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Physiology > Chapter 21 > Flashcards

Chapter 21 Flashcards

1
Q

Trace a piece of undigested food from mouth to anus.

A
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2
Q

Describe the four layers of the GI tract wall.

A

1) mucosa
- Mucosal epithelium
- Lamina propria (connective tissue)
- Muscularis mucosae
2) submucosa
- Connective tissue
- Contains submucosal plexus of the
enteric nervous system
3) muscularis externa
- Consists of two layers of smooth muscle
- Contains myenteric plexus of the enteric
nervous system
4) serosa
- Continuation of the peritoneal membrane, which forms sheets of mesentery

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3
Q

In what areas do modifications increase surface area and match functions?

A

1) Rugae and plicae
2) Villi
3) Gastric glands, crypts, and submucosal glands

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4
Q

Describe the primary function of the digestive system.

A

To move nutrients, water, and electrolytes from external environment into internal environment.

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5
Q

Explain the challenges of autodigestion, mass balance, and defense.

A
  • Avoiding autodigestion
  • Mass balance
  • Defense
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6
Q

Describe and compare secretion, digestion, absorption, and motility.

A

1) Digestion –> chemical + mechanical breakdown of food into absorbable units
2) Absorption –> movement of material from GI lumen to ECF
3) Secretion –> movement of material from cells into lumen or ECF
4) Motility –> movement of material thru the GI tract as a result of muscle contraction

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7
Q

Describe single-unit smooth muscle, slow wave potentials, tonic and phasic contractions.

A
  • slow wave potentials –> spontaneous depolarizations in GI smooth muscle
  • tonic contractions –> minutes or hours
  • phasic contractions –> seconds
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8
Q

Describe and compare peristalsis and segmentation.

A
  • peristalsis –> moving food thru the tract
  • segmentation –> mechanically mixing food to break it into uniformly small particles
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9
Q

What are the four basic processes that occur in digestion?

A

1) Digestion
2) Absorption
3) Secretion
4) Motility

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10
Q

How many fluids per day are consumed (L/day)?

A

2 L/day

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11
Q

How many fluids per day are secreted (L/day)?

A

7 L/day

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12
Q

where are digestive enzymes secreted?

A

mouth, stomach, and intestine

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13
Q

Digestive enzymes may be secreted as inactive proenzymes, called _____ when active.

A

zymogens

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14
Q

What cells are mucins (mucous) produced by?

A

mucous cells, serous cells, and goblet cells

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15
Q

Compare the enteric nervous system to the central nervous system.

A

Enteric Nervous System:
- can act independently
- controls motility, secretion and growth of the digestive system –> Intrinsic neurons are neurons in ENS (extrinsic are from CNS to digestive system)
- Short reflexes integrate in the enteric nervous system
- Long reflexes integrate in CNS –> called cephalic reflexes
- shares features with CNS –> neurotransmitters + integrating center

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16
Q

Contrast long reflexes, short reflexes, and control involving GI peptides.

A

Short Reflexes:
- secretory cells of the stomach + small intestine affect GI peptides
- GI peptides affect smooth muscles + exocrine cells

Long Reflexes:
- GI peptides affect the brain –> hunger/satiety
- GI peptides affect endocrine pancreas –> increases insulin and decreases glucagon

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17
Q

What is the stimulus for release of gastrin (G cells)?

A

peptides and amino acids + neural reflexes

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18
Q

What are the primary targets of gastrin (G cells)?

A

ECL cells and parietal cells

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19
Q

What are the primary effects of gastrin (G cells)?

A

stimulates gastric acid secretion + mucosal growth

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20
Q

What inhibits the release of gastrin (G cells)?

A

somatostatin

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21
Q

What is the stimulus for release of cholecystokinin (CCK)?

A

fatty acids and some amino acids

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22
Q

What are the primary targets of cholecystokinin (CCK)?

A

gallbladder, pancreas, and stomach

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23
Q

What are the primary effects of cholecystokinin (CCK)?

A
  • stimulates gallbladder contraction + pancreatic enzyme secretion
  • inhibits gastric emptying and acid secretion
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24
Q

What is the stimulus for release of secretin?

A

acid in small intestine

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25
Q

What are the primary targets of secretin?

A

pancreas and stomach

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26
Q

What are the primary effects of secretin?

A
  • stimulates bicarbonate secretion
  • inhibits gastric emptying + acid secretion
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27
Q

What is the stimulus for release of motilin?

A

fasting –> periodic release every 1.5-2 hours

28
Q

What are the primary targets of motilin?

A

gastric + intestinal smooth muscle

29
Q

What are the primary effects of secretin?

A

stimulates migrating motor complex

30
Q

what is motilin inhibited by?

A

eating a meal

31
Q

What are the primary targets of gastric inhibitory peptide (GIP)?

A

glucose, fatty acids, and amino acids in small intestine

32
Q

What are the primary effects of gastric inhibitory peptide (GIP)?

A
  • stimulates insulin release –> feedforward mechanism
  • inhibits gastric emptying + acid secretion
33
Q

What are the primary effects of gastric-like peptide-1 (GLP-1)?

