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Year 1 NME > Motility of the Upper GIT > Flashcards

Motility of the Upper GIT Flashcards

1
Q

What are the 4 main functions of the GIT prior to absorption?

A

1 - ingestion of food/formation of bolus

2 - digestion (mechanical and chemical) called chyme

3 - motility

4 - secretion

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2
Q

What are the 2 systems in the body that drain the GIT?

A

1 - portal venous system

2 - lymphatic system

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3
Q

What are the 3 additional functions of the GIT (not including ingestion, digestion, motility and secretion)?

A
  • absorption
  • storage/elimination
  • protection
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4
Q

How many basic layers does the GIT have?

A
  • 4
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5
Q

What are the 4 basic layers of the GIT?

A

1 - mucosa

2 - submucoas

3 - muscularis externa also known as muscularis propria

4 - serosa

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6
Q

What are the 3 basic levels within the first layer of the GIT tract called the mucosa?

A

1 - epithelium

2 - lamina propria (connective tissue) contain lymphatic tissues

3 - muscularis mucosae

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7
Q

The second basic layer of the GIT is called the submucosa. What is this?

A
  • thin layer of connective tissue
  • contains blood and lymphatic vessels
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8
Q

Within the submucosa is the nerve plexus, also referred to as the submucosa plexus. What is the main function of this?

A
  • controlling localised blood flow
  • controlling secretions into the GIT
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9
Q

What are the 2 types of muscle within the muscularis externa?

A

1 - circular muscles (higher up)

2 - longitudinal muscles

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10
Q

Within the muscularis externa is a second plexus of the GIT, placed in the middle of the circular muscles (higher up) and the longitudinal muscles. What is the plexus called, and what is its function?

A
  • myenteric nerve plexus
  • controls contraction and motility of GI
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11
Q

What are the 2 nerve plexus within the GIT wall called?

A

1 - submucosal nerve plexus

2 - mysenteric nerve plexus (myo = muscle, enteric = GIT)

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12
Q

The serosa is the last layer of the GIT wall. What is it?

A
  • encompasses the GIT
  • protection
  • secrete substance to reduce friction between GIT and neighbouring structures
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13
Q

In the histology image, from left to right, keeping in mind all 4 structures contain the 4 basic layers of the GIT, what part of the GIT is depicted in each image?

A
  • oesophagus (transports bolus)
  • stomach
  • small intestines
  • large intestines
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14
Q

What muscles facilitate motility in the GIT?

A
  • smooth muscle
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15
Q

The GIT is lined with smooth muscle which allows motility, however, there are exceptions to this, where voluntary control is needed. What are they and why?

A
  • upper oesophagus, external anal and urethra sphincter are skeletal muscle
  • allows voluntary control
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16
Q

Smooth muscles in the GIT are arranged as single cell units. However, to facilitate peristaltic contractions what joins them to allow electrical currents to move throughout?

A
  • gap junctions
  • allows unitary movements
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17
Q

Smooth muscles in the GIT are arranged as single cell units. However, they are joined by gap junctions to allow for unitary contraction. What is the term given to the joining of multiple cells in this manner?

A
  • functional syncitium
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18
Q

There are 2 types of contraction in the GIT, what are these called?

A

1 - segmentation

2 - peristalsis

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19
Q

Segmentation is a type of contraction in the GIT. What is the purpose of this type of contraction?

A
  • bursts of circular muscle contraction
  • muscles contract and relax giving backwards and forwards movement
  • important for mechanical digestion
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20
Q

Peristalsis is a type of contraction in the GIT. What is the purpose of this type of contraction?

A
  • movement of the digesta
  • local distension of contraction and relaxation
  • appears like a wave
  • requires functional myenteric plexus
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21
Q

There are 3 stages to swallowing, also called deglutination. What are the 3 stages called

A

1 - oral

2 - pharyngeal

3 - oesophageal

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22
Q

The oral phase is the first phase of swalloing/deglutination. What happens here and is this volunary or involuntary?

A
  • voluntary movement
  • tongue pushes against hard palate
  • pushing propells bolus into oropharynx
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23
Q

The pharyngeal phase is the 2nd phase of swallowing/deglutination. What structure in the brain is stimulated by this?

A
  • medulla oblongata in brain stem
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24
Q

The pharyngeal phase is the 2nd phase of swallowing/deglutination. What are the 3 nerves that facilitate this action?

A

1 - vagus nerve

2 - trigeminal nerve

3 - glossopharyngeal nerve

25
Q

Once we have swallowed/deglutination, what is the basic steps of how the bolus is propelled?

A
  • soft palette elevates over posterior nares.
  • epiglottis is raised closing off the larynx
  • respiration is temporarily inhibited
  • upper oesophageal sphincter relaxes
  • pharyngeal muscle contraction propels bolus into oesophagus
26
Q

The oesophageal phase is the 3nd phase of swallowing/deglutination. How is the bolus moved throughout the oesophageal phase?

A
  • primary phase = smooth muscle contractions
  • secondary phase = if primary is not sufficient then strertch receptors will propel bolus into stomach innervated by vagal nerve
27
Q

What does the oesophagus connect?

A
  • pharynx and stomach
28
Q

What is located at either end of the oesophagus, and what is the oesophagus composed of?

A
  • muscular tube
  • upper and lower sphincters
29
Q

What type of contraction moves the bolus through the oesophagus, and can this be moved both way?

