Nasal septum

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Anatomy: The Nasal Septum

High-Yield Revision Notes for NEET PG / NEXT

The nasal septum divides the nasal cavity into two osteofibrocartilaginous halves. For postgraduate exams, focus heavily on the structural core, the highly integrated blood supply, and the critical surgical complications following septal corrections.

1. Osteofibrocartilaginous Framework

The septum is composed of three primary structural elements, supplemented by smaller bony contributions along its margins:

  • Septal Cartilage (Quadrilateral Cartilage): Forms the anterior-inferior cartilaginous component. It projects into the space between the nasal bones and the bony palate.
  • Perpendicular Plate of the Ethmoid: Forms the superior-posterior bony component. It descends from the cribriform plate to meet the septal cartilage and vomer.
  • Vomer: Forms the posterior-inferior bony component. It articulates with the sphenoid body superiorly and the nasal crest of the maxilla and palatine bones inferiorly.
  • Minor Contributors: The crest of the nasal bones, the nasal spine of the frontal bone, the crest of the maxilla, and the crest of the palatine bone.

2. Blood Supply: Little’s Area & Kiesselbach’s Plexus

The nasal septum features an exceptional blood supply derived from both the internal and external carotid systems.

Little’s Area (Kiesselbach’s Plexus): Located on the anterior-inferior quadrant of the nasal septum, this hyper-vascular zone is the single most common site for **epistaxis (90% of clinical cases)**. It is formed by the anastomosis of four principal arteries:
Artery Parent Vessel & System Pathway
1. Sphenopalatine Artery Terminal branch of Maxillary Artery ← External Carotid System
2. Anterior Ethmoidal Artery Branch of Ophthalmic Artery ← Internal Carotid System
3. Greater Palatine Artery Branch of Maxillary Artery ← External Carotid System
4. Septal Branch of Superior Labial Artery Branch of Facial Artery ← External Carotid System

3. Nerve Innervation Grid

Sensory pathways are divided geographically, primarily mapped via the trigeminal divisions:

  • Anterior-Superior Zone: Innervated by the internal nasal branches of the anterior ethmoidal nerve (← Nasociliary nerve ← CN V1).
  • Posterior-Inferior Zone: Innervated by the nasopalatine nerve (← Pterygopalatine ganglion ← CN V2). This nerve runs obliquely down the septum to exit through the incisive fossa.
  • Olfactory Area: Restricted to the absolute superior-most strip adjacent to the cribriform plate, supplied by the specialized filaments of the olfactory nerve (CN I).

4. Critical Surgical Complications & Board Traps

A. Septal Hematoma & Septal Perforation

The quadrilateral cartilage has no intrinsic vascular supply; it depends entirely on the overlying perichondrium for metabolic diffusion.

Pathology Loop: Traumatic fractures or septal surgeries can tear vessels, collecting blood between the cartilage and perichondrium (Septal Hematoma). If this collection is left undrained, it completely cuts off the nutrient supply, leading to **avascular ischemic necrosis of the septal cartilage** within 48 to 72 hours. This produces a structural breakdown resulting in a septal perforation or a cosmetic **saddle nose deformity** due to collapse of the nasal dorsum.

B. Deviated Nasal Septum (DNS) Variants

  • Septal Spur: A sharp bony projection usually located at the junction of the vomer and quadrilateral cartilage. It can press against the lateral nasal wall, irritating sensory nerve endings and causing neuralgic headaches (Sluder’s Neuralgia).
  • Compensatory Hypertrophy: Long-standing DNS causes a massive airway gap in the opposite, patent nostril. Over time, the contralateral **inferior turbinate undergoes marked mucosal hypertrophy** to close this dead space and regulate air humidification.