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4 - Case 1 > Swallowing physiology > Flashcards

Swallowing physiology Flashcards

1
Q

Muscle types in each stage and voluntary level

A

Oral - striated and full voluntary
Pharyngeal - striated and some voluntary
Oesophageal - Striated/smooth and no voluntary control

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2
Q

Factors that cause upper oesophageal sphincter opening

A
  • Hyoid and laryngeal elevation > pulls relaxed sphincter open
  • Cricopharyngeal relaxation > allows opening to occur
  • Cricopharyngeal compliance > controls degree of opening
  • Pharyngeal pressure wave pushes bolus through open sphincter
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3
Q

Neurophysiological control of swallowing

A

CORTEX sends signals to the brain stem central programme gerenator (CPG).
This then sent down motor neurones to the muscles of swallowing.
Sensory receptors in oropharynx, larynx and oesophagus detect bolus and sent info back up to cortex through various cranial nerves

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4
Q

Which cranial nerves send motor information to the muscles of swallowing?

A 
V - trigeminal
VII - facial
IX - glossopharyngeal
X- vagus
XII - hypoglossal
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5
Q

Which cranial nerves send information back up to the cortex?

A

V
IX
X

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6
Q

What are the muscles of swallowing

A 
Mylohyoid
Geniohyoid
Palatopharyngeus
Post tongue
superior constrictor
Thyrohyoid
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7
Q

How is pharyngeal stage initiated

A

Bolus in contact with palatoglossal and palatopharyngeal arches
Stimulates epithelial swallowing receptor area which transmits impulses via CN V and IX to solitary nucleus of medulla.

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8
Q

Physiological changes in the pharyngeal stage of swallowing

A
  • soft palate pulled up to posterior nares
  • palatopharyngeal folds on both sides are pulled medially to form slit which food that has been sufficienly masticated can pass through.
  • larynx is pulled upwards and anteriorly, causing vocal muscles to pull together
  • epiglottis swings backwards over opening of larynx
  • upwards larynx causes opening to oesophagus to enlarge and UES relax —> entire muscle wall of pharynx contracts, propelling food down.
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9
Q

How are each of the phys. stages of the pharyngeal swallowing inititated?

A

By reticular subtance of medulla and lower pons, collectively called the swallowing centre

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10
Q

What innervates the UOS

A

Vagus nerve

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11
Q

What does the UOS consist of

A

Cricopharyngeus
Adjacent inferior pharyngeal constrictor
Proximal portion of cervial oesophagus

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12
Q

How the UES opened

A

Cessation of vagus excitation to cricopharyngeus

Cotnraction of suprahyoid and geniohyoid muscels that pull open UES with the upwards and forwards movement of larynx

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13
Q

Why does UOS remain closed at rest

A

Because of it’s elastic structure

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14
Q

What are the stages of swallowing

A
  1. Oral
  2. Pharyngeal
  3. Oesophageal
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15
Q

Oesophageal stage of swallowing

A

Primary peristalsis is sequence of inhibtion (deglutive inhibition) and contraction of muscle along the oesophagus. If food left in oesophagus then secondary peristalsis occurs

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16
Q

Stages of the oral phase

A
  • Chewing - preparation of food for transfer through pharynx
  • Salivation - lubricate bolus (mucus, amylase, lipase, water, HCO3-)
  • Movement of bolus to oropharynx using the tongue
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16
Q

How long does oesophageal stage last usually?

A

9 seconds

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18
Q

What is the LOS

A

Distal end of the oesophagus, with assistance of the right diaphragm crus.

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19
Q

What causes the secondary peristalsis

A

Initiated by intrinsic neural ciruits in myenteric nerve plexus and reflexes that begin in pharynx, travel through vagal afferents to medulla, then back to oes through CN IX and X.

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20
Q

How is LOS and distal oesophagus nervously controlled

A

Via excitatory and inhibitory neurones in oesophageal myenteric plexus.

21
Q

How is peristalsis triggered

A

From DMN of vagus sends excitatory or inhibitory signals which are relayed in the myenteric plexus

22
Q

Excitatory neurotransmitters

A

Acetylcholine

Substance P

23
Q

Inhibitory neurotransmitters

A

Vasoactive intestinal peptide

Nitric oxide

24
Q

Pressure difference between oesphagus and abdominal cavity

A

Pressure in oes is equal to intrathoracic pressure, which is negative compared to that in the abdominal cavity.
Therefore LOS works to stop reflux of gastric contents into oes.

