9. Nasal cavity and paranasal sinuses Flashcards Preview

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Flashcards in 9. Nasal cavity and paranasal sinuses Deck (15)
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1
Q

describe the components of the external nose

A

predominantly CARTILAGE but frontal processes of MAXILLAE and 2 NASAL BONES form its root

2
Q

name the boundaries of the nasal cavity

A
  • roof: frontal bone, cribiform plate of ethmoid and sphenoid
  • floor: hard palate
  • lateral walls: 2 superior conchae of ethmoid and inferior concha (own bone)
  • medial wall: perpendicular plate of ethmoid, vomer and septal cartilage
3
Q

name the openings of the nasal cavity

A
  • anterior nasal apertures = nares/nostrils

- posterior nasal apertures = choanae

4
Q

why does airflow slow in the nasal cavity

A

nasal cavity has greater cross-sectional area than nostrils/vestibule so air flow slows

5
Q

what are the 2 types of mucous membrane in the nasal cavity, and describe their function

A
  1. olfactory mucous membrane (superiorly): olfaction - contains ends of CN I nerves
  2. respiratory mucous membrane: pseudostratified columnar ciliated epithelium for:
    - filtering air (mucous/cilia)
    - humidifying air (watery secretions)
    - warming air (rich vascular supply)
6
Q

what is the function of the conchae and meatuses

A
  • chonchae: slow airflow by causing turbulence and increasing surface area over which air passes
  • meatuses: paranasal sinus and lacrimal ducts drain here
7
Q

how can trauma to nose cause ‘saddle-nose’ deformity

A

i. trauma causes buckling of nasal septum and shearing of blood vessels…
ii. blood accumulates between perichondrium and cartilage - septal haematoma…
iii. lifts perichrondrium off cartilage, stripping away its blood supply (avascular necrosis) and causing pressure necrosis from increased pressure by haematoma…
iv. irreversible cartilage necrosis - saddle-shape deformity

8
Q

what are nasal polyps, describe symptoms

A

Common (>40yrs) benign swellings of nasal mucosa, usually bilateral.

Symptoms:

  • blocked nose
  • watery rhinorrhoea, post-nasal drip
  • decreased smell and taste

(Unilateral polyp +/- blood-tinged secretion may suggest tumour)

9
Q

describe the sensory innervation of the nasal cavity

A

General sensory: trigeminal n., mainly maxillary br. but also ophthalmic branch anteriorly

Special sensation: olfactory n.

10
Q

describe the arterial supply to the nasal cavity

A
  • anteriorly via greater and lesser branches of ethmoidal a. (from ophthalmic a.)
  • posteriorly from sphenopalatine and greater palatine aa. (from maxillary a.)
  • form arterial anastamoses in anterior septum (Keisselbach’s area)
11
Q

from which vessels to epistaxis arise from - how does this affect treatment

A
  • 90% from Keisselbach’s plexus: usually self-treated by pinching in front of bony bridge of nose and leaning head forwards
  • 10% from sphenopalatine a.: can be more serious and difficult to treat as blood at high pressure and posteriorly located in nasal cavity.
  • if initial management unsuccessful try:
    i. cauterising visible bleeding point with silver nitrates
    ii. anterior packing using nasal tampons
    iii. posterior packing or surgical intervention as last resort
12
Q

where does venous blood from nasal cavity drain to

A

facial v, pterygoid venous plexus, cavernous sinus

13
Q

what are the paranasal sinuses and how do these relate to the nasal cavity

A

Air-filled spaces lined with respiratory mucosa (ciliated pseudostratified columnar with goblet cells) that are extensions of nasal cavity - drain into a meatus (mostly middle) via small ostia (channels). Help humidify and warm inspired air.

14
Q

name the 4 different paranasal sinuses and state their innervation

A
  1. frontal (above eyes) - ophthalmic n. (CN Va)
  2. ethmoid air cells (medial to eyes) - ophthalmic n.
  3. sphenoid sinus (posterior to eyes) - ophthalmic n.
  4. maxillary (under eyes) - maxillary n. (CN Vb)
15
Q

how can rhinitis (inflammation of nasal mucosa) cause sinusitis

A

Rhinitis causes decreased ciliary function, oedema of nasal mucosa and sinus ostia, and increased nasal secretions… impedes drainage from sinus… stagnant sinus secretions can be secondarily infected by bacteria