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Physiology > Exam 4 - Digestive System 2 > Flashcards

Exam 4 - Digestive System 2 Flashcards

1
Q

Functions of saliva: moistens food

A

99.5% water and solutes

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2
Q

Functions of saliva: binds food together into bolus

A

Mucus - aids in swallowing, binds and lubricates food mass

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3
Q

Functions of saliva: inhibits bacteria

A
  • Lysozyme - enzyme that kills bacteria

- immunoglobulin A - inhibits bacterial growth

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4
Q

Functions of saliva: begins starch digestion

A

Salivary amylase - works at NEUTRAL pH and is deactivated at low pH (stomach)

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5
Q

Functions of saliva: PREPARES FOR fat digestion

A

Lingual lipase - digests fat activated by stomach acid (after food is swallowed)

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6
Q

Mucous acinus

A

secretes mucus

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7
Q

Serous acinus

A

secretes thin fluid rich in AMYLASE

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8
Q

Mixed acinus

A

secretes both

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9
Q

Intrinsic salivary glands

A

indefinite number of small glands in mucosa that secrete relatively small amounts of saliva at a constant rate
CONTAIN LINGUAL LIPASE AND LYSOZYME

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10
Q

Extrinsic salivary glands

A
  • parotid
  • submandibular
  • sublingual
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11
Q

Parotid

A
  • largest, SEROUS, just anterior to the ear
  • parotid duct (Stinson’s) crosses over masseter, penetrates buccinators, and ENTERS THE ORAL CAVITY ADJACENT TO THE 2ND UPPER MOLAR
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12
Q

Submandibular

A
  • mixed but mostly MUCOUS

- each has 10-12 ducts that enter the floor of the oral cavity

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13
Q

Food stimulates receptors that signal salivatory nuclei in…?

A

MEDULLA AND PONS

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14
Q

Parasympathetic control of salivation and swallowing

A

salivary glands produce thin saliva, RICH IN ENZYMES

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15
Q

Sympathetic control of salivation and swallowing

A

produce less abundant, thicker saliva, w/ MORE MUCOUS

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16
Q

What can also stimulate salivatory nuclei to cause salivation?

A

higher brain centers so sight, smell, and though of food cause salivation

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17
Q

Skeletal muscles in pharynx

A

OPPOSITE FROM MOST OF GI TRACT
- deep layer has LONGITUDINALLY ORIENTED SKELETAL MUSCLE
- superficial layer has CIRCULARLY ORIENTED SKELETAL MUSCLE
(superior, middle, and inferior pharyngeal constrictors)

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18
Q

Upper esophageal sphincter

A

inferior constrictor remains contracted when not swallowing to prevent air from entering esophagus

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19
Q

What do the muscles of the pharynx contribute to?

A

swallowing by forcing food downward

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20
Q

Where does the esophagus begin

A

Cricoid cartilage, inferior to larynx, dorsal to trachea

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21
Q

Epithelium that lines the esophagus

A

NONKERATINIZED stratified squamous epithelium (abrasion resistant)

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22
Q

Extension of esophagus

A

extends from pharynx to cardiac orifice of stomach passing through ESOPHAGIAL HIATUS

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23
Q

Food pauses at the esophageal hiatus before entering the stomach due to

A

lower esophageal sphincter (LES)

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24
Q

purpose of lower esophageal sphincter

A

will keep acidic materials from refluxing back into esophagus causing GERD/heartburn

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25
Q

Upper 1/3 muscularis externa of esophagus

A

skeletal muscle (voluntary)

26
Q

Middle 1/3 muscularis externa of esophagus

A

mixture of skeletal and smooth muscle

27
Q

Lower 1/3 muscularis externa of esophagus

A

only smooth muscle (involuntary)

28
Q

Series of muscular contractions for deglutition/swallowing are coordinated by

A

medulla and pons

29
Q

For deglution/swallowing, motor signals from cranial nerves…?

A

5, 7, 9, 12

30
Q

Two phases of swallowing

A
  • Buccal phase

- Pharyngeal-esophageal phase

31
Q

Buccal phase of swallowing

A

tongue collects food and pushes it back into oropharynx

32
Q

Pharyngeal-esophageal phase

A
  • soft palate rises and blocks nasopharynx
  • infrahyoid muscles lift larynx; epiglottis folded back (prevents food going to lungs)
  • pharyngeal constrictors push bolus down esophagus
33
Q

Primary function of stomach

A

food storage organ
- mechanically breaks up and liquefies food AND begins chemical digestion of protein and fat (lingual lipase needs acidic environment( resulting in a soupy mixture called CHYME

34
Q

Volumes of stomach

A
  • 50 mL when empty
  • 1.0-1.5 L after a typical meal
  • May hold up to 4.0 L and extend to pelvis
35
Q

