NOSE, PARANASAL SINUSES, NASAL OBSTRUCTION & EPISTAXIS

What are the major functions of the nose?

The nose functions as an airway and an "air conditioner": it warms, humidifies, and filters inspired air; removes particulate matter and microorganisms; conserves heat and moisture from expired air; and provides olfaction and important contributions to facial appearance.

Why is nasal breathing important for pulmonary function?

Nasal breathing conditions inspired air by warming, humidifying, and filtering it before it reaches the lower respiratory tract and contributes to normal respiratory physiology.

What is the Schneiderian membrane?

The Schneiderian membrane, or Schneiderian mucosa, is the respiratory mucosa lining most of the nasal cavity and paranasal sinuses. It is predominantly ciliated pseudostratified columnar epithelium with goblet cells and mucous glands.

What type of epithelium lines most of the nasal cavity?

Most of the nasal cavity is lined by respiratory epithelium, classically ciliated pseudostratified columnar epithelium containing goblet cells and other supporting cell types.

What are important immune defenses present in the nasal mucosa?

Nasal mucosal defenses include mucociliary clearance, antimicrobial substances such as lysozyme, secretory IgA, mucus, and innate and adaptive immune mechanisms.

What is mucociliary clearance?

Mucociliary clearance is the coordinated movement of mucus and trapped particles toward the nasopharynx by the beating of respiratory epithelial cilia.

What is the olfactory epithelium?

Olfactory epithelium is specialized neuroepithelium responsible for olfaction. In adults it is concentrated mainly in the roof of the nasal cavity, superior nasal septum, and superior nasal concha.

What are the major cell types of olfactory epithelium?

Olfactory epithelium contains olfactory receptor neurons, supporting (sustentacular) cells, and basal cells; Bowman glands are located in the underlying lamina propria.

What is the primary sensory neuron of the olfactory system?

The olfactory receptor neuron is a bipolar neuron whose dendrites extend toward the epithelial surface and whose axons pass through the cribriform plate to the olfactory bulb.

Where do olfactory receptor neuron axons terminate?

The axons of olfactory receptor neurons pass through the foramina of the cribriform plate and synapse in the olfactory bulb, the first major relay station of the olfactory pathway.

Where is the olfactory epithelium primarily located?

It is primarily located in the roof of the nasal cavity, including the superior nasal septum and superior nasal concha, adjacent to the cribriform plate.

What is the external nose?

The external nose is the pyramidal facial structure that projects anteriorly from the face and surrounds the anterior openings of the nasal cavities (nares).

What is the orientation of the nares?

The nares generally face anteriorly and somewhat inferiorly, allowing entry of air into the nasal vestibules.

What structures provide the skeletal framework of the external nose?

The external nose is supported by a combination of bone and cartilage, including the paired nasal bones, frontal process of the maxilla, frontal bone, septal cartilage, upper lateral cartilages, lower lateral cartilages, and smaller accessory cartilages.

What are the three major structural regions of the external nose?

The external nose can be divided conceptually into the bony vault, cartilaginous vault, and nasal lobule.

What forms the bony vault of the external nose?

The bony vault is formed primarily by the paired nasal bones and the frontal processes of the maxilla, with additional contribution from adjacent frontal bone structures.

What forms the cartilaginous vault of the external nose?

The cartilaginous vault is formed mainly by the paired upper lateral cartilages and the quadrangular septal cartilage.

What forms the nasal lobule?

The nasal lobule is the mobile inferior portion of the external nose, supported primarily by the lower lateral cartilages along with associated soft tissues.

What are the major cartilages of the external nose?

The major cartilages include the septal (quadrangular) cartilage, paired upper lateral cartilages, and paired lower lateral cartilages. Smaller accessory alar cartilages may also contribute to support.

What is the role of the nasal septal cartilage in the external nose?

The quadrangular septal cartilage forms the anterior cartilaginous portion of the nasal septum and provides important structural support to the nasal dorsum, nasal tip, and nasal airway.

What are the upper lateral cartilages?

The upper lateral cartilages are paired cartilages forming much of the middle cartilaginous vault of the nose and contributing to the internal nasal valve region.

What are the lower lateral cartilages?

The lower lateral cartilages are paired cartilages that form much of the nasal tip and alar framework and help maintain the shape and patency of the nostrils.

What is the internal nose?

The internal nose refers to the paired nasal cavities extending from the anterior nasal openings through the posterior choanae into the nasopharynx.

What is the nasal vestibule?

The nasal vestibule is the most anterior portion of the nasal cavity, immediately inside the nostril, and is lined predominantly by skin with vibrissae before transitioning to respiratory mucosa.

What is the limen nasi?

The limen nasi is the mucocutaneous transition region within the nasal vestibule where the skin-lined vestibule transitions toward the respiratory mucosa.

