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MD2001 Week 4 > Gastrointestinal System > Flashcards

Gastrointestinal System Flashcards

1
Q

What is the primary function of the GI system?

A

break down of food and absorption of dietary nutrients to be used for energy

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2
Q

What helps the process of digestion?

A

secretions added along the tract - these convert large molecules to smaller ones - “digestion”

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3
Q

What are other functions of the GI system? (not including digestion)

A

storage

excretion

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4
Q

What does the GI system consist of?

A
  • oral cavity
  • pharynx
  • oesophagus
  • stomach
  • small intestine
  • large intestine
  • rectum
  • anus
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5
Q

What do accessory organisms do?

A

secrete enzymes to break down food

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6
Q

What are the accessory organs?

A
  • salivary glands
  • liver
  • pancreas
  • gall bladder
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7
Q

What are the layers of the GI system?

A
  • mucosa
  • submucosa
  • muscular externa
  • serosa
    different layers come into prominence at different locations along the tube depending on location and function
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8
Q

What does the mucosa consist of?

A
  • epithelium
  • lamina propria
  • muscular mucosa
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9
Q

What are the epithelium lining the GI tract like?

A
  • single layered
  • shed and replaced every 2-3 days
  • villi and crypts vary by section function - for absorption and motility
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10
Q

Where do the apical and basolateral sides of the GI tract face?

A

apical - GI lumen

basolateral - interstitium and vasculature

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11
Q

What does the lamina propria (of mucosa) consist of?

A
  • loose CT - made of elastin and collagen fibers

- contains sensory nerves, blood and lymph vessels, secretory glands

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12
Q

What does the muscular mucosa (of mucosa) consist of?

A
  • thin layer of smooth muscle

- further increases surface area by creating ridges and folds

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13
Q

What does the submucosa consist of?

A
  • thick layer with similar composition to lamina propria ( CT - thick layer - elastin and collage fibres)
  • blood vessels and nerve bundles form a submucosal plexus - part of enteric nervous system
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14
Q

What does the Muscular external (ME) consist of?

A
  • circular muscle
  • myenteric plexus
  • longitudinal muscle
  • ENS co-ordinates contractions to move contents between compartments
  • sphincters regulate flow from compartment to next
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15
Q

What does the serosa consist of?

A
  • layer of CT
  • layer of squamous epithelial cells
  • some sections do not have a serial layer (oesophagus) but connect directly with asventina (CT blends into abdominal or pelvic wall)
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16
Q

What 3 divisions of the autonomic nervous system regulate GI function?

A
  • parasympathetic (PSNS)
  • sympathetic (SNS)
  • enteric (ENS)
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17
Q

What is absorption?

A

the process of transporting dietary contents across the gastrointestinal barrier into the body

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18
Q

What is digestion?

A

the chemical breakdown of food

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19
Q

How does the body mechanically breakdown food?

A

using smooth (mixing) or skeletal (chewing) muscle contractions

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20
Q

What is secretion?

A

the act of transporting molecules or fluid from the body to the gastrointestinal lumen

  • facilitates digestion by delivering enzymes and water
  • protects endothelial surface by secreting HC03- and mucus
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21
Q

What role does the sympathetic nervous system play in the GI system?

A

decreases the functions of the parasympathetic nervous system - facilitates secretion and motility

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22
Q

What role does the parasympathetic nervous system play in the GI system?

A

facilitates secretion and motility

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23
Q

What role does the enteric nervous system play in the GI system?

A

can operate independently and is involved with reflexes and the majority of GI functions

24
Q

List GI hormones?

A
  • cholecystokinin
  • gastrin
  • glucose-dependent insulinotropic peptide
  • motilin
  • secretin
25
Q

List GI paracrines?

A
  • histamines
  • prostaglandins
  • somatostatin
26
Q

What are the phases of digestion?

A
  • cephalic
  • gastric
  • intestinal
27
Q

What occurs in cephalic phase?

