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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
What do gap junction between smooth muscle cells of the GI tract form, by allowing spread of electrical currents from cell to cell?
Functional syncytium in which hundreds of cells are depolarised and contract at the same time.
26
What two factors modulate spontaneous smooth muscle activity in the GI tract?
1. Intrinsic (enteric) and extrinsic (autonomic) nerves | 2. Numerous hormones
27
In the stomach, small intestine and large intestine, what does spontaneous electrical activity occur as?
Slow waves
28
In the GI tract, what determines maximal frequency, direction and velocity of rhythmic contractions?
Slow wave electrical activity
29
What drives slow waves?
Interstitial cells of Cajal - pacemaker cells
30
When does contraction only occur?
When the slow wave amplitude is sufficient to trigger action potentials
31
In slow wave amplitude - what mediates upstroke and what mediates downstroke?
Upstroke - calcium ions | Downstroke - potassium ions
32
What is force of contraction related to?
Number of action potentials discharged
33
Where are interstitial cells of Cajal located?
Between longitudinal and circular muscle layers and in the submucosa
34
In the enteric nervous system, where are cell bodies located?
In ganglia largely within the myenteric and submucous plexus
35
What is another name for the myenteric and submucosa plexus?
Myenteric - Auerbach's | Meissner's plexus
36
What are ganglia in the enteric nervous system connected by?
Interganglionic fibre tracts
37
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?
Enteric nervous system
38
What three neurones comprise the enteric nervous system?
1. Sensory neurones 2. Interneurones 3. Effector neurones
39
What type of neurones supply longitudinal and circular muscle, secretory epithelium, endocrine cells and blood vessels?
Effector neurones
40
In the parasympathetic innervation of the GI tract, what do preganglionic fibres release?
AcH
41
What do preganglionic fibres synpase with, in the essence post-ganglinic neurones within the ENS? (parasmpathetic)
Ganglion cells
42
What innervation increases gastric, pancreatic and small intestinal secretion, blood flow and smooth muscle contraction?
Parasympathetic
43
What does parasympathetic innervation of GI tract inhibit?
Relaxation of some sphincters, receptive relaxation of stomach.
44
In the sympathetic innervation of GI tract, where do preganglionic fibres, releasing ACh, synapse?
In the prevertebral ganglia.
45
In the sympathetic innervation of GI tract, what do postganglionic fibres, releasing NA, innervate?
Mainly enteric neurones
46
What is the inhibitory influence of sympathetic innervation of GI tract?
Decreased motility, secretion and blood flow
47
Give an example of local reflex, short reflex and long reflex?
Local - peristalsis Short - intestino-intestinal inhibitory reflex Long - gastroileal reflex
48
What is peristalsis triggered by?
Distension of the gut wall
49
In perstalsis, what happens after distension activates sensory neurones?
Altered activity of interneurones
50
What do altered activity of interneuornes cause?
Altered activity of motoneurones
51
When circular muscle contracts, what is released from excitatory motoneurone?
ACh and substance P
52
When circular muscle contracts during perstalsis, what happens to longitudinal muscle and what two substances cause this?
Relaxes | Release of VIP and NO from inhibitory motoneurone
53
In the propulsive segment of perstalsis, what does the longirtudinal and circular muscle do?
Circular - contracts | Longitudinal - relaxes
54
In the receiving segment of perstalsis, what does the circular and longitudinal muscle do?
Circular - relaxes | Longitudinal - contracts
55
What is the term for rhythmic contractions of the circular muscle layer that mix and divide luminal contents?
Segmentation
56
What is segmentation called in the large intestine?
Haustration
57
What are tonic contractions?
Sustained contractions found in the sphincters of teh GI tract
58
What two sphincters have skeletal muscle?
Upper oesophageal sphincter | External anal sphincter
59
What action closes the upper oesophageal sphincter?
Inspiration
60
What does closure of the lower oesophageal sphincter prevent?
Reflux of gastric contents to the oesophagus
61
What does the pyloric sphincter prevent?
Duodenal gastric reflux
62
What opens and what closes the ileocecal sphincter?
Distension of ileum opens, distension of proximal colon closes
63
What reflexes mediate chewing?
Masseteric and diagastric reflexes
64
What structure seperates the mouth from nasal passages, sllowing breathing and chewing simultaneously?
Palate
65
What structure helps seal off nasal passages during swallowing?
Uvula
66
Where is the major location of taste buds?
On the tongue
67
What structure has tonsils on side walls which are lymphoid tissues?
Pharynx
68
Where does the tongue force a bolus?
Into pharynx at back of mouth
69
What does pressure of bolus at rear of mouth stimulate?
Pharyngeal pressure receptors
70
What do the pharyngeal pressure receptors do?
Afferent impulses to swallowing centre in medulla
71
What does the swallowing centre in the brain inhibit?
The respiratory centre
72
What triggers primary peristaltic wave and closure of the upper oesophageal sphincter?
Swallowing centre in medulla
73
If sticky food becomes lodged what two responses to the local pressure receptors cause?
1. Secondary perstaltic wave - mroe forceful than primary | 2. Increased saliva production

JL Gastrointestinal (33 decks)

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