Anatomy of Internal Nose

ANATOMY OF THE INTERNAL NOSE

The internal nose plays a crucial role in breathing, filtering, and conditioning inhaled air. The internal nose comprises two nasal cavities, separated by the nasal septum. Each nasal cavity is approximately 5 cm in height and 5–7 cm in length. It is narrow transversely, measuring approximately 1.5 cm at the floor and only 1–2 mm at the roof. Each cavity extends from the nares (nostrils) anteriorly to the choanae (posterior nasal apertures), which open into the nasopharynx.

Functional Divisions. Based on function, the nasal cavity proper is divided into two regions:

1. Olfactory region – It is lined by olfactory cells containing specialised olfactory receptors for the sense of smell. It is located at the apex of the nasal cavity (superior 1/3rd of the septum/lateral wall).
2. Respiratory part – It is lined by a ciliated pseudostratified epithelium, which includes mucus-secreting goblet cells. It is primarily responsible for air conditioning by filtration, warmification, and humidification of the inhaled air. It is located at the inferior 1/3rd of the septum/lateral wall.

Anatomical Divisions. Each nasal cavity can be divided into two main anatomical regions for clarity.

1. The Vestibule: The anterior and inferior portion, lined with skin containing vibrissae (coarse hairs).
2. The Nasal Cavity Proper: The main respiratory and olfactory area, lined with mucosa.

The Vestibule and Nasal Valve (The Airflow Regulator)

1. Vestibule: The vestibule forms the anterior and inferior part of the nasal cavity. It is lined with skin containing sebaceous glands, hair follicles, and small hairs called vibrissae. The limen nasi marks the upper limit of the vestibule, also referred to as the nasal valve.

• Acute infection of the hair follicle by Staphylococcus aureus causes an exquisitely painful furuncle or boil.
• Behind the vestibule is the atrium, a smooth region lined by nasal mucosa. The atrium, when pneumatized, exhibits a bulge caused by the agger nasi cell, which lies anterior to the middle turbinate. The agger nasi cells are the most anterior ethmoid air cells. They communicate with the frontal recess and play a critical role in frontal sinus drainage. When an agger nasi cell becomes enlarged or excessively pneumatized, it may encroach upon the frontal recess, narrowing or constricting this area. This mechanical obstruction can impede the drainage pathway of the frontal sinus, potentially leading to conditions such as frontal sinusitis due to poor ventilation and mucus retention.

2. Nasal Valve Area: The Nasal Valve Area is located at the junction of the vestibule and the nasal cavity proper and has the least cross-sectional area of the entire nose. Therefore, it is the most critical area for regulating airflow and nasal resistance on inspiration. The angle between the nasal septum and the lower border of the upper lateral cartilage is nearly 30° (a few sources say 10° to 15°). When this angle narrows (e.g., after trauma or rhinoplasty), it causes significant nasal obstruction.

Nasal Valve Boundaries:

• Laterally: The lower border of the Upper Lateral Cartilage and fibrofatty tissue (along with the anterior head of the inferior turbinate).
• Medially: The cartilaginous nasal septum.
• Caudally (Floor): The bony floor of the pyriform aperture.

Nasal Cavity Proper

The structure of each nasal cavity proper includes:

1. Lateral wall: Turbinates and the Osteomeatal Unit (OMU).
2. Medial wall: Nasal septum.
3. Roof: Narrow and formed by several bones.
4. Floor: Wide and relatively simple.

1. Lateral wall: Turbinates and the Osteomeatal Unit (OMU). The lateral wall is the most important surgical area of the internal nose because it houses the drainage pathways for most paranasal sinuses. This wall is formed by eight separate bones, creating projections (Turbinates/Conchae), and channels (Meatuses) that contribute to airflow regulation, humidification, and drainage of the sinuses.

• Bones of the lateral nasal wall: The lateral nasal wall is formed by eight separate bones, each of which has processes that articulate intricately with each other.
  • Large bones: Maxilla (paired bone), Ethmoid, Frontal, Sphenoid bone (unpaired bones lying in the midline)
  • Small bones: Palatine, Lacrimal, Inferior turbinate, Nasal bones (all are paired bones)
  • Despite the presence of two sphenoid, two frontal, and two ethmoid sinuses, there is only one sphenoid bone, one frontal bone, and one ethmoid bone in the midline of the skull. This arrangement highlights the shared role of these unpaired bones in creating bilateral structures within the nasal cavity.