25
Q

What is the barrier for gastro-oesophageal reflux?

A

The lower oesophageal sphincter

26
Q

How does the muscle in oesophagius differ

A

Cervical oes is STRIATED
Then gets MIXED
The distal oes and LOS are SMOOTH muscle

27
Q

What does gastric distention do

A

triggers relaxation of the lower oeophageal sphincter

28
Q

Mechanisms to prevent reflux of gastric acid in order to prevent oesophageal injury

A
  • Anti reflux barrier
  • Oesophageal clearance
  • Acid neutralization
  • Tissue resistance
29
Q

How does efferent neural pathway for different parts of oesophagus differ?

A

Signals sent from DMN and NA down vagus nerve.
In stirated it connected directly.
In smooth it has to go through intramural ganglion to connect

30
Q
  1. Anti reflux barrier
A

formed by LES and right crus of diaphragm

They limit the frequency of reflux

31
Q
  1. Oesophageal clearance
A

Caused by gravity and peristalsis

Limits duration of acid contact w oesophagus

32
Q

How is oesphageal sensation transmitted back to the cortex?

A

Through vagal afferents and spinal afferents

33
Q
  1. Acid neutralization
A 
From saliva (HCO3) and HCO3 secreted and in the blood
This also limits duration of acid contact w oesophagus
34
Q

Vagal afferents pathway

A 
For chemo, mechano and nociception
- goes to nodose ganglion
- synapses w nucleus of solitary tract in the medulla
- this sent to parabrachial nuclie
- to the thalamus
then to the CORTEX
35
Q

Spinal afferents pathway

A

For mechano and nociception

  • to dorsal root ganglion
  • synapses on dorsal horn of spinal cord
  • travels up spinothalamic tract
  • synapses with nucleus of solitary tract in medulla
  • THEN THE SAME AS VAGAL
36
Q

Oropharyngeal dysphagia

A
  • Abnormal bolus transfer to oesp
  • Difficulty initiating swallow
  • Only one manifestation
    usually stroke
37
Q

Oesophageal dysphagia

A
  • Abnormal bolus transport through oesophagus
  • Food stops after the swallow
  • Oesophagus is location of primary disease (achalasia)
38
Q

Causes of oropharngeal dysphagia

A

Anatomic - eg. Zenker’s diverticulum: decreased compliance of cricopharyngeus
Neurologic - eg. Stroke: weak pharyngeal contraction, incoordination on UES and pharyngeal contract
Muscular - eg. Mysathenia gravis: weak pharyngela contraction

39
Q

What can barium video show

A

Bolus transport
Aspiration
Movement of anatomic structures

40
Q

What can manometry show

A

Pressure changes of pharynx and UES

Timings of pressure changings

41
Q

What is achalasia

A

Failure of a ring of muscle fibres to relax (eg. sphincter of oesophagus)

42
Q

Pathophysiology of achalasia

A

Degeneration of neurons in oesphageal wall in the myenteric plexus.
Inflammatory degeneration of inhibitory neurones which produce nitric oxide and effect relaxation of oeophageal smooth muscle.
cholinergic neruones are spared
Therfore sphincter cant relax without NO.

43
Q

Mechanism of achalasia

A

Loss of inhibitoru innervation in the LOS causes

  • basal sphincter pressure to rise
  • sphincter muscle incapabel or relaxation
  • oespphageal body smooth muscle aperistalsis
44
Q

Prevalance of achalasia

A

1 case per 100,000 per year
men=women
onset after adolescence (diag between 25 and 60 yo)

45
Q

Clinical presentation

A

Dysphagia with solids and liquids
Difficulty breathing
(less so: chest pain, regurgitation, weight loss, heart burn)

46
Q

Diagnosis

A

Diagnosis w barium swallow is 95% accurate. Dilated oesophagus w beak like narrowing (swan neck). Could be so severe that a sigmoid shape.

Manometry shows aperistalsis of oesophagus and failure of relaxation of LOS

47
Q

Why does LOS remain closed at rest

A

Tonically constricted due to excitatory ganglionic stimulation and intrinsic myogenic tone.

48
Q

Treatments for achalasia

A
  • Endoscopic dilation of LOS using hydrostatic baloon under Xray control (middle aged)
  • Endoscopic injection of botulinum toxin into LOS (old)
  • Heller’s myotomy: surgery where LOS is cut allowing passage of liquid. Up to 100% recovery
49
Q

What is a hiatus hernia

A

When part of stomach comes up through the LOS

4 - Case 1 (5 decks)

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