

Effect of Parasympathetic NS

Increases salivation

Effect of Sympathetic NS

Decreases salivation

Initial Saliva is high in

Na, Cl

Final saliva is high in

HCO3, K

Hormone involved in absorbing Na at the ductal cells

Aldosterone

At high flow rates, saliva has

High Na, Cl, Low K & High HCO3

At low flow rates, saliva has

Low Na, Cl, High K & Low HCO3

For proteins

HCL and Pepsinogen

For Vitamin B12 absorption

Intrinsic factor

For protection of gastric mucosa against HCL

Mucus

Body | HCL, intrinsic factor

Parietal cells

Body | Pepsinogen

Chief cells

Antrum | Gastrin

G cells

Antrum | Mucus, Pepsinogen

Mucus cells

Contains mucus neck cells, parietal cells and chief cells

Oxen tic glands (body)

Contains G cells, Mucus cells

Pyloric glands (antrum)

Secreted Mucus and HCO3

Mucus cells, Mucus Neck cells

Secreted Hcl and IF

parietal cells/oxyntic cells

Secretes gastrin

G cells

Secretes serotonin

Enterochromaffin cells

Secretes Histamine

Enterochromaffin-like Cells ECL

Secretes Pepsinogen

Chie/Peptic cells

Which of the following is the site of secretion of intrinsic factor?

Gastric Fundus of parietal cells

What are the 3 substances that stimulate HCL secretion?

Histamine (paracrine) - acting on H2 receptors Ach (Neurocrin) - act on M3 receptors Gastrin (GI hormone) - act on CCKb receptors

What are the inhibitors of HCL secretion?

Low pH (<3.0) of the stomach Somatostatin Prostaglandins

Give examples of anti-Muscarinic drug

Atropine

Example of H2-blocker

Cimetidine | S/e gynecomastia

PPI

Omeprazole -most effective

Stimuli of cephalic phase - 30%

Sight, smell, taste, thought of food

Stimuli of Gastric phase - 60%

Stomach Distention, AA, small peptides, alcohol, caffeine

Stimuli of Intestinal Phase - 10%

AA, peptides

What substances protects the mucosa from HCL and pepsin?

HCO3, Mucus

What are the protective factors against PUD?

Prostaglandins, mucosal blood flow, growth factors

What are the damaging factors?

H, pylori, NSAIDS, stress, smoking, alcohol

A patient with a duodenal ulcer is treated successfully with the drug cimetidine. The basis for cimetidine's inhibition of gastric H secretion is that it

Block H2 receptors on parietal cells

Secreted by S cells

Secretin

Acts on ductal cells | Increases HCO3 secretion

Secretin

Secreted by I cells

CCK

Acts on CCKa receptors in actin are cells and ductal cells | Potentials effect of secrets in increasing HCO3 secretion

CCK

Acts on Muscarinic receptors in actin are cells and ductal cells Also potentials effect of secretin in increasing HCO3 secretion

Ach

Via vagovagal reflexes

Ach

Most common component of Bile

Water

Active component of bile

Bile salts

Primary bile acid

Chenodeoxycholic acid

Secondary bile acid

Deoxycholic acid

Store bile

Gall bladder

Create bile

Liver

Causes Gall bladder contraction

CCK & Ach

Causes sphincter of ODDI relaxes

CCK

94% bile salts are recirculated back to the liver using

Na-Bile salt cotransporter in the terminal ileum (enterohepatic circulation)

Digestion of carbohydrates in the Mouth

Ptyalin

Digestion of carbohydrates in the Small intestine

Pancreatic amylase, brush-border enzymes, disaccharidases

How do you absorb Glucose and Galactose from lumen to intestinal cell

SGLT-1

How do you absorb Fructose from lumen to intestinal cell?

Glut 5

How do you absorb Glucose, Galactose, and Fructose from intestinal cell to the blood?