• Turbinates/Conchae and Meatuses:

1. • Turbinates or Conchae. There are three and occasionally four scroll-like bony projections present on the lateral wall of the nose called as turbinates or conchae. They are covered by the mucus membrane. The function of the conchae is to expand the surface area of the nasal cavity, allowing more inspired air to come into contact with the cavity walls. They also regulate the airflow so that the air remains in the nasal cavity longer, allowing sufficient time for humidification and temperature regulation. The turbinates create four channels. Three of these channels are termed meatuses, and the fourth is the sphenoethmoidal recess
   • Meatuses. The spaces below the turbinates are called meatuses, creating pathways for the air to flow. These pathways are vital for directing air to different regions of the cavity and into the respiratory tract. The sphenoethmoidal recess is located above and medial to the superior turbinate, which is the drainage site of the sphenoid sinus.

 

Inferior turbinate. It is a distinct, scroll-like bone located on the lateral wall of the nasal cavity. It is larger and more straight in course compared to the middle and superior turbinates. The superior border is firmly attached to the maxilla (anteriorly) and the palatine bone (posteriorly), while the lower edge is free and hangs over the inferior meatus, creating a passage for airflow and drainage. The eustachian tube lies approximately 1 cm behind the posterior attachment of the inferior turbinate.

Inferior meatus. It is a space below the inferior turbinate. The nasolacrimal duct drains into the inferior meatus. It is approximately 1 cm behind the anterior end of the inferior turbinate, and it is guarded by a mucosal valve called Hasner’s valve.

Middle turbinate. The middle turbinate is part of the ethmoid bone. It has an S-shaped, dried leaf-like, curved structure. The posterior end of the middle turbinate ends at the level of the roof of the posterior choana. The middle turbinate is divided into three parts based on its orientation and attachments:

• • Anterior Third part: Lies in the sagittal plane and is attached to the cribriform plate.
  • Middle Third part: Lies in the coronal plane and is attached to the lamina papyracea, forming the ground lamella or basal lamella. The basal lamella divides the ethmoid cells into two groups: The anterior ethmoid cells, which lie anterior to the ground lamella of the middle turbinate and drain in the middle meatus. The posterior ethmoid cells, which lie behind (posterior) the ground lamella and drain into the superior meatus or sphenoethmoidal recess.
  • Posterior Third part: Lies in the horizontal plane and is attached to the lamina papyracea, the medial wall of the maxillary sinus and the perpendicular plate. It forms the roof of the middle meatus. The lamina papyracea and, consequently, the orbit are located 2-3 mm above the level of the maxillary ostium.

Concha bullosa. Pneumatization of the middle turbinate leads to an enlarged, balloon-out middle turbinate called concha bullosa. It drains into the frontal recess directly or through agger nasi cells.

Middle meatus. The middle meatus is an important area in the nasal cavity that plays an important role in frontal, maxillary and anterior ethmoidal sinuses drainage. Most anteriorly in the middle meatus, there is a curved bony structure called the uncinate process. Just behind the uncinate lies the ethmoidal bulla, a well-pneumatized and consistent anterior ethmoidal cell. Between the uncinate process and the ethmoidal bulla is a semilunar gap called the hiatus semilunaris, which is a flat, two-dimensional space. This gap leads to a three-dimensional area known as the infundibulum. Together, the uncinate process, the ethmoidal bulla, hiatus semilunaris and the infundibulum form the osteomeatal unit. The OMU is the common functional pathway for drainage of the frontal, maxillary, and anterior ethmoid sinuses into the middle meatus. 

Important structures in the middle meatus.

