Chapter 52: The nose and paranasal sinuses
The nose (L., nasus; Gk, rhis, rhinos) includes the external nose on the face and the nasal cavity, which extends posteriorly from it. The nose functions in smell and provides filtered, warm, moist air for inspiration.
The external nose presents a root (or bridge), a dorsum, and a free tip or apex. The two inferior openings are the nostrils (or nares), bounded laterally by the ala and medially by the nasal septum. The superior part of the nose is supported by the nasal, frontal, and maxillary bones; the inferior part includes several cartilages. The continuous free margin of the nasal bones and maxillae in a dried skull is termed the piriform aperture.
The nasal cavity extends in an antero-posterior direction from the nostrils, or nares, to the choanae. The choanae are the posterior apertures of the nose. Each choana is bounded medially by the vomer, inferiorly by the horizontal plate of the palatine bone, laterally by the medial pterygoid plate, and superiorly by the body of the sphenoid bone (see figs. 42-12 and 42-13). Posteriorly, the nasal cavity communicates with the nasopharynx, which in many respects may be regarded as the posterior portion of the cavity. The nasal cavity is related to the anterior and middle cranial fossae, orbit, and paranasal sinuses and is separated from the oral cavity by the hard palate. In addition to the nostrils and choanae, the nasal cavity presents openings for the paranasal sinuses and the nasolacrimal duct. Further openings, covered by mucosa in vivo, are found in a dried skull, e.g., the sphenopalatine foramen. The nasal cavity is divided into right and left halves (each of which may be termed a nasal cavity) by the nasal septum. Each half has a roof, floor, and medial and lateral walls.
The roof of the nasal cavity is formed by nasal cartilages and several bones, chiefly the nasal and frontal bones, the cribriform plate of the ethmoid (fig. 52-1), and the body of the sphenoid. The floor, wider than the roof, is formed by the palatine process of the maxilla and the horizontal plate of the palatine bone, i.e., by the palate. The medial wall, or nasal septum, is formed (from anteiror to posterior) by (1) the septal cartilage (destroyed in a dried skull), (2) the perpendicular plate of the ethmoid bone, and (3) the vomer (fig. 52-2B). It is usually deviated to one side. The lowest part of the septum (the columella) is membranous and mobile.
The lateral wall is uneven and complicated and is formed by several bones: nasal, maxilla, lacrimal and ethmoid, inferior nasal concha, perpendicular plate of palatine, and medial pterygoid plate of sphenoid (fig. 52-2A). The lateral wall presents three or four medial projections termed nasal conchae, which overlie passages (meatuses). The inferior concha is a separate bone; the others are portions of the ethmoid bone. The conchae were formerly known as turbinates. It should be noted that the plural of meatus is meatus in Latin and meatuses in English (cf fetus).
The spheno-ethmoidal recess, above and posterior to the superior concha, receives the opening of the sphenoidal sinus. The superior meatus, under cover of the superior concha, receives the openings of the posterior ethmoidal cells and (in a dried skull) the sphenopalatine foramen. The middle meatus, under cover of the middle concha, receives the openings of the maxillary and frontal sinuses. Most anterior ethmoidal cells open on an elevation (ethmoidal bulla, fig. 52-3B). A curved slit (hiatus semilunaris) inferior to the bulla receives the opening of the maxillary sinus. The frontal sinus and some anterior ethmoidal cells open either into an extension (ethmoidal infundibulum) of the hiatus or directly into the anterior part (frontal recess) of the middle meatus. The inferior meatus, which lies between the inferior concha and the palate, receives the termination of the nasolacrimal duct.
The nasal cavity can be examined in vivo either through a nostril or through the pharynx. A nasal speculum in a nostril is used in anterior rhinoscopy. A postnasal mirror inserted into the pharynx through the mouth enables the choanae to be inspected in posterior rhinoscopy (figs. 52-4 and 53-11B).
