GI secretion

Question 1

Role of secretion

Answer 1

facilitate digestion

provide cell protection (production of mucus and neutralization of acid)

Question 2

Mucus cells

Answer 2

goblet cells, neck mucus cells, and surface mucus cells

throughout the GI tract from mouth to large intetsine

Question 3

Acinar Cells

Answer 3

watery secretions containing proteins such as digestive enzymes which are emptied into a duct system

Question 4

Acinous glad principle location

Answer 4

Pancrease, salivary glands

Question 5

Secretory cells

Answer 5

located in the mucosa of the small intestine (Crypts of Lieberkuhn) - secrete a large volume of extracellular fluid

Question 6

Mucins

Answer 6

glycoproteins that lubricat the food (and throat) and are made primarily in the submandibular and sublingual salivary glands

Question 7

Salivary Amylase

Answer 7

breaks down starch to oligosaccharide molecules

terminated when gastric pH <4

Question 8

Xerostomia

Answer 8

absence of saliva due to lack or block of salivary gland

Question 9

Types of salivary glands

Answer 9

Parotid
Submandibular
Sublingual

Question 10

Parotid salivary gland

Answer 10

exclusivley serous (acinous) gland

secretes a watery fluid that is high in salivary amylase (no mucins)

Question 11

Parasympathetic stimulation of salivary glands

Answer 11

vasodilation ( increases blood flow)

Question 12

INITIAL tonicity of saliva in the acinus

Answer 12

Isotonic

Question 13

End tonicity of saliva

Answer 13

Hypotinic

Na, Cl absorbed (to blood)

K and bicarb are sectreted

Question 14

concentrtaions of K and Bicarb in saliva?

Answer 14

High- saliva is hypotonic to serum (because Na Cl go absorbed)

Question 15

Parietal cells

Answer 15

located in oxyntic region (fundus and corpus) and secrete HCl and intrinsic factor

Question 16

Chief Cells

Answer 16

located in oxyntic region secrete pepsinogen

Question 17

Mucous neck cells

Answer 17

located below the epithelium and secrete soluble mucus

Question 18

Enteroendocrine cells

Answer 18

hormone secreting cells (somatostatin)

Question 19

Oxcyntic glands

Answer 19

lots of parietal cells - lots of HCl

Question 20

Pyloric glands

Answer 20

G-cells- Gastrin

Question 21

Pepsinogen

Answer 21

becomes pepsin at pH<5 Protease

Question 22

Intrinsic factor

Answer 22

secreted by parietal cells

Required for B12 absorption

Question 23

Bicarbonate

Answer 23

produced by epithelial cells

Question 24

Mechanism of acid secretion by parietal cells

Answer 24

H+/K+ ATPase (proton pump) - Hydrogen is pumped into the lumen against and enormous gradient

K and Cl are cotransported to the lumen and K is recycled

Bicarbonate ions leave the cell

Question 25

Alkaline tide

Answer 25

Bicarbonate ions leave the cell and enter the blood raising the pH of the venous blood leaving the stomach

Question 26

What stimulates the release of pepsin from chief cells?

Answer 26

``` hitamine ACh Gastrin Secretin CCK ```

Question 27

what is the only gastric function required for life?

Answer 27

secretion of intrinsic factor by parietal cells

Question 28

Prostaglandin

Answer 28

increase mucosal blood flow as well as bicrob adn mucus secretion (stimulate cell repair and renewal)

Question 29

Parietal cell receptors

Answer 29

1. Histamine 2. Ach 3. Gastrin

Question 30

ACh on parietal cell

Answer 30

From Vagus nerve stimulates muscarinic receptors on parietal cell or on enterochromafin like cells if on parietal cell: IP3 to Ca2+ causing release of HCl If on enterochromafin like cell = release of histamine

Question 31

Histamine on parietal cell

Answer 31

released from enterochromaffin like cell (ECL) in mucusa. Diffuses into the parietal cells and stimulates H2 receptors (CAMP to HCl release)

Question 32

How do you block muscarinic receptors

Answer 32

Atropine

Question 33

How do you block H2 receptors

Answer 33

cimetidine

Question 34

Gastrin on parietal cells

Answer 34

released from G-cells in the stomach antrum and duodenum stimulates the release of ACh or histamine

Question 35

Potentiation (histamine)

Answer 35

Histamine potentiates the effects of ACh and gastrin

Question 36

Cephalic phase of gastric acid secretion

Answer 36

sight or smell of food as well as chewing and swallowing causes vagal refelxes to parietal and G-cells (ACh and gastrin release to stimulate acid production)

Question 37

Gastric phase of gasrtic acid secretion

Answer 37

Gastric distention causes both local and vagovagal reflexes to parietal and G-cells (more ACh and gastrin release)

Question 38

Intestinal phase of gastric acid secretion

Answer 38

protein digestion products in the duodenum lead to stimulation of intestinal G cells and release of gastrin

Question 39

Somatostatin

Answer 39

released by D cells Decrease gastrin release by G-cells

Question 40

Secretin

Answer 40

released by S cells when there is too much acid in the duodenum inhibit gastrin release and inhibit secretion by parietal cells

Question 41

effect of CCK and Secretin on pepsinogen secretion

Answer 41

Stimulate chief cells to secrete pepsinogen but inhibit the release of acid

Question 42

Secretin and pancreatic secretion

Answer 42

aqueous pancreatic juices by causing fluid retention in the ducts Bicarb and fluid

Question 43

CCK and pancreatic secretion

Answer 43

stimulates secretion rich in enzymes (Proteases, amylases, lipases)

Question 44

tonicity of aqueous component of pancreatic juices

Answer 44

isotonic

Question 45

What cannel is required for pumping bicarbonate into pancreatic juices?

Answer 45

Cl channel Bicarb in the lumen attracts NaCl (water follows NaCl)

Question 46

What activates trypsinogen

Answer 46

enteropeptidase

Question 47

what activates Chymotrypsin

Answer 47

trypsin

Question 48

what activates carboxypeptidase?

Answer 48

trypsin