Nose_and_Paranasal_Sinuses_with_Olfaction.pptx

Paranasal air sinuses

1. Anatomy of Nose & Paranasal Sinuses, and Physiology of Olfaction Reference: Dhingra – Diseases of Ear, Nose & Throat (7th Ed.) Presented by: Dr. Ritik Department of Anatomy & Physiology

2. Introduction The nose functions as both a respiratory passage and organ of smell. Divided into external nose and nasal cavity. Functions: Air conduction, filtration, humidification, resonance, smell.

3. External Nose Framework: Nasal bones, frontal process of maxilla, septal and alar cartilages. Skin: Contains sebaceous glands (especially at tip and ala). Blood supply: Facial, ophthalmic, and maxillary arteries.

4. Nasal Cavity Divided by nasal septum into right and left halves. Roof: Cribriform plate, sphenoid, frontal bone. Floor: Hard palate. Walls: Medial (septum) and lateral (conchae + meatuses).

5. Nasal Septum Components: Perpendicular plate of ethmoid, vomer, and septal cartilage. Clinical importance: Deviated nasal septum (DNS).

6. Lateral Wall of Nasal Cavity Contains 3 conchae (turbinates): Superior, middle, and inferior. Each concha has a corresponding meatus beneath it. Openings: Middle meatus – frontal, maxillary, anterior ethmoidal sinuses. Superior meatus – posterior ethmoidal sinus. Sphenoethmoidal recess – sphenoidal sinus.

7. Paranasal Sinuses Overview Air-filled cavities lined by mucosa that drain into the nasal cavity. Functions: Lighten skull, resonance of voice, and mucus secretion.

8. Types of Sinuses Frontal – drains into middle meatus via frontonasal duct. Maxillary – drains into middle meatus (hiatus semilunaris), largest sinus. Ethmoidal – anterior, middle, posterior groups; open into superior and middle meatuses. Sphenoidal – opens into sphenoethmoidal recess.

9. Clinical Anatomy of Sinuses Sinusitis: inflammation of paranasal sinuses (maxillary most common). Referred pain to forehead or upper teeth. Orbital cellulitis: may arise from ethmoidal sinus infection. Transillumination test used for diagnosis.

10. Olfactory Epithelium Located at roof of nasal cavity, superior concha, and upper nasal septum. Composed of receptor neurons, supporting, and basal cells. Olfactory neurons are bipolar and capable of regeneration.

11. Olfactory Pathway Odorant → olfactory receptor → olfactory nerve → olfactory bulb. Second-order neurons → olfactory tract → primary olfactory cortex (uncus). Unique feature: No thalamic relay.

12. Mechanism of Smell Odorant dissolves in mucus and binds to G-protein coupled receptors. Triggers depolarization and action potential in receptor neurons. Signal interpreted in limbic system (emotion and memory link).

13. Clinical Correlations of Olfaction Anosmia: loss of smell (head injury, infections, COVID-19). Hyposmia and Parosmia: partial or distorted smell perception. Olfactory aura: seen in temporal lobe epilepsy.

14. Summary Nose: dual role in respiration and olfaction. Paranasal sinuses: lighten skull, resonance, mucus drainage. Olfaction: chemical to neural signal transduction.

15. References Dhingra PL, Diseases of Ear, Nose and Throat, 7th Ed. Gray’s Anatomy. BD Chaurasia (Head & Neck). Guyton & Hall: Textbook of Physiology.