Functions of the Nose
The nose assists with numerous body functions, ranging from the vital process of respiration to the augmentation of taste.
- Inhaled air enters the nose through the nostrils and exits during exhalation.
- From the nose, the inhaled air travels to the nasopharynx → oropharynx → larynx → lungs
- Inhaled air comes in contact with the olfactory epithelium, located on the roof of the nasal cavity.
- Within the epithelium, olfactory receptors bind odor molecules.
- The receptors are connected to the olfactory nerve, which transmits these signals to the brain.
- Purification of inhaled air:
- The walls of the nasal cavity are covered with hair, or cilia.
- The cilia trap dust and harmful particles to purify the inhaled air.
- The trapped dust particles are either:
- Moved to the throat, where they are swallowed
- Excreted through the nasal cavity (sneezing)
- Moisturizing of inhaled air:
- Nose hair moisturizes and warms the air to the approximate temperature and moisture within the lungs.
- During exhalation, the heat and moisture in the CO2 is absorbed by the nasal hair and then released into the atmosphere.
- Sense of taste:
- While chewing, chemicals from food activate olfactory receptors inside the nose.
- These receptors work in coordination with the taste buds to identify food flavor.
- Nasal airflow can modify speech and produce nasal clicks or click consonants.
- Paranasal sinuses also contribute to vocal resonance.
The External Nose
The external nose is pyramidal in shape. The nose consists of:
- A proximal nasal root
- The apex at the tip of the nose
- 2 inferior nares/nostrils (openings to the nasal cavity)
- The skin over the bony part of the nose is thin.
- The skin over the cartilaginous part is thicker and has many sebaceous glands.
- The skin extends into the vestibule of the nose via the nares.
- Vestibular skin has hairs that function to filter air.
- Bony component is located superiorly and consists of:
- Superiorly: inferior border of the nasal bones
- Laterally: frontal processes of the maxilla
- Inferiorly: alveolar processes of the maxilla
- Cartilaginous component: located inferiorly and consists of
- 2 lateral cartilages
- 2 alar cartilages
- 1 septal cartilage
The external nose contains muscles that aid with facial expression and in maintaining patency of the nostrils.
- Procerus muscle:
- Originates in the fascia overlying the nasal bone
- Inserts into the inferior forehead
- Contraction depresses the medial eyebrows and wrinkles the skin of the superior dorsum.
- Nasalis muscle:
- Sphincter-like muscle
- Transverse portion: assists the procerus muscle
- Alar portion:
- Arises from the maxilla
- Inserts into the major alar cartilage
- Contraction dilates the nares, flaring them.
The Nasal Cavity
- Most superior component of the respiratory tract
- Has 3 divisions:
- Skin-lined cavity directly behind the nostrils
- Divided into left and right cavities by the septum
- Respiratory region: lined by ciliated pseudostratified epithelium with mucus-secreting goblet cells
- Olfactory region:
- Located at the apex of the nasal cavity
- Lined by olfactory cells with olfactory receptors
- Each nasal cavity extends from the mucous ridge (limen nasi) anteriorly to the choanae posteriorly, ultimately extending to the nasopharynx.
- Walls of each nasal cavity (lined with respiratory epithelium):
- Roof: cribriform plate of the ethmoid, nasal bones, and body of the sphenoid
- Floor: horizontal plate of the palatines and palatine process of the maxillas
- Lateral walls:
- Anterior: nasal bones, lacrimal bones, and frontal process of the maxilla
- Middle: superior, inferior, and middle conchae with corresponding meatus
- Posterior: perpendicular plate of the palatine and the sphenoid
- Medial wall or septum:
- Septal cartilage
- Perpendicular plate of the ethmoid
- Maxillary crest (maxilla and palatine bones)
The Nasal Conchae
- 3 bony shelves arising from the lateral wall of the nasal cavity, curling inferomedially
- Also called turbinates, as they function similarly to a turbine, regulating air flow
- Slow the flow of air so it can be cleaned, warmed, and humidified in the nasal cavity
- Maximize the surface area of nasal mucosa:
- Superior concha: smallest, protect the olfactory bulb (structure housing smell receptors)
- Middle concha: protects the openings of the maxillary and ethmoid sinuses from pressurized nasal airflow
- Inferior concha: largest, responsible for the majority of airflow modification
- The conchae divide the nasal airway into 4 groove-like air passages called meatuses.
