Week 1

Question 1

Diverticulitis

Answer 1

Multiple diverticulum (diverticulosis) which are pouches protruding from the alimentary tract that become impacted w/ feces, inflamed, painful, and if blood vessel is eroded hemorrhage.

True divertucula - all layers of bowel

False divertucla - includes only serosa and mucosal layer.

Question 2

4 basic processes facilitating caloric uptake

Answer 2

Digestion
Absorption
Secretion
Motility

Question 3

Absorption of amino acids

Answer 3

D and J through secondary active transport (sodium)

Question 4

Absorption of monosaccharides

Answer 4

D and J through secondary active transport (sodium)

Question 5

Fat absorption

Answer 5

Bile salts facilitate absorption which occurs primarily in the ileum.

Question 6

B12 absorption

Answer 6

Ileum

Question 7

Mesenteric Ischemia

Answer 7

Causes:

• Occlusive mechanisms including thrombi
• Non-occlusive mechanisms including prologed refelx vasoconstriction (hypovolemia, heart failure) or abnormal levels of circulating vasoconstrictors (epi, at II)

Effects:

• Posprandial pain and sitophobia (fear of eating)
• Necrosis of the tips of the villi
• Loss of barrier function of the wall of the gut –>uptake of the vasodilator toxins from the gut –> septic shock.

Question 8

Osmotic diarrhea

Answer 8

Small bowel overgrowth of bacteria leads to increased production of organic acids sufficient to pull water from the blood streams by osomosis

I.e. lactose intolerance

Question 9

Secretory diarrhea

Answer 9

Infection leads to excess secretion of chloride drawing water into the lumen.

I.e. cholera

Question 10

Average Transit time

Answer 10

Esophagus 10 s
Stomach 4-5hrs
Small Intestine 2.5-3 hrs
Large Intestine 30-40 hrs.

Question 11

Gi Smooth Muscle Contraction

Answer 11

1. Rhythmic “phasic” (seconds) contractions (peristaltic waves) and long “tonic” contractions (minutes to hours –> sphincters)
2. ) Basal resting tension or tone is maintained without elevation in intracellar Ca++ and without energy expenditure (sphincters)
3. ) GI smooth muscle has a remarkable ability to shorten (to 50%)
4. ) Can initialte depolarization in response to stretch –> contraction

Question 12

Migrating motor complex

Answer 12

Relaxation of sphincters and contractions in stomach and si occurring during fasting (inter-digestive) controlled by hormone motilin.

Question 13

Excitatory (contraction) Neurotransmitters

Answer 13

Ach

Neurokinin A

Substance P

Question 14

Inhibitory (relaxation Neurotransmitters

Answer 14

Vasoactive Intestinal Peptide (VIP) and Nitric Oxide

Question 15

Vago-vagal reflex

Answer 15

Vagal afferent info is transmitted to autonomic centers in the medulla

Vagal efferents coordinate excitatory and inhibitory activity within the Enteric Nervous System to mediate peristalsis.

Question 16

Acetylcholine

Answer 16

Primary excitatory NT from sensory cells and from motor neurons to muscle, epithelium, secretory cells, and at intraneural junctions –> increases ic CA++

Question 17

Gastrin Releasing Peptide

Answer 17

Released from vagal nerve endings to stimulate G cell secretion of gastrin

Question 18

Substance P (tachykinin)

Answer 18

An excitatory transmitter generally coreleased w/ Ach

Question 19

Vasoactive Intestinal Peptide

Answer 19

Promotes motility

Releases smooth muscle in esophagus and stomach

Stimulates fluid secretion and promotes dilation of the GI vasculature.

Increases cAMP

Question 20

Nitric Oxide

Answer 20

Inhibitory transmitter co-released w/ VIP from inhibitory motor neurons, hydrophobic intracellular targets.

Question 21

Gastrin

Answer 21

G cells in the antrum of stomach detect amino acids leading to pepsinogen and H+ release by parietal cells

Question 22

Cholecystokinin (CCK)

Answer 22

I cells in D/J detect fat and amino acids, secretion of pancreatic enzymes and bile salts involved in fat uptakes

Question 23

Secretin

Answer 23

S cells primarily in D/J detect acid stimulates secretion of pancreatic juice including bicarb and inhibits gastric motility

Question 24

Gastric Inhibitory Peptide or Glucose-Dependent Insulinotropic Peptide (GIP)

Answer 24

K cells in D/J detect carbs and fat to inhibit gastric acid secretion and stimulate insulin release from pancreas

Question 25

Motilin

Answer 25

Secreted by endocrine cells; released cyclically during fasting state to initiate Migrating Motor Complex

Question 26

Small intestine bacterial overgrowth syndrome

Answer 26

Occurs due to delayed small intestine transit and diverticulum

Sx: Gas and bloating from fermentation;
Compete for B12 uptake leading to anemia;
deconjugate bile acids –> steatorrhea;
produce toxins altering epithelium

Question 27

GI properties that limit colonization by microbes

Answer 27

Saliva contains lactoferrin, lysozyme, and secretory IgA

Acidic stomach

More lymphocytes in GI than in circulating immune system

Mucus -mucins, IgA, lysozyme, lactoferrin

Paneth cells secrete defensins (antimicrobial peptides)

Peyer’s patches contain M cells to transport antigens to B and T cells

Digestive enzymes cleave bacteria

Diarrhea & Vomiting

Microflora prevent colonization of pathogenic organisms (probiotics and prebiotics)

Peristalsis, Ileoceccal valve