GI Secretory Functions, Digestion, Absorption

Question 1

What are the gland types of the digestive tract?

Answer 1

Unicellular mucous glands
Crypts of Lieberkuhn
Tubular glands
Complex glands:
-Salivary glands
-Pancreas
-Liver

Question 2

What are the mechanisms of stimulation?

Answer 2

Food contact and local epithelial stimulation
Autonomic stimulation (parasympathetic mostly)
Higher brain centers
Hormonal stimulation

Question 3

What are the functions of mucous (secretion of water and electrolytes?

Answer 3

Adheres to food and other particles
Spreads thin film over surfaces
Coats wall of gut, preventing actual contact of food.

Question 4

What causes fecal particles to adhere to one another?

Answer 4

Mucous

Question 5

What is resistant to digestion by GI enzymes and has amphoteric properties making it useful for buffering small amounts of acids and bases?

Answer 5

Mucous

Question 6

What are the salivary glands?

Answer 6

Parotid, submandibular and sublingual

Question 7

Parotid gland secretions are what?

Answer 7

Almost entirely serous

Question 8

Submandibular and sublingual secretions are waht?

Answer 8

Mixed

Question 9

Where does the first stage of salivary secretion of ions occur?

Answer 9

In acini

Question 10

First stage of salivary secretion of ions contains what?

Answer 10

ptyalin (alpha-amylase)

Question 11

First stage of salivary secretion of ions is typical of what?

Answer 11

Extracellular fluid

Question 12

Where does the second stage of salivary secretion of ions occur?

Answer 12

In salivary ducts

Question 13

In the salivary ducts there is active and passive secretion and reabsorption of what ions?

Answer 13

Active reabsorption of sodium ions
Active secretion of potassium ions
Active/passive secretion of bicarbonate ions
Passive reabsorption of chloride ions due to -70 mv in ducts

Question 14

What is the final ionic concentration of saliva normally?

Answer 14

?

Question 15

What is the concentration of ions during maximal secretion?

Answer 15

?

Question 16

Nervous regulation of salivary secretion is via what?

Answer 16

parasympathetic system

Question 17

List factors that stimulate or inhibit salivary secretions

Answer 17

?

Question 18

What are the secretory cell types in gastric glands?

Answer 18

Mucous neck cells
Chief (peptic) cells
Parietal (oxyntic) cells

Question 19

What cell secretes pepsinogen?

Answer 19

Chief cells

Question 20

What is pepsinogen?

Answer 20

The inactive form of pepsin

Question 21

What is pepsin?

Answer 21

A proteolytic enzyme that functions at a pH range of 1.8 to 3.5

Question 22

What is the release of pepsinogen stimulated by?

Answer 22

Ach from vagus nerves or gastric enteric nervous plexus

Response to acid in stomach

Question 23

Chief cells also release what in addition to pepsinogen?

Answer 23

Intrinsic factor

Question 24

What cell secretes HCl?

Answer 24

Parietal cells

Question 25

Describe how HCL is made by parietal cells?

Answer 25

H2O in the cell breaks down into H and OH Hydrogen is pumped out in exchange of K K leaks out OH combines with CO2 in the cell to form HCO3 HCO3 is pumped into the extracellular fluid in exchange for Cl Cl is secreted through chloride channels into the canaliculi *Na+ is reabsorbed into the cell due to Na+-K+ basolateral pump

Question 26

Stimulation of gastric secretions is via what nervous system?

Answer 26

parasympathetic

Question 27

What is gastrin secreted by?

Answer 27

By gastrin (G) cells in pyloric glands

Question 28

What are the two forms of gastrin?

Answer 28

G-34 and G-17 (more abundant)

Question 29

The release of gastrin is in response to what?

Answer 29

To the presence of protein in pylorus

Question 30

Gastrin in the pylorus causes what?

Answer 30

enterochromaffin-like cells to release histamine

Question 31

What does the presence of histamine cause?

