Week 1: Gross Anatomy of Oral Cavity, Pharynx & Oesophagus

Question 1

Oral Cavity Functions

Answer 1

Ingestion, masication, taste, speech, breathing

Mixing of food and saliva

Initiation of digestion: mechanical and chemical

First steps of swallowing

Secretions from oral cavity and salivary glands contribute to many of the above functions (water, mucous, ions, small molecules, enzymes etc)

Question 2

Point at which oropharynx continues posteriorly from oral cavity

Answer 2

Palatoglossal Arch

Question 3

Muscle contained within palatoglossal arch

Answer 3

Palotoglossal muscle

Question 4

Major Muscles involved in chewing (mastication)

Innervation of these muscles

Answer 4

Temporalis, Masseter
Lateral and Medial Pterygoids

CNV3: Mandibular Division of Trigeminal Nerve

Also intrinsic and extrinsic muscles of the tongue. Innervated by CNXII Hypoglossal n. Except Palatoglossus which is innervated by CNX Vagus n.

Question 5

Joint at which movement of mandible occurs, relative to the rest of the skull (i.e. jaw movements).

Type of joint, and the movements allowed by this joint.

Specific position of the joint

Answer 5

Temporomandibular Joint (TMJ)

Synovial Hinge Joint

Elevation/ depression of jaw (opening/closing of mouth)

Protrusion and retraction of mandible

Side to side grinding (ab/adduction of mandible)

Mandible portion moves within the mandibular fossa of the temporal bone

Question 6

Muscles of mastication (chewing) - actions occurring at the TMJ

Answer 6

Temporalis: Anterior portion closes jaw, and posterior fibers retract jaw

Masseter: closes and protracts jaw

Lateral Pterygoid: Projects jaw, and allows ab/adduction of jaw from side to side

Medial Pterygoid: Elevates jaw, and allows ab/adduction of jaw from side to side

Question 7

Name the permanent teeth from anterior to posterior

Answer 7

Total of 4 quadrants x 8 teeth: incisors, canines (cuspids), premolars (bicuspids), molars.

2 Incisors

1 canine/cuspid

2 premolars/bicuspids

3 molars

Total = 32 teeth

Question 8

Name the deciduous teeth from anterior to posterior

Answer 8

Aka Primary teeth: there are 4 quadrants x 5 teeth (total of 20)

2 incisors

1 canine/cuspid

2 molars

Question 9

Joints of the teeth to skull/jaw bones, and the specific locations involved

Answer 9

The teeth are secured by gomphoses: fibrous ‘peg in socket’ joints.

Secured to the superior alveolar process of the maxilla and inferior alveolar process of the mandible

Question 10

Innervation of maxillary and mandible teeth

Answer 10

Maxillary teeth: Superior Alveolar nerve. CNV2 - 2nd (maxillary) division of Trigeminal nerve (CNV)

Mandibular teeth: Inferior Alveolar nerve. CNV3 - 3rd (mandibular) division of the trigeminal nerve (CNV)

Question 11

Functions of the tongue

Answer 11

Mechanical Digestion (moving bolus of food around mouth, mashing it against roof of mouth)
Speech
Taste
Initial phase of swallowing
Immune protection (MALT of lingual tonsils on posterior 1/3 of tongue)

Question 12

Muscular innervation of the tongue

Answer 12

Most muscles innervated by Hypoglossal nerve (CNXII)

Exception: Palatoglossus innervated by Vagus nerve (CNX)

This makes sense as palatoglossus is also a palate muscle and most palate muscles are innervated by vagus

Question 13

General Sensory innervation of the tongue

Answer 13

Anterior 2/3 innervated by Mandibular division of Trigeminal nerve (CNV3)

Posterior 1/3 innervated by Glossopharyngeal nerve (CNIX)

Question 14

Taste Innervation of the Tongue

Answer 14

Anterior 2/3 innervated by Facial Nerve (CNVII)

Poster 1/3 innervated by Glossopharyngeal nerve (CNIX)

Question 15

Intrinsic muscles of the tongue. Names and type of muscle.

Answer 15

All skeletal.

Longitudinal, Transverse and Vertical mm

Question 16

Extrinsic muscles of the tongue: names, attachments, actions

Answer 16

Genioglossus = attached to deep surface of mandible. Positioned inferoanterior relative to body of tongue. Depresses and projects tongue.

Hyoglossus = attached to hyoid bone. Depresses and slightly retracts tongue.

Styloglossus = attached to Styloid process of Temporal bone. Raises and retracts tongue.

Palatoglossus = attached to palatine aponeurosis. Also a muscle of the palate. Moves tongue posteriorly and depresses palate.

Question 17

Name the salivary glands. How much saliva produced daily?