- Superior meatus:
- Between the middle and superior conchae
- The posterior ethmoidal sinuses drain into it.
- The sphenopalatine foramen opens into it.
- Middle meatus:
- Between the inferior and middle conchae
- Frontal, maxillary, and anterior and middle ethmoidal sinuses drain into it.
- Inferior meatus:
- Between the inferior concha and the floor of the nasal cavity
- The auditory (Eustachian) tube opens into it.
- The nasolacrimal gland drains into it.
- Sphenoethmoidal recess:
- Located posterior and superior to the superior concha
- The sphenoid sinus drains into it.
- Superior meatus:
Neurovasculature of the Nose
- Internal carotid:
- Anterior and posterior ethmoidal arteries supply the septum.
- Lateral nasal branch of the facial artery supplies the nasal ridge/alae.
- External carotid branches:
- Supply the lateral walls, dorsum, and septum
- Sphenopalatine artery
- Greater palatine artery
- Lateral nasal arteries
- Superior labial artery
- Angular artery (terminal branch of facial nerve)
- Common carotid artery system: Kiesselbach’s plexus at the anterior lower part of the septum (most common source of bleeding in epistaxis)
The veins tend to follow the arteries. The veins drain into:
- Pterygoid plexus
- Facial vein
- Cavernous sinus
- Sensory innervation to the superior wall and anterior aspect of the inner nose: ophthalmic nerve
- Sensory innervation to the septum and lateral walls: branches of the maxillary nerve
- Sensory perception of smell: olfactory nerve
- Choanal atresia: congenital condition characterized by obstruction of the posterior nasal aperture leading into the nasopharynx. Choanal atresia can manifest unilaterally or bilaterally. In the event of bilateral choanal atresia, individuals will present with nasal obstruction and intermittent cyanosis after birth.
- Epistaxis: can be loosely defined as a nosebleed, which can be an anterior bleed or a posterior bleed based on the site of origin. Epistaxis is very common in children (50% within the 1st 10 years of life) and is usually benign and underreported, but a few cases can be related to neoplastic disease. Epistaxis usually occurs because of trauma to the nose from repeated nose picking, direct traumatic injury to the face or nose, or as a side effect of anticoagulant medications. Management consists of squeezing the nostrils together for 5 to 30 minutes along with head elevation while breathing through the mouth.
- Nasal bone fractures: fracture of the bridge of the nose, which usually presents with nasal bleeding, swelling, bruising, and nasal obstruction. Nasal bone fractures may be complicated by other concomitant facial fractures and most commonly occur because of direct trauma during athletic activities, falls, and motor vehicle collisions.
- Cribriform plate fracture: usually the result of trauma and sometimes iatrogenic because of inappropriate insertion of nasogastric tubes or nasal airways. The fractured plate can perforate the meninges, causing leakage of CSF, which can lead to meningitis, encephalitis, and brain abscess. The olfactory bulb lies on top of the cribriform plate, and fracture can lead to its irreversible damage, resulting in anosmia.
- Nasal papilloma: benign epithelial tumors of the nasal cavity that mainly affect older males (45–60 years) and always require surgical excision. Risk factors include human papillomavirus infection, smoking, and chronic sinusitis. Individuals typically present with unilateral nasal obstruction, anosmia, and intermittent epistaxis. Diagnosis is based on biopsy or surgical resection.
- Nasal polyps: noncancerous outgrowths of nasal mucosa, usually forming around the ostia of the maxillary sinuses. Associated conditions include allergic rhinitis, aspirin allergy, asthma, cystic fibrosis, and sinus infections. Symptoms may include trouble breathing through the nose (nasal obstruction), loss of smell, decreased sense of taste, postnasal drip, and rhinorrhea. Nasal polyps can be treated with topical or systemic glucocorticoids or with resection, though recurrence is common.
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