Phar 371 - Structure/ Function And Diseases Of The Gi Tract

Front 1

From the outside to inside, what are the layers of the GI tract?

Back 1

1. Mucosa

2. Submucosa

3. Muscularis (propria) externa

4. Serosa

Front 2

What are the structures found in the mucosa?

Back 2

1. Epithelium

2. Lamina propria (blood vessels, lymph, lymphocytes, nerves, glands)

3. Muscularis mucosa (thin layer of smooth muscle)

Front 3

What nerve structures are found in the submucosa?

Back 3

Submucosal plexus (meissner's plexus)

- preganglionic parasympathic neurons synapse with postganglionic nerve fibers

- muscularis mucosae is regulated

Front 4

What are the functions of the layers of smooth muscle in muscularis externa?

Back 4

The circular (inner layer) contracts to prevent backward movement.

The longitudinal (external layer) advances food by shortening tract.

Front 5

The intrinsic pacemaker activity of the enteric nervous system is controlled by:

Back 5

Interstitial cells of cajal, and modulated by CNS

Front 6

What is the function and location of auerbach's plexus?

Back 6

Between layers of muscularis external.

Vagus nerve control from brain stem controls peristalsis (motor innervation)

Front 7

What are the different morphologies of the serosa?

Back 7

1. Intraperitoneal (covering GI tract with CT and mesentery)

2. Continuous boundary between gut and surrounding itssues (covers small intestines, appendix, colon and rectum)

3. Reteroperitoneal - covered with adventitia (connective tissue covering organs blend directly into surroundings, such as oral cavity, esophagus, pylorus of stomach)

Front 8

What is the difference between segmental and tonic contractions?

Back 8

1. Segmental contractions (mixing in stomach, small and large intestines)

2. Tonic contractions (sphincter tightening in upper esophageal, pyloric, anal)

Front 9

How and why do segmental contractions occur?

Back 9

They occur during and after ingestion.

Dual directionality of alternating contractions of circular muscles.

These mix chyme to help chemical and mechanical digetion, and improves absorption by increasing contact with epithelium.

Front 10

How is blood supplied to the GI?

Back 10

By the splanchnic circulation

Front 11

What are the 3 main arteries in the GI?

Back 11

1. Celiac (stomach, spleen)

2. Superior mesenteric (pancrease, small/ large intestine, colon)

3. Inferior mesenteric (large intestine)

Front 12

Where is mucus secreted, and function?

Back 12

Stomach - mucus cells

Intestine - goblet cells

Mucus lubricates and protects GI

Front 13

What is the purpose of bile?

Back 13

Helps with eliminating body wastes and aids fat absorption.

Bile salts enable micelle formation for fat absorption.

Front 14

How is the GI tract regulated chemically and neuronally?

Back 14

Neuronal:

• ENS (intrinsic and isolated to GI tract)
• CNS ((para)sympathetic)

Chemical:

• paracrine
• endocrine

Front 15

T/F: The enteric nervous system can operate independently without CNS signals.

Back 15

True

Front 16

What are the two sections of the ENS?

Back 16

1. Myenteric (auerbach's plexus) - between inner/ outer layers of muscularis externa

2. Submucosal (meissner's plexus) - in submucosa

Front 17

Function of auerbach's plexus?

Back 17

Regulates GI motility (peristaltic, rhythmic, tonic contractions)

Also interacts with CNS sensory data (e.g. sight, smell)

Front 18

Function of meissner's plexus?

Back 18

Innervaates epithelium and smooth muscle for GI secretion and local blood flow.

Front 19

What are some GI hormones (specialized peptide molecules)?

Back 19

Gastrin, CCK, Secretin, Gastric inhibitory peptide, glucagone-like peptide 1, motilin

Front 20

When and where is gastrin secreted from?

Back 20

Secreted from G cells in stomach (plus duodenum and pancreas). Triggered by stomach distension (eating), vagal stimulation, and amino acids from digestion.

Front 21

Function of gastrin?

Back 21

Increase gastric acid secretion, stimulate growth of gastric mucosa, and increase/ strengthen muscle contraction.

Front 22

When and where is CCK secreted from?

