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Physiology Fall 21' > CH. 20 The Gastrointestinal System > Flashcards

CH. 20 The Gastrointestinal System Flashcards

1
Q

How is the gastrointestinal system divided? and what belongs to each division?

A
  1. Gastrointestinal tract: mouth - pharynx - esophagus - stomach - small intestine - colon - rectum - anus
  2. Accessory glands: several glands outside the GI tract that secrete fluids and enzymes into the lumen of the GI tract
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2
Q

What are the 4 walls of the GI tract?

A
  1. Mucosa: lining of the lumen
  2. Submucosa: connective tissue
  3. Muscularis externa: smooth muscle
  4. Serosa: connective tissue
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3
Q

What are the 3 layers of the mucosa?

A
  1. Mucous membrane: separates GI lumen from internal environment
  2. Lamina propria: connective tissue
  3. Muscularis mucosae: thin layer of smooth muscle functions in mixing lumenal contents
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4
Q

What are the three different types of enterocytes?

A
  1. absorptive cells
  2. exocrine cells
  3. endocrine cells
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5
Q

What are the two layers of smooth muscle of the muscularis externa and how do they function?

A
  1. inner circular layer: changes diameter

2. outer longitudinal layer: changes length

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6
Q

What are the two parts of the enteric nervous system?

A
  1. submucosal plexus (Meissner’s plexus): from submucosa layer
  2. myenteric plexus (Auerbach’s plexus): from muscularis externa
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7
Q

What kind of tissue is the inner layer of the serosa vs. the outer layer?

A

Inner layer: connective tissue

Outer layer: epithelial tissue (mesothelium)

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8
Q

What does digestion begin with and what is secreted to aid this process?

A

Begins with mastication in the mouth.

- saliva is secreted that contains salivary amylase to breakdown cell walls and digest starch and glycogen (carbs)

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9
Q

What is the function of the pharynx?

A

common passageway for air and food and where respiratory and digestive system meet

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10
Q

How is the esophagus broken down?

A

tube from pharynx to stomach

  • upper esophageal sphincter: skeletal muscle between pharynx and esophagus
  • lower esophageal sphincter: smooth muscle between esophagus and stomach
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11
Q

How does the stomach function?

A

stores food after it is swallowed and secretes gastric juice to help break it down
- then releases food as chime into small intestine

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12
Q

What are the secretory products of the gastric pits and what are they secreted by?

A
  1. pepsinogen: secreted by chief cells
  2. hydrogen ions: secreted by parietal cells
  3. intrinsic factor: secreted by parietal cells
  4. gastrin: secreted from G cells
  5. mucus: secreted from neck cells
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13
Q

What purpose does the acidic environment of the stomach serve?

A
  1. necessary for activating pepsinogen
  2. denatures proteins
  3. kills bacteria
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14
Q

What acts as a protective barrier in relation to the acidic environment of the stomach?

A

gastric mucosal barrier

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15
Q

What is the primary site of digestion and absorption and how is it divided?

A

small intestine

  • duodenum
  • jejunum
  • ileum
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16
Q

What two secretions enter the duodenum?

A
  1. pancreatic juice: contains digestive enzymes and bicarbonate that helps to neutralize acidic chyme
  2. bile: secreted from liver and contains bile salts that aid in fat digestion
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17
Q

Where is absorption completed in the small intestine?

A

within the first 20% of the small intestine

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18
Q

What is the function of the villi and microvilli of the small intestine wall?

A

Villi: increase surface area of epithelium
- contain blood vessels and lacteal for absorption of nutrients

Microvilli: increase surface area of epithelial cells
- form brush border

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19
Q

What is the function of the Crypts of Lieberkuhn?

A

epithelial cells in crypts secrete bicarbonate-rich fluid

  • secreted in proximal small intestine
  • absorbed in distal small intestine
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20
Q

What is the role of the liver in absorption?

A

absorbs nutrients traveling in the blood to the liver before entering the general circulation
- detoxify substances and processes certain nutrients

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21
Q

What is the hepatic portal system?

A

vasculature that delivers absorbed nutrients to the liver before nutrients enter the general circulation

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22
Q

What is the large intestine comprised of?

A

consists of cecum, colon, and rectum

- ileocecal sphincter is between ileum and colon

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23
Q

What are the functions of the colon?

A
  1. concentration of wastes into feces
  2. absorption of most water
  3. storage of feces until defecation
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24
Q

What are the four sections of the colon?

A
  1. ascending colon
  2. transverse colon
  3. descending colon
  4. sigmoid colon
25
Q

What muscle comprises the internal and external anal sphincters?

A

internal anal sphincter: smooth muscle

external anal sphincter: skeletal muscle

26
Q

What are the four types of glands of the GI tract and how are its products secreted?

A
  1. salivary glands: saliva
  2. pancreas: pancreatic juice
  3. acini
  4. liver: secretes bile

secreted via ducts into the lumen of the GI tract

27
Q

What are the characteristics of saliva?

