The Mouth and The Oesophagus

Question 1

What is the function of the mouth

Answer 1

Mouth digests food to form a bolus which can enter the oesophagus

Question 2

How does the mouth digest food

Answer 2

Physical disruption: teeth, tongue, muscles of mastication

Chemical disruption: lipase and amylase

Question 3

What is the function of the oesophagus

Answer 3

Moves bolus by rapid peristaltic transport to the stomach

Question 4

What types of muscle are found in the oesophagus and where are they found

Answer 4

Skeletal muscle - upper end oesophagus (voluntary)

Smooth muscle - lower end oesophagus (involuntary)

Question 5

Describe the structure of the oesophagus

Answer 5

Mucosa - stratified squamous non-keratinised epithelium

Submucosa - layer of CT containing mucus-secreting glands

Muscularis externa - circular and longitudinal smooth muscle layer (peristalsis)

Question 6

What two sphincters are found in the oesophagus

Answer 6

Upper oesophageal sphincter - prevents air entering GI

Lower oesophageal sphincter - prevents relfux into oesophagus

Question 7

What are the functions of saliva

Answer 7

Lubrication

Digestion - amylase and lipase

Immune protection

Route by which pathogens spread

Maintains oral hygiene

Dissolves and moistens food

Versatile solvent

Question 8

Name the salivary glands

Answer 8

Parotid gland

Submandibular gland

Sublingual gland

Question 9

Where do the salivary glands drain into the oral cavity

Answer 9

Parotid - inner surface of the cheek, opposite to the crown of the 2nd upper molar

Submandibular - drains into the oral cavity close to the midline

Sublingual - drains into the oral cavity lateral to where submandibular drains

Question 10

What nerves innervate the salivary glands

Answer 10

Facial innervates submandibular and sublingual

Glossopharyngeal innervates parotid

Question 11

What are the phases of swallowing

Answer 11

Oral preparatory phase

Pharyngeal phase

Oesophageal phase

Question 12

Describe the oral preparatory phase of swallowing

Answer 12

Voluntary phase where bolus is pushed towards pharynx

Once bolus touches pharyngeal wall, pharyngeal phase begins

Bolus is compressed against palate and pushed into oropharynx by tongue and soft palate

Question 13

Describe the pharyngeal phase of swallowing

Answer 13

Involuntary

Tongue positioned against hard palate by CN XII

Soft palate seals off nasopharynx - CN Vc and CN X

Suprahyoids (CNs Vc, VII, XII) and longitudinal muscles (CNs IX, X) shorten

Pharynx widens and shortens to recieve bolus while larynx elevates and is sealed off by vocal folds

Epiglottis closes over larynx due to elevated hyoid

Bolus moves through pharynx by sequential contraction of constrictors

Relaxation of UOS -> UOS opens

Question 14

Describe the oesophageal phase of swallowing

Answer 14

Involuntary

Upper oesophageal sphincter closes and peristaltic waves carry bolus into oesophagus

Upper striated muscle of oesophagus (CN X) and lower smooth muscle are involved

Question 15

What is the neuronal pathway for swallowing and the gag reflex

Answer 15

Mechanoreceptors -> glossopharyngeal nerve -> medulla -> vagus nerve -> pharyngeal constrictors

Question 16

Where are the narrowings in the oesophagus

Answer 16

Junction of the oesophagus with the pharynx - upper oesophageal sphincter

Where oesophagus is crossed by arch of aorta

Where oesophagus is compressed by left main bronchus

At oesophageal hiatus

Question 17

What prevents gastro-oesophageal reflux

Answer 17

Distal oesophageal sphincter

Diaphragm compressing on oesophagus

Increased intra-abdominal pressure compresses intra-abdominal oesophagus

Acute angle of oesophagus

Question 18

Why do babies ahve an increased risk of aspiration and what adaptations are there to prevent aspiration

Answer 18

Babies ahve increased risk of aspiration as they are neurologically immature

To prevent aspiration, baby’s soft palate and epiglottis are close together to separate the airway from the oesophagus -> epiglottis projects into nasopharynx

This set up not compatible with speaking so epiglottis descends during development