It is convenient to divide the nasal cavity into a vestibule, a respiratory region, and an olfactory region. The vestibule is a slight dilatation inside the nostril (see fig. 52-3A), limited by a ridge (limen nasi) over which skin becomes continuous with mucosa. The respiratory region is covered by mucoperichondrium and mucoperiosteum. The posterior two thirds show active ciliary motion for rapid drainage backward and downward into the nasopharynx. The nasal mucosa is highly vascular, and it warms and moistens the incoming air. The mucosa contains large venous-like spaces ("swell bodies"), which may become congested during allergic reactions or infections. The middle meatus is continuous on the anterior side with a depression (atrium; see fig. 52-3A) that is limited above by a ridge (agger nasi). The olfactory region is bounded by the superior concha and the superior third of the nasal septum. The olfactory mucosa contains bipolar neurons (olfactory cells), the dendrites of which reach the surface. The axons are collected into about 20 bundles known collectively as the olfactory (first cranial) nerve. These pass through the cribriform plate of the ethmoid bone and synapse in the olfactory bulb. The olfactory nerve is tested by closing one nostril and presenting a test substance to the other.
The nerves of ordinary sensation are derived from the first two divisions of the trigeminal nerve (fig. 52-5A, B, and C). These are responsible for sensations of touch, pressure and temperature in the nose.
The nerves for the posterior and larger portion of the nasal cavity
come from branches of the pterygopalatine ganglion that are derived
from the maxillary nerve. The chief sympathetic (vasoconstrictor)
and parasympathetic (vasodilator and secretory) innervation of the
nasal cavity follow nerve branches arising in the region of the
pterygopalatine ganglion, but some
sympathetic fibers are carried along the walls of arteries.
Parasympathetic preganglionic nerve fibers to the nose leave the brain
facial nerve and pass through the greater petrosal nerve and the nerve
of the pterygoid canal to reach the pterygopalatine ganglion, where
they synapse. Sympathetic preganglionic nerve fibers leave the upper
thoracic spinal cord and traverse white rami communicans in that
region, ascend the cervical sympathetic chain and synapse in the
superior cervical sympathetic ganglion. The postganglionic nerve fibers
follow the internal carotid artery and then the nerve of the pterygoid
canal to reach the pterygopalatine fossa. These nerve fibers pass
through the ganglion to join branches of the maxiallary nerve and
artery to reach the nasal mucosa.
The most important arteries to the nasal cavity are the sphenopalatine (from the maxillary) artery and the anterior ethmoidal (from the ophthalmic) artery. Bleeding from the nose (epistaxis) occurs usually from the junction between septal branches of the superior labial and sphenopalatine arteries. The lymph vessels drain into deep cervical nodes. Communications probably occur between the nasal lymphatics and the subarachnoid space, probably through the sheath of the olfactory nerve.
Paranasal sinuses (fig. 52-6)
The paranasal sinuses are cavities in the interior of the maxilla and the frontal, sphenoid, and ethmoid bones. The sinuses develop as outgrowths from the nasal cavity; hence they all drain directly or indirectly into the nose. Nasal infection (rhinitis), e.g., during a "cold in the head," may spread to the sinuses (sinusitis). The lining of the sinuses (muco-endosteum) is continuous with the nasal mucosa. The sinuses develop mostly after birth, and their degree of development varies greatly. Their function is obscure but they provide resonance to the voice, shape to the face and some degree of warmth and humidification to inspired air. The paranasal sinuses are supplied by branches of the ophthalmic and maxillary nerves. The sinuses can be examined radiographically, and a light placed agains the roof of the mouth enables the maxillary sinus to be transilluminated.
Maxillary sinus (see fig. 42-6).
The maxillary sinus, the largest of the sinuses, is within the body of the maxilla. It is shaped like a pyramid; its base is usually medial, with its apex in the zygomatic process of the maxilla. Its roof is the floor of the orbit, and its floor is the alveolar process of the maxilla. The maxillary sinus drains into the middle meatus by means of the semilunar hiatus. The floor of the maxillary sinus is slightly below the level of the nasal cavity, and it is related to the upper teeth (varying from teeth 3 to 8 to teeth 6 to 8). Maxillary sinusitis is frequently accompanied by toothache. Infection may spread among the various sinuses, the nasal cavity, and the teeth. The opening of the maxillary sinus can be cannulated in vivo through the nostril.
The ethmoidal sinus comprises numerous small cavities (ethmoidal cells) in the ethmoidal labyrinth. The walls of these cavities are completed by the surrounding bones. Anterior and posterior groups drain into the middle and superior meatuses, respectively (see fig. 52-3).