Glut 2

Digestion of proteins in the stomach

Pepsin, desaturation by HCL

Digestion of proteins in the Small intestine

Enterokinase, trypsin, chymotrypsin, Carboxypeptidases, peptidases

What is the optimum pH for pepsin activity?

Ph 1.0-3.0 | Inactivated at pH >5.0 (ex in duodenum)

Digestion of Triglycerides in the mouth

Lingual Lipase secreted

Digestion of Triglycerides in the Stomach

Lingual lipase activated, gastric lipase activated, mechanical pulverized ion of fat, CCK decreasing gastric emptying

Digestion of Triglycerides in the small intestine

Emulsification by bile salts, pancreatic lipase activated

Micelles

From lumen to intestinal cell

For absorption from intestinal cell to lacteals

Chylomicrons

Bile salts inactivated pancreatic lipase. What pancreatic coenzyme is secreted to prevent this from happening?

Procolipase -> Colipase

What is the only product of TGA metabolism that is NOT hydrophobic?

Glycerol

What type of fatty acids go directly to the portal vein instead of the lacteals

Short-chain and medium-chain fatty acids

Main site for water absorption

Jejunum

Potassium is absorbed at the following sites

Small intestines

Potassium is secreted at the following sites

Large intestine

Primary ion secreted in the intestinal lumen

Chloride (Na, H2O follows)

Needed to absorb vitamin B12

Intrinsic factor

Needed to absorb calcium

1,25 (OH)2 cholecalciferol

Needed to absorb iron

Vitamin C

Part of the metabolism of these vitamins involved colonic flora

Vitamin K, Vitamin B1, Vitamin B2, Vitamin B12

Is absorbed in the SI via passive diffusion using Paracellular route

Potassium

Is secreted in the Colon similar to renal distal tubule

Potassium

ADP ribosylation of As subunit of Gs protein coupled to adenylyl Cyclades -> permanent activation -> water follows

V. Cholera

Increases Calbindin D-28K (calcium-binding proteins in the SI)

Calcitriol

Initiation digestion of fats starts in the

Stomach

Mechanism of transport associated with glucose absorption in the intestine via SGLT1?

Secondary active transport

Transport protein responsible for transport of glucose from the intestinal cells basement membrane to the blood?

glut 2

``` All of the following are absorbed through the intestine through secondary active transport except? A. Galactose B. Amino acids C. Bile salts D. Vitamin A E. Vitamin B ```

D. Vitamin A - fat soluble- simply diffuse

``` Which of the following is not an endopeptidase? A. Trypsin B. Chymotrypsin C. Elastase D. Aminopeptidase ```

D. Aminopeptidase

``` All of the following can hinder dietary absorption of calcium except? A. Excess fatty fooods B. phytic acid C. Oxalate from some vegetables D. Nota ```

D. Nota

Site of iron absorption in the gut?

Duodenum

``` All of the following assist in iron absorption except? A. Heme form of iron from meat B. Reduction of iron to Fe2 C. Vitamin C D. Alcohol E. Fructose F. None ```

F. None

Binding protein that assist in the absorption of vitamin B12 secreted in the saliva?

cobalophilin

Largest organ

Liver

2% of total body weight, receives 25% of cardiac output

Liver

Detoxification and excretion of waste products is using

Cytochrome P450 enzymes (Phase 1 reactions) | Conjugation (phase 2 reactions)

Fat soluble -> Glucoronic acid (polar)

UCB/IB

Urobilinogen -> stercobilin (yellow color feces)

CB/DB

Functional unit of the liver

Classic liver lobule

High O2 and nutrients | First to encounter toxins

Zone 1 / Periportal

Mid zonal

Zone 2

Low o2 and nutrients | Last to encounter toxins

Centrilobular/Zone 3

Are extremely effective in blood cleansing

Kuppfer cells

Liver

Space of disse | Vitamin A storage

ITO cells

Liver sinusoids | APC

Kuppfer cells

Gastrointestinal Physiology Flashcards

(222 cards)