Lecture 10.1 Nasal Cavity skeletal structure and paranasal sinuses

Question 1

What are the 3 regions of the nasal cavity - lining, special features and position in the nasal cavity

Answer 1

1. Nasal vestibule: small dilated space located anteriorly and lined with skin, containing hair
2. Respiratory region
   Largest part in middle lined by respiratory epithelium (ciliated and mucous cells)- has rich neurovascular supply
3. Olfactory region
   Small part of the apex of the cavity lined with olfactory epithelium and contains olfactory receptors

Question 2

What type of tissue makes up the External nose and what are the different parts

Answer 2

This is the cartilaginous part of the nose
Forming the lateral wall/anterior part
-Superior margin and Lateral process of the septal cartilage
- Major and minor alar cartilages

Medial wall is Septal cartilage.

It is supported to be held open by the skeletal framework underneath - Nasal bone

Question 3

What bones contribute to the roof of the nasal cavity from anterior to posterior

Answer 3

• Nasal bones
• Nasal spine from the frontal bone,
• Cribriform plate of ethmoid bone
• Anterior surface of sphenoid bone
• Ala of the vomer

Question 4

What bones contribute to the floor of the nasal cavity

Answer 4

Floor= hard palate

= palatine process of the maxilla, horizontal plate of the palatine bone

Question 5

What bones contribute to the Medial wall separating right and left nasal cavities

from anterior to posterior

Answer 5

• Septal cartilage
• Perpendicular plate of the ethmoid bone (superiorly)
• Vomer (inferiorly)

+ (small contribution from incisor crest of the maxilla, nasal crests of maxilla and palatine bones, nasal bones, rostrum of sphenoid bone)

Question 6

What 7 bones contribute to the Lateral wall of the nasal cavity

• contains openings of the paranasal sinuses, nasolacrimal duct and can be felt

from anterior to posterior

Answer 6

• Nasal bone
• Frontal process of the maxilla
• Lacrimal bone
• Ethmoidal labyrinth, Superior and Middle concha + uncinate process from Ethmoid bone
• Inferior concha
• Perpendicular plate of palatine bone
• Medial pterygoid plate of sphenoid bone

Question 7

What are the 4 paranasal sinuses and what are their common features

They develop as outgrowths from the nasal cavities and erode into the surrounding bone.

Answer 7

Ethmoidal air sinuses/cells, sphenoidal, maxillary and frontal sinuses.

• All are lined by respiratory mucosa: ciliated and mucous secreting
• Open into the nasal cavity on the lateral wall
• Innervated by branches of CN5

Question 8

What are the 3 sites the paranasal sinuses drain to, which paranasal sinuses - and where is this site in relation to the 3 concha/turbinates

Answer 8

1. Middle Meatus of the Lateral wall = between to middle & inf turbinate
   - Frontal sinus=semilunar hiatus
   - Maxillary sinuses= semilunar hiatus
   - anterior ethmoidal cells= semilunar hiatus
   - middle ethmoidal cells= on to/above ethmoid bulla,
2. Superior Nasal meatus of the Lateral wall = between superior & middle turbinate
   - Posterior ethmoidal cells

3.Spheno-ethmoidal recess of the Roof of nasal cavity
between the roof of nasal cavity and sup turbinate

-Sphenoidal sinus

Question 9

What is the specific branch innervation of the 4 sinuses

Answer 9

Frontal = V1
Maxillary = V2
Ethmoidal cells and Sphenoid sinuses = V1 and V2

Question 10

Where does the Nasolacrimal duct and the Eustachian tube (Pharyngotympanic) drain

Answer 10

Nasolacrimal: Inferior nasal meatus of the Lateral wall- between inf turbinate and floor

Eustachian: Posterior to the inferior meatus

Question 11

What are the two areas where there is very thin bone separating nasal cavity from other cranial structures and what does this mean clinically

Answer 11

1. There is around 1 mm distance from the medial sheet of ethmoidal bone (lateral nasal cavity) and lateral sheet - (medial wall of orbit known as the orbital plate).

Therefore operating in this area, there is high risk of orbital fracture, damaging medial rectus or superior oblique leading to diplopia, shift of these extra occular muscles into the nasal cavity.

2. On the roof the nose,
   Thin shelves of bone separate sphenoid sinuses from nasal cavity below and hypophyseal fossa above so is good for surgical approach to the pituitary gland going through the sphenoid sinus.

Question 12

What is the ethmoid bulla and why is it important

Answer 12

It is a surgical landmark on the lateral wall of the nasal cavity made from the middle ethmoidal cell
around which paranasal sinuses have openings around

Question 13

What tubes connect to the Semilunar hiatus and what does it drain

Answer 13

Anteriorly it is connected to frontonasal duct and ethmoidal infundibulum and this is where it drains Frontal sinus and Anterior ethmoidal cells

The Maxillary sinus opens directly into the semilunar hiatus

Question 14

What is the importance of knowing where the paranasal sinuses drain and what the turbinates look like

Answer 14

1. Can help to identify the location of sinusitis by looking at sinus openings for signs of infection
2. Help to differentiate turbinates from nasal polyps

Question 15

Why can the external nose be clinically important - two cases

Answer 15

1. The growth plate for the maxillary sinus (in the midface) sits in the external part of the nose. If damaged it can lead to abnormal face growth/distortion during infancy-2-3 yrold.
2. Frontal trauma is likely to cause nasal fracture. The septal cartilage needs to be examined for haematoma otherwise the cartilage can necrotise due to pressure on the bv there and the external nose can be lost causing nose to drop.