What is the nasal valve?

The nasal valve is the narrowest region of the nasal airway and is a major site of resistance to nasal airflow. The term may refer to the internal nasal valve region or, depending on the classification, the broader nasal valve complex.

What is the internal nasal valve?

The internal nasal valve is the region between the caudal septum and the caudal margin of the upper lateral cartilage, with contributions from the inferior turbinate and surrounding soft tissues. It is a major determinant of nasal airway resistance.

Where does the nasal cavity extend posteriorly?

The nasal cavity extends posteriorly to the choanae, which are the posterior openings connecting each nasal cavity with the nasopharynx.

What is the roof of the nasal cavity?

The roof of the nasal cavity is formed by several structures, including the nasal and frontal bones anteriorly, the cribriform plate of the ethmoid centrally, and the sphenoid region posteriorly.

What is the cribriform plate?

The cribriform plate is the horizontal portion of the ethmoid bone forming part of the roof of the nasal cavity and separating it from the anterior cranial fossa.

What passes through the cribriform plate?

Axons of olfactory receptor neurons pass through numerous small foramina in the cribriform plate to reach the olfactory bulb.

Why is the cribriform plate clinically important?

Its thin bony structure makes it vulnerable to trauma, and injury can cause cerebrospinal fluid rhinorrhea and anosmia by damaging olfactory nerve fibers.

Where is the olfactory mucosa located relative to the cribriform plate?

Olfactory mucosa lies immediately below the cribriform plate in the superior nasal cavity, particularly along the superior septum and superior turbinate region.

What is the posterior continuation of the nasal roof?

Posteriorly, the nasal roof slopes toward the sphenoid region and contributes to the superior boundary of the posterior nasal cavity.

Is the entire nasal cavity involved in olfaction?

No. Olfaction is concentrated in a relatively small specialized region of olfactory epithelium in the superior nasal cavity; most of the remaining nasal cavity is lined by respiratory mucosa.

Where are the nasal turbinates located?

The turbinates are projections along the lateral nasal wall and include the superior, middle, and inferior turbinates; a supreme turbinate may occasionally be present as a fourth turbinate.

What is the main function of the nasal turbinates?

Turbinates increase the effective surface area of the nasal cavity and create airflow turbulence, facilitating warming, humidification, and filtration of inspired air.

Why can the turbinates change in size?

Turbinate mucosa contains a rich vascular/erectile venous plexus that can engorge or decongest in response to physiologic and autonomic changes, altering nasal airway resistance.

Why are the turbinates important in nasal obstruction?

Turbinate hypertrophy or excessive mucosal engorgement can significantly narrow the nasal airway and is a common contributor to nasal obstruction.

What is a nasal meatus?

A nasal meatus is a passageway beneath a corresponding turbinate along the lateral nasal wall.

What structures are found in the inferior meatus?

The inferior meatus contains the opening of the nasolacrimal duct.

Where does the nasolacrimal duct drain?

The nasolacrimal duct drains into the inferior meatus, usually beneath the anterior portion of the inferior turbinate.

What structures drain into the middle meatus?

The middle meatus receives drainage from the frontal sinus, maxillary sinus, and anterior ethmoid air cells through the osteomeatal complex and related pathways.

What is the semilunar hiatus?

The semilunar hiatus is a curved cleft in the lateral wall of the middle meatus that forms part of the drainage pathway of the frontal and maxillary sinuses and anterior ethmoid cells.

What is the osteomeatal complex?

The osteomeatal complex is the functional drainage region of the anterior ethmoid, frontal, and maxillary sinuses, centered around structures of the middle meatus including the uncinate process, ethmoid infundibulum, hiatus semilunaris, and middle turbinate region.

What drains into the superior meatus?

The posterior ethmoid air cells drain into the superior meatus.

What is the sphenoethmoidal recess?

The sphenoethmoidal recess is the space superior and posterior to the superior turbinate where the sphenoid sinus ostium opens.

Where does the sphenoid sinus drain?

The sphenoid sinus drains into the sphenoethmoidal recess.

What is the major arterial supply of the nasal cavity?

The nasal cavity receives blood from branches of both the internal carotid artery (via the ophthalmic artery) and external carotid artery (via the maxillary and facial arteries).

Which internal carotid artery branches supply the nasal cavity?

The ophthalmic artery gives rise to the anterior and posterior ethmoidal arteries, which supply portions of the superior nasal cavity and septum.

Which external carotid artery branches supply the nasal cavity?

The major ECA contributions come from the sphenopalatine and greater palatine arteries via the maxillary artery and the superior labial artery via the facial artery.

What is the terminal branch of the maxillary artery that supplies the nasal cavity?

