Turbinates

Turbinates, also known as nasal conchae, are long, narrow, curled bony structures that protrude into the nasal cavity. They are covered by mucosa and play a crucial role in filtering, humidifying, and warming inspired air. There are typically three pairs of turbinates—superior, middle, and inferior—with a fourth, the supreme turbinate, present in some individuals.

Structure

Each turbinate consists of a bony core covered by highly vascularized mucosa. They form ridges along the lateral walls of the nasal cavity and are arranged in a stacked configuration:

• Inferior turbinate: The largest and most prominent, it is an independent bone (inferior nasal concha)
• Middle turbinate: Part of the ethmoid bone
• Superior turbinate: Also part of the ethmoid bone, smaller and located above the middle turbinate
• Supreme turbinate: An anatomical variant seen in some individuals, located above the superior turbinate

Location

Turbinates are located along the lateral walls of the nasal cavity. Each turbinate overhangs a corresponding passageway called a meatus:

• Inferior meatus: Lies beneath the inferior turbinate
• Middle meatus: Beneath the middle turbinate
• Superior meatus: Beneath the superior turbinate

These meatuses serve as drainage pathways for the paranasal sinuses and nasolacrimal duct.

Function

Turbinates are vital for normal nasal physiology. Their functions include:

• Air filtration: Trap dust, pathogens, and particles using mucosa and cilia
• Humidification: Moisturize inhaled air using glandular secretions
• Warming: Vascular beds heat the air before it reaches the lungs
• Airflow regulation: Direct airflow through the nasal passages, influencing olfaction and resonance

Histology

The mucosal covering of turbinates is lined with **pseudostratified columnar epithelium with cilia and goblet cells**. Beneath this epithelium lies a submucosal layer rich in seromucous glands and venous sinusoids that contribute to the warming and humidification functions.

Drainage Pathways

Turbinates are closely associated with sinus drainage:

• Inferior meatus: Receives the nasolacrimal duct (tear drainage)
• Middle meatus: Drains the maxillary, frontal, and anterior ethmoidal sinuses
• Superior meatus: Drains the posterior ethmoidal sinus

Blood Supply

Turbinates are highly vascular and receive blood from:

• Sphenopalatine artery (branch of maxillary artery)
• Anterior and posterior ethmoidal arteries (branches of ophthalmic artery)
• Greater palatine artery
• Facial artery branches

Nerve Supply

Sensory innervation is provided by branches of the trigeminal nerve (CN V), particularly the ophthalmic (V1) and maxillary (V2) divisions:

• Anterior ethmoidal nerve (V1): Supplies the anterior portions
• Nasopalatine and greater palatine nerves (V2): Supply the posterior and inferior regions

Autonomic fibers from the pterygopalatine ganglion modulate glandular secretion and vascular tone.

Clinical Significance

Inferior Turbinate Hypertrophy

Chronic inflammation from allergies or infections can cause the turbinates, especially the inferior ones, to enlarge, resulting in nasal obstruction, congestion, and mouth breathing.

Allergic Rhinitis

In allergic rhinitis, the turbinates become swollen due to histamine-mediated vasodilation, leading to nasal congestion, sneezing, and rhinorrhea.

Nasal Surgery

Turbinate reduction (e.g., inferior turbinate reduction) may be performed in cases of persistent nasal obstruction unresponsive to medical therapy. Care is taken to preserve mucosal function.

Empty Nose Syndrome

This rare condition occurs after excessive turbinate removal, leading to paradoxical nasal obstruction and dryness despite wide nasal passages.

Development

Turbinates develop from the lateral wall of the nasal cavity during embryogenesis. The inferior turbinate forms as a separate ossification center, while the middle and superior turbinates originate from the ethmoid bone primordium.

Imaging

CT scans of the paranasal sinuses provide detailed visualization of the turbinates and their relationship to the sinuses. MRI can assess mucosal thickening or soft tissue abnormalities.