A
  • peristaltic contractions
  • one way only
30
Q

To facilitate movement through the oesophagus what does the oesophagus secrete?

A
  • mucous glands in submucosal layer
  • secrete thick mucous
31
Q

The oesophagus is lined with muscle. As the oesophagus moves the bolus there are stretch receptors that signal to what system to make it aware of exactly where the bolus is?

A
  • enteric nervous system
  • nervous sytem controlling GIT
32
Q

How does the lower sphinctor open?

A
  • pressure in oesophagus exceeds pressure in lower sphincter and the stomach
  • lower sphincter is forced open
33
Q

What is the purpose of sphinctors in the GIT?

A
  • allow one way movement only
  • similiar to valves of the heart
34
Q

What sphincter connects the stomach and duodenum?

A
  • phyloric sphincter
35
Q

What sphincter connects the end portion of the common bile duct and pancreatic duct?

A
  • sphincter of Oddi
36
Q

What sphincter connects the ileum and ascending colon?

A
  • ileocecal sphincter
37
Q

What are the internal and external anal sphincters and what type of muscle is present at each?

A
  • sphinctors of the anus
  • internal = smooth muscle under involuntary control
  • external = skeletal muscle under voluntary control
38
Q

What part of the nervous system controls the GIT?

A
  • enteric nervous sytem
39
Q

What are the 2 plexi of the enteric nervous sytem?

A

1 - Myenteric [Auerbach’s] plexus

2 - Submucosal [Meissner’s] plexus

40
Q

What is the primary function of the myenteric [Auerbach’s] plexus, which is part of the enteric nervous sytem?

A
  • controls motility/contraction
  • located in muscular layer
41
Q

What is the primary function of the aubmucosal [Meissner’s] plexus, which is part of the enteric nervous sytem?

A
  • controls glandular secretions/blood flow
  • located in the submucosal layer
42
Q

Is the enteric nervous system voluntary or involuntary?

A
  • involuntary
  • contain afferent, interneurons, efferent and secretomotor neurons
43
Q

The enteric nervous system is responsible for intrinsic control of the GIT, but what is the extrinsic control of the GI?

A
  • autonomic system
  • sympathetic = reduced GIT motility
  • para-sympathetic = increased GIT motility
44
Q

How does parasympathetic control of the GIT, as part of the extrinsic control impact the GIT?

A
  • through postganglionic fibres (ACh is dominant)
  • stimulates motor and secretory activity
  • primarily, but not exclusively, via vagus nerve
45
Q

How does sympathetic control of the GIT, as part of the extrinsic control, impact the GIT?

A
  • inhibits motor and secretory activity (both submucosa and myenteric plexi)
  • stimulates sphincter and blood vessel contraction
  • innervates via the prevertebral ganglia
46
Q

What are the 3 main functions of the stomach?

A

1 - storage facilitated by vagal nerve

2 - mixing by chemical and mechanical digestion

3 - emptying

47
Q

What are the 3 main parts of the stomach called, from top to bottom?

A

1 - fundus

2 - body

3 - antrum

48
Q

What is the region between the fundus and oesophagus called?

A
  • cardiac orifice
49
Q

What is the region between the antrum and duodenum called?

A
  • phloric canal
50
Q

What are the folds in the stomach called, and what is the funtion of these?

A
  • rugae folds
  • allows stomach to stretch
51
Q

When the stomach is relaxed in a fasting state smooth muscle tone is maintained. However, when food enters the stomach it stretches. What nerve facilitates this stretching?

A
  • vagel nerve
  • vasovagal stimulation allows fundus to relax and stretch
52
Q

When the stomach contains food what type of contraction will move the bolus towards the antrum and pyloric sphincter?

A
  • peristalsis
  • come from body of the stomach
53
Q

Once the bolus reaches the lower end of the stomach, the antrum and pyloric sphincter, what happens to the bolus?

A
  • peristaltic contractions push bolus into antrum and pyloric canal
  • propulsion and retropulsion (forwards and backwards) mix and break down the bolus
  • create chyme
54
Q

What excitatory pathways (nerves) are able to stimulate the stomach and move food through the GIT?

A
  • enteric nervous system (submucosa and myenteric plexus)
  • autonomic nervous system (vagal nerve)
55
Q

What pathways (nerves) innervate and slow the contractions of the stomach?

A
  • enteric nervous system
  • duodenal enterogastric reflexes
56
Q

The duodenal enterogastric reflexe is able to inhibit the stomach emptying, how does it do this?

A
  • duodenum stretch receptors are activated
  • this inhibts the stomach contractions
57
Q

What non-excitatory pathways (nerves) are able to stimulate the stomach and move food the bolus/chyme through the stomach and towards the phloric sphincter?

A
  • hormonal
  • motilin
  • relaxes phyloric sphincter and increases stomach peristalsis
58
Q

What non-excitatory pathways (nerves) are able to innervate the stomach and slow down the movement of the bolus/chyme through the stomach and towards the phloric sphincter?

A
  • hormonal
  • cholecystokinin secreted by enteroendocrine cells, specifically I cells
  • relaxes stomach so no contracts and causes phyloric sphincter to contract
  • pronounce = Kolo-cyst-a-kinin
59
Q

What is an enteroendocrine cell of the GIT?

A
  • entero = GIT
  • endocrine = hormone secreting
  • cells secrete into plasma without ducts

Year 1 NME (61 decks)

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