A
  1. rich in bicarbonate ions
  2. contains mucus
  3. enzymes present: salivary amylase and lysozyme
28
Q

What is produced by the exocrine portion of the pancreas?

A

pancreatic juice

  • rich in bicarbonate
  • relative to weight, secretes more protein than any other tissue in body
  • enzymes present: pancreatic amylase, lipases, proteases, and nucleases
29
Q

What are the functions of the liver?

A
  1. secretes bile into gallbladder
  2. processes nutrients
    - glucose into glycogen
    - amino acids into fatty acids
    - triglycerides and cholesterol synthesis
    - lipoprotein synthesis
  3. removal of old red blood cells: generates bilirubin
  4. synthesis of plasma proteins
  5. secretion and modification of hormones
30
Q

What is the function of the Sphincter of Oddi?

A

regulates flow from pancreas and gallbladder to duodenum

31
Q

What are the enzymes of digestion and where are they located?

A
  1. dextrinase: limit dextrins -> glucose
  2. glucoamylase: polysaccharides -> glucose
  3. sucrase: sucrose -> fructose + glucose
  4. lactase: lactose -> galactose + glucose
  5. maltase: maltose -> 2 glucose

location of enzymes: brush border of small intestine

32
Q

What are the two ways in which glucose and galactose are absorbed?

A
  1. secondary active transport across apical membrane

2. facilitated diffusion across basolateral membrane

33
Q

How is fructose absorbed?

A

facilitated diffusion across both membranes

34
Q

What are the products of protein digestion?

A
  1. amino acids
  2. dipeptides
  3. tripeptides
35
Q

What are the three kinds of proteases?

A
  1. Endopeptidases: split polypeptides at interior peptide bonds into small peptide fragments
  2. Exopeptidases: cleave amino acids from one end of polypeptide
  3. Zymogens: inactive storage form of proteases
36
Q

Where does protein digestion begin?

A

in the stomach

37
Q

Where does protein digestion begin?

A

in the stomach

38
Q

What kind of transport is used in the absorption of amino acids?

A
  1. sodium-linked secondary active transport or facilitated diffusion to cross the apical membrane
  2. facilitated diffusion to cross the basolateral membrane
39
Q

What kind of transport is used in the absorption of dipeptides and tripeptides?

A
  1. cross the apical membrane by active transport

2. when broken into amino acids, cross the basolateral membrane by facilitated diffusion

40
Q

What problems do lipids face in digestion and absorption?

A
  1. not water soluble
  2. do not mix with stomach or intestinal contents
  3. form fat droplets
41
Q

How do bile salts aid in lipid digestion?

A

increase the surface area of droplets by breaking each large droplet into several small droplets (emulsification)

42
Q

What are the criteria in which fat-soluble vitamins can be absorbed?

A
  1. absorbed with lipids

2. dissolve in lipid droplets, micelles, and chylomicrons

43
Q

How is sodium absorbed?

A

solvent drag with water reabsorption

- actively absorbed in jejunum, ileum, and colon

44
Q

How is chloride absorbed?

A

passively follows sodium absorption

45
Q

How is potassium absorbed?

A

passively absorbed

- secreted when lumenal concentrations are very low

46
Q

How is bicarbonate absorbed and secreted in the jejunum, ileum. and colon?

A

jejunum: bicarbonate ions are passively absorbed

ileum and colon: bicarbonate are secreted in exchange for chloride ions

47
Q

How is water absorbed?

A

water absorption is passive

- water follows absorption of solutes by osmosis

48
Q

What are the 4 gastrointestinal hormones?

A
  1. gastrin
  2. cholecystokinin
  3. secretin
  4. glucose-dependent insulinotropic peptide
49
Q

What are the 3 phases of the gastrointestinal control and where do their stimuli originate?

A
  1. cephalic phase: stimulate originate in head
  2. gastric phase: stimuli originate in stomach
  3. intestinal phase: stimuli originate in small intestine
50
Q

What is leptin?

A

a hormone released from adipose cells when calories exceed demands

51
Q

What are the stimuli of cephalic phase secretion?

A
  1. sight of food
  2. taste
  3. small
  4. chewing
  5. swallowing
52
Q

What are the stimuli of gastric phase secretion?

A
  1. proteins, peptides, and amino acids

2. distension of stomach

53
Q

What inhibits secretion in the gastric phase?

A
  • exit of food removes stimuli for secretion

- increased acidity inhibits gastrin release

54
Q

What inhibits secretion in the intestinal phase?

A
  • food entry into the duodenum

- long and short reflex pathways

55
Q

What is the function of GI motility?

A

mix and propel GI tract contents

56
Q

What is the bolus?

A

chewed food + saliva

57
Q

What is the integration center for swallowing?

A

swallowing center of medulla oblongata

58
Q

What are the stimuli for vomitting?

A 
1. illness
2, emotions
3. pain
4. distension in GI tract
5. rotation of head
6. ingestion of certain substances (emetics)

Physiology Fall 21' (15 decks)

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