Back 22

I cells in stomach, duodenum and jejunem.

Secreted by fatty acid, monoglycerides, and amino acids in chyme. Also secreted with acetylcholine release from vagus.

Front 23

Function of CCK?

Back 23

Gall bladder release bile

Pancreatic enzymes secretion

Inhibit bicarbonate secretion

Inhibit gastric emptying and acid secretion

Front 24

When and where are secretin secreted from?

Back 24

From S cells in duodenum, triggered by low pH entering duodenum.

Front 25

Function of secretin?

Back 25

– Increase bicarbonate release from pancreas (Acid neutralization)
– Bile release from gall bladder
– Inhibits gastrin release to reduce gastric acid secretion
– Regulates water homeostasis
– Enhance cholecystokinin (CCK) release

Front 26

When and where are gastric inhibitory peptides (GIP) synthesized from?

Back 26

Made in K cells in mucosa of duodenum and jenunum. Triggered released by glucose, amino acids and fatty acid.

Note: GIP is incorrectly named and originally thought was secretin.

Front 27

Function of gastric inhibitory peptides (GIP)?

Back 27

Stimulates insulin release and lipase activity for fatty acid digestion.

Note: GIP is incorrectly named and originally thought was secretin.

Front 28

When and where are glucagone-like peptide-1 (GLP1) secreted from?

Back 28

Secreted in L cells in intestine

Triggered by fatty acids, amino acids, glucose

Front 29

Function of glucagon-like peptide-1 (GLP-1)?

Back 29

Stimulates proliferation of beta cells in pancrease

Inhibit glucacon secretion

Inhibit gastric acid secretion

Inhibit gastric motility

Minor role as incretin

Front 30

When and where is motilin secreted from?

Back 30

Non-payer's patch M cells in small intestine

Generally released during non-ingestion (fasting) every 100 minutes.

Front 31

Function of motilin?

Back 31

Stimulate migrating motor complex

General maintenance of gut motility

Muscle contraction

Front 32

Which of the following paracrine hormones have excitatory functions for GI?

a. Prostaglandins

b. Histamine

c. Serotonin

d. Somatostatin

Back 32

b. Histamine

Front 33

Function of histamine?

Back 33

Produced by enterochromaffin-like cells to stimulate gastric secretion. Is also stimulated by gastrin.

Front 34

Function of prostaglandins?

Back 34

Inhibits gastric acid secretion

Front 35

Function of serotonin?

Back 35

Decreases appetite. Produced by enterochromaffine cells in GI tract.

Front 36

Function of somatosatin?

Back 36

Reduces gastric emptying and muscle contraction by inhibiting gastrin, CCK, motilin, secretin and histamine. Secreted in stomach, intestines and pancreas.

Front 37

What are the properties of the sphincters in the esophagus?

Back 37

1. Upper esophagus sphincter (UES) - striated circular muscle

2. Lower esophageal sphincter (LES) - constantly contracted smooth muscle (tonic)

Front 38

When does transiet LES relaxation (TLESR) occur?

Back 38

During swallowing, belching, and vomitting.

Front 39

What is esophagitis?

Back 39

Esophageal inflammation, caused by irritation or infection.

Can be acute or chronic and also causes heartburn and nausea.

Front 40

What is achalasia?

Back 40

Failed motility in esophagus due to problems with innervation. Results in LES staying contract, or loss or peristalsis.

Causes chest pain, regurgitation, and difficulty swallowing.

Front 41

Function of stomach? (3)

Back 41

• Food resevoir
• Mix with gastric secretions
• Chemical and mechanical digestion

Front 42

What cells types are present in the stomach?

Back 42

1. Mucus cells (mucus)

2. Parietal cells (HCl)

3. Enterchromaffin-like cells (histamine)

4. Chief cells (pepsinogen)

5. G cells (gastrin)

6. D cells (somatostatin)

Front 43

In chronological order, what are the percentages of acid secretion based on each phase? (4)

Back 43

1. Basal (low background acid secretion)

2. Cephalic phase (sight, smell, taste, etc) - 30%

3. Gastric phase - 60%

4. Intestinal phase - 10%

Front 44

What are the lengths of the regions of the small intestine?

