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The Gastrointestinal System 2023 > Overview of the Physiology of the GI Tract > Flashcards

Overview of the Physiology of the GI Tract Flashcards

1
Q

What are the two main layers of smooth muscle that can move material within the lumen of the digestive tract?

A
  1. Muscularis mucosae
  2. Muscularis externa
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2
Q

What are the 4 main layers of the digestive tract wall?

A
  1. Mucosa
  2. Submucosa
  3. Muscularis externa
  4. Serosa
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3
Q

What is the mucosa comprised of?

A
  • Epithelial cells
  • Exocrine cells
  • Endocrine glands
  • Lamina propria
  • Muscularis mucosae
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4
Q

What is the name given to epithelial cells in the mucosa?

A

Enterocytes

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5
Q

Exocrine glands in the mucosa will release what?

A

Regulatory peptides and amines

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6
Q

What is the submucosa composed of?

A

Loose connective tissue

Largery lymph and blood vessels

Glands

Nerve network - submucosal plxus

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7
Q

What is the name of the nervous system associated with the GI tract?

A

Enteric nervous system

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8
Q

What is the enteric nervosu system composed of?

A

Submucosal plexus

Myenteric plexus (of the muscularis externa)

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9
Q

What is the muscularis externa composed of?

A
  1. A circular muscle layer
  2. Nerve network - myenteric plexus
  3. Longitudinal muscle layer
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10
Q

What is the nerve network associated with the muscularis externa?

A

Myenteric plexus

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11
Q

Where is the myenteric plexus found?

A

Between the two layers of smooth muscle

(circular layer and longitudinal layer)

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12
Q

What is the serosa?

A

Connective tissue, part of the mesentery

This is the outermost layer

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13
Q

What allows for GI motility?

A

Mainly - joint action of the circular and longitudinal layers of muscle

Also - action of the muscularis mucosae

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14
Q

What is the collective name of the three bands of muscle that make up the longitudinal muscle?

A

Teniae coli

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15
Q

What is the main purpose of the muscularis mucosae?

A

Change absoptive and secretory area

Also aids mixing

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16
Q

What connects smooth muscle cells allowing from spread of electric current?

A

Gap junctions

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17
Q

In the stomach, small and large intestines how does the electrical activity present?

A

Slow waves

18
Q

What are the pacemaker cells that given rise to the slow waves called?

A

Interstitial cells of Cajal

19
Q

What mediates the upstroke and downstroke of action potentials for the slow waves?

A

Upstroke - voltage activated calcium channels

Downstroke - volateg activated potassium channels

20
Q

The force of contraction of the muscularis externa is directly related to what?

A

The number of action potentials released by the interstitial cells of Cajal

21
Q

How many slow wave normally occur per minute in:

a) Stomach
b) Small intestine
c) Large intestine

A

a) 3
b) 12 in duodenum, 8 in terminal ileum
c) 8 in proximal colon and 16 in the distal colon

22
Q

Which factors act to inhibit slow wave activity?

A

Vasoactive internal polypeptides (VIP)

Nitric oxide

23
Q

What is the function for the myenteric plexus?

A

Regulates motility and sphincters

24
Q

In terms of function, what is special about the enteric nervous system?

A

It can function independently to the brain

(yet, it will respond to cues from the autonomic nervous system and hormones)

25
Q

What are the 3 main roles of the enteric nervous system?

A
  1. Coordinate muscular activity
  2. Control secretory action
  3. Coordinate absorptive action
26
Q

How does the enteric nervous system achieve its roles?

A
  • Sensory neurones - mechano, chemo and thermoreceptors
  • Inter-neurones - makes up majority of receptors, co-ordinatign reflexes, motor programs
  • Effector neurones - excitory and inhibitory motor neurones supply both muscle layers, secretory epithelium, endocrine cells and blood vessels
27
Q

Why are there no parasympathetic post ganglion neurones in gut?

A

Pre-synaptic neurones synapse with the ganglia in the enteric nervous system instead

28
Q

During peristalsis, which substances cause contraction of either the longitudinal or circular smooth muscle?

A

Acetylcholine and substance P

(from excitory neurone)

29
Q

During peristalsis, which substances cause inhibition of either the longitudinal or circular smooth muscle?

A

Vasoactive internal polypeptide (VIP) and nitric oxide

(released from inhibitory neurone)

30
Q

The mixing/churning movements of the intestine have different names based on whether they occur in the small or large intestines, what are these?

A

Small intestine - segmentation

Large intestine - haustration

31
Q

Name the 6 sphincters of the MAIN GI tract pathway

A
  1. Upper oesophageal
  2. Lower oesophageal
  3. Pyloric
  4. Ileocaecal
  5. Internal anal
  6. External anal
32
Q

As well as the 6 main sphincters, what is the other sphincter related to the main GI tract?

A

Sphincter of oddi

(controls release of bile and pancreatic enzymes into duodenum)

33
Q

Which three phases are involved in swallowing?

A
  1. Oral
  2. Pharyngeal
  3. Oesophageal
34
Q

Which is the voluntary phase in swallowing?

A

Oral phase

35
Q

By stimulating mechanoreceptors (as food is pushed towards oropharynx during swallowing) afferent nerve impulses are sent where, by which nerves?

A

CN IX and CNX

Pons and medulla

36
Q

The pharyngeal phase of swallowing consists of inhibition of what whilst the food bolus passes?

A

Ventilation

(breathing)

37
Q

In the oesophageal phase of swallowing, the swallowing centre within the pons and medulla will trigger what?

A
  • Closure of the upper oesophgeal sphincter
  • Initiate primary peristaltic wave (via CN X)
38
Q

If food becomes lodged in the oesophagus, what is the response from the body?

A

Local pressure receptors are stimulated

Secondary peristaltic waves are stimulated for a more forceful contraction

Saliva production also increases

39
Q

What controls peristalsis?

A

Enteric nervous system

40
Q

Why does the lower oesophageal sphicter close after the food bolus passes?

A

To prevent gastro-oesopheal reflux

The Gastrointestinal System 2023 (27 decks)

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