Digestion

Question 1

Why is the mouth acidic?

Answer 1

Anaerobic environment => carb turned into lactic acid => pH < 5.5 => tooth decay/demineralization => cavities

Higher pH => enzymes non functional

Question 2

2 major + 3 minor digestive enzymes found in saliva?

Answer 2

Major:
Alpha-amylase
Lingual lipase

Minor:
Superoxide dismutase
Glutathione transferase
Immunoglobulin A

Question 3

Function of alpha amylase?

Answer 3

Initiates digestion of amylose/amylopectin chains => maltotriose, maltose, amylose, glucose, oligosaccharides

Question 4

Function of lingual lipase?

Answer 4

Initiates hydrolysis of long chain TGs into diacylglycerol and free FAs (pH~4)

Question 5

Function of superoxide dismutase?

Answer 5

Reduces highly reactive superoxide holecules

Question 6

Function of Glutathione transferase?

Answer 6

Detoxification

Question 7

Function of IgA?

Answer 7

Antibacterial

Main Ig in saliva => immunity

Question 8

What is meth mouth?

Answer 8

Meth acts on alpha-adrenergic receptors => reduces saliva => counteract buffering of acids => BEAUTIFUL tooth decay

Question 9

pH of stomach? Regulated how?

Answer 9

Enzymes are activated by pH~1-2

Regulated by ANS and hormones controlled by Vagus Nerve

Question 10

Cell types in gastric mucosa of stomach + secretory product

Answer 10

Mucous surface cells+ Mucous (neck) or foveolar cells => producing mucous HCO3, H2O => protective barrier from corrosive gastric acid and digestive enzymes

Oxyntic (parietal) cells => H/Cl/IF/H2O

Peptic (chief) cells => pepsinogen, H2O

Question 11

All secretory mucosa cells therefore produce?

Answer 11

Water

Question 12

Secretions of parietal cells are stimulated by?

Answer 12

Located in fundus:

Histamine via H2 receptor

Gastrin => via CCK2/gastrin receptor => histamine

Vagus nerve => via ACh/M3

Question 13

Chief (zygomenic/peptic) cells produce? Regulated by?

Answer 13

Pepsinogen = proenzyme of pepsin => cleaves peptide bonds at hydrophobic/aromatic AAs such as phe,trp,tyr

Stimulated by: vagus nerve, acidic conditions, hormones gastrin/secretin

Question 14

Function and location of Enterochromaffin-like and G cells?

Answer 14

Enteroch.. ELC:
Found in gastric glands => stimulated by gastrin, pituitary adenyl cyclase-activating peptide => inhibited by somatostatin

G cells:
Found in pyloric antrum => secretes gastrin => increased by vagus nerve activity or large amounts of AAs in stomach

Question 15

Function of PGE2?

Answer 15

Decreases parietal cell secretion of gastric acid

Increases mucus production

Question 16

What is misoprostol? What is it used for?

Answer 16

= synthetically produced PGE1 => prevent gastric ulcers (short term care)

Question 17

Where in the GI is gastrin produced?

Answer 17

Antrum of stomach until end of jejunum

Question 18

Where in the GI is CCK and Secretin produced?

Answer 18

Beginning of Duodenum until end of Ileum

Question 19

Where in the GI is GIP and Motilin produced?

Answer 19

Beginning of Duodenum until end of Jejunum

Question 20

5 major digestive hormones?

Answer 20

Cholecystokinin CCK

Enteroglucagon

Gastrin

GIP (gastric inhibitory peptide)

Motilin

Secretin

Somatostatin

VIP (vasoactive intestinal polypeptide)

Question 21

Function of Gastrin (this is a Q on the exam for sure)?

Answer 21

Inhibited by pH<4 and somatostatin
Stimulates HCl, IF, pepsinogen, rening, histamine

=> Increases smooth muscle contraction of stomach

Question 22

Which hormones promote smooth muscle relaxation aka decreased smooth muscle contraction?

Answer 22

GIP

VIP

Question 23

Which hormones inhibit stomach emptying and HCl?

Answer 23

CCK
Enteroglucagon
Somatostatin

Question 24

What is Achlorhydria and Hypochlorhydria?

Answer 24

=> production of HCl in stomach is absent/low => due to destruction/damage of parietal cells

=> increase in pH, bacterial growth, diarrhea
=> decrease of essential ion absorption

Question 25

What is GERD?

Answer 25

Gastroesophageal Reflux Disease => basically when the upper sphincter in the stomach is absent/damaged => acid exposure to lower esophagus => cancer Treatment: H2 blockers => block histamine action on parietal cells or Proton pump inhibitors => same result => lower pH

Question 26

One of the liver functions is production of coagulation factors. What do they do?

