Oral anatomy

Question 1

What forms the first part of the respiratory tract?

Answer 1

The left and right nasal cavities

Question 2

What is contained in the mucosa in the upper part of the nasal cavity?

Answer 2

Olfactory receptors

Question 3

Where are olfactory receptors found?

Answer 3

In the mucosa in the upper part of the nasal cavity

Question 4

What do the axons of olfactory receptors form?

Answer 4

• Olfactory nerves (CN1)

Question 5

How are the left and right nasal cavities separated from
- Each other
- the oral cavity
- the brain

Answer 5

• They are separated from each other by a thin midline septum, formed of cartilage and bone (septum will only be seen on one half when the head is bisected)
• They are separated from the oral cavity by the hard palate
• They are separated from the brain superiorly by bone

Question 6

What are 2 things the nasal cavity communicates with?

Answer 6

• The nasopharynx posteriorly
• The paranasal sinuses - cavities within the skull bones

Question 7

How is the septum of the nasal cavities formed?

Answer 7

• It is formed of cartilage anteriorly and two thin plates of bone posteriorly
• The perpendicular plate of ethmoid bone forms the superior part of the posterior septum.
• The vomer forms the inferior part of the posterior septum.

Question 8

How many projections of bone are there in the lateral all of the nasal cavity and what are they?

Answer 8

• There are 3 projections of bone. The superior, middle and inferior conchae/turbinates

Question 9

What are the spaces inferior to the turbinates called? And what happens as inspired air passes through them?

Answer 9

• Meatuses (singular meatus)
• As air passes through them, it is warmed, humidified and filtered

Question 10

What is the cribiform plate and what is its function?

Answer 10

• The cribiform plate (a portion of the ethmoid bone) separates the nasal cavity from the cranium and the brain
• It is a delicate section of bone that is perforated with tiny holes.
• The axons of olfactory neurons pass through the perforations to form the olfactory nerves which travel to the brain.

Question 11

Where are the olfactory nerves located?

Answer 11

• They are located in the spheno-ethmoidal recess in the upper nasal cavity, between the superior concha and cribiform plate.

Question 12

How many paranasal sinuses are there and where do they lie?

Answer 12

4.
- Frontal sinuses- lie within the anterior part of the frontal bone (it lies over the orbit and across the superciliary arch aka eyebrow)

• Ethmoid air cells- lies within the ethmoid bone (located in between the eyes, superior to the nasal cavity and medial to the orbits)
• Sphenoid sinuses lie within the sphenoid bone (just posterior to the ethmoid sinus and inferior to the pituitary gland)
• Maxillary sinuses lie within the maxilla of the facial skeleton (roof is the floor of the orbit and the floor is the alveolar process- structure holding the roots of our teeth in place)

Question 13

Where do the 4 paranasal sinuses drain via small ducts?

Answer 13

• Frontal sinus drains into middle meatus
• Spehnoid sinus drains into spheno-ethmoidal recess
• Ethmoid air cells drain into the superior and middle meatuses
• The maxillary sinus drains into the middle meatus

Question 14

What is the nasolacrimal duct?

Why do we have running nose when we cry?

Answer 14

• The nasolacrimal duct (which is received by the nasal cavity) drains the fluid that lubricates the anterior surface of the eye (tears).
• The duct opens into the inferior meatus
• When we cry, we get a runny nose as excess fluid runs down the nasolacrimal duct

Question 15

The nasal cavity communicates with the middle ear. What is the middle ear?

Answer 15

• A small cavity within the temporal bone that is modified for hearing (it has 3 tiny bones which transmit sound waves to the inner ear)

Question 16

What is the auditory tube?
Where can its opening be seen?
What is its function?

Answer 16

• The auditory tube connects the nasopharynx to the middle ear
• Its opening can be seen on the lateral wall of the nasopharynx, surrounded by a slight bulge formed of tonsillar tissue
• The auditory tube allows air to pass into the middle ear, so that pressure on either side of the tympanic membrane (ear drum- located between the middle and external ear) is equal
• This equal pressure is important for optimal conduction of soundwaves.

Question 17

What is the nasal cavity supplied and innervated by?

Answer 17

• It is supplied by several arteries including branches of the maxillary artery- terminal branch of the external carotid artery.
• An anastomotic network formed supplies the nasal septum (which is often the site of bleeding in a nose bleed- epistaxis)
• The sensory innervation of the nose is via branches of the trigeminal nerve (CN V)

Question 18

What is the function of the palate and what is it made up of?

