GIT Movement: Mouth & esophagus (chewing & swallowing)

Question 1

Mastication is controlled by motor branch of —-

Answer 1

Trigemnal N (5th Cranial N)

Question 2

Describe Chewing (mastication) reflex

Answer 2

1. Bolus of food detected by oral mucosa causes drop of jaw
2. the drop causes stretch in Muscles of Mastication
3. Causing a stretch reflex: muscles contract, raise the jaw & compress the teeth against the food
4. repeats rhythmically

Question 3

enumerate Stages of Swallowing

Answer 3

• Voluntary oral stage
• Involuntary Pharyngeal stage
• Involuntary esophageal stage

Question 4

describe Voluntary oral stage of swallowing

Answer 4

1. Movement of the tonuge upwards & backwards & pressing it against hard palate
2. Food is rolled posteriorly into the pharynx

This phase is helped by Mylohyoid contraction

Question 5

Stimulus of Involuntary Pharyngeal stage of swallowing

Answer 5

presence of food in pharynx

Question 6

site of Receptor for Involuntary Pharyngeal stage of swallowing

Answer 6

around the opening of pharynx, especially on Tonsillar pillars

Question 7

Describe Involuntary Pharyngeal stage of swallowing

Answer 7

• Rapid paristaltic wave occuring successively in Superior, then middle, then inferior pharyngeal constrictors
• Relaxation of upper Pharyngoesophageal sphincter to allow food to pass from Pharynx to esophagus

Question 8

Explain how the airway is protected during swallowing

Answer 8

• Nasal Cavity protection: Closure of posterior Naris by elevation of soft palate
• Closure of glottis
• Elevation of larynx to be covered by epiglottis
• Swallowing apnea (physiological respiratory inhibition) for 1-2 sec

Question 9

Describe peristaltic movements of Involuntary esophageal stage of swallowing

Answer 9

Primary peristaltic movement:
* It is a continuation of the peristaltic wave that began in the pharynx, passes from pharynx to stomach in 8-10 seconds

Secondary Peristaltic movement:
* Occurs when primary peristaltic movement fails to propel all the food down the esophagus

Question 10

peristaltic movements of Involuntary esophageal stage of swallowing continues until____.

Answer 10

all the food has emptied into the stomach

Question 11

difference between LES & other esophageal sphincters

Answer 11

LES is always tonically contracted

Question 12

Function of LES

Answer 12

prevent Gastric reflux into esophagus when intragastric pressure rises during meals

Question 13

Effect of Peristaltic waves passing down in esophagus on LES

Answer 13

Receptive relaxation of LES:
LES releaxes before arival of Peristaltic wave

Question 14

Control of tone of LES

Answer 14

Contraction:
* Acetylcholine/parasympathetic/Vagal

Relaxation:
* NO/VIP (during feeding)
* High progesterone levels (pregnency)–> heartburn
* Diet high in sugar & fat–> heartburn

Question 15

define & Cause of Achalasia

Answer 15

Incomplete relaxation of LES during feed leading to accumulation of food in esophagus & massive esophageal dilution

Cause:
Defiecent Myenteric plexus, leading to defiecient secretion in NO & VIP

Question 16

explain why boulinum toxin injection is effective for treating Achalasia

Answer 16

inhibits acetlycholine release, therefor decreasing tone