Answer 26

=> clot formation/breakdown Coagulation factors: I = fibrinogen II = prothrombin V, VII, IX-XI

Question 27

Function of bile?

Answer 27

Fat emulsification

Question 28

How is hemoglobin degraded to bilirubin?

Answer 28

Spleen: heme+NADPH -> biliverdin + Fe3+ => biliverdin + NADH -> conjugated bilirubin Blood: transport by albumin Liver: conjugated with glucoronic acid = make soluble => excreted in bile => small intestine Intestine: bacteria => convert to urobilinogen/stercobilin => partly reabsorbed/excreted

Question 29

How is bilirubin measured/test?

Answer 29

Reported as conjugated: azo dye reacts directly with conjugated bilirubins => red/violet color

Question 30

Main points of detoxification process in liver? (Very likely on the exam)

Answer 30

Start with less polar molecule => phase I Phase I: (increase polar nature, uses cytochrome p450) 1) oxidation => lipophilic => electrophile (some oxygen ring/double bond) 2) reduction => nucleophile (some special group attached) Phase II: (permanently inactivate toxin/drug) 1) glutathione conjugation leading to R-SG (hydrophilic) 2) sulfation/acetylaction/glucuronidation

Question 31

Detoxification of alcohol?

Answer 31

Ethanol --alcohol dehydrogenase--> acetaldehyde (toxic) --acetaldehyde dehydrogenase-->acetic acid (vinegar) First reaction is faster than second.

Question 32

Which organ is the only one capable of disposing cholesterol?

Answer 32

Liver => bile salts or distributed as LDL

Question 33

How do u get fat?

Answer 33

TGs are packed with cholesterol into VLDL => secreted into blood to deliver FAs to adipose cells

Question 34

What is the role of the gallbladder?

Answer 34

Stores/concentrates bile produced by liver => released into duodenum in response to CCK secretion

Question 35

What is bile?

Answer 35

Contains water, ions, lipids, proteins, bile acids and Glycine- and taurine-conjugated bile acids => enables lipid degrading enzymes to act and promotes absorption of fats/fat soluble Vit

Question 36

What does CCK do?

Answer 36

Induces bile expression from gall bladder Stimulates release of pancreatic digestive enymes: trypsin, chymotripsin, pancreatic lipase/amylase to aid fat/protein digestion

Question 37

Five F's of cholesterol gallstone formation?

Answer 37

Cholesterol gallstones = type of cholelithiasis ``` Female Forty Fertile (had many pregnancies) Fat Fair ``` Think of that woman with the 19 kids and counting. Ridiculous

Question 38

2 functions/cell types of pancreas?

Answer 38

Exocrine function => release enzymes => proteases etc Endocrine function => release hormones, under ANS control => alpha cell => sympathetic/adrenergic innervation => glucagon => beta cell => insulin, amylin => both: parasympathetic/ muscarinic innervation

Question 39

Other two cell endocrine pancreatic cell types and hormone associated with it?

Answer 39

Delta cells => somatostatin Epsilon => ghrelin "hunger hormone"

Question 40

Small intestine portion, elongation factor, and absorbed molecule?

Answer 40

Elongated by x500 due to folds Duodenum: Fe/Ca/Carb/Fat/Protein Jejunum: Carb/Fat/Protein Ileum: Fat/Protein/Bile salts/Vit B12

Question 41

Functions of ileum?

Answer 41

Provides continued digestion and absorption and immunoprotection Absorption of Vit B12/IF/bile salts

Question 42

What is Pernicious Anemia?

Answer 42

Decrease in RBC count => decrease in absorbed B12 due to lack of IF Cause: immune attack against IF/cells producing it

Question 43

Functions of large intestine by location?

Answer 43

Ascending: absorption of H2O/ions Transverse: bacterial fermentation of nonabsorbed nutrients Descending: storage of waste/indigestible stuff

Question 44

Importance of gut flora?

Answer 44

``` Bacteria digest/ferment carbs/proteins, aid absorption of lipids/Ca/Mg/Fe, augment levels of vit K/biotin=B7 Produces modified/secondary bile salts Important for growth of intestinal lymph tissue Helps eliminate ingested carcinogens ```

Question 45

Problem with antibiotics and Clostridium difficile?

Answer 45

Barrier effect destroyed by antibiotics => C. Difficile releases toxins causing chronic diarrhea/bloating etc => pseudomembraneous colitis Diagnosed via cell culture (cytotoxins)/EIA/PCR Treatment: vancomycin, fecal transplant aka ingesting somebody else's doodoo :o)