Oral Cavity, Pharynx and Oesophagus

Question 1

What does the oral cavity continue into?

Answer 1

The oropharynx posteriorly at the palatoglossal arch.

Question 2

What are the muscles of mastication? What are they innervated by?

Answer 2

• Temporalis, masseter
• Lateral and medial pterygoids
• Innervated by CN V₃ (mandibular division of the trigeminal nerve)

Question 3

What movements does the temporomandibular joint allow?

Answer 3

The TMJ allows movement of the mandible relative to the rest of the skull.

• Hinge, gliding, side-to-side movements
• Elevation/depression (close/open jaw), protrusion/retraction, ab/adduction of mandible (side to side grinding)

Question 4

Describe the different types of dentition

Answer 4

Permanent (32 teeth): 4 quadrants, with eight teeth in each quadrant

• 2 incisors
• 1 canine/cuspid
• 2 premolars/bicuspids
• 3 molars

Primary (deciduous; 20 teeth): 4 quadrants, with 5 teeth in each

• 2 incisors,
• 1 canine,
• 2 molars

Question 5

Intrinsic muscles of the tongue

Answer 5

Longitudinal, transverse and vertical (change the shape of the tongue)

Question 6

Salivary glands

Answer 6

• Parotid
• Submandibular
• Sublingual
• Many small intrinsic

Question 7

Functions of pharynx and oesophagus

Answer 7

1. Swallowing and propulsion of food to stomach
2. Pharynx also a part of upper respiratory tract for breathing
3. Secretions (mucous) to protect mucosa
4. Upper and lower oesophageal sphincters - limit air entering oesophagus and reflux of stomach contents

Question 8

Components of the pharynx

Answer 8

1. Nasopharynx
2. Oropharynx
3. Laryngopharynx

Question 9

What vertebral levels does the pharynx run across?

Answer 9

Base of the skull to C6/C7 vertebral level

Question 10

Innervation of the pharynx

Answer 10

Sensory innervation mostly by CN IX (glossopharyngeal nerve) and CN X (vagus nerve)

Question 11

Muscles of the pharynx

Answer 11

• Superior, middle and inferior pharyngeal constrictors. Inferior constictor includes cricopharyngeus (upper oesophageal sphincter, UOS or UES)
• Palatopharyngeus

All are innervated by CN X (vagus nerve) except for the **stylopharyngeus **which is innervated by CN IX (glossopharyngeal n).

Question 12

Muscles of the soft palate

Answer 12

• Levator veli palatini and tensor veli palatini - elevate the palate duirng swallowing to prevent food moving into nasopharynx.
• Palatoglossus, palatopharyngeus - depress the palate and narrow opening to oropharynx - allow chewing an dbreathing simultaneously.

All are innervated by the vagus nerve (CNX) except tensor veli palatini, by V₃

Question 13

Innervation of the oesophagus

Answer 13

CN X (vagus n)

Question 14

What are the anatomical relationships of the oesophagus in the superior mediastinum?

Answer 14

In the superior mediastinum the oesophagus is anterior to the thoracic vertebrae, and posterior to the trachea.

Question 15

What are the anatomic relationships of the oesophagus in the posterior mediastinum?

Answer 15

Posterior to the oesophagus, the thoracic duct is on the right side inferiorly, but crosses to the left more superiorly. Also on the left side of the oesophagus is the thoracic aorta.

Anterior to the oesophagus, below the level of the tracheal bifurcation, are the right pulmonary artery and the left main bronchus. The oesophagus then passes immediately posteriorly to the left atrium, separated from it only by pericardium. Inferior to the left atrium, the oesophagus is related to the diaphragm.

Structures other than the thoracic duct posterior to the oesophagus include portions of the hemiazygous veins, the right posterior intercostal vessels, and near the diaphragm, the thoracic aorta.

Question 16

What controls swallowing?

Answer 16

Swallowing is initiated voluntarily.

The pharyngeal and oesophageal phases are controlled automatically by somatic and autonomic neurons.

Question 17

What are the phases of swallowing?

Answer 17

1. Pharyngeal phase
2. Oesophageal phase

Question 18

Describe the pharyngeal phase of swallowing

Answer 18

1. Soft palate elevates to close off nasopharynx
2. Elevation and anteiror movement of hyoid bone and larynx (suprahyoid mm) opens laryngopharynx
3. Elevation of the pharynx by stylopharyngeus, palatopharyngeus
4. Larynx protected by contraction of muscles around largeal inlet to narrow the inlet, and epiglottis pulled posteriorly by the aryepiglotic muscle and the tyroepigloti muscle.
5. The vocal and vestibular folds are adducted by the lateral cricoarytenoid and transverse arytenoid muscles.
6. A wave of relaxation and contraction of pharyngeal constrictions from superior to inferior moves the bolus inferiorly.
7. The UOS relaxes to allow the bolus to enter the

Question 19

Describe the control of swallowing

Answer 19

• The bolus contacting the soft palate an doropharynx initiates the swallowing reflex
• Afferents: CN V, IX, X
• Swallowing centre in medulla coordinates motor neurons in the pons, medulla and upper cervical spinal cord.

Question 20

Describe what happens in the oesophageal phase of swallowing

Answer 20

1. A wave of peristalsis (contraction, relaxation) propels the bolus from superior to inferior, to the stomach. This is controlled via the swallowing centre and locallyv ia the enteric nervous system.
2. UOS, LOS tonically contracted; relax to let bolus pass
3. A second wave of peristalsis may occur if some material remains in oesophagus (local reflex)

Question 21

Describe oesophageal pressures

Answer 21

The pressure in the UOS is much higher than that in the LOS (60mmHg compared to 20-40 mmHg). Between the UOS and LOS, there is subatmospheric (intrathoracic) pressure at rest. Peristaltic wave proceeds at 2-6 cm/sec (varies depending on consistency of bolus).