• • Uncinate Process. The uncinate process is a sickle-shaped, hook-like bony structure located on the lateral wall of the nasal cavity. Positioned almost freely within the middle meatus, it partially covers the opening of the maxillary sinus. Anteriorly, the uncinate process articulates with the lacrimal bone, while posteriorly, it connects to the inferior turbinate and the perpendicular plate of the palatine bone. Its orientation extends from an anterosuperior to a posteroinferior direction. The anteroinferior border of the uncinate process attaches to the lateral nasal wall, whereas the posteroinferior end attaches to the inferior turbinate. This attachment divides the membranous portion of the lower middle meatus into two regions: the anterior and posterior fontanelle.
  • Hiatus Semilunaris. The posterosuperior border of the uncinate process is sharp and runs parallel to the anterior border of the ethmoidal bulla. This configuration creates a narrow gap between these two structures, referred to as the hiatus semilunaris (inferior). The hiatus semilunaris is a two-dimensional space approximately 1–2 mm in width.
  • Infundibulum. The infundibulum is a three-dimensional space bordered medially by the uncinate process, the frontal process of the maxilla, and sometimes the lacrimal bone. Laterally, it is bounded by the lamina papyracea. The natural opening (ostium) of the maxillary sinus is located in the lower portion of the infundibulum. Additionally, accessory ostia of the maxillary sinus may occasionally be observed in the anterior or posterior fontanelle.
  • Bulla Ethmoidalis (Anterior ethmoidal cell). The bulla ethmoidalis is a prominent ethmoidal air cell located posterior to the uncinate process. Its anterior surface forms the posterior boundary of the hiatus semilunaris. The degree of pneumatization of the bulla varies; it may present as a pneumatized cell or as a solid bony prominence. The bulla may extend superiorly to the skull base and posteriorly to fuse with the ground lamella. In some cases, the bulla does not reach the skull base or the ground lamella, resulting in the formation of recesses: the suprabullar recess (above the bulla) and the retrobullar recess (behind the bulla).
  • Lateral sinus (sinus lateralis of Grunwald). The suprabullar recess and the retrobullar recess together create a semilunar space known as the lateral sinus. The lateral sinus opens into the middle meatus via a semilunar cleft, the hiatus semilunaris superioris, which is oriented opposite to the hiatus semilunaris inferioris. Therefore, the hiatus semilunaris inferioris leads into the infundibulum, while the hiatus semilunaris superioris opens into the lateral sinus. Posteriorly, the lateral sinus may extend to the basal lamella of the middle turbinate.
    Boundaries of the lateral sinus:

• • • Superiorly: Skull base
    • Laterally: Lamina papyracea
    • Medially: Middle turbinate
    • Inferiorly: Ethmoidal bulla

• • Frontal recess. The frontal recess is an opening at the lower part of the frontal sinus that facilitates its drainage. The frontal sinus outflow tract varies based on the attachment of the uncinate process. In most cases, the uncinate process attaches to the lamina papyracea, allowing direct drainage into the middle meatus. Alternatively, when the uncinate attaches to the ethmoid roof or middle turbinate, the sinus drains into the ethmoid infundibulum. The frontal infundibulum, frontal ostium, and frontal recess form an “hour-glass configuration,” with the frontal sinus positioned more anteriorly than the frontal recess in endoscopic views. The upper end of the uncinate process resides within the frontal recess.
    Boundaries of the Frontal Recess:
    • Anteriorly: Anterior wall of the agger nasi cell.
    • Posteriorly: Bulla ethmoidalis (or the suprabullar recess if present).
    • Laterally: Lamina papyracea, which appears yellowish due to the underlying orbital fat.
    • Medially: Middle turbinate.
    • Superiorly: The frontal recess opens via the frontal ostium into the frontal sinus.
  • Agger nasi. It is a distinct bulge just anterior to the attachment of the middle turbinate. Pneumatization of the frontonasal process, along with the adjacent lacrimal bone, contributes to the formation of the agger nasi cells. They are usually 1-3 in number. Their size depends on the extent of pneumatization of the lacrimal bone and the adjacent frontonasal process of the maxilla. When pneumatized, it contains air cells, the agger nasi cells, which communicate with the frontal recess. An enlarged agger nasi cell may encroach on the frontal recess area, constricting it and causing mechanical obstruction to frontal sinus drainage.
  • Haller cells are air cells located in the roof of the maxillary sinus (or floor of the orbit), derived from the pneumatization of anterior or posterior ethmoid cells. Enlargement of Haller cells can intrude on the ethmoid infundibulum, disrupting normal drainage of the maxillary sinus via its natural ostium.

Endoscopic approaches to the frontal recess and associated structures require careful navigation through four main anatomical barriers in the coronal plane:

1. 1. 1. The uncinate process.
      2. The anterior wall of the bulla ethmoidalis.
      3. The ground lamella.
      4. The anterior wall of the sphenoid sinus.

Understanding the spatial relationships and variations of these structures is critical for effective endoscopic sinus surgery.

