Anatomy

Anatomy of the nose

External Nose

The anatomy of the nose begins with the external nose. The nose is pyramidal in conformation with its root up and the base directed downwards. Various terms used in its description. The nasal pyramid consists of osteocartilaginous framework bound by muscles and skin.

Osteocartilaginous Framework Bony Part

Higher 1/3rd of the external nose is bony while lower 2/3rd are cartilaginous. The bony part consists of two nasal bones which meet in the midline and rest on the upper part of the nasal process of the frontal bones and are themselves held between the frontal processes of the maxillae (Figure23.2)

Cartilaginous Part

It consists of:

  1. Upper later cartilages. They aggrandize from the under the surface of the nasal bones above, to the alar cartilages below. They fuse with each other and with the upper border of the septal cartilage in the midline anteriorly. The lower free edge of upper lateral cartilage is seen intranasally as limen vestibule, nasal valve or limen nasi on each side.
  2. Lower lateral cartilages (alar cartilages). Each alar cartilage is U-shaped. It has a lateral crus which forms the ala and a medical crus which runs in the columella. Lateral crus overlaps the lower edge of upper lateral cartilage on each side.
  3. Lesser alar (or sesamoid) cartilages. Two or more in number. They lie above and lateral to alar cartilages. The various cartilages are connected with one another and with the adjoining bones by perichondrium and periosteum. Most of the free allowance of the nostril is consummate of fibrofatty tissue and not the alar cartilage.
  4. Septal cartilage. Its anterosuperior border runs from bottom the nasal bones to the nasal tip. It abide by the dorsum of the cartilaginous part of the nose. In septal abscess or after excessive removal of septal cartilage as in submucosal resection (SMR) operation, support of nasal dorsum is lost and a supratip depression results.

Nasal Musculature

An osteocartilaginous framework of the nose is covered by muscle which brings about movements of the nasal tip, ala and the overlying skin. They are the procerus, nasalis (transverse and alar parts), levator labii superioris alaeque nasi, anterior dilator nares and depressor septi.

Nasal Skin

The skin over the nasal bones and upper lateral cartilages is attenuated and advisedly mobile while that covering the alar cartilages is thick and adherent, and contains many sebaceous glands. It is the hypertrophy of these sebaceous glands which gives rise to a lobulated tumour called rhinophyma.

Internal Nose

The internal nose is also one of the parts of the anatomy of the nose. It is branched into right and left nasal cavities by the nasal septum. Each nasal cavity communicates with the exterior through naris or nostril and with the nasopharynx through the posterior nasal aperture of the choana. Each nasal cavity consists of a skin-lined portion—the vestibule and a mucosa-lined portion, the nasal cavity proper.

VESTIBULE OF NOSE

Antecedent and inferior part of the nasal cavity is called vestibule. It is lined by the skin and bottle up sebaceous glands, hair follicles and the hair called vibrissae. It’s a higher limit on the lateral wall is prominent by limen nasi (also called nasal valve).

  1. Nasal valve. It is bounded laterally by the lower border of upper lateral cartilage and fibrofatty tissue and anterior end of inferior turbinate, medially by the cartilaginous nasal septum, and caudally by the floor of pyriform aperture. The angle between the nasal septum and lower border of the upper lateral cartilage is nearly 30°.
  2. Nasal valve area. It is the cross-sectional area bounded by the structures forming the valve. It is the least cross-sectional area of the nose and regulates airflow and resistance on inspiration.

NASAL CAVITY PROPER

Each nasal cavity has a lateral wall, a medium wall, a roof and a floor.

Lateral Nasal Wall

Three and periodically four turbinates or conchae mark the lateral wall of the nose. Conchae or turbinates are scroll-like bony computation covered by mucous membrane. The spaces below the turbinates are called meatuses.

INFERIOR TURBINATE:  It is a separate bone and below it, into the inferior meatus, opens the nasolacrimal duct guarded at its terminal end by a mucosal valve called Hasner’s valve.

