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Flashcards in Ward: Gastric physiology of digestion Deck (49):
1

Two primary types of secretion

Digestive enzymes
Mucus

2

Type of gland: located in the epithelium, found in most parts of the GI tract, respond to local stimulation of the epithelium by extruding their mucus onto the epithelial surface to act as a lubricant and to protect the epithelial surface

single cell mucous glands

3

In the small intestine, invaginations of the epithelium into the submucosa

Crypts of Leiberkuhn

4

Located in the stomach and upper duodenum, often secrete acid and pepsinogen.

Tubular glands

5

More complex glands with a primary function to provide secretions for digestion and emulsification of food

salivary glands, pancreas, and liver

6

Briefly discuss the mechanism of secretion by glandular cells.

Capillaries transport nutrients into the glandular cell
Secretory substances synthesized in ER/Gogli
Transported into Golgi where modification occurs
Discharged into cytoplasm as secretory vesicles which are stored in the apical ends of cells until the cell gets a signal to empty its contents

7

Briefly describe water and electrolyte secretion

1. nerve stimulation moves Cl- ions into cell
2. Na+ follows into cell
3. Water follows and creates hydrostatic pressure
4. Ruptures secretory border

8

Local stimulation can occur in two ways

Direct contact
Epithelial stimulation

9

How does the parasympathetic ANS stimulate secretion?

increases the rates of glandular secretions, especially the glands of the upper GI tract, also glands of the distal large intestine

10

How does the sympathetic ANS stimulate secretion?

If parasympathetic innervation is low, sympathetic stimulation will increase secretion. If parasympathetic stimulation is high, it will reduce secretion.

11

Hormones in the stomach and intestine are liberated from the mucosa in response to what?

the presence of food in the lumen

12

Constituents of saliva

Serous secretion
Mucus secretion
Lactoferrin
Proteolytic enzymes
Thiocyanate ions
Binding glycoprotein for IgA

13

What is saliva composed of?

Electrolytes, glycoproteins, and water

14

Properties of mucus (ABDAS)

Adherent so it tightly binds to particles
Barrier to mucosa
Decreases resistance
Amphoteric properties
Strongly resistant to digestion

15

Four types of salivary glands

Parotoid (1/4)
Sublingual
Submandibular (2/3)
Buccal

16

How are all the salivary glands drained?

By a single major excretory duct

17

Lie outside the wall of the GI tract and are connected via ducts that empty into the GI tract itself

Acinus glands

18

Involved with directing fluids into the oral cavity.

Ductal cells

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Contractile cells involved in helping move serous and mucous secretions into ducts.

Myoepithelial cells

20

What happens to Na, Cl, and K+ levels in the saliva during maximal saliva secretion?

Concentrations of these ions begin to reach the level found in the plasma, because reabsorption cannot occur quick enough relative to the marked increase in saliva production. Na+ and Cl- increase, and K+ decreases

21

Things that activate salivary nucleus of the medulla

Reflexes
Smell
Taste
Pressure
Nausea

22

Things that inhibit salivary nucleus of the medulla

Fatigue
Sleep
Fear
Dehydration

23

Secretion is increased by contractions of these cells, which are innervated by the parasympathetic system

Myoepithelial cells

24

What is released in response to parasympathetic stimulation? What does this produce? What does this result in?

Kallikrein
Bradykinin
Vasodilation and growth of salivary glands

25

Pathophysiology: Associated with chronic ulcerations of the buccal mucosa and with dental caries.

Xerostomia (dry mouth)

26

Pathophysiology: Absence of saliva

Congenital xerostomia

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Pathophysiology: Atrophy of the glands and decreased saliva production

Siogren's syndrome

28

Pathophysiology: Na+ concentrations increased

Addison's disease

29

Pathophysiology: Na+ concentrations decreased

Cushing's syndrome

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Pathophysiology: Causes excessive salivation

Tumors

31

Four constituents of gastric juice

1. intrinsic factor
2. H+ ions
3. pepsin
4. mucus

32

secretes acid, pepsinogen, mucus and intrinsic factor and is located on the proximal 80% of the stomach.

Oxyntic gland area

33

The distal 20% of the stomach, which synthesizes and secretes the hormone gastrin and mucus.

Pyloric gland area

34

Gastric mucosa made up of two areas

Oxyntic gland area
Pyloric gland area

35

Contain the acid-producing parietal cells and the peptic or chief cells, which secrete the enzyme precursor pepsinogen

Oxyntic glands

36

What do parietal cells produce?

HCl

37

What is the pH created by HCl secretion of parietal glands?

0.8-1

38

Between meals the cytoplasm of the parietal cell is dominated by numerous (blank)

tubulovesicles

39

The cell also possesses an intracellular (blank) that is continuous with the lumen of the oxyntic gland. During acid secretion the tubulovesicles become microvilli and project into the (blank). This increases the (blank) of the cell.

canaliculus; canaliculus; surface area

40

The activities of what two enzymes increases during HCl secretion?

carbonic anhydrase
ATPase

41

Summarize the mechanism of HCl secretion by parietal cells.
How does H+ get pumped out?
Where does the supply of H+ come from?

H+ pumped out of APICAL cell membrane by H+/K+ ATPase if adequate supply of K+ outside cell
(H+ comes from dissociation of H20
Carbonic acid is formed from Co2 and H20 in a rxn catalyzed by carbonic anhydrase)
BASOLATERAL membrane exchanges Cl- for bicarb

42

What things occur when parasympathetic stimulation of salivary glands?

Vasodilation
Secretion
Myoepithelial cell contraction

43

Sympathetic activation of salivary glands increases (blank), while parasympathetic stimulation increases (blank) and (blank)

cAMP; IP3; Ca+

44

Component of gastric secretion; required for the absorption of vitamin B12 by the ileal mucosa (released from Parietal cells).

intrinsic factor

45

Component of gastric secretion; necessary for the conversion of pepsinogen to pepsin; also kills bacteria

H+

46

Component of gastric secretion; begins the breakdown of protein; released from chief cells

pepsin

47

Component of gastric secretion; protects the mucosa lining of the stomach, lubricates and neutralizes a small amount of acid

mucus

48

The gastric glands lie deep in the stomach wall and receive these two things.

rich blood supply
autonomic innervation

49

Present where the glands open into the pits. These cells divide and the daughter cells migrate to the surface where they become mature mucous cells and down into the glands where they become parietal cells in the oxyntic gland area or G cells in the region of the pyloric gland mucosa

mucous neck cells