Anatomy_of_Nose_Paranasal_Sinuses_and_Olfaction.pptx

Nose description

1. Anatomy of Nose & Paranasal Sinuses and Physiology of Olfaction For MBBS Pre-final Year ENT Class By Dr. Ritik (Department of ENT)

2. External Nose – Surface Anatomy & Framework • Pyramidal structure projecting from face • Root, dorsum, tip, ala, and external nares • Framework: nasal bones, upper & lower lateral cartilages, septal cartilage • Covered by skin and subcutaneous tissue

3. Nasal Cavity – Boundaries & Divisions • Extends from nostrils to choanae • Divided by nasal septum into two halves • Roof: nasal bones, cribriform plate, sphenoid • Floor: palatine process of maxilla and horizontal plate of palatine bone

4. Nasal Septum – Parts & Blood Supply • Parts: bony (vomer, perpendicular plate of ethmoid) and cartilaginous (septal cartilage) • Kiesselbach’s plexus: site of common epistaxis • Blood supply: sphenopalatine, anterior & posterior ethmoidal, superior labial arteries

5. Lateral Wall of Nose • Contains superior, middle, and inferior conchae • Meatuses beneath conchae for sinus openings • Middle meatus – most important for sinus drainage

6. Blood Supply & Nerve Supply of Nose • Arterial: branches of maxillary, facial, and ophthalmic arteries • Venous drainage → facial vein and pterygoid plexus • Nerve supply: olfactory (smell), trigeminal (sensation), autonomic (vasomotor)

7. Clinical Anatomy of Nose • Deviated Nasal Septum (DNS) → obstruction • Epistaxis (bleeding from Kiesselbach’s area) • Rhinitis, nasal polyps, and allergic conditions

8. Paranasal Sinuses – Overview • Air-filled cavities around nasal cavity • Function: reduce skull weight, resonance, humidify air • Four pairs: maxillary, frontal, ethmoidal, sphenoidal

9. Maxillary Sinus • Largest sinus (~15 ml capacity) • Pyramidal in shape; drains into middle meatus via hiatus semilunaris • Common site of sinusitis due to poor drainage

10. Frontal Sinus • Located in frontal bone above orbits • Drains via frontonasal duct into middle meatus • Variable in size and number

11. Ethmoidal Sinuses • Numerous small air cells between orbit and nasal cavity • Anterior → middle meatus; posterior → superior meatus • Related to orbit → risk of orbital cellulitis in infection

12. Sphenoidal Sinus • Situated in body of sphenoid bone • Opens into sphenoethmoidal recess • Closely related to optic nerve, pituitary gland, and internal carotid artery

13. Drainage Pathways & Clinical Importance • Most sinuses drain into middle meatus • Obstruction leads to sinusitis • Functional Endoscopic Sinus Surgery (FESS) used for treatment

14. Physiology of Olfaction – Introduction • Sense of smell → detects volatile chemicals • Important for flavor perception, warning signals

15. Olfactory Epithelium • Located in roof of nasal cavity, upper septum, and superior concha • Contains olfactory receptor cells, supporting cells, and basal cells • Receptor cells are bipolar neurons

16. Olfactory Pathway • Receptor cells → olfactory nerve fibers → olfactory bulb → olfactory tract → olfactory cortex • No thalamic relay (unique among sensory systems) • Ends in temporal lobe (piriform cortex)

17. Mechanism of Olfactory Transduction • Odorant binds to receptor → G-protein activation → cAMP ↑ → Na+/Ca2+ influx → depolarization • Action potential transmitted to olfactory bulb

18. Factors Affecting Olfaction • Age, smoking, upper respiratory infection • Chronic rhinitis, nasal polyps, and trauma

19. Clinical Correlations • Anosmia – loss of smell (COVID-19, head injury) • Hyposmia – decreased smell sensitivity • Parosmia – distorted perception of odors

20. Summary • Nose: external + internal structure, septum, conchae • Paranasal sinuses: 4 pairs, function & drainage • Olfaction: receptors → pathway → cortex • Clinical importance: epistaxis, sinusitis, anosmia

21. References • Gray’s Anatomy, 42nd Ed. • BD Chaurasia: Head and Neck, 7th Ed. • Guyton & Hall: Textbook of Medical Physiology, 14th Ed.