Superior turbinate. The superior turbinate is part of the ethmoid bone. It is located posterior and superior to the middle turbinate. It may become pneumatized by one or more cells. It serves as a key landmark for identifying the ostium of the sphenoid sinus (sphenoethmoidal recess). Sphenoethmoidal recess gets its name from the fact that this area forms a niche between the posterior ethmoid cells and the sphenoid sinus. The sphenoid sinus ostium is positioned 2–3 mm above and medial to the superior turbinate and can be accessed endoscopically approximately 1–1.5 cm above the roof of the posterior choana, near the posterior border of the nasal septum. 

Superior meatus. It is a space below the superior turbinate. Posterior ethmoid cells open into it. The number of posterior ethmoid cells varies from 1 to 5. In 10 percent of cases, a posterior ethmoidal cell may extend posteriorly above or by the side of the sphenoid sinus. It may extend for as much distance as 1.5 cm from the anterior surface of the sphenoid. This extension of the cell is called as the Onodi cell (extension of the posterior ethmoidal cell). The Onodi cell is surgically important as the Onodi cell, when present, insinuates itself between the optic nerve and the sphenoid sinus. The optic nerve, therefore, produces a bulge in the lateral wall of the Onodi cell instead of in the sphenoid sinus. Normally, the lateral wall of the sphenoid sinus features two distinct bulges: the optic nerve superiorly and the internal carotid artery inferiorly and posteriorly.

Supreme turbinate. It is sometimes present above the superior turbinate and has a narrow meatus beneath it.

Arterial Supply of the Lateral Wall of the Nasal Cavity

The nose is richly supplied by both the external and internal carotid systems on the lateral walls and septum.

Internal carotid system

1. 1. Anterior ethmoidal artery – Originates from the ophthalmic artery in the orbit. Both anterior and posterior ethmoidal artery supply the anterosuperior quadrant. During sinus surgeries, transection of this artery can result in retraction of the bleeding end into the orbit causing serious complications, such as pressure haematoma and potential loss of vision.
   2. Posterior ethmoidal artery – Originates from the ophthalmic artery in the orbit. It is smaller than the anterior ethmoidal artery and is present in only 80% of individuals.

External carotid system

1. 1. Branches of sphenopalatine artery – It is a terminal branch of the maxillary artery. It enters the nasal cavity via the sphenopalatine foramen.

• • • Posterior lateral nasal branch supplies a large part of the lateral wall (inferior and middle turbinate and meatii) and septum.
    • Posterior septal branch supplies the posterior part of the septum.

1. 2. Greater palatine artery – Originates from the maxillary artery in the pterygopalatine fossa. Supplies the anterior nasal cavity floor and medial wall-anastomoses with sphenopalatine and superior labial arteries.
   3. Nasal branch of anterior superior dental – Originates from the infraorbital branch of maxillary artery
   4. Branches of the facial artery to nasal vestibule.

 

• • Anterosuperior part: supplied by anterior/posterior ethmoidal arteries.
  • Anteroinferior part: supplied by the branches from the facial artery.
  • Posterosuperior part: dominantly supplied by the sphenopalatine artery.
  • Posteroinferior part: supplied by the greater palatine artery.

Venous drainage of the Lateral Wall of the Nasal Cavity

The veins follow the arteries within the mucosa. The veins form a plexus that drains anteriorly into the facial vein; the middle part to the pterygoid plexus of veins and posteriorly, into the pharyngeal plexus of veins.

Key features and areas of the Lateral Wall of the Nasal Cavity

1. 1. Retrocolumellar Vein.The retrocolumellar vein runs vertically 2mm behind the columella (the tissue separating the nostrils). It crosses the floor of the nose and drains into the venous plexus located on the lateral nasal wall. This vein is a common site of venous bleeding, particularly in young individuals.
   2. Woodruff’s Plexus. Woodruff’s plexus is a network of veins located below the posterior end of the inferior turbinate. It is a significant site for posterior epistaxis (nosebleeds), which is more commonly seen in adults.

Nerve Supply of the Lateral Wall of the Nasal Cavity

1. General Sensory Nerves. General sensory nerves, branches of the trigeminal nerve, innervate the entire lateral wall of the nasal cavity. The distribution is divided into four quadrants:

• • Anterosuperior Quadrant – Supplied by the anterior ethmoidal nerve, a branch of the ophthalmic nerve (V1).
  • Anteroinferior Quadrant – Supplied by the infraorbital nerve, which is a continuation of the maxillary nerve (V2).
  • Posterosuperior Quadrant – Supplied by the lateral posterior superior nasal branches from the pterygopalatine ganglion (V2).
  • Posteroinferior Quadrant – Supplied by the anterior palatine nerve, another branch from the pterygopalatine ganglion (V2).