Answer 18

• The palate separates the nasal cavities from the oral cavity
• It is composed anteriorly of bone - the hard palate
• It is composed posteriorly of muscle - the soft palate
• The palate forms the roof of the oral cavity

Question 19

What is the hard palate formed by and what is its function?

Answer 19

• The hard palate is composed of 2 bones.
  + The palatine bone of the maxilla
  + The horizontal plate of the palatine bone

Its function include
- Preventing food or fluid from entering the nasal cavity
- We push our food agains the hard palate during the first phase of swallowing, forcing food and fluid into the oropharynx
- We push our tongue against the hard palate to articulate certain sounds

Question 20

What would happen when someone’s palate does not form properly during embryological development?

Answer 20

• This is called a cleft palate
• It would result in difficulty eating, swallowing and with speech if not repaired

Question 21

Where is the uvula found?

Answer 21

The uvula hangs on the posterior border of the soft palate which lies posterior to the hard palate.

Question 22

What happens to the soft palate during swallowing?

Answer 22

• The soft palate is composed of several muscles which contract during swallowing, elevating the soft palate.
• Elevation of the soft palate closes off the nasopharynx from the oral cavity, preventing reflux of food and fluid into the nasal cavity.

Question 23

What are muscles of the soft palate innervated by?

Answer 23

• The vagus nerve

Question 24

What are the boundaries of the oral cavity?

Answer 24

• Superiorly by the hard and soft palate
• Inferiorly by soft tissues and muscles
• Laterally by the cheeks (containing buccinator muscles, used in swallowing, blowing and sucking)

Question 25

What does the oral cavity contain?

Answer 25

• It is continuous with the oropharynx posteriorly
• It contains the tongue, teeth, gum and openings of the salivary duct.

Question 26

How many teeth do adults have and how many of each type?

Answer 26

32. 16 embedded in the maxilla (upper jaw) and 16 embedded in the mandible (lower jaw)
    2 canines
    4 incisors
    4 premolars
    6 molars
    All multiplied by 2

Question 27

What are teeth composed of?

Answer 27

• An inner pulp containing blood vessels
• Dentin surrounding the pulp
• An outer hard coating of enamel

Question 28

What happens when enamel and dentin are eroded by bacteria and food (e.g. sugar and acids)?

Answer 28

• It can lead to decay, inflammation and infection of the pulp which is painful.
• Infection may spread to the bone leading to abscess formation. (collection of pus)

Question 29

Tell me about the function of the tongue as well as two things that are contained on it.

Where are the anterior and posterior parts of the tongue located?

Answer 29

• The tongue is essential for normal chewing, swallowing and speech
• It bears papillae on its superior surface, some of which detect taste (taste buds)
• The space between the posterior tongue and the anterior aspect of the epiglottis is the vallecula
• The anterior aspect of the tongue lies in the oral cavity while the posterior aspect of the tongue extends into the oropharynx.

Question 30

Where and what are the intrinsic and extrinsic muscles of the tongue?

Answer 30

• The intrinsic muscles lie entirely within the tongue. They are paired bilaterally and fuse in the midline- they change the shape of the tongue
• The extrinsic muscles are attached to the tongue but originate from the mandible and hyoid bone. They move the tongue.

Question 31

What are the muscles of the tongue (motor) innervated by?

Answer 31

• The hypoglossal nerve (CN XII)

Question 32

What provides the sensory innervation of the tongue?

Answer 32

• Taste in the anterior two thirds is served by the facial nerve (CN VII)
• General sensation (touch, pain, temperature) in the anterior two thirds is served by the trigeminal nerve (CN V)
• Taste and general sensation in the posterior third are served by the glossopharyngeal nerve (CN IX)

Question 33

What arteries is the oral cavity supplied by?

Answer 33

• The lingual, maxillary and facial arteries, all branches of the external carotid artery

Question 34

What is the innervation of the oral cavity?

Answer 34

• It is quite complex
• While innervation of the soft palate is by the vagus nerve
• The tongue is innervated by 4 cranial nerves, hypoglossal, facial, trigeminal and glossopharyngeal

Question 35

How many tonsils are there in the nasal and oral cavity.

What and where are they?

Answer 35

• 4
• The pharyngeal tonsil lies in the roof of the posterior wall of the nasopharynx (adenoid)
• The tubal tonsil surrounds the opening of the auditory tube on the lateral walls of the nasopharynx
• The palatine tonsil lies on the lateral wall of the oropharynx (visible on either side of the oropharynx when the mouth is open)
• The lingual tonsil - a collection of lymphoid tissue in the posterior tongue