Recapitulación de los rasgos aspectuales de todavía

1. Maxillary Artery

• Branches of sphenopalatine artery: Nasopalatine, posterior nasal septal branches and posterior lateral nasal branches.

• Greater palatine artery

• Nasal branch of anterior superior dental artery, which is a branch of infraorbital artery.

2. Facial Artery

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„ _{Trigeminal Nerve: The ophthalmic division (anterior}

ethmoidal nerve) and maxillary division (sphenopalatine and infraorbital branches) carry common sensation (such as

touch and irritation from acrid odors). Both these divisions supply to the skin of external nose.

 _{Branches of infraorbital nerve supply vestibule of nose.}  _{The posterior two-third of nasal cavity (septum and}

lateral wall) is supplied by branches of sphenopalatine ganglion, which pass through the sphenopalatine foramen situated near the posterior end of middle turbinate, where it can be blocked by placing a pledget of cotton of 4% xylocaine.

 _{Anterosuperior part of the nasal cavity (lateral wall and}

septum) is supplied by anterior ethmoidal nerve, which can be blocked by placing the cotton pledget impreg- nated in 4% xylocaine high up inside of nasal bones.

„ _{Autonomic Nervous System}

 _{Parasympathetic: Parasympathetic nerve fibers are}

secretomotor and supply the nasal glands. The greater superficial petrosal nerve, which carry preganglionic fibers from the parasympathetic nucleus situated in brain stem, joins deep petrosal nerve (postganglionic vasomotor sympathetic fibers) and forms nerve to pterygoid canal (vidian nerve), which reaches to the sphenopalatine ganglion where only parasympathetic fibers relay. The branches of sphenopalatine ganglion pass through sphenopalatine foramen and supply nasal cavity. Parasympathetic fibers, which supply to nasal blood vessels, cause vasodilation.

 Sympathetic: The preganglionic sympathetic nerve fibers

come from upper two thoracic segments of spinal cord (origin from hypothalamus) and relay in superior cervical ganglion. The postganglionic fibers form a plexus around internal carotid artery, from which deep petrosal nerve arises that joins the preganglionic parasympathetic fibers of greater petrosal nerve to form the nerve to pterygoid canal (vidian nerve). These postganglionic sympathetic vasomotor fibers reach the nasal cavity without relaying in the sphenopalatine ganglion and cause vasoconstric- tion of nasal vessels (decongestion of nasal cavity). Some surgeons are of opinion that excessive rhinorrhea (vasomotor and allergic rhinitis) can be controlled by section of the vidian nerve (vidian neurectomy).

„ _{Facial Nerve: It supplies to the muscles of the external nose.}

Fig. 14: Blood supply of nasal septum

Fig. 15: Blood supply of lateral wall of nose

Fig. 16: Nerve supply of lateral wall of nose

Fig. 17: Artery (red color) and nerve (yellow color)

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Anatomy and Physiology of Nose and Paranasal Sinuses

Lymphatic Drainage

„ _{Submandibular Lymph Nodes: The external nose and anterior}

part of nasal cavity drain into submandibular lymph nodes.

„ _{Retropharyngeal Nodes: Posterior part of nasal cavity drains}

into upper jugular nodes and retropharyngeal nodes, which drain to upper jugular nodes.

„ _{Perineural Intracranial Spread: The perineural intracranial}

spread of cancer is possible through the lymphatics of the upper nasal cavity, which communicate with subarachnoid space along the olfactory nerves.

ANATOMY OF PARANASAL SINUSES

On each side there are four paranasal air sinuses in four cranial bones: frontal, maxilla, ethmoid and sphenoid. They are divided into two groups:

1. Anterior Group: The sinuses, which open anterior to basal lamella of middle turbinate in the middle meatus, form anterior group of paranasal sinuses. They are maxillary, frontal and anterior ethmoid sinuses.

2. Posterior Group: The sinuses, which open posterior and superior to basal lamella of middle turbinate, form posterior group of paranasal sinuses. They are posterior ethmoid and sphenoid sinuses. The posterior ethmoidal sinuses open in the superior meatus and sphenoid sinuses open in sphe- noethmoidal recess.