A
  • triggered by thought of food
  • stimulates secretion by salivary glands, stomach, pancreas, intestines
  • initiates primarily neural responses
  • ACh and VIP release
28
Q

What occurs in gastric phase?

A
  • begins when food and oral secretions enter stomach
  • concedes with distension
  • triggers neural, hormonal, paracrine responses
29
Q

What occurs in intestinal phase?

A
  • begins when stomach contents reach duodenum

- initiates primarily hormonal, but also paracrine and neural responses

30
Q

What is a paracrine hormone?

A

works locally

31
Q

What do phases of digestion allow for?

A 
preparation
timing 
regulation feedback
- cephalic - feedfoward regulation
- gastric and intestinal - feedback mechanisms
32
Q

What forms the upper GI tract?

A
  • mouth
  • oesophagus
  • stomach
33
Q

What is the function of the GI tract?

A
  • transports and prepares food to be absorbed
    (breaking into smaller pieces, hydrating to improve environment for enzymatic actions)
  • minimal role in nutrient absorption
34
Q

What is the function of the mouth?

A
  • reduces food size and mixes with secretions from salviery glands
    (mastication = chewing)
35
Q

Hat are the three salivary glands?

A
  • sublingual
  • submandibular
  • parotid
36
Q

What NS are salivary glands controlled by?

A

both sympathetic and parasympathetic

37
Q

What is the process of salivary secretions?

A

Cl-, Na+, water are transported into duct lumen

then ductal cells reabsorb Na+ and Cl- and secrete K+ and HCO-3

38
Q

What is the function go the oesophagus?

A

transports food from the mouth to the stomach

39
Q

How does oesophagus peristalsis occur?

A

series of coordinates muscle contractions and relaxations - “wave”
- commences after oesophageal sphincter

40
Q

What is swallowing?

A

a conscious act that moves food from mouth through the upper oesophageal sphincter
- voluntarily then involuntary when intitiated - parasympathetic process

41
Q

What are the functions of the stomach?

A
  • accept and store food
  • mix food with secretions
  • digest food
  • deliver food to small intestine
42
Q

Where do secretions in the stomach originate from?

A
  • gastric invaginations “pits”

- these contain multiple cell types

43
Q

What are the three primary motility functions of the stomach?

A
  • accommodation via receptive relaxation
  • mixing via slow wave-initiated contractions and retropulsion
  • gastric emptying
44
Q

What do gastric secretions include?

A
  • ions and water
  • mucous from mucous neck cells
  • pepsinogen fro chief seeks
    0 intrinsic factor and H+ from parietal cells
45
Q

What increases secretion?

A
  • acetylcholine (from nerves)
  • gastrin (from G cells)
  • histamine (enterochromaffin)
46
Q

What decreases secretion?

A
  • somatostatin from d cells

- prostaglandins

47
Q

What are the parts of the small intestine?

A
  • duodenum
  • jejunum
  • ileum
48
Q

What part of the GI tract does most absorption occur?

A
  • small intestine
49
Q

What allows high absorption in the small intestine?

A

large surface area from Ville and microvilli

50
Q

What are the parts of the large intestine?

A
  • caecum
  • ascending colon
  • descending colon
  • sigmoid colon
  • rectum
  • anus
51
Q

What occurs in the large intestine?

A
  • significant water and ion absorption

- motility of contents - mixing and propulsion

52
Q

What does motility in the small intestines involve?

A
  • segmentation (mixing)
  • peristalsis
  • reflexes that control sphincter contraction and relaxation
53
Q

What is peristalsis?

A
  • smooth muscle of wave contractions move food in one direction along GI tract
54
Q

What is segmentation?

A

smooth muscle back and fourth contractions to mix and break food further down

55
Q

What is the function of the ileocecal sphincter?

A

regulates the amount of chyme entering the large intestine

56
Q

What is a sphincter?

A

A circular muscle that normally maintains constriction of a natural body passage and which relaxes as required by normal physiological functioning.

57
Q

What do the internal and external sphincters do?

A

regulate feces exiting gastrointestinal system

MD2001 Week 4 (10 decks)

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