Answer 31

The secretion of HCl

Question 32

What are the phases of gastric secretions?

Answer 32

Cephalic phase Gastric phase Intestinal phase

Question 33

Describe the cephalic phase

Answer 33

Via the vagus nerve and is stimulated when food is seen or smelled. Parasympathetics excite pepsin and acid production

Question 34

Describe the gastric phase

Answer 34

It is the phase when food is in the stomach Local nervous secretory reflexes Vagal reflexes Gastrin-histamine stimulation

Question 35

Describe the intestinal phase

Answer 35

Feedback to the stomach in result of the material being feed to it

Question 36

HCl + NaHCO3 ->

Answer 36

NaCl + H2CO3

Question 37

What are the digestive enzymes for proteins?

Answer 37

Trypsin, chymotrypsin, and carboxypolypeptidase (pancreatic secretions and by glandular cells)

Question 38

What inhibitor is secreted by the pancreas?

Answer 38

Trypsin inhibitor

Question 39

What is the purpose of trypsin inhibitor?

Answer 39

Necessary to prevent the action of trypsin on the pancreatic tissues themselves

Question 40

What are the digestive enzymes for carbohydrates?

Answer 40

Pancreatic amylase

Question 41

What are the digestive enzymes for fat?

Answer 41

Pancreatic lipase, cholesterol esterase, phospholipase | pancreatic secretions

Question 42

How are bicarbonate ions produced for pancreatic secretion?

Answer 42

H20 + CO2 (from the blood) (involves carbonic anhydrase) -> H2CO3 -> HCO3 + H HCO3 + Na are actively transported into duct lumen Hydrogen ions are exchanged for sodium ions

Question 43

What regulates pancreatic secretions?

Answer 43

Acetylcholine, cholecystokinin, secretin

Question 44

Acetylcholine for pancreatic secretion regulation comes via what?

Answer 44

Parasympathetic nerves and enteric nervous system

Question 45

Cholecystokinin release is stimulated by what?

Answer 45

Presence of food in upper intestine

Question 46

What is cholecystokinin secreted by?

Answer 46

Duodenal and upper jejunal mucosal cells

Question 47

What does the release of cholecystokinin result in?

Answer 47

Dramatic increase in secretion of pancreatic enzymes

Question 48

The release of secretin is stimulated by what?

Answer 48

Presence of acidic food in upper intestine

Question 49

What is secretin secreted by?

Answer 49

Duodenal and upper jejunal mucosal cells

Question 50

What does secretin stimulate?

Answer 50

Release of large amounts of sodium bicarbonate

Question 51

Bile is secreted continuously by what?

Answer 51

Hepatocytes in the liver

Question 52

Where is bile stored?

Answer 52

In the gallbladder until needed

Question 53

In the gallbladder, how is bile concentrated?

Answer 53

By active transport of sodium followed by secondary absorption of chloride ions, water, and other diffusible constituients

Question 54

What factors stimulate the release of bile from the gall bladder?

Answer 54

Presence of fatty food in duodenum

Question 55

How is bile salts synthesized in liver?

Answer 55

Cholesterol is converted to cholic acid or chenodeoxycholic acid, which are then conjugated with glycine or taurine

Question 56

What are the functions of bile salts?

Answer 56

Emulsification | Complex with lipids to form micelles for absorption across intestinal mucosa

Question 57

What are the causes of gallstones?

Answer 57

Too much absorption of water from bile Too much absorption of bile acids from bile Too much cholesterol in bile Inflammation of eptihelium

Question 58

What are the main cell types that make up crypt of Lieberkuhn?

Answer 58

Goblet cells | enterocytes

Question 59

List the secretions of Paneth cells

Answer 59

?

Question 60

Describe condensation reactions

Answer 60

Used to remove hydrogen ions and hydroxyl ions from building block in order to allow the bonding of monomer into polymers

Question 61

Describe hydrolysis

Answer 61

Incorporating water molecules in such as a way that polymers are broken down into monomers