The frontal sinus may be regarded as an anterior ethmoidal cell that has invaded the frontal bone postnatally. The right and left frontal sinuses, frequently of different sizes, are separated by a bony septum that is usually deviated to one side. The frontal sinus drains into the middle meatus in a variable manner directly or by a frontonasal duct, which opens into the frontal recess or the ethmoidal infundibulum. The frontal sinus commonly extends posterorward in the roof of the orbit (see fig. 45-10).
The sphenoidal sinus is in the body of the sphenoid bone, and it varies greatly in size. Its superior aspect is related to the hypophysis (pituitary) and the optic nerves and chiasma and laterally to the cavernous sinus and internal carotid artery (fig. 43-22). The sphenoidal sinus drains into the spheno-ethmoidal recess superior to the superior concha. The sinus is divided into right and left parts by a bony septum.
Proetz, A. W., Essays on the Applied Physiology of the Nose, 2nd ed., Annals Publishing Co., St. Louis, 1953. An interesting functional account.
Ritter, F. N., The Paranasal Sinuses, Mosby, St. Louis, 1973. Includes a photographic atlas of coronal sections and radiograms.
Schaeffer, J. P., The Nose, Paranasal Sinuses, Nasolacrimal Passageways, and Olfactory Organ in Man, Blakiston, Philadelphia, 1920. A classic text on the anatomy and development of these structures.
Terracol, J., and Ardouin, P., Anatomie des fosses nasales et des cavites annexes, Maloine, Paris, 1965. A detailed account.
52-1 What are the anterior and posterior apertures of the nose termed?
52-2 What are the nasal conchae?
52-3 List the main openings into the nasal meatuses.
52-4 Where is the olfactory region of the nasal cavity?
52-5 Which nerves are responsible for general sensation in the nasal cavity?
52-6 Which are the most important arteries to the nasal cavity?
52-7 How do the paranasal sinuses develop?
52-8 List the chief paranasal sinuses.
52-9 What is the ethmoidal labyrinth?
52-10 What can be seen on posterior rhinoscopy?
Figure 52-1 Scheme of the ethmoid bone viewed from posterior. The two ethmoidal labyrinths are united by the cribriform plate. The perpendicular plate, which forms the superior part of the nasal septum, is set at a right angle to the horizontally placed cribriform plate. The lateral surface of each labyrinth forms a part of the medial wall of the orbit and is termed the orbital plate of the ethmoid bone. F indicates the portion of the labyrinth completed by the frontal bone; S, the portion completed by the sphenoid bone. The ethmoidal labyrinth contains ethmoidal air cells known collectively as the ethmoidal sinus. (After Grant.)
Figure 52-2 A, Medial aspect of the bony framework of the lateral wall of the right nasal cavity. The lateral boundary of the piriform aperture is formed by the nasal bone and the maxilla; that of the choana is formed by the medial pterygoid plate of the sphenoid bone. Note the line of the spheno-occipital junction. B, Lateral aspect of the medial wall (nasal septum) of the right nasal cavity. The lower limit of the ethmoidal contribution to the septum varies widely. The attachment of the septal cartilage to the vomer and the maxilla allows considerable movement without dislocation.
Figure 52-3 Medial aspect of the lateral wall of the right nasal cavity. A shows the four conchae. Note that each meatus is named after the concha that forms its roof. In B, the conchae have been largely removed. The frontal sinus may open into (1) the frontal recess (as shown here) or (2) the ethmoidal infundibulum.
Figure 52-5 Innervation and blood supply of the right nasal cavity. A shows the main nerve territories on the lateral wall: those on the medial wall are similar. Apart from the olfactory region, the chief innervation of the nasal cavities is from the ophthalmic and maxillary nerves, the latter by way of the pterygopalatine ganglion. B and C show the nerves in the lateral and medial walls, respectively. D shows the main arterial territories on the medial wall: those on the lateral wall are similar. On the nasal septum, a septal branch of the superior labial artery (from the facial) and septal branches of the sphenopalatine artery anastomose near the point X, which is the chief site from which bleeding from the nose occurs.
Figure 52-6 Coronal scheme of the nasal cavity to show the conchae, meatuses, and certain paranasal sinuses. The size of the nasal passages is based on an instructive laminogram by Proetz.