2. Special Sensory Nerves (Olfactory Nerves)

• • The olfactory nerves (cranial nerve I) provide special sensory innervation and are responsible for the sense of smell. It innervates the olfactory mucosa on the lateral nasal wall and nasal septum. These nerves originate from receptors present in the olfactory mucosa/ epithelium. The central filaments of the olfactory cells are arranged into 12–20 nerves which pass through the cribriform plate to the olfactory bulb in the brain. They can carry sheaths of dura, arachnoid and pia into the nasal cavity. Damage to these nerves may lead to conditions like cerebrospinal fluid (CSF) rhinorrhea or meningitis due to the disruption of the CSF barrier.

2. Medial wall (Nasal septum)

The nasal septum is a central partition wall dividing the nasal cavity into two halves. Composed of bone and cartilage, it is lined on both sides by a mucous membrane and forms the medial wall of the nasal cavities. Although typically positioned in the midline, the nasal septum is often slightly deviated, which may impact airflow and breathing efficiency. It plays a critical role in maintaining the structural integrity of the nose, supporting the nasal tip and bridge (dorsum of the cartilaginous part of the nose). The septal cartilage is essential for maintaining the shape and function of the nose. Its damage or removal, such as in septal abscess, injuries, tuberculosis or excessive removal during septal surgery, leads to depression of the lower part of the nose and drooping of the nasal tip.

Parts of the nasal septum:

1. 1. Columellar septum. It is formed by columella which contains the medial crura of alar cartilages united together by fibrous tissue and covered on either side by skin.
   2. Membranous septum. It is made of double skin layers with no bony or cartilaginous support. It is located between the columella and the caudal edge of the septal cartilage. Both the columellar septum and the membranous septum are freely movable from side to side.
   3. Septum proper. It is formed by a rigid osteocartilaginous framework, covered with the membrane of the nasal mucosa.

Its principal constituents are:

• • • The perpendicular plate of ethmoid bone,
    • The vomer
    • A large septal (quadrilateral) cartilage is wedged between the perpendicular plate of the ethmoid bone and the vomer bone anteriorly.
    • Other bones that make minor contributions at the periphery are the crest of nasal bones, the nasal spine of the frontal bone, the rostrum of the sphenoid, the crest of palatine bones and the crest maxilla, and the anterior nasal spine of the maxilla.

The septal cartilage rests in a groove on the anterior edge of the vomer and rests anteriorly on the anterior nasal spine vomer. Trauma or dislocation can lead to conditions like caudal septal deviation or septal spur respectively, both of which may obstruct the nasal airway. Additionally, the septum is fused to the upper lateral cartilages, so deviations often involve external nasal deformities.

Arterial supply of the Medial Wall of the Nasal Cavity (Nasal septum)

The nasal septum is supplied by both the internal and external carotid systems:

• • Internal carotid system
    • Anterior and posterior ethmoidal arteries (branches of the ophthalmic artery).
  • External carotid system
    • Sphenopalatine artery (nasopalatine and posterior medial nasal branches).
    • Septal branch of the greater palatine artery.
    • Septal branch of the superior labial artery.

• • Anterosuperior part: supplied by anterior/posterior ethmoidal arteries.
  • Anteroinferior part: supplied by the superior labial artery.
  • Posterosuperior part: dominantly supplied by the sphenopalatine artery.
  • Posteroinferior part: supplied by the greater palatine artery which pierces the perpendicular plate of palatine bone and passes up through the incisive fossa.

Key features and areas of nasal septum

1. 1. Little’s area (Kiesselbach’s plexus)
      • James Little in 1879 and the same plexus was described one year later by Kiesselbach.
      • It is a vascular network in the anteroinferior nasal septum.
      • It is formed by anastomoses of the anterior ethmoidal, sphenopalatine, greater palatine, and superior labial arteries.
      • The common site for epistaxis (nosebleeds) and site for the origin of the bleeding polypus (haemangioma) of the nasal septum
   2. Trauma and deviation
      • The septal cartilage is vulnerable to displacement from the vomerine groove or anterior nasal spine, leading to nasal obstruction.

Venous drainage of nasal septum

• • Plexus forms in Little’s area, draining:
    • Anteriorly into the facial vein.
    • Posteriorly via the sphenopalatine vein to the pterygoid plexus.

Nerve supply of nasal septum

1. 1. General sensory nerves
      • Anterosuperior: anterior ethmoidal nerve (V1).
      • Anteroinferior: infraorbital nerve (V2) and greater palatine nerve (V2).
      • Posterior 2/3rd: nasopalatine nerve (pterygopalatine ganglion).
   2. Special sensory nerves
      • The olfactory nerves (cranial nerve I) provide special sensory innervation and are responsible for the sense of smell. It innervates the olfactory mucosa on the lateral nasal wall and nasal septum. These nerves originate from receptors present in the olfactory mucosa/ epithelium. The central filaments of the olfactory cells are arranged into 12–20 nerves which pass through the cribriform plate to the olfactory bulb in the brain. They can carry sheaths of dura, arachnoid and pia into the nasal cavity. Damage to these nerves may lead to conditions like cerebrospinal fluid (CSF) rhinorrhea or meningitis due to the disruption of the CSF barrier.

3. Roof of the Nasal Cavity

The roof of the nasal cavity is divided into three parts:

• Anterior sloping part: Formed by the nasal bones and nasal part of the frontal bone.
• Posterior sloping part: Composed of the inferior surface of the body of the sphenoid bone.
• Middle horizontal part: Made by the cribriform plate of the ethmoid bone, allowing olfactory nerve fibres to pass.

4. Floor of the Nasal Cavity

The floor consists of two main structures:

• Anterior three-fourths: Palatine process of the maxilla.
• Posterior one-fourth: Horizontal plate of the palatine bone.

——– End of the chapter ——–

High-Yield Points for Quick Revision

• The Nasal Valve is the narrowest part of the airway and the primary site of nasal resistance.
• The Osteomeatal Unit (OMU) is the functional drainage pathway for the frontal, maxillary, and anterior ethmoid sinuses.
• Little’s Area on the anteroinferior septum is the most common site for anterior epistaxis.
• Woodruff’s Plexus behind the inferior turbinate is a common site for posterior epistaxis.
• The Middle Turbinate is the most important landmark for endoscopic sinus surgery.
• The Uncinate Process is the key to locating the maxillary sinus natural ostium and understanding frontal sinus drainage.
• The Lamina Papyracea is the paper-thin medial orbital wall, a common site for iatrogenic orbital entry during surgery.
• The Anterior Ethmoidal Artery is at risk during surgery; if severed, it can retract into the orbit, causing a sight-threatening hematoma.
• The Cribriform Plate is the thinnest part of the anterior skull base; injury causes CSF rhinorrhea and risk of meningitis.
• An Onodi Cellcan harbour the optic nerve, making it vulnerable during posterior ethmoidectomy.
• The Nasolacrimal Duct drains into the inferior meatus, about 1 cm behind the anterior end of the inferior turbinate.

Mnemonic for Bones of Lateral Wall: My Eye Please Look In Some New Places (Maxilla, Ethmoid, Palatine, Lacrimal, Inferior Turbinate, Sphenoid, Nasal).

Mnemonic for Little’s Area Arteries: Please Send Great Softness And Love (sPhenopalatine, Superior labial, Greater palatine, Anterior ethmoidal).

NEET PG & University Exam Style MCQs

1. A 45-year-old male presents with recurrent episodes of severe posterior epistaxis requiring posterior nasal packing. Which of the following is the most likely source of bleeding?
   A. Kiesselbach’s plexus
   B. Sphenopalatine artery
   C. Anterior ethmoidal artery
   D. Superior labial artery

Answer: B. Sphenopalatine artery
Explanation: Posterior epistaxis often arises from the sphenopalatine artery or its branches, such as those contributing to Woodruff’s plexus. Anterior epistaxis (A) is more common but less severe. (C) and (D) supply the anterior septum.

2. During Functional Endoscopic Sinus Surgery (FESS) for chronic sinusitis, the surgeon must identify the middle turbinate as a key landmark. Which of the following structures forms the posterior attachment of the middle turbinate?
   A. Cribriform plate
   B. Lamina papyracea
   C. Uncinate process
   D. Basal lamella (Ground Lamella)

Answer: D. Basal lamella (Ground Lamella)
Explanation: The middle turbinate has three attachments. Its middle third attaches to the lamina papyracea in the coronal plane, forming the basal lamella, which separates the anterior and posterior ethmoid cells.