The sphenopalatine artery is a terminal branch of the maxillary artery and is a major arterial supply to the posterior nasal cavity.

What are the major branches of the sphenopalatine artery within the nose?

The sphenopalatine artery gives posterior lateral nasal branches to the lateral wall and posterior septal branches to the nasal septum.

What is the arterial supply of the lateral nasal wall?

The lateral nasal wall receives superior contributions from the anterior and posterior ethmoidal arteries and major posterior/inferior contributions from the sphenopalatine artery, with additional contributions from the greater palatine and facial arterial systems.

What arteries supply the nasal septum?

The nasal septum is supplied by the anterior and posterior ethmoidal arteries, posterior septal branches of the sphenopalatine artery, the greater palatine artery, and the superior labial artery.

What is Kiesselbach's plexus?

Kiesselbach's plexus, or Little's area, is a vascular anastomotic network in the anteroinferior nasal septum where branches from the sphenopalatine, anterior ethmoidal, greater palatine, and superior labial arteries converge.

Which arteries contribute to Kiesselbach's plexus?

The principal contributors are the anterior ethmoidal artery, posterior septal branch of the sphenopalatine artery, greater palatine artery, and superior labial artery.

Is the posterior ethmoidal artery considered a major contributor to Kiesselbach's plexus?

No. The posterior ethmoidal artery supplies the superior/posterior nasal cavity but is not usually listed among the principal arterial contributors to Kiesselbach's plexus.

Where does most anterior epistaxis occur?

Most anterior epistaxis occurs in Kiesselbach's plexus (Little's area) on the anteroinferior nasal septum.

Why is Kiesselbach's plexus clinically important in epistaxis?

It is a highly vascular superficial region exposed to airflow, drying, trauma, and digital manipulation, making it the most common site of anterior epistaxis.

How can uncomplicated anterior epistaxis from Kiesselbach's area often be controlled initially?

Initial management commonly includes firm continuous compression of the soft, anterior portion of the nose against the septum for about 10-15 minutes, with the patient leaning forward.

What is the difference between anterior and posterior epistaxis?

Anterior epistaxis usually arises from Kiesselbach's plexus and is more common and easier to visualize/control, whereas posterior epistaxis often arises from branches of the sphenopalatine artery in the posterior nasal cavity and may cause significant bleeding into the pharynx.

What is the arterial supply of the external nose?

The external nose receives contributions from branches of the ophthalmic artery, facial artery, and maxillary artery, including the dorsal nasal, angular, and infraorbital arteries.

What artery supplies the dorsum of the external nose superiorly?

The dorsal nasal artery, a branch of the ophthalmic artery, supplies the upper/dorsal external nose.

What artery supplies the lateral/inferior external nose from the facial artery?

The angular artery, a terminal branch of the facial artery, contributes to the vascular supply of the lateral external nose.

What artery from the maxillary artery contributes to external nasal blood supply?

The infraorbital artery, a branch of the maxillary artery, contributes to the blood supply of the lateral/inferior external nose.

What is the general pattern of venous drainage of the nasal cavity?

Nasal venous drainage generally parallels the arterial distribution and drains through facial, ophthalmic, and pterygoid venous pathways.

Why is the venous drainage of the nose clinically important?

Nasal veins are largely valveless and communicate with the facial vein, ophthalmic veins, and pterygoid plexus, providing potential routes for spread of infection toward the cavernous sinus.

How can infection from the nose potentially reach the cavernous sinus?

Infections in the facial/nasal region can spread through valveless venous connections, including facial-to-ophthalmic and pterygoid pathways, potentially reaching the cavernous sinus.

What is the lymphatic drainage of the anterior nasal cavity?

The anterior nasal cavity primarily drains to the submandibular lymph nodes.

Where does lymph from the posterior nasal cavity drain?

Posterior nasal lymphatics drain primarily toward the retropharyngeal and upper deep cervical lymph nodes.

What is the clinical importance of nasal lymphatic drainage?

The lymphatic drainage pattern helps explain why lesions of different portions of the nasal cavity may metastasize to different regional lymph-node groups.

What nerves provide general sensory innervation to the external and internal nose?

General sensation of the nose is supplied mainly by branches of CN V1 (ophthalmic division) and CN V2 (maxillary division) of the trigeminal nerve.

Which division of the trigeminal nerve supplies sensation to the anterosuperior nose?

CN V1 supplies the anterosuperior nasal region through branches including the anterior ethmoidal and infratrochlear nerves.

Which division of the trigeminal nerve supplies sensation to much of the posteroinferior nasal cavity?

CN V2 supplies much of the posteroinferior nasal cavity through branches including the nasopalatine and posterior lateral nasal nerves.

Which cranial nerve is responsible for olfaction?

