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Physiology II > GI secretion > Flashcards

GI secretion Flashcards

1
Q

Role of secretion

A

facilitate digestion

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

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2
Q

Mucus cells

A

goblet cells, neck mucus cells, and surface mucus cells

throughout the GI tract from mouth to large intetsine

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3
Q

Acinar Cells

A

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

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4
Q

Acinous glad principle location

A

Pancrease, salivary glands

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5
Q

Secretory cells

A

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

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6
Q

Mucins

A

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

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7
Q

Salivary Amylase

A

breaks down starch to oligosaccharide molecules

terminated when gastric pH <4

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8
Q

Xerostomia

A

absence of saliva due to lack or block of salivary gland

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9
Q

Types of salivary glands

A

Parotid
Submandibular
Sublingual

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10
Q

Parotid salivary gland

A

exclusivley serous (acinous) gland

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

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11
Q

Parasympathetic stimulation of salivary glands

A

vasodilation ( increases blood flow)

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12
Q

INITIAL tonicity of saliva in the acinus

A

Isotonic

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13
Q

End tonicity of saliva

A

Hypotinic

Na, Cl absorbed (to blood)

K and bicarb are sectreted

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14
Q

concentrtaions of K and Bicarb in saliva?

A

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

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15
Q

Parietal cells

A

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

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16
Q

Chief Cells

A

located in oxyntic region secrete pepsinogen

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17
Q

Mucous neck cells

A

located below the epithelium and secrete soluble mucus

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18
Q

Enteroendocrine cells

A

hormone secreting cells (somatostatin)

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19
Q

Oxcyntic glands

A

lots of parietal cells - lots of HCl

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20
Q

Pyloric glands

A

G-cells- Gastrin

21
Q

Pepsinogen

A

becomes pepsin at pH<5 Protease

22
Q

Intrinsic factor

A

secreted by parietal cells

Required for B12 absorption

23
Q

Bicarbonate

A

produced by epithelial cells

24
Q

Mechanism of acid secretion by parietal cells

A

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

25
Q

Alkaline tide

A

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

26
Q

What stimulates the release of pepsin from chief cells?

A 
hitamine 
ACh
Gastrin 
Secretin
CCK
27
Q

what is the only gastric function required for life?

A

secretion of intrinsic factor by parietal cells

28
Q

Prostaglandin

A

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

29
Q

Parietal cell receptors

A
  1. Histamine
  2. Ach
  3. Gastrin
30
Q

ACh on parietal cell

A

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

31
Q

Histamine on parietal cell

A

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

32
Q

How do you block muscarinic receptors

A

Atropine

33
Q

How do you block H2 receptors

A

cimetidine

34
Q

Gastrin on parietal cells

A

released from G-cells in the stomach antrum and duodenum

stimulates the release of ACh or histamine

35
Q

Potentiation (histamine)

A

Histamine potentiates the effects of ACh and gastrin

36
Q

Cephalic phase of gastric acid secretion

A

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)

37
Q

Gastric phase of gasrtic acid secretion

A

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

38
Q

Intestinal phase of gastric acid secretion

A

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

39
Q

Somatostatin

A

released by D cells

Decrease gastrin release by G-cells

40
Q

Secretin

A

released by S cells when there is too much acid in the duodenum

inhibit gastrin release and inhibit secretion by parietal cells

41
Q

effect of CCK and Secretin on pepsinogen secretion

A

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

42
Q

Secretin and pancreatic secretion

A

aqueous pancreatic juices by causing fluid retention in the ducts

Bicarb and fluid

43
Q

CCK and pancreatic secretion

A

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

44
Q

tonicity of aqueous component of pancreatic juices

A

isotonic

45
Q

What cannel is required for pumping bicarbonate into pancreatic juices?

A

Cl channel

Bicarb in the lumen attracts NaCl (water follows NaCl)

46
Q

What activates trypsinogen

A

enteropeptidase

47
Q

what activates Chymotrypsin

A

trypsin

48
Q

what activates carboxypeptidase?

A

trypsin

Physiology II (17 decks)

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