Absorption in stomach

A

the stomach DOES NOT ABSORB A SIGNIFICANT AMOUNT OF NUTRIENTS, but can absorb aspirin and some lipid-soluble drugs

36
Q

Innervation of the stomach

A
  • PARASYMPATHETIC fibers from VAGUS

- SYMPATHETIC fibers from CELIAC GANGLIA

37
Q

Blood in the stomach

A

enters HEPATIC PORTAL CIRCULATION and is “filtered” through liver before returning to heart

38
Q

Secrete mucous

A

Mucous cells

39
Q

Divide rapidly to produce new cells

A

Regenerative cells

40
Q

Secret HCL acid and intrinsic factor

A

Parietal cells

41
Q

Secrete pepsinogen and chymosin and lipase in infancy

A

Chief cells

42
Q

Secrete hormones and paracrine messengers

A

Enteroendocrine cells

43
Q

Secrete gastrin

A

G cells

44
Q

Mucous

A
  • VISCOUS and ALKALINE

- PROTECTS STOMACH from the acidic chime and enzyme pepsin

45
Q

Intrinsic factor

A
  • BINDS W/ VITAMIN B12 AND HELPS IT TO BE ABSORBED

- B12 is necessary for DNA synthesis

46
Q

HCl

A
  • kills bacteria
  • STOPS CARBOHYDRATE DIGESTION BY INACTIVATING SALIVARY AMYLASE
  • HELPS CONVERT PEPSINOGEN TO PEPSIN (ACTIVATES IT AND LINGUAL LIPASE
  • converts ingested FERRIC iron to FERROUS iron
47
Q

Pepsinogen

A
  • packaged granules released by exocytosis

- pepsin catalyzes breaking of covalent bonds in PROTEINS

48
Q

How does the stomach produce HCl?

A

Parietal cells contain CARBONIC ANHYDRASE (CAH)

  • CO2 goes from bloodstream into parietal cells
  • CO2 and water make H2CO3
  • H2CO3 breaks down so we put acid in the stomach lining and we put HCO3- back into the bloodstream
49
Q

Action of pepsin

A

autolytic effect - as some pepsin is formed it converts more pepsinogen into more pepsin (both are proteins)

50
Q

Gastric motility

A 
swallowing center (medulla) signals stomach to relax and food stretching stomach also activates a receptive response which allows stomach to accommodate more food
(when you swallow the stomach will automatically expand because it is anticipating that food is en route; once the food gets there it expands even more)
51
Q

What controls rhythm of peristalsis

A

pacemaker cells in longitudinal muscle layer

52
Q

Gentle ripple of contraction every 20 seconds

A

churns and mixes food w/ gastric juice

53
Q

Stronger contraction at pyloric regions

A

ejects content in 3mL boli

  • enables duodenum to neutralize acid
  • allows for digestion of nutrients a little at a time (duodenum is not a storage area)
  • requires 4 HOURS for a typical meal to be emptied from stomach
54
Q

Cephalic phase of gastric function

A

in response to sight, smell, taste, or though of food, vagus never stimulates gastric secretion and motility

55
Q

Gastric phase of gastric function

A

Secretion stimulated by ACh (parasympathetic fibers), gastrin (from pyloric G cells) and histamine (from gastric enteroendocrine cells).

56
Q

Stimulate all parietal cell secretions

A

ACh
Gastrin
Histamine

57
Q

Stimulate CHIEF CELL secretion (which secrete pepsinogen)

A

ACh and Gastrin

58
Q

Stimulates mucous secretion

A

ACh

59
Q

What does protein digestion produce during the gastric phase?

A

Produces peptides and amino acids (that stimulate G cells to secrete more gastrin) that buffer stomach acid (which stimulates parietal cells)

stimulate gastrin to stimulate pepsinogen to do something about the peptides; the pH of the stomach is supposed to be low, protein buffers it so you need something to digest the proteins to get the stomach to its normal acidic environment

60
Q

Negative feed back during gastric phase

A

as stomach empties and peptides and amino acids leave, BUFFERING CAPACITY GOES DOWN AND pH FALLS BELOW 2 which INHIBITS PARIETAL CELLS and G CELLS

as the protein leaves, you don’t need the pepsinogen anymore, protein leaving leads to less buffering and the pH of the stomach falls which will tell the parietal cells that they don’t need to make anymore acid

61
Q

Intestinal phase

A

(Enterogastric reflex)
- acid (and semi-digested fats) in duodenum, sends inhibitory signals to stomach via enteric nervous system and then to medulla which REDUCES VAGAL STIMULATION of stomach

62
Q

What do duodenal endocrine cells release during intestinal phase?

A
  • secretin
  • cholecystokinin (CCK)
  • gastric inhibitory peptide

ALL 3 SUPPRESS GASTRIC SECRETION AND MOTILITY

Physiology (13 decks)

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