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JL Gastrointestinal > Structure of GI Tract and Motility > Flashcards

Structure of GI Tract and Motility Flashcards

1
Q

What structure of the GI tract, chop food, lubricate it, start carbohydrate and fat digestion and propel food to oesophagus?

A

Mouth and oropharynx

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2
Q

What structure of the GI tract, delivers food to the stomach?

A

Oesophagus

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3
Q

What structure of the GI tract stores food temporarily, continues carbohydrate and fat digestion and regulates delivery of chyme to the small intestine?

A

Stomach

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4
Q

What structure in the GI tract is the principal site of digestion and absorption of nutrients?

A

Small intestine

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5
Q

What structure of the GI tract reabsorbs fluids and electrolytes and stores faecal matter before regulated expulsion?

A

Large intestine

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6
Q

What are the three accessory structures of the GI tract?

A

Salivary glands, pancreas and the liver and gall bladder (hepatobiliary system)

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7
Q

What are the four basic digestive processes?

A
  1. Motility
  2. Secretion
  3. Digestion
  4. Absorption
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8
Q

What type of muscle does mechanical activity for motility in the mouth, pharynx, upper oesophagus and external anal sphincter?

A

Skeletal muscle

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9
Q

In motility, what are the three types of movements?

A
  1. Propulsive movements
  2. Mixing movements
  3. Tonic contractions
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10
Q

What do digestion and protection both require?

A

Secretion

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11
Q

What three things does digestive secretion contain?

A
  1. Water
  2. Electrolytes
  3. Organic compounds
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12
Q

What is the term for the biochemical breakdown (enzymatic hydrolysis) of complex foodstuffs to smaller, absorbable units?

A

Digestion

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13
Q

In digestion, what are carbohydrates [mostly polysaccharides such as starch and glycogen] converted to, and what mediates this conversion?

A

Monosaccharides (glucose, galactose and fructose)

Mediated by amylases and dissacharidases.

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14
Q

In digestion, what are proteins converted to and what mediates it?

A

Amino acids, dipeptides and tripeptides

Mediated by proteases and dipeptidases

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15
Q

In digestion, what are fats converted to [mostly triglycerides] and what mediates it?

A

Monoglycerides and free fatty acids.

Mediated by lipases

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16
Q

What term is given to the process involving the transfer of the absorbable products of digestion from the digestive tract to the blood or lymph?

A

Absorption

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17
Q

What part of the digestive tract wall has: epithelial cells, exocrine cells, endocrine gland cells, lamina propria and muscularis mucosa? State the components roles also.

A

Mucosa. Epithelial cells - absorption. Exocrine cells - secrete digestive juices. Endocrine gland cells - secrete digestive hormones. Lamina propria - capillaries, enteric neurones and immune cells.

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18
Q

What structure of the digestive tract wall contains connective tissue, larger blood and lymph vessels and a nerve network - submucosa plexus?

A

Submucosa

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19
Q

What part of the digestive tract wall is a circular muscle layer, has a nerve network - myenteric plexus and longitudinal muscle layer?

A

Muscularis externa

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20
Q

What is the outer layer of the digestive tract wall and what does it contain?

A

Serosa - connective tissue

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21
Q

What does circular muscle contraction do to the lumen?

A

Becomes narrower and longer

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22
Q

What does longitudinal muscle contraction do to the intestine?

A

Becomes shorter and fatter

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23
Q

What does muscularis mucosae contraction do to the mucosa?

A

Change in absorptive and secretory area of mucosa

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24
Q

What are adjacent smooth muscle cells in the GI tract coupled by?

A

Gap junctions

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25
Q

What do gap junction between smooth muscle cells of the GI tract form, by allowing spread of electrical currents from cell to cell?

A

Functional syncytium in which hundreds of cells are depolarised and contract at the same time.

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26
Q

What two factors modulate spontaneous smooth muscle activity in the GI tract?

A
  1. Intrinsic (enteric) and extrinsic (autonomic) nerves

2. Numerous hormones

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27
Q

In the stomach, small intestine and large intestine, what does spontaneous electrical activity occur as?

A

Slow waves

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28
Q

In the GI tract, what determines maximal frequency, direction and velocity of rhythmic contractions?

A

Slow wave electrical activity

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29
Q

What drives slow waves?

A

Interstitial cells of Cajal - pacemaker cells

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30
Q

When does contraction only occur?

A

When the slow wave amplitude is sufficient to trigger action potentials

31
Q

In slow wave amplitude - what mediates upstroke and what mediates downstroke?

A

Upstroke - calcium ions

Downstroke - potassium ions

32
Q

What is force of contraction related to?

A

Number of action potentials discharged

33
Q

Where are interstitial cells of Cajal located?