Maxillary Sinus (Antrum of Highmore) (Fig. 18)

It is the first to develop in human fetus. This largest paranasal sinus (15 ml capacity in adult). It occupies the body of maxilla and is pyramidal shape. The base faces towards lateral wall of nose and apex is directed laterally into the zygomatic process.

„ _Boundaries

 _{Anterior wall: The anterior facial surface of maxilla}

(canine fossa) is related to cheek.

 _{Posterior wall: It is in relation with the infratemporal and}

pterygopalatine fossa.

 Medial wall: It is thin and membranous at places and

faces middle and inferior meatuses.

 _{Floor: It is situated about 1 cm below the level of floor of}

nose in adults. Until 3 years of age, sinus floor is 4–5 mm above the nasal floor. It is formed by alveolar process of the maxilla. The roots of all the molars, second premolar and sometimes first premolar (depending on the extent of pneumatization and age of the person), are situated in the floor of maxillary sinuses. These teeth roots are separated from the sinus mucosa by a thin lamina of bone, which may be dehiscent. The chances of oroantral fistulae are high after the extraction of these teeth, the infection of which can result in maxillary sinusitis.

 _{Roof: The roof of the maxillary sinus is the floor of the}

orbit and is traversed by infraorbital nerve and vessels.

„ _{Ostium of Maxillary Sinus: It is situated higher in medial wall}

and opens in the posterior part of ethmoidal infundibulum.

„ _{Accessory Ostium: In 30% of population, an accessory ostium,}

which may be quite large, is seen behind and in front of the natural main ostium. The maxillary sinus does not drain through accessory ostium and is bypassed by the mucus blanket.

During endoscopic sinus surgery, accessory maxillary ostium is joined with the natural maxillary ostium to prevent recirculation of the mucopus into the maxillary sinus.

Frontal Sinus

The frontal sinus is situated above and deep to the supraorbital margin. It lies between the inner and outer tables of the lower part of frontal bone. The shape and size of this loculated sinus vary (very large to absent). The bilateral frontal sinuses are often asymmetric. The intervening bony septum, which is thin and often obliquely placed, may be deficient in some cases. A very large sinus may extend into the roof of the orbit.

„ _Relations:

 Anterior wall of the sinus is related to the forehead skin.

 _{Floor is in relation with orbit.}

 _{Posterior wall relations are meninges and frontal lobe}

of brain.

„ _{Ostium of frontal sinus is situated in its floor and opens into}

the frontal recess, which depending upon the attachment of uncinate process opens either in the infundibulum or medial to the uncinate process into the middle meatus.

Ethmoidal Sinuses (Fig. 19)

Ethmoidal sinuses are thin walled air cavities in lateral masses of ethmoid bone. They vary in number (3–18) and lie between upper third of lateral nasal wall and the medial wall of orbit. Clinically they are divided into two groups: anterior and posterior. Anterior ethmoid group opens into the middle meatus. Posterior ethmoid group opens into the superior meatus and some in sphenoethmoidal recess.

„ _Boundaries

 _{Roof: It is closed by the frontal bone, which forms the}

floor of anterior cranial fossa.

 _{Lateral wall: Lamina papyracea separates it laterally}

from the orbit.

Lamina papyracea is paper thin and can be easily damaged during intranasal surgery and destroyed by ethmoidal infections. Optic nerve, which is at risk during posterior ethmoid surgery, is in close relationship with posterior group of ethmoidal air cells.

Fig. 18: Coronal section of nose and paranasal sinuses seen

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„ _{Agger nasi cells: These are most anterior of anterior}

ethmoid cells and lie in close proximity of frontal recess. They are situated at the agger ridge, which is present just anterior to anterosuperior attachment of middle turbinate.

„ _{Grand (Basal) lamella: This bony insertion of middle turbi-}

nate into the skull base and lateral nasal wall separates anterior from posterior ethmoid cells. Grand lamella can be divided into three parts. Anterior one-third inserts into lamina cribrosa, middle one-third (oblique anterosuperior to posteroinferior course) into lamina papyracea and posterior one-third horizontal part inserts into lateral nasal wall.

