The Nose and Paranasal Sinuses Flashcards
What functions do the nose and nasal cavity have?
The nose and nasal cavity are involved in functions such as olfaction, filtering and humidifying inspired air, resonating chamber for speech and allowing drainage of secretions form the paranasal sinuses and nasolacrimal ducts.
Describe the structure of the external nose
Externally the nose is mostly (hyaline) cartilaginous but its root is formed from the maxillae and two nasal bones. If you look directly into the nostril you will be able to see the vestibule of the nose which is lined with skin and sebaceous glands and hair follicles.
Describe the boundaries of the nasal cavity
Medial wall – nasal septum (cartilage) and bony part made up of vomer ethmoid
Roof – Nasal bone, frontal bone, ethmoid bone (crista gali) and sphenoid bone
Lateral wall – maxilla + bony projections forming the turbinates (inferior conchae separate)
Floor – roof of the oral cavity – hard (maxilla and palatine bones) and soft palate
What is the crista gali and what is its clinical significance?
Note Crista gali protrudes up into the brain and attaches to dura. If there is a facial trauma then this could rupture and cause the leak of CSF through the nose.
What must you check for when someone breaks their nose?
Fracture of the nasal bone is common and often results in large amounts of swelling which must be allowed to regress before the nose can be re set. Must also assess for other damage, i.e. septal haematoma, basilar skull fractures, orbital blow outs and vertebrae fracture etc.
Describe how a septal haematoma occurs?
The nasal septum consists of the perpendicular plate of the ethmoid bone, septal cartilage and the vomer. The cartilaginous part of the septum relies on the overlying perichondrium for its blood supply. This means in trauma of the nose a septal haematoma can form between the cartilage and the perichondrium splitting them apart. This can cause pressure necrosis and if not caught early and drained then this will result in a permanent deformity called a saddle.
Describe the histological structures of the nasal cavity and where things drain into the cavity
Olfactory mucous membrane can be located at the top of the nasal cavity. The respiratory mucous membrane is pseudostratified columnar ciliated epithelium and filters, humidifies and warms the air as you breath it in. Paranasal sinuses mostly drain into the middle and superior meatuses whilst the lacrimal duct drains the eye into the inferior meatus. The Eustachian tube drains into the nasopharynx.
What are conchae?
These act to slow air flow and increase surface are over which air passes. This occurs by the conchae creating meatuses. The space above the superior conchae is not a meatus – this is called a spheno-ethmoidal recess.
What are nasal polyps?
Fleshy, benign swellings arising from the nasal mucosa. Usually affect both sides of the nasal cavity and are pale or yellow in appearance or fleshy and reddened. Common in people over the age of 40. Symptoms include blocked nose, and watery rhinorrhoea, post nasal drip, decreased smell and reduced taste, unilateral polyp +/- blood tinged secretions may suggest tumour.
What is rhinitis?
Inflammation of the nasal mucosal lining. Many causes such as viral in the common cold and allergic rhinitis. All leading to: nasal congestion, rhinorrhoea (runny nose) sneezing, nasal irritation and postnasal drip.
Describe the paranasal sinuses?
There are 4 paired paranasal sinuses: maxillary, frontal, ethmoidal and sphenoid. The maxillary occupies most of the maxillary bone and the ethmoidal consists of a collection of anterior, middle and posterior air cells.
What happens in sinusitis, where is this most common and how is it treated?
If there is any obstruction of the sinuses, then mucosal secretions will build up causing acute sinusitis and an infection. This will cause tenderness and nasal secretions, fever and a general feeling of unwell. These can occur due to a nose, throat or dental infection.
The Maxillary sinus is most prone to infection because of its location opening high on the medial wall of the nasal cavity near the roots of the posterior teeth. Usually self-limiting although if a secondary bacterial infection is suspected then a course of antibiotics may be needed.
What are the important complications of sinusitis?
Complications of sinusitis are rare but for example ethmoidal infection may break through the thin medial wall of the orbit spreading first to the periorbital tissue and eventually resulting in an orbital cellitus. This can be dangerous if it spreads to the optic nerve and intracranial structures.
What kind of epithelia line the sinuses?
The sinuses are air filled spaces that are extensions of the nasal cavity, also lined with respiratory mucosa.
Describe the blood supply and venous drainage of the nose
Blood supply to the nose is joint from branches of the maxillary (sphenopalatine and greater petrosal) and the ophthalmic (from internal carotid). These anastomose together at 5 points in the cartilage of the nose known as Little’s Area (keisselbach’s plexus). Venous drainage from nasal cavity into cavernous sinus, facial vein and pterygoid sinus.
