Anatomy of the Respiratory Tract - Lecture 16 Flashcards
What are the functions of the respiratory system?
○ Provides oxygen to all body tissues
○ Removes carbon dioxide
○ Regulates blood pH
○ Defence against pathogens
○ Produces sound
○ Olfaction (smell)
How is the respiratory tract organised?
○ Upper respiratory tract
○ Lower respiratory tract
What makes up the upper respiratory tract?
○ Nose
○ Pharynx
○ Paranasal sinuses
○ Larynx
What makes up the lower respiratory tract?
○ Trachea
○ Bronchi
○ Bronchioles
○ Alveoli
What is the function of the upper respiratory tract?
○ Warms and moistens and filters the air
○ Olfaction (smell)
○ Production and resonation of sound
What are the functional adaptations of the nose (first three)?
Vibrissae:
○ Hairs at the entrance to the nose which traps large dust particles
Conchae:
○ Shelf-like projections from lateral wall which produce turbulene
○ Covered in mucosa
○ Allows more time to warm and moisten the air
Mucosa:
○ Pseudostratified ciliated columnar epithelium with goblet cells
○ Goblet cells produce mucous to trap particles
○ Cilia waft the trapped particles to pharynx where they can be swallowed
What are the functional adaptations of the nose (last four)?
Rich capillary network:
○ Blood warms the air
Seromucous glands:
○ Secretions moisten the air
Olfactory mucosa:
○ Located in the upper aspect of the nose, above the superior conchae
○ Contains receptors for smell
Paranasal sinuses:
○ Air filled spaces in bones around the nose
○ Lighten the skull and resonate sound
○ Secretions for the sinuses drain into nasal cavity
What is the pharynx?
○ Fibromuscular tube: a communal passageway for respiratory and gastrointestinal systems
○ The close proximity can lead to swallowing difficulties and aspiration of food and fluid
What are the three regions of the pharynx and where are they located?
○ Nasopharynx: posterior to nose
○ Oropharynx: posterior to mouth
○ Laryngopharynx: posterior to larynx
What are the main functions of the larynx?
○ Maintains an open airway
○ Prevents food and drinks entering the lower respiratory tract
○ Sound production
○ Involved in coughing and defaecation
What does the larynx consist of?
○ A cartilaginous skeleton
○ A lining made of membranes
○ Vocal chords
○ Muscles which move the vocal chords
What makes up the cartilaginous skeleton of the larynx?
From top to bottom:
○ Epiglottis
○ Hyoid bone
○ Thyroid cartilage (Adam’s apple)
○ Arytenoid cartilage
○ Cricoid cartilage
What is the glottis?
○ Space between vocal chords
○ Usually open to allow air flow
○ Closed during swallowing to prevent aspiration
○ Air vibrated over the vocal chords to produce sound
Describe the trachea
○ Tough, flexible tube
○ 4.5cm long, 2.5cm in diameter
○ Extends from larynx to carina
○ Lies anterior to the oesophagus
What does the trachea consist of?
○ Contains 15-20 horseshoe shaped cartilages: keep the airway open
○ Posterior ends of cartilage are joined by trachealis muscle: constricts during coughing
○ Trachea lined by pseudostratified columnar epithelium: acts as a mucociliary escalator
What are the three levels of bronchi?
○ Primary
○ Secondary
○ Tertiary
What are the three levels of bronchioles?
○ Bronchioles
○ Terminal bronchioles
○ Respiratory bronchioles
What trends are seen as you move down the bronchial tree?
○ Tubes get smaller in diameter
○ Amount of cartilage decreases
○ Amount of smooth muscle increases
○ Height of epithelial cells decrease
Describe the primary bronchi and its function
○ Supply each lung
○ 2-3cm long
○ right is wider and more vertical than left
○ C-shaped cartilages
Describe the secondary bronchi (lobar) and its function
○ Supply lobes of the lung:
- 3 on the right
- 2 on the left
○ Plates of cartilage that completely encircle it
Describe the tertiary bronchi (segmental) and its function
○ Supply segement of the lung:
- 10 on the right
- 8 on the left
○ Smaller plates of cartilage that completely encircle it
Describe the bronchioles and their function
○ No cartilage
○ Simple columnar epithelium with cilia
○ Few goblet cells
○ Smooth muscle: can constrict and dilate
○ Each gives rise to 50-80 terminal bronchioles
Describe terminal bronchioles and their function
○ Simple columnar epithelium with cilia
○ No goblet cells or mucous glands
○ Clara cells - produce surfactants to reduce surface tension
○ Each gives rise to 2 or more respiratory bronchioles
Describe respiratory bronchioles and their function
○ Simple cuboidal epithelia
○ No cilia
○ Clara cells
○ Alveoli extend from lumen: gas exchange
What are the levels to alveoli and describe them
○ Respiratory bronchioles -> alveolar ducts
○ Alveolar ducts: elongated airways with walls made of alveoli -> alveolar sacs
○ Alveolar sacs: spaces surrounded by clusters of alveoli
What are the key facts of alveoli?
○ 150-250 million alveoli per lung
○ Surrounded by a network of capillaries
○ Provides an extensive surface area for gas exchange
What is the structure of alveolus?
○ Type I alveolar cell: simple squamous epithelium that forms wall of alveolus
○ Type II alveolar cell: secretes surfactant that reduces surface tension so that can re-expand when air is expelled
○ Macrophages: phagocytosis of small inhaled particles and bacteria
○ Thin respiratory membrane
What is the respiratory membrane made up of?
○ Epithelium of type I cell
○ Endothelium of capillary
○ Fused basement membranes of type I cell and capillary
What is the conductive portion of the respiratory tract and what comes under it?
Concerned with getting air into the lungs:
○ Nasal cavity & paranasal sinuses
○ Pharynx
○ Larynx
○ Trachea
○ Primary bronchi
○ Secondary bronchi
○ Tertiary bronchi
○ Bronchioles
○ Terminal bronchioles
What is the respiratory portion of the respiratory tract and what comes under it?
Parts where gas exchange takes place:
○ Respiratory bronchioles
○ Alveolar ducts
○ Alveolar sacs
○ Alveoli