• Big agger nasi cells can obstruct drainage of frontal sinus and their removal provides better view of nasofrontal duct during endoscopic sinus surgery.

• Haller cells: These ethmoid cells extend into the roof of maxillary sinus in the region of maxillary sinus ostium. These cells may remain asymptomatic or affect maxillary sinus ventilation and drainage resulting in recurrent or chronic maxillary sinusitis. They are present in 10% of population. • Onodi cells: These are posterior ethmoid cells and extend

either laterally or superiorly along the sphenoid sinus. The optic nerve can lie within them. Onodi cells must be recognized during the endoscopic sinus surgery on posterior ethmoid to avoid optic nerve injury.

Sphenoid Sinus (Figs 20 and 21)

The two sphenoid sinuses, one on each side are rarely symmet- rical. They occupy body of sphenoid bone and are separated by a thin bony septum, which is usually obliquely situated and may even be deficient. The ostium, which is situated in the upper part of anterior wall, drains into sphenoethmoidal recess.

The anterior wall of sphenoid sinus is 7 cm away from nasal sill at 30°angle.

„ _{Relations: The relations are important during the endo-}

scopic sinus surgery and trans-sphenoidal hypophy- sectomy. The extent and relations of sphenoid sinus depend upon the degree of pneumatization, which may

extend into the wings of sphenoid, pterygoid plates and clivus.

 Anterior part: The superior relations are olfactory tract,

optic chiasma and frontal lobe. The lateral wall relations are optic nerve, internal carotid artery and maxillary nerve. These structures may be dehiscent in the lateral wall of sinus.

 Posterior part: Roof of sinus is floor of sella turcica (pitu-

itary gland fossa). Lateral wall is related to cavernous sinus, which contains internal carotid artery and CN III, IV, V and ophthalmic and maxillary divisions CN V (trigeminal).

Mucous Membrane of Paranasal Sinuses

The mucous membrane of paranasal sinuses is thinner and less vascular and is continuous with that of the nasal cavity through the sinuses’ openings. It is ciliated pseudostratified columnar epithelium with numerous mucoserous glands and goblet cells. They produce mucus blanket which has two layers: inner thin serous layer or sol phase and outer viscous mucus layer or gel phase. Cilia, which help in drainage of mucus, are more marked near the ostia.

Mucus Drainage of Sinuses

Mucus secretions of paranasal sinuses travel to their ostium in a spiral manner. The cilia propel mucus through the ostium into the respective meatuses.

Fig. 20: Sphenoidal sinuses coronal section showing important

structures situated in relation with sphenoid sinus walls

Fig. 21: Relations of sphenoid sinus with cavernous sinus and

pituitary fossa and gland

Fig. 19: Axial section of nose and paranasal sinuses in the up-

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Anatomy and Physiology of Nose and Paranasal Sinuses

The mucus from anterior groups of sinuses passes along the lateral pharyngeal gutter. Hypertrophy of lateral pharyngeal lymphoid occurs in infection of anterior sinuses. The mucus from posterior group of sinuses spreads over the posterior pharyngeal wall.

„ _{Maxillary Sinus: In the maxillary sinus, secretion transports}

(stellate pattern) begin from floor and along all the four walls (anterior, posterior, medial and lateral) and roof and converge at the natural ostium.

„ _{Frontal Sinus: Frontal sinus secretions flow in both direc-}

tions along medial aspect of ostium. They flow out of sinus along floor and inferior parts of anterior and posterior walls. From the medial aspect of ostium, secretions flow superiorly and then laterally along the roof of frontal sinus.

The plain CT scan without contrast is the first line of screening study of the nose and paranasal sinuses. The plain PNS X-rays do not offer adequate views of osteomeatal complex, sphenoid and ethmoid sinuses due to the overlapping of structures.

Lymphatic Drainage

The lymphatic of sinuses form a capillary network in mucosa. They drain into upper deep cervical nodes lateral retropharyn- geal, nodes either directly or through group of lymph nodes.