CN I (olfactory nerve) provides the special sensory pathway for olfaction.

Where are the autonomic fibers supplying the nasal mucosa relayed?

Parasympathetic fibers from the facial nerve travel through the greater petrosal nerve and nerve of the pterygoid canal to the pterygopalatine ganglion, where they synapse; sympathetic fibers pass through the ganglion without synapsing.

What is the parasympathetic effect on the nasal mucosa?

Parasympathetic stimulation increases nasal glandular secretion and contributes to vasodilation and mucosal congestion.

What is the sympathetic effect on the nasal mucosa?

Sympathetic stimulation causes vasoconstriction of nasal vascular tissue, reducing mucosal congestion and contributing to regulation of nasal airway resistance.

What is the role of the superior cervical ganglion in nasal autonomic innervation?

Sympathetic fibers destined for the nasal cavity arise from neurons in the superior cervical ganglion and travel along periarterial plexuses to the nasal mucosa.

Which cranial nerve supplies the muscles of facial expression affecting the external nose?

CN VII (facial nerve) supplies the muscles of facial expression, including muscles that move or alter the external nose such as the nasalis and depressor septi nasi.

What are the paranasal sinuses?

The paranasal sinuses are air-filled, mucosa-lined cavities within the facial and cranial bones that communicate with the nasal cavity through their drainage pathways.

What are the four paired paranasal sinuses?

The four paired paranasal sinuses are the frontal, maxillary, ethmoid, and sphenoid sinuses.

What are the major functions attributed to the paranasal sinuses?

Proposed functions include reducing the weight of the skull, contributing to voice resonance, conditioning inspired air, and providing mucosal surface area; some historical functions remain incompletely established.

How are the paranasal sinuses grouped according to their drainage pathways?

They can be divided into an anterior group, consisting mainly of the frontal, maxillary, and anterior ethmoid sinuses, and a posterior group consisting mainly of the posterior ethmoid and sphenoid sinuses.

Where does the frontal sinus drain?

The frontal sinus drains through the frontal recess into the middle meatus, usually through the frontal drainage pathway.

Where does the maxillary sinus drain?

The maxillary sinus drains into the middle meatus through the ethmoid infundibulum/hiatus semilunaris region.

Where do the anterior ethmoid cells drain?

The anterior ethmoid cells drain into the middle meatus through pathways associated with the ethmoid infundibulum and middle meatus.

Where do the posterior ethmoid cells drain?

The posterior ethmoid cells drain into the superior meatus.

Where does the sphenoid sinus drain?

The sphenoid sinus drains into the sphenoethmoidal recess.

Why is knowledge of the lateral nasal wall important in rhinosinusitis?

The drainage pathways of the paranasal sinuses are closely related to the lateral nasal wall; obstruction or inflammation of these narrow pathways can impair sinus ventilation and mucociliary clearance and contribute to rhinosinusitis.

What is the ostiomeatal complex (OMC)?

The ostiomeatal complex is a functional region of the lateral nasal wall centered in the middle meatus that provides drainage pathways for the frontal, maxillary, and anterior ethmoid sinuses.

Why is the OMC clinically important?

Obstruction or inflammation of the OMC can impair drainage and ventilation of the frontal, maxillary, and anterior ethmoid sinuses and is therefore important in the pathophysiology and surgical management of rhinosinusitis.

What is olfaction?

Olfaction is the special sensory process by which volatile chemical substances are detected by olfactory receptor neurons and interpreted as odors.

What is the first step in olfactory transduction?

Odorant molecules dissolve in the mucus overlying the olfactory epithelium and interact with receptors on the cilia of olfactory receptor neurons, initiating intracellular signaling that produces an electrical response.

What are the major historical theories of olfaction mentioned in older texts?

Historical theories include the chemical theory, which proposes interaction between odorant molecules and olfactory receptors, and the undulatory/vibrational theory, which proposes that molecular vibrations contribute to odor recognition. Modern evidence strongly supports receptor-mediated chemical transduction, while vibrational theories remain controversial.

What determines nasal airway resistance?

Nasal airway resistance is strongly influenced by the dimensions of the nasal valve region, turbinate mucosal volume, septal anatomy, and the degree of vascular engorgement of the nasal mucosa.

How do the turbinates regulate nasal airflow?

The turbinates alter the geometry and resistance of the nasal airway through changes in vascular engorgement, helping regulate airflow and optimize warming, humidification, and filtration.

What is the nasal cycle?

The nasal cycle is the physiologic alternating congestion and decongestion of the nasal mucosa between the two sides of the nose, producing cyclical changes in nasal airflow resistance.

How long does a typical nasal cycle last?

The nasal cycle commonly occurs over a period of several hours, often approximately 2-6 hours, although the duration varies considerably among individuals.