3. A patient develops clear, watery rhinorrhea after a head injury. A beta-2 transferrin test is positive. Which anatomical structure is most likely injured?
   A. Lamina papyracea
   B. Cribriform plate of ethmoid
   C. Vomer bone
   D. Perpendicular plate of ethmoid

Answer: B. Cribriform plate of ethmoid
Explanation: The cribriform plate is perforated by the olfactory nerve filae, which are surrounded by meningeal sheaths. A fracture here can tear these sheaths, leading to a CSF leak.

4. The natural ostium of the maxillary sinus opens into which of the following anatomical spaces?
   A. Superior meatus
   B. Hiatus semilunaris
   C. Inferior meatus
   D. Infundibulum

Answer: D. Infundibulum
Explanation: The maxillary sinus ostium drains into the infundibulum, which then drains into the middle meatus via the hiatus semilunaris.

5. What is the most common site of nasal obstruction due to its role as the major flow-limiting segment?
   A. The choana
   B. The nasal vestibule
   C. The internal nasal valve
   D. The sphenoethmoidal recess

Answer: C. The internal nasal valve
Explanation: The internal nasal valve, located at the junction of the upper lateral cartilage and the septum, is the narrowest part of the nasal passage and thus the primary regulator of airflow and resistance.

6. An enlarged air cell located in the roof of the maxillary sinus, which can compromise the maxillary sinus ostium, is known as:
   A. Agger nasi cell
   B. Onodi cell
   C. Haller cell
   D. Concha bullosa

Answer: C. Haller cell
Explanation: Haller cells are infraorbital ethmoid cells that, when enlarged, can narrow the infundibulum and maxillary sinus ostium, leading to impaired drainage.

7. Which artery is a branch of the ophthalmic artery and is at risk of retracting into the orbit if transected during sinus surgery, potentially causing an orbital hematoma?
   A. Sphenopalatine artery
   B. Posterior ethmoidal artery
   C. Greater palatine artery
   D. Anterior ethmoidal artery

Answer: D. Anterior ethmoidal artery
Explanation: The anterior ethmoidal artery runs from the orbit through the anterior ethmoidal canal to supply the nasal cavity. If cut, its orbital end can retract, causing a sight-threatening retrobulbar hematoma.

8. The nasolacrimal duct drains into which part of the nasal cavity?
   Superior meatus
   B. Middle meatus
   C. Sphenoethmoidal recess
   D. Inferior meatus

Answer: D. Inferior meatus
Explanation: The nasolacrimal duct opens into the inferior meatus, approximately 1 cm behind the anterior end of the inferior turbinate, guarded by Hasner’s valve.

9. A pneumatized posterior ethmoid air cell that extends superiorly and laterally to the sphenoid sinus, creating a close relationship with the optic nerve, is called:
   A. Agger nasi cell
   B. Onodi cell
   C. Haller cell
   D. Concha bullosa

Answer: B. Onodi cell
Explanation: The Onodi cell is a posterior ethmoid cell that pneumatizes around the sphenoid sinus. The optic nerve can be dehiscent in its lateral wall, making it vulnerable during surgery.

10. The sensory nerve supply to the anteroinferior part of the nasal septum is provided by:
    A. Anterior ethmoidal nerve
    B. Nasopalatine nerve
    C. Infraorbital nerve
    D. Greater palatine nerve

Answer: C. Infraorbital nerve
Explanation: The infraorbital nerve (V2) supplies the anteroinferior quadrant of the lateral wall and septum. The nasopalatine nerve (B) supplies the posterior septum.

Clinical Scenario-Based Viva Questions

1. Scenario: A 20-year-old medical student presents with a painful, red, and swollen bump at the entrance of his right nostril. It is exquisitely tender to touch.
   • What is the most likely diagnosis?
     • Answer: A furuncle or boil of the nasal vestibule, commonly caused by Staphylococcus aureus infection of a hair follicle.
   • Why is this condition considered dangerous?
     • Answer: Because the venous drainage of this area connects to the cavernous sinus via the facial vein and ophthalmic veins. Squeezing the lesion can cause the infection to spread, leading to cavernous sinus thrombosis, a life-threatening condition.