A
34
Q

What is the stimulus for release of gastric-like peptide-1 (GLP-1)?

A

mixed meal that includes carbohydrates or fats in the lumen

35
Q

What is the primary target of gastric-like peptide-1 (GLP-1)?

A

endocrine pancreas

36
Q

Explain feedforward control in digestion.

A
  • smelling, seeing, or thinking about food
  • Reflex begins in brain
  • Anticipation of or presence of food in oral
    cavity activates neurons in medulla
  • Initiates cephalic phase
37
Q

Map the processes and control pathways of the cephalic phase.

A

whiteboard

38
Q

Explain the functions of saliva.

A

1) soften + lubricate food
2) digestion of starch (chemical)

39
Q

Describe salivary secretions.

A
  • exocrine –> goes into ducts
  • under autonomic control
40
Q

what does deglutition mean?

A

swallowing + moving food from mouth to stomach

41
Q

Map the processes and control pathways of the gastric phase.

A

whiteboard

42
Q

what are the 2 functions of the stomach?

A

1) storage
2) digestion

43
Q

Digestive activity in the stomach begins with what?

A

begins with long vagal reflex of cephalic phase then food in stomach initiates short reflexes of gastric phase

44
Q

Describe mucus and their function(s).

A
  • cell type –> mucous surface cell
  • function –> physical barrier between lumen and epithelium
  • stimulus for release –> tonic secretion + irritation of mucosa
45
Q

Describe bicarbonate and their function(s).

A
  • cell type –> mucous neck cell
  • function –> buffers gastric acid to prevent damage to epithelium
  • stimulus for release –> secreted with mucus
46
Q

Describe gastric acid (HCl) and their function(s).

A
  • cell type –> parietal cells
  • function –> activates pepsin + kills bacteria
  • stimulus for release –> acetylcholine, gastrin, histamine
47
Q

Describe intrinsic factor and their function(s).

A
  • cell type –> parietal cells
  • function –> complexes with vitamin B12 to permit absorption
  • stimulus for release –> acetylcholine, gastrin, histamine
48
Q

Describe histamine and their function(s).

A
  • cell type –> enterochromaffin-like cell
  • function –> stimulates gastric acid secretion
  • stimulus for release –> acetylcholine + gastrin
49
Q

Describe pepsin(ogen) and their function(s).

A
  • cell type –> chief cells
  • function –> digests proteins
  • stimulus for release –> acetylcholine + acid secretion
50
Q

Describe gastric lipase and their function(s)

A
  • cell type –> chief cells
  • function –> digests fats
  • stimulus for release –> acetylcholine + acid secretion
51
Q

Describe somatostatin and their function(s).

A
  • cell type –> D cells
  • function –> inhibits gastric acid secretion
  • stimulus for release –> acid in the stomach
52
Q

Describe gastrin and their function(s).

A
  • cell type –> G cells
  • function –> stimulates gastric acid secretion
  • stimulus for release –> acetylcholine, peptides, and amino acids
53
Q

Compare and contrast digestion and motility in the large and small intestines.

A
  • most digestion occurs in the small intestine
54
Q

Describe the anatomy and function of the hepatic portal system.

A

absorbed nutrients from intestinal epithelium must go to circulatory system for distribution

55
Q

Describe the major secretions of the pancreas and liver.

A

Pancreas:
1) enzymes –> Brush border enteropeptidase converts trypsinogen to trypsin
2) bicarbonate –> Neutralizes gastric acid

Liver:
1) bile –> helps digest lipids
*stored + concentrated in gall bladder

56
Q

What intestinal secretions promote digestion in the intestinal phase?

A
  • digestive enzymes
  • bile
  • bicarbonate secretion
  • mucus
  • isotonic NaCl secretion
57
Q

What do bile salts facilitate?

A

fat digestion

58
Q

Describe fat digestion.

A

1) Lingual and gastric lipases begin lipid digestion, assisted by pancreatic lipases in the duodenum
2) Lipids are absorbed into the apical side of mucosal cells by diffusion
3) Then packaged and exported from the basolateral side by exocytosis
4) Enter lymphatic lacteals

59
Q

How are carbohydrates absorbed?

A

as monosaccharides

60
Q

Describe carbohydrate digestion.

A

1) Salivary and pancreatic amylases break starches into disaccharides
2) Brush border enzymes break disaccharides into monosaccharides
3) Monosaccharides absorbed on apical side through co-transport with sodium (2O active transport)
4) Monosaccharides diffuse through transporters on basolateral side
5) Enter capillaries in villi

61
Q

Describe protein digestion.

A

1) Pepsin begins digestion in the stomach
2) Pancreatic and intestinal proteases digest further into single amino acids and di- and tri-peptides
3) Amino acids are absorbed through co-transport with sodium
4) Di- and tri-peptides are absorbed via endocytosis
5) Enter capillaries in villi

62
Q

How are proteins digested?

A

digested into small peptides and amino acids

63
Q

What are nucleic acids digested into?

A

bases and monosaccharides

64
Q

What organ absorbs vitamins, minerals, ions, and water?

A

intestine

65
Q

The large intestine concentrates _______.

A

waste

Physiology (18 decks)

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