2. Basic Structure of the Airway Flashcards
Describe the anatomy of the bronchi
• Trachea branches into bronchi at T4 (sternal angle)
• Right bronchus - more vertical, wider diameter, more susceptible to aspiration
• Secondary bronchi - supply each lobe
• Tertiary bronchi - supply each pulmonary segment
• As branching increases:
- cartilage rings decrease
- smooth muscle increases
Describe the anatomy of the trachea
- 20 horseshoe-shaped cartilage rings, regularly arranged
- Anterior surface lined with epithelium
- Posterior surface has trachealis muscle (anterior to oesophageal muscle, required for swallowing)
- Cartilage ring not continuous at posterior
What is the function and anatomy of the larynx?
- Modulates sound (low pitch without larynx)
- Makes sound using Arytenoid cartilage (attached to vocal folds)
- Cartillagenous structure
- Supported from the floor of the mouth by the hyoid bone
- Associated with the lateral carotid arteries
- Superior and posterior to the thyroid gland
- Superior to the trachea
- Lined by a membrane
Describe the function of the Arytenoid cartilage
- Attached to vocal ligaments which open and close entry to the larynx
- Act as sphincter - prevent entry into lower airways
- Open during inspiration
- Partially open during phonation (speech)
- Increased thorax and abdomen pressure - close the vocal folds during expulsive forced e.g. sneezing
What is the function and anatomy of the pharynx?
- Post conditioning of air
- Nasopharynx - posterior to nasal cavity, eustachian tube opening (tube to ear)
- Oropharynx - posterior to tongue, lymphoid tissue, channels food posteriorly to oesophagus
- Laryngopharynx - after epiglottis
- Includes nasal cavities
Describe the anatomy of the nasal cavities
- Roughly triangular cross-section
- Smooth medial and inferior walls
- Lateral wall - respiratory epithelium with hair mucosa, covering 3 scroll-like plates (conchae)
- Air warmed & humidified by moist, warm plates - prevents cold shock
- Mucous and hair traps airborne particles
- Olfaction (smell) - olfactory tract has a specialised epithelium with a specialised nerve supply
How does the nasal lining remain moist during breathing?
- Nasal lining cools down as it warms air during inspiration
* During expiration, nasal lining cools the air and retrieves the water by condensation
What happens in the pharynx during exercise?
- Respiratory muscles can’t propel air through the nose fast enough
- Resort to open-mouth breathing - increased loss of water & exposure to airborne particles
Describe the anatomy and function of the Paranasal sinuses?
- 4 sets of blind-ended out-pocketings of the lateral walls
- Slow air turnover - little role in heat or water transfer
- Infection common in maxillary sinus - opening is high up
- Reduce weight of facial bones
- Crumple zone in facial trauma
- Resonator for the voice
- Insulate sensitive structures (eyes from temperature fluctuations)
Explain how the nasal cavities/pharynx, lower airways and bronchioles/alveoli resist collapse?
- Nasal cavities/pharynx - attachments to bone
- Lower airways - walls of larynx, trachea and bronchi held by cartilage
- Bronchioles/alveoli - surfactant phospholipid prevents collapse via surface tension
What membranes surround the lungs?
- Parietