ear, nose and throat

What is the function of the nasal cavity?

• Warms inhaled air

• Humidifies inhaled air

• Filters and cleans the air

• Houses olfactory receptors for smell

• Drains lacrimal secretions

What bones and structures make up the nasal cavity?

• Roof: Cribriform plate of the ethmoid

• Floor: Hard palate (front) & soft palate (back)

What are the three regions of the nasal cavity

• Nasal vestibule – Hairs (vibrissae) trap particles.

• Olfactory region – Contains olfactory receptors (CN I) for smell.

• Respiratory region – Lined with pseudostratified columnar epithelium with blood vessels that warm and humidify air.

What causes epistaxis (nosebleeds)?

The nasal cavity has extensive and superficial blood vessels, making it prone to bleeding.

How do we detect smells?

Volatile molecules dissolve in mucus and bind to olfactory receptors in the olfactory region of the nasal cavity

What cranial nerve is responsible for smell?

The olfactory nerve (CN I).

Where do olfactory signals get processed in the brain?

The olfactory bulb, which sends signals to the olfactory cortex (temporal lobe), hypothalamus, and amygdala

Why do strong smells seem to fade over time?

Smell adaptation occurs as ion channel changes slow down new action potentials.

How does ageing affect smell

Olfactory bulb atrophies with age, leading to decreased smell sensitivity, which is an early sign of neurodegenerative diseases like Alzheimer’s and Parkinson’s.

What are the three parts of the pharynx?

• Nasopharynx – Contains pharyngeal tonsils and openings to the Eustachian tubes which equalise middle ear pressure

• Oropharynx – Behind the mouth, contains the palatine tonsils. Serves as a passageway for food and air

• Laryngopharynx – The lowest part, connects to the oesophagus and larynx. Facilitates the separation of food and air

what muscles are in the pharynx?

• pharyngeal muscle: keep it permanently open so breathing is unobstructed

• constrictor muscles: close pharynx while swallowing to push food down the oesophagus

What is the larynx made of?

Irregularly shaped cartilages:

• Thyroid cartilage (forms Adam’s apple)

• Cricoid cartilage (completely encircles the larynx)

• Arytenoid cartilages (involved in vocal cord movement)

• Epiglottis (prevents food from entering the trachea)

What are the functions of the larynx?

• Sound production (pitch, volume, resonance)

• Air passage

• Protects lower respiratory tract (epiglottis prevents food inhalation)

• Humidifies, filters, and warms air

How do vocal cords control pitch?

• Abducted (open/ relaxed) – Low-pitch sounds

• Adducted (closed/ stretched) – High-pitch sounds

What are the functions of the larynx?

• Sound production (pitch, volume, resonance)

• Protects lower respiratory tract (epiglottis prevents food inhalation)

how do vocal cord produce sound

air passing through the glottis vibrates vocal cords to produce sound in conjunction with tongue.

What are the functions of the mouth?

• Entrance to the digestive system

• Mastication (chewing)

• Speech production

• Taste and sensory reception