MIDDLE TURBINATE:  It is an ethmoturbinal—a part of the ethmoid bone. It is attached to the lateral wall by a bony lamella called ground or basal lamella. Its attachment is not straight but in an S-shaped manner. In the anterior third, it lies in the sagittal plane and is attached to the lateral edge of the cribriform plate. In the middle third, it belongs in the frontal plane and is allocate to lamina papyracea while in its posterior third, it runs horizontally and forms the roof of the middle meatus and is appointed to lamina papyracea and medial wall of the maxillary sinus.

The Ostia of various sinuses draining anterior to basal lamella form anterior group of paranasal sinuses while those which open posterior and superior to it form the posterior group.

MIDDLE MEATUS

It shows several important structures which are important in endoscopic surgery of the sinuses.

The uncinate process is a hook-like structure running in form anterosuperior to the posteroinferior direction. Its posterosuperior border is sharp and runs parallel to the anterior border of bulla ethmoidal; the gap between the two is called hiatus semilunaris (inferior). It is a two-dimensional space of 1-2mm width.

The anteroinferior circumference of uncinate process is attached to the lateral wall. The posteroinferior borderline of uncinate process is attached to inferior turbinate dividing the membranous part of lower-middle meatus into anterior and posterior fontanelle. The fontanel area is devoid of bone and consists of membrane only and leads into maxillary sinus when perforated. The upper attachment of the uncinate process shows great variation and may be inserted into the lateral nasal wall, upwards into the base of the skull or medially into the middle turbinate. This also accounts for variations in drainage of the frontal sinus.

The space bounded medially by the uncinate process and frontal process of the maxilla and sometimes lacrimal bone, and laterally by the lamina papyracea is called infundibulum.

The natural ostium of the maxillary sinus is situated in the lower part of the infundibulum. Accessory ostium or Ostia of the maxillary sinus are constantly seen in the anterior or posterior fontanel.

BULLA ETHMODIALIS: It is an ethmoidal cell situated behind the uncinate process. The anterior surface of the bulla composes the posterior boundary of hiatus semilunaris. Depending on pneumatization, bulla may be a pneumatized cell or a solid bony prominence. It may extend superiorly to the skull base and posteriorly to fuse with ground lamella. When there is a space above or behind the bulla, it is called suprabulla or retrobullar recesses, respectively. The suprabullar and retrobulbar adjourn together to form the lateral sinus (sinus lateralis of Grunwald). The lateral sinus is thus encompassed superiorly by the skull base, laterally by lamina papyracea, medially by middle turbinate. The cleft-like communication between the bulla and skull base and opening into middle meatus is also called hiatus semilunaris superior in contrast to hiatus semilunaris inferior referred to before.

ATRIUM OF THE MIDDLE MEATUS: It is a shallow depression lying in front of middle turbinate and above the nasal vestibule.

AGGER NASI: It is an elevation just anterior to the attachment of middle turbinate. When pneumatized it contains air cells, the agger nasi cells, which communicate with the frontal recess. A broadened agger nasi cell may impinge on frontal recess area, constricting it and causing mechanical blocking to frontal sinus drainage.

Pneumatization of middle turbinate leads to an enlarged ballooned out middle turbinate called concha bullosa. It cesspool into frontal recess directly or through agger nasi cells. Haller cell is air cells situated in the roof of the maxillary sinus. They are pneumatized from anterior or posterior ethmoid cells. Enlargement of Haller cells encroaches on ethmoid infundibulum, impending draining of maxillary sinus.

SUPERIOR TURBINATE: It is also an ethmoturbinal and is situated posterior and superior to the middle turbinate. It may also pneumatized by one or more cells. It forms an important landmark to identify ostium of sphenoid sinus which lies medial to it.

SUPERIOR MEATUS: It is a space below the superior turbinate. Posterior ethmoid cells open into it. A number of posterior ethmoid cells varies from 1 to 5. Onodi cell is a posterior ethmoidal cell which may grow posteriorly by the side of sphenoid sinus or superior to it for as much distance as 1.5 cm from the anterior surface of the sphenoid. Onodi cell is surgically important as the optical nerve may be related to its lateral wall.

SPHENOETHMOIDAL RECESS: It is situated above the superior turbinate. Sphenoid sinus opens into it.

