MRCS Part B (OSCE) - Online Resources

The boundaries of the nasal cavity are:
 Roof : Frontal, ethmoid and sphenoid bones
 Floor : Palatine bones of the maxilla
 Medial : Nasal septum
 Lateral : Nasal conchae (superior, middle and inferior)

The blood supply of the nasal cavity is from the:
 Sphenopalatine artery
 Anterior ethmoid artery
 Posterior ethmoid artery
 Greater palatine artery
 Superior labial artery

Kiesselbach's plexus, also known as the ‘Little's area’, is a region in the
anteroinferior part of the nasal septum where four arteries anastomose to form a
vascular plexus:
 Anterior ethmoidal artery (from the ophthalmic artery)
 Sphenopalatine artery (terminal branch of the maxillary artery)
 Greater palatine artery (from the maxillary artery)
 Septal branch of the superior labial artery (from the facial artery)

Ninety percent of all epistaxis arise from this plexus. Patients present with
anterior nasal bleeds.

Conservative treatment:
 Nasal pressure/nasal packing

Surgical techniques:
 Silver nitrite cautery
 Electrocautery
 Anterior/posterior ethmoidal artery ligation
 Sphenopalatine artery ligation
 Maxillary artery ligation

 External carotid artery ligation

 Anterior-superior : Anterior and posterior ethmoid nerves (CN V1 )
 Posterior-inferior : Maxillary nerve (CN V2)
 Olfactory area : Olfactory nerve (CN I)

The paranasal sinuses are the:  Maxillary  Ethmoid  Sphenoid  Frontal

The boundaries of the maxillary sinus are:
 Base : Lateral wall of nose
 Apex : Zygoma
 Roof : Orbital floor
 Floor : Maxilla

The boundaries of the ethmoid sinus are:  Lateral : Lamina papyracea (or orbital lamina)  Roof : Frontal bone anteriorly, sphenoid and palatine bone posteriorly

The boundaries of the sphenoid sinus are:
 Anterior : Posterior part of the nasal cavity
 Inferior : Nasopharynx
 Lateral : Cavernous sinus, carotid artery, mandibular nerve (V3) and
temporal lobe of the brain
 Posterior : Midbrain
 Superior : Pituitary fossa, pituitary gland, optic chiasm and hypothalamus
 Medial : Contralateral sphenoid sinus

The boundaries of the frontal sinus are:
 Posterior wall : Anterior cranial fossa
 Inferior (floor) : Orbit

A septal haematoma is a serious complication that can arise from a trauma to the
nose.
Note: This is a collection of blood between the mucoperichondrium and quadrangular
cartilage of the septum. Septal cartilage is avascular and derives its blood supply from the
perichondrium.

If left untreated, a septal haematoma may lead to cartilage necrosis or abscess formation leading to ascending infection. Deficient septal cartilage may result in a septal perforation or saddle nose deformity both of which are difficult to correct surgically.

Eustachian tube (nasopharyngeal tube) consists of a bony (lateral 1/3rd) and a cartilaginous (medial 2/3rd) part that connects the anterior wall of the middle ear to the lateral aspect of nasopharynx. It is covered with respiratory epithelium.

Tensor veli palatini (innervated by the mandibular division of the trigeminal nerve - CN V3).