A

Between longitudinal and circular muscle layers and in the submucosa

34
Q

In the enteric nervous system, where are cell bodies located?

A

In ganglia largely within the myenteric and submucous plexus

35
Q

What is another name for the myenteric and submucosa plexus?

A

Myenteric - Auerbach’s

Meissner’s plexus

36
Q

What are ganglia in the enteric nervous system connected by?

A

Interganglionic fibre tracts

37
Q

What forms a complete reflex circuit that can operate independently of the rest of the nervous system, but is strongly modulated by hormones and extrinisc nerve input?

A

Enteric nervous system

38
Q

What three neurones comprise the enteric nervous system?

A
  1. Sensory neurones
  2. Interneurones
  3. Effector neurones
39
Q

What type of neurones supply longitudinal and circular muscle, secretory epithelium, endocrine cells and blood vessels?

A

Effector neurones

40
Q

In the parasympathetic innervation of the GI tract, what do preganglionic fibres release?

41
Q

What do preganglionic fibres synpase with, in the essence post-ganglinic neurones within the ENS? (parasmpathetic)

A

Ganglion cells

42
Q

What innervation increases gastric, pancreatic and small intestinal secretion, blood flow and smooth muscle contraction?

A

Parasympathetic

43
Q

What does parasympathetic innervation of GI tract inhibit?

A

Relaxation of some sphincters, receptive relaxation of stomach.

44
Q

In the sympathetic innervation of GI tract, where do preganglionic fibres, releasing ACh, synapse?

A

In the prevertebral ganglia.

45
Q

In the sympathetic innervation of GI tract, what do postganglionic fibres, releasing NA, innervate?

A

Mainly enteric neurones

46
Q

What is the inhibitory influence of sympathetic innervation of GI tract?

A

Decreased motility, secretion and blood flow

47
Q

Give an example of local reflex, short reflex and long reflex?

A

Local - peristalsis
Short - intestino-intestinal inhibitory reflex
Long - gastroileal reflex

48
Q

What is peristalsis triggered by?

A

Distension of the gut wall

49
Q

In perstalsis, what happens after distension activates sensory neurones?

A

Altered activity of interneurones

50
Q

What do altered activity of interneuornes cause?

A

Altered activity of motoneurones

51
Q

When circular muscle contracts, what is released from excitatory motoneurone?

A

ACh and substance P

52
Q

When circular muscle contracts during perstalsis, what happens to longitudinal muscle and what two substances cause this?

A

Relaxes

Release of VIP and NO from inhibitory motoneurone

53
Q

In the propulsive segment of perstalsis, what does the longirtudinal and circular muscle do?

A

Circular - contracts

Longitudinal - relaxes

54
Q

In the receiving segment of perstalsis, what does the circular and longitudinal muscle do?

A

Circular - relaxes

Longitudinal - contracts

55
Q

What is the term for rhythmic contractions of the circular muscle layer that mix and divide luminal contents?

A

Segmentation

56
Q

What is segmentation called in the large intestine?

A

Haustration

57
Q

What are tonic contractions?

A

Sustained contractions found in the sphincters of teh GI tract

58
Q

What two sphincters have skeletal muscle?

A

Upper oesophageal sphincter

External anal sphincter

59
Q

What action closes the upper oesophageal sphincter?

A

Inspiration

60
Q

What does closure of the lower oesophageal sphincter prevent?

A

Reflux of gastric contents to the oesophagus

61
Q

What does the pyloric sphincter prevent?

A

Duodenal gastric reflux

62
Q

What opens and what closes the ileocecal sphincter?

A

Distension of ileum opens, distension of proximal colon closes

63
Q

What reflexes mediate chewing?

A

Masseteric and diagastric reflexes

64
Q

What structure seperates the mouth from nasal passages, sllowing breathing and chewing simultaneously?

65
Q

What structure helps seal off nasal passages during swallowing?

66
Q

Where is the major location of taste buds?

A

On the tongue

67
Q

What structure has tonsils on side walls which are lymphoid tissues?

68
Q

Where does the tongue force a bolus?

A

Into pharynx at back of mouth

69
Q

What does pressure of bolus at rear of mouth stimulate?

A

Pharyngeal pressure receptors

70
Q

What do the pharyngeal pressure receptors do?

A

Afferent impulses to swallowing centre in medulla

71
Q

What does the swallowing centre in the brain inhibit?

A

The respiratory centre

72
Q

What triggers primary peristaltic wave and closure of the upper oesophageal sphincter?

A

Swallowing centre in medulla

73
Q

If sticky food becomes lodged what two responses to the local pressure receptors cause?

A
  1. Secondary perstaltic wave - mroe forceful than primary

2. Increased saliva production

JL Gastrointestinal (33 decks)

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