Blood Supply

The paranasal sinuses are supplied by the branches of both external carotid artery (facial artery and sphenopalatine branch of maxillary artery) and internal carotid artery (ante- rior and posterior ethmoidal branches of ophthalmic artery) (Table 1). Sphenopalatine artery, which divides into two main branches, enters the nasal cavity through sphenopalatine foramen (posterior to middle turbinate).

The septal branch of sphenopalatine artery passes across the inferior aspect of anterior surface of sphenoid sinus and can be damaged during ESS sphenoidectomy.

Nerve Supply

Paranasal sinuses are mainly supplied by branches of CN V (trigeminal nerve) (Table 2).

„ _{The supraorbital, supratrochlear and anterior and posterior}

ethmoidal nerves are branches of ophthalmic division of (CN V₁).

„ _{The greater palatine, posterolateral nasal and superior nasal}

branches of the infraorbital nerve (branches of maxillary division of CN V) supply maxillary sinus.

„ _{The sphenopalatine nerve, which also carries parasym-}

pathetic secretomotor fibers, is the branch of maxillary division of CN V.

Development of Paranasal Sinuses

The paranasal sinuses, which develop as out-pouchings from the mucous membrane of nose, continue to grow during child- hood and early adult life (Table 2). At the time of birth, only the maxillary and ethmoidal sinuses are present. Radiologically, maxillary sinus is distinguished at 4–5 months, ethmoid at 1 year and sphenoid at 4 years and frontal at 6 years of age.

At birth, both frontal as well as sphenoid sinuses are absent and therefore not clinically significant in young children.

PHYSIOLOGY OF NOSE

The functions of the nose include (1) respiration, (2) air condi- tioning of inspired air, (3) protection of lower airway, (4) vocal resonance, (5) nasal reflex and (6) olfaction.

RESPIRATION

Humans are natural nose breathers. A newborn with bilateral choanal atresia may asphyxiate to death if immediate airway management is not done. Mouth breathing is learned later on in life. The nose allows breathing during eating.

Inspiratory and expiratory air currents during quite respira- tion pass between the turbinates and nasal septum (Figs 22A and B). Little air passes below (i.e. inferior meatus) and above TABLE 1 Blood and nerve supplies of paranasal sinuses

Sinuses Arteries Nerves

Frontal Supraorbital, supratrochlear Supraorbital, supratrochlear Maxillary Maxillary (main) and facial Maxillary

Anterior ethmoidal Anterior ethmoidal Anterior ethmoidal

Posterior ethmoidal Posterior ethmoid and sphenopalatine Posterior ethmoid and sphenopalatine Sphenoidal Posterior ethmoid and sphenopalatine Posterior ethmoid and sphenopalatine

TABLE 2 Development and growth of paranasal sinuses

Sinus At birth Adult size Growth Radiological appearance (Age) Maxillary Present 15 years Biphasic growth: Birth–3 years, 7–12 year 4–5 months Ethmoid Present 12 years Size increases up to 12 years 1 year Frontal Absent 13–18 years Invades frontal bone (2–4 yrs), size increases until teens 6 years Sphenoid Absent 12–15 years Reaches sella turcica (7 yrs), dorsum sellae (late teens),

basisphenoid (adult)

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the level of turbinates (i.e. olfactory region). Sniffing helps weak odorous substances reaching olfactory area.

during expiration, friction offered at nasal valve converts air currents into eddies under cover of inferior and middle turbinates and ventilates the sinuses through their openings in the nose. Anterior end of inferior turbinate increases and decreases in size and thus regulates inflow of air.

Nasal Cycle

The alternate opening and closing of each side of nose is called nasal cycle. It varies every few hours and is character- istic of an individual. Kayser first described it in 1895. Nasal cycle, which is observed in up to 80% of normal subjects, has also been studied with the help of rhinomanometry. There occur rhythmic cyclical congestion and decongestion of nasal mucosa (perhaps under the control of autonomic innervation), which control the airflow through nasal cavity. Most of the people are not conscious about this alteration in airflow because the total resistance of nasal airflow remains constant.

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