URT Notes (Lecture 14)

Describe the structures of the respiratory system and state their functions
Describe the structures of the upper respiratory tract
Describe the epithelia of the upper respiratory tract
Pre-reading references: anatomy of URT and its epithelia (as per Martini Visual Anatomy & Physiology modules)

URT (upper respiratory tract)
LRT (lower respiratory tract)
Thoracic cavity
Joints
Respiratory muscles
Link structure to function; cellular-level understanding of the respiratory mucosa is needed

Consists of: Nose, Nasal Cavity, Conchae, Paranasal Sinuses, Pharynx (Nasopharynx, Oropharynx, Laryngopharynx)

Nose: external nares, nasal bridge, nasal septum; anterior nasal cavity cartilage; vestibule lined with skin and hair follicles; vibrissae filter inhaled air
Nostrils separated by nasal septum; nasal bones form nasal bridge
Conchae (turbinates): superior, middle, inferior; swirl air to enhance contact with mucosa; humidify and warm air; aid in olfaction; lined by respiratory epithelium
Nasal Epithelium: predominantly respiratory epithelium (pseudostratified ciliated columnar with goblet cells); small area on roof lined by olfactory epithelium with olfactory receptors
Lamina propria beneath epithelium; thin-walled vascular plexus underneath
Functions of vascular plexus: warms incoming air; prone to nosebleeds when damaged
Goblet cells produce mucus; mucus traps debris and moistens air
Ciliated cells move mucus cephalad toward the pharynx; mucus swallowed and digested
Mucus components: mucins, lysozymes, immunoglobulins, glycoproteins, salts

Sinuses are air-filled cavities within skull bones (frontal, sphenoid, ethmoid, maxillary) surrounding the nose
Lined with respiratory mucosa; drain into the pharynx
Functions: lighten the skull, increase surface area to humidify/clean air, sound resonance
Infection can block drainage (sinusitis)

Three regions: Nasopharynx (air passage only), Oropharynx (air & food), Laryngopharynx (air & food)
Lined by respiratory mucosa in all regions except where protection is needed; oropharynx and laryngopharynx have stratified squamous epithelium to protect against abrasion
Nasopharynx: located posterior to nasal cavity; soft palate and uvula block nasopharynx during swallowing; auditory tubes drain here; pharyngeal tonsils present
Oropharynx: posterior to oral cavity; extends from soft palate to the hyoid; contains palatine and lingual tonsils
Laryngopharynx: extends from hyoid bone to the opening of the larynx/esophagus; ends where respiratory and digestive tracts diverge; during swallowing, food has right of way

Nasal epithelium sits on a mucosa that includes lamina propria
Two main epithelial types in the nasal region:
- Respiratory epithelium: pseudostratified ciliated columnar with goblet cells
- Olfactory epithelium: on the roof; contains olfactory receptor cells
Goblet cells produce mucus; ciliated cells help transport mucus toward pharynx
Olfactory region contains sensory receptors for smell; nerves project to olfactory bulb

Mucosa consists of epithelia + basement membrane + lamina propria (connective tissue)
Submucosa lies beneath, may contain glands
The mucosa + submucosa organization varies by region and function

Why does the nose run on cold days? (temperature/warmth and mucus production balance)
Why do we cough up mucus when unwell? (clearing mucus and debris from airways)
Why do smokers cough frequently? (cilia fatigue/impairment and mucus buildup)

URT includes nose, nasal cavity, conchae, paranasal sinuses, pharynx
Functions: air conditioning, olfaction, speech resonance
Epithelia: respiratory epithelium (ciliated + goblet cells) and olfactory epithelium on roof
Pharynx regions and their epithelial and functional characteristics
Sinuses: air-filled, drain to pharynx, functions in lightening skull and resonance