2. Scenario: A 55-year-old hypertensive man arrives at the ER with active bleeding from the nose. Anterior rhinoscopy reveals no obvious bleeding point in the anterior septum. The bleeding seems to be trickling down from above the inferior turbinate.
   • What is the most likely source of this posterior epistaxis?
     • Answer: The sphenopalatine artery or Woodruff’s plexus (a venous plexus) is located in the posteroinferior aspect of the lateral wall.
   • What is the first-line management step for controlling such bleeding?
     • Answer:Insertion of a posterior nasal pack (e.g., Foley’s catheter or a dedicated balloon) combined with an anterior pack. If this fails, the definitive management is endoscopic cauterisation or sphenopalatine artery ligation.

3. Scenario: A young adult undergoes septoplasty. Postoperatively, the patient reports a loss of smell.
   • Which anatomical structure was most likely injured during the surgery?
     • Answer: The olfactory neuroepithelium is located high in the nasal vault (superior turbinate, superior septum, and cribriform plate) or the delicate cribriform plate itself.
   • What is the anatomical explanation for CSF rhinorrhea as a complication of this surgery?
     • Answer: If the cribriform plate is fractured, it can tear the meningeal sheaths that surround the olfactory nerve filaments as they pass from the nose to the brain, creating a communication between the subarachnoid space and the nasal cavity.

4. Scenario: A CT scan of a patient with recurrent frontal sinusitis shows a well-defined air cell located immediately anterior and inferior to the frontal recess, causing significant narrowing.
   • Which anatomical variant is this?
     • Answer: An enlarged Agger Nasi cell.
   • How does this cell affect sinus physiology?
     • Answer: It mechanically obstructs the frontal recess, which is the drainage pathway of the frontal sinus. This obstruction impedes mucus clearance and ventilation, leading to sinusitis.

Frequently Asked Questions in Viva

• What is the most common site for nosebleeds?
  The most common site for epistaxis is Little’s area (Kiesselbach’s plexus) on the anteroinferior part of the nasal septum.
• Why is the lateral wall of the nose more important than the medial wall for surgeons?
  The lateral wall houses the drainage pathways (osteomeatal unit) for all the major paranasal sinuses, making it the primary focus of endoscopic sinus surgery.
• What is the function of the turbinates?
  Turbinates increase the surface area of the nose to warm, humidify, and filter inspired air, and they help regulate airflow by creating turbulence.
• How can a nasal septal abscess lead to a saddle nose deformity?
  A septal abscess can destroy the nutrient supply to the septal cartilage, leading to its necrosis and resorption. Since this cartilage supports the nasal dorsum, its loss causes the bridge to collapse.
• What is the danger area of the face?
  The danger area comprises the upper lip, nose, and adjacent areas, as infections here can spread via venous connections to the cavernous sinus in the skull.
• Which nerve is responsible for the sense of smell?
  The Olfactory Nerve (Cranial Nerve I) is responsible for the special sense of smell.
• What is the key landmark for locating the sphenoid sinus ostium during endoscopy?
  The superior turbinate is the key landmark. The sphenoid sinus ostium is located in the sphenoethmoidal recess, medial and superior to the superior turbinate’s posterior attachment.

——– End ——–

 

Reference Textbooks.

• Scott-Brown, Textbook of Otorhinolaryngology-Head and Neck Surgery.
• Cummings, Otolaryngology-Head and Neck Surgery.
• Stell and Maran’s, Textbook of Head and Neck Surgery and Oncology.
• Ballenger’s, Otorhinolaryngology Head And Neck Surgery
• Susan Standring, Gray’s Anatomy.
• Frank H. Netter, Atlas of Human Anatomy.
• B.D. Chaurasiya, Human Anatomy.
• P L Dhingra, Textbook of Diseases of Ear, Nose and Throat.
• Hazarika P, Textbook of Ear Nose Throat And Head Neck Surgery Clinical Practical.
• Mohan Bansal, Textbook of Diseases of Ear, Nose and Throat Head and Neck Surgery.
• Hans Behrbohm, Textbook of Ear, Nose, and Throat Diseases With Head and Neck Surgery.
• Logan Turner, Textbook of Diseases of The Nose, Throat and Ear Head And Neck Surgery.
• Arnold, U. Ganzer, Textbook of  Otorhinolaryngology, Head and Neck Surgery.
• Ganong’s Review of Medical Physiology.
• Guyton & Hall Textbook of Medical Physiology.

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