Answer 17

Parotid, submandibular and sublingual.

There are also many small intrinsic salivary glands

1-1.5 L saliva produced per day

Question 18

Pharynx and Oesophagus: Functions

Answer 18

Swallowing and propulsion of food to stomach.

Pharynx also involved in breathing (forms part of URT)

Secretions from mucosa have protective function

Lower and upper oesophageal sphincters (LOS and UOS) prevent air entering oesophagus (upper) and prevent reflux of stomach contents into oesophagus (LOS)

Question 19

Pharynx: its 3 components, vertebral levels, sensory innervation

Answer 19

Naso-, oro- and laryngo- pharynx

Pharynx extends from base of skull to C6/7

Sensory innervation = Mostly Glossopharyngeal nerve (CNIX) and Vagus nerve (CNX)

Question 20

What are the muscles of the pharynx and their attachment points?

Innervations?

Answer 20

Superior pharyngeal constrictor = attached to mandible

Middle pharyngeal constrictor = attached to Hyoid

Inferior pharyngeal constrictor = attached to thyroid and cricoid

**The inferior constrictor includes the upper oesophageal sphincter (UOS) - the cricopharyngeus muscle

Palatopharyngeus muscle = Palatine Aponeurosis and hard palate to the upper border of the thyroid muscle

Stylopharyngeus muscle = Styloid process of temporal bone to the pharynx

All pharynx muscles innervated by Vagus nerve (CNX) except Stylopharyngeus which is innervated by the Glossopharyngeal nerve (CNIX)

Question 21

Muscles of the soft palate, their actions and innervations

Answer 21

Lavator veli palatini = “elevator of soft palate” elevates soft palate during swallowing

Tensor veli palatini = ‘tensor of soft palate” tenses the palate, which helps the levator veli palatini to elevate the soft palate during swallowing

*Elevation of palate during swallowing prevents food moving into nasopharynx

Palatoglossus & Palatopharyngeus = both depress the palate and narrow the opening to the oropharynx (at palatoglossal arch)

*Depression of palate and narrowing of opening into oropharynx (at palatoglossal arch) allows simultaneous chewing and breathing

All innervated by Vagus nerve (CNX) except Tensor veli palatini which is innervated by the inferior alveolar nerve - mandibular division of the Trigeminal nerve (CNV3)

Question 22

Oesophagus: Types of muscle and innervations, and locations of constrictions

Answer 22

Comprised of skeletal (superiorly), then mixed skeletal/smooth, then smooth muscle only (more inferiorly).

All innervated by vagus (CNX)

Constrictions:
Origin: UOS
Arch of Aorta
Diaphragm (as it passes through)
LOS

Question 23

What is the clinical significance of the constrictions of the oesophagus?

Answer 23

Constrictions, due to sphincters (UOS and LOS) and obstruction from adjacent structures (Arch of aorta, diaphragm) are areas often associated with oesophageal injury. These areas are thus at higher risk of meta- or neo-plasia.

Question 24

Anatomical relationships of oesophagus in neck and superior mediastinum?

Answer 24

Neck: anteriorly = trachea, posteriorly = cervical vertebral bodies

Superior mediastinum: anteriorly = trachea, arch of aorta, brachiocephalic veins, etc. Posteriorly = thoracic vertebral bodies

Question 25

Anatomical relationships of oesophagus in inferior mediastinum and abdominal cavity?

Answer 25

Inferior mediastinum: anterior = heart, posterior = descending aorta

Abdominal cavity: Passes posteriorly to left lobe of liver before entering stomach

Question 26

Explain the basic control of swallowing, and the functions of swallowing. What are the phases?

Answer 26

Swallowing moves bolus of food from oral cavity, through the oro- and laryngo-pharynx, into the oesophagus and then into the stomach.

Swallowing is initiated voluntarily.

Pharyngeal and Oesophageal phases are controlled automatically by somatic and somatic + autonomic neurons

1) Buccal phase = voluntary
2) Pharyngeal phase = somatic / somatic + autonomic neural control
3) Oesophageal phase = somatic / somatic + somatic autonomic neural control

Question 27

Describe buccal phase of swallowing

Answer 27

Voluntary phase (initial)

Tongue moves bolus of food towards oropharynx.

