Upper GI Structure & Anatomy

Question 1

Describe the voluntary control of chewing

Answer 1

Somatic nerves allow voluntary control over the skeletal muscle of the mouth and jaw via the mandibular branch of the trigeminal nerve (CN V)

Question 2

Describe the stages of Swallowing

Answer 2

Oral Phase
Pharyngeal Phase
Oesophageal Phase

Question 3

What Coordinates the reflex action of the pharyngeal phase

Answer 3

The swallowing centre is coordinated by the medulla.

Question 4

Define Oral Phase

Answer 4

Mastication and the formation of the bolus under voluntary control. Food is moved to the back of the mouth by the tongue

Question 5

Names the involuntary nerves that coordinate swallowing

Answer 5

vagus (pharynx & larynx (X)

glosso-pharyngeal (IX)

Question 6

Describe the Esophageal Phase

Answer 6

Waves of peristalsis move the ingesta down the oesophagus to the stomach propelling the bolus to the stomach. ~ten seconds

As the bolus nears the stomach the LOS relaxes. The relaxation causes the stomach to relax (vagal reflexes)

Question 7

Name the 3 salivary glands and type of glands

Answer 7

Sub mandibular
Sublingual
Parotid

Exocrine

Question 8

Components of Saliva

Answer 8

Water
Mucins (lubricant)
a-Amylase 
Electrolytes (tonicity/pH)
Lysosomes (sterilisation)

Question 9

Tonicity

Answer 9

Total concentration of non-penetrating solutes

Question 10

Define Exocrine gland

Answer 10

Exocrine glands secrete into ducts and not direclty into the bloodstream like their endocrine counterparts.

Question 11

What triggers the salivary secretion

Answer 11

Parasympathetic (cranial VII & IX (glosso-pharyngeal) stimulates high volume of watery secretion

Sympathetic stimulates small volume of high mucual (a2 receptors) and high amylase (b2 receptors)

OR presence of food in mouth - mechanoreceptors

Question 12

Describe the epithelia of the Oesophagus

Answer 12

Stratified squamous epithelia containing submucsal mucous exocrine glands that secrete mucous

Question 13

Describe the muscularis externa of the oesophagus

Answer 13

1/3 skeletal muscle

2/3 smooth muscle

Question 14

Pharyngeal Phase

Answer 14

The pressure of the bolus at the back of the mouth is detected by the mechanoreceptors. This triggers a sequence of contractions of the pharyngeal muscles.

The soft palate is reflected backward and upwards to seal the nasopharynx

The upper oesophageal spincter relaxes and the epiglottis covers opening of the larynx.

Once food has entered the oesophagus the UOS contracts

Question 15

Expansion of the stomach on the arrival of food

Answer 15

The stomach can expand from 50ml to 1500ml. This increase in size does not put tension of the stomach wall due