Back 44

Duodenum - 25cm

Jejunum - 2.5m

Ileum - 4m

Front 45

Function of small intestine?

Back 45

Digestion

Absorption of nutrients and minerals

Front 46

Which cell types are found on villi? (4)

Back 46

1. Stem cells

2. Enterocytes (columnar epithelium for the brush border)

3. Goblet cells

4. Endocrine cells

Front 47

Which digestive enzymes are secreted by enterocytes on villi? (3)

Back 47

Glycopeptidases, lactase, sucrase

Front 48

In order of first to last, what are the regions of the large intestine?

Back 48

1. Cecum (with appendix)

2. Ascending colon

3. Transverse colon

4. Descending colon

5. Sigmoid colon

6. Recum

Front 49

What cell types are present in the large intestine?

Back 49

Way more goblet cells than SI

Columnar epithelium and invaginations (not villi fingers)

Front 50

Function of large intestine? (3)

Back 50

Absorption of water and electrolytes

Absorb vitamin (B and K especially) produced by flora

Waste concentration and storage

Front 51

Diarrhea is defined as: (3)

Back 51

1. Increase stool frequency

2. Increase stool volume

3. Decrease stool consistency

Causes loss of fluids leading to dehydration and electrolyte imbalance.

Front 52

What are the types and duration of diarrhea?

Back 52

1. Acute (<2weeks, self limited and resolving. Usually infection based.)

2. Persistent diarrhea (2-4 weeks)

3. Chronic diarreah (>4 weeks)

5. Dysentry

Front 53

Define: dysentry

Back 53

Dysentry is bloody diarrhea that produces serous, sanguinous, and purulent exudate. Can be caused by bacillary (bacterial) or amoebic infections.

Front 54

What are the causes of diarrhea?

Back 54

1. Secretory (water large volume, painless output)

2. Osmotic (ingested poorly absorbed solutes)

3. Motility-related (too rapid movement through intestines)

4. Inflammatory/ exudate (inflammation damages mucosa, causing epithelium leaking protein-rich fluids)

Front 55

What is irritable bowel disease? (IBD)

Back 55

Immune mediated chronic and recurring inflammation of digestive tract. Divided into ulcerative colitis (UC) and Crohn's disease (CD)

Front 56

Where are ulcers located in UC and CD?

Back 56

UC: begins in rectum and spreads to colon. Ulcers in mucosa/ submucosa to make continuous or pseudopolyps

CD: Mouth to anus (ileum most common) and affects all layers, leading to "cobblestone" look

Front 57

Which age group(s) are most likely to get UC or CD?

Back 57

UC: 15-30 or >50

CD: >50

Front 58

Risk factors to IBD? (7)

Back 58

• Hypersensitivity to endogenous flora/ enteropathogens
• Autoimmunity
• Genetic predisposition
• Intestinal flora composition
• Epithelial integrity in intestine
• Mucosal immunity
• Lifestyle

Front 59

Symptoms of UC? (4)

Back 59

• Diarrhea (blood and mucus)
• Tenesmus (constant feeling of needing to crap)
• Weight Loss
• Pain

Front 60

Symptoms of CD? (4)

Back 60

• Diarrhea (consistency depends on region infected)
• Pain or no pain (usually right lower quadrant)
• Weight loss
• Malnutrition fever

Front 61

What are complications of IBD?

Back 61

Fibrosis can cause intestinal obstruction. Perforations also can form fistulas - abnormal connection between adjacent organs.

Front 62

Define: irritable bowel syndome (IBS)

Back 62

Characterized by chronic abdominal pain

Occurs without apparent structural or chemical abnormality

Front 63

Classification of IBS? (4)

Back 63

D - Diarrhea dominant

C - Constipation dominant

A - Alernating pain predominant

PI - Post infection onset

Front 64

Symptoms of IBS? (4)

Back 64

1. Chronic abdominal pain (episodic cramps increase with eating and stress)

2. Discomfort and bloating

3. Alternation of bowel habits (form and frequency change)

4. Pooping improves symptoms