Question 28

Describe the Pharyngeal phase of swallowing: major movements and muscles involved

Answer 28

Soft palate elevates to close off nasopharynx

Suprahyoid mm move larynx superiorly and anteriorly, opening the laryngopharynx allowing the passage of the bolus

Stylopharyngeus and Palatopharyngeus mm elevate pharynx

*Larynx protected by contraction of muscles around laryngeal inlet which narrow the inlet and pull the epiglottis posteriorly: via aryepiglottic and thyroepiglottic mm

Vocal and vestibular folds also adduct via lateral cricoarytenoid and transverse arytenoid mm

A wave of of contraction then relaxation of pharyngeal constrictors (sup, mid and inferior) moves bolus inferiorly

UOS relaxes to allow bolus into oesophagus

Question 29

Describe the control of swallowing and the main muscles and nerves involved

Answer 29

The swallowing reflex is triggers by the bolus of food contacting the palate and the oropharynx

The swallowing centre in the medulla coordinates motor neurons in the pons, medulla and upper cervical spinal cord

Muscle groups involved:

Muscles of tongue = mainly CNXII (hypoglossal)

Muscles of soft palate = mainly CNX (vagus)

Muscles of the pharynx = mainly CNX (vagus)

Suprahyoid muscles = CNV, VII and C1 fibers (Trigeminal, facial nerves, and fibers from C1)

Question 30

Describe the oesophageal phase of swallowing

Local and central control via?

Answer 30

Wave of peristalsis propels bolus from the superior portion (beginning at UOS) to inferior portion (terminating at LOS) of the oesophagus, into the stomach

Controlled via swallowing centre in the medulla, and locally controlled via enteric nervous system

**The UOS and LOS are naturally (tone) contracted, and thus relax to allow bolus to pass. The rest of the oesophagus contracts to propel the food downwards, then relaxes

**A 2nd wave of peristalsis may occur if some food still left in oesophagus

Question 31

Describe the passage of a bolus through the oesophagus with relation to the pressures of each section of the oesophagus

Answer 31

The natural pressure (due to tone contraction) of the UOS and LOS are above atmospheric pressure as they are usually contracted. These sphincters must relax to allow the bolus through.

The remainder of the oesophagus has a sub-atmospheric pressure as it is within the thoracic cavity. Thus, these sections of the oesophagus contract to propel the bolus downwards, and then relax

**A 2nd wave of peristalsis may occur if some food still left in oesophagus

Question 32

What are the pressures of each component of the oesophagus?

What is the average speed of the peristaltic wave?

Answer 32

UOS = ~60mmHg
LOS = ~20-40mmHg

everything in-between = subatmospheric (as within thoracic cavity)

Peristaltic wave = ~2-6cm/sec. Varies depending on the consistency of the bolus

Question 33

List some common oesophageal disorders

Answer 33

Gastro-oesophageal reflux & associated complications

Achalasia: poor relaxation of LOS, and loss of peristalsis throughout oesophagus, leading to simultaneous contraction of full length. Associated with difficulty swallowing/regurgitation, etc.

Scleroderma (autoimmune) causes fibrosis of oesophagus

Tumours

Question 34

Formative: What are the actions of the extrinsic muscles of the tongue?

Answer 34

Genioglossus = projection and depression of tongue

Hyoglossus = depression and slight retraction of tongue

Styloglossus = Elevation and retraction of tongue

Palatoglossus = Moves tongue posteriorly. (Also depresses soft palate as is also a palate muscle)

Question 35

Formative: Summarise motor and sensory innervation of the tongue

Answer 35

Motor innervation of tongue: all muscles innervated by hypoglossus (CNXII) except the palatoglossus which is innervated by vagus (CNX)

General sensory innervation: Anterior 2/3 = mandibular division of trigeminal nerve (CNV3). Posterior 1/3 = glossopharyngeal nerve (CNIX)

Taste innervation: Anterior 2/3 = facial nerve (CNVII). Posterior 1/3 = Glossopharyngeal nerve (CNIX)

Question 36

What trigger the stimulation of salivary gland secretions? What is the mechanism and the nerves/ganglia involved?

Answer 36

Stimulated by thought, sight, smell and presence of food in mouth

This stimulates the PSNS - specifically, the craniosacral division of the ANS - to stimulate saliva production.

Parotids = preganglionic nucleus in medulla. Fibers with CNIX (Glossopharyngeal). Otic Ganglion.

Submandibular and Sublinguals = preganglionic nucleus in pons. Fibers with CNXII (hypoglossal n). Submandibular ganglion.

Question 37

List the muscles around the mouth and their innervation:

Answer 37

“Muscles of facial expression” are those that move the lips. These also assist in speech.

Sphincter of the lips = orbicularis oris (“orbits the mouth”)

Numerous other muscles levitate, depress the angle of the mouth, and of upper and lower lips

Buccinator muscle = muscle of the cheek. Helps to position bolus between the molars for grinding

All of these muscles are innervated by the facial nerve (CNVII)

Question 38

What is the sphincter that surrounds the mouth?

The muscle of the cheek?

Answer 38

Orbicularis Oris

Buccinator