SUPREME TURBINATE: It is sometimes nonce above the superior turbinate and has a narrow meatus beneath it. The ostium of the sphenoid sinus is situated in the sphennoethmoidal recess medial to the superior or supreme turbinate. It can be occupying endoscopically about 1cm above the upper margin of posterior choana close to the posterior border of the septum.

Medial Wall

Nasal septum forms the medial wall and is described on p.165.

Roof

Anterior acclivous part of the roof is formed by nasal bones, the posterior sloping part is formed by the body of the sphenoid bone and the middle horizontal part is formed by the cribriform plate of ethmoid through which the olfactory nerves enter the nasal cavity.

Floor

It is arranged by the palatine process of the maxilla in its anterior three-fourths and horizontal part of the palatine bone in its posterior one-fourth.

The lining membrane of the internal nose

  1. VESTIBULE. It is lined by skin repressing hair, hair follicles and sebaceous glands.
  2. OLFACTORY REGION. Upper one-third of the lateral wall (up to superior concha), corresponding part of the nasal septum and the roof of the nasal cavity from the olfactory region. In this region, the mucous membrane is paler in colour.
  3. RESPIRATORY REGION. Lower two-thirds of the nasal cavity from the respiratory region. Here in respiratory region mucous membrane conduct variable thickness being thickest over nasal conchae conspicuously at their ends, quite thick over the nasal septum but very thin in the meatuses and floor of the nose. It is highly vascular and also contains erectile tissue. Its surface is lined by pseudostratified ciliated columnar epithelium which contains plenty of goblet cells. In the submucosa layer of the mucous membrane are situated serous, mucous, both serous and mucous secreting glands, the duct of which open on the surface of the mucosa.

Nerve supply

  1. OLFACTORY NERVES. They cart sense of smell and supply olfactory region of the nose. They are the central filaments of the olfactory cells and are arranged into 12-20 nerves which pass through the cribriform plate and end in the olfactory bulb. These nerves can carry sheaths of dura, arachnoid and pia with them into the nose. Injury to these nerves can open CSF space leading to CSF rhinorrhoea or meningitis.
  2. NERVES OF COMMON SENSATION. They are:
  3. The anterior ethmoidal nerve.
  4. Branches of the sphenopalatine ganglion.
  5. Branches of the infraorbital nerve. They source vestibule of the nose both on its medial and lateral side.

Most of the posterior two-thirds of the nasal cavity (both septum and lateral wall) are supplied by branches of sphenopalatine ganglion which can be blocked by placing a pledget of cotton soaked in anaesthetic solution near the sphenopalatine foramen situated at the posterior extremity of the middle turbinate. The anterior ethmoidal nerve which supplies anterior and superior part of the nasal cavity (lateral wall and septum) can be blocked by placing the pledget high up on the inside of nasal bones where the nerve enters.

3.AUTONOMIC NERVES. Parasympathetic nerve fibres supply the nasal glands and control nasal secretion. They come from the greater superficial petrosal nerve, travel in the nerve of pterygoid canal (vidian nerve) and reach the sphenopalatine ganglion where they relay before reaching the nasal cavity. They also surplus the blood vessels of nose and cause vasodilation.

Sympathetic nerve fibres come from upper two thoracic segments of the spinal cord, pass through superior cervical ganglion, travel in deep petrosal nerve and add the parasympathetic fibres of greater petrosal nerve to anatomy the nerve of pterygoid canal (vidian nerve). They ambit the nasal cavity without relay in the sphenopalatine ganglion. Their simulation causes vasoconstriction. Excessive rhinorrhoea in cases of vasomotor and allergic rhinitis can be controlled by a section of the vidian nerve. The anatomy of the nose also includes the nerve supply of the nose.

Blood supply

Both the internal and external carotid system supply the nose.

Lymphatic Drainage

Lymphatics from the external nose and anterior part of the nasal cavity drain into submandibular lymph nodes while those from the rest of the nasal cavity drain into upper jugular nodes either directly or through the retropharyngeal nodes. Lymphatics of the upper part of the nasal cavity communicate with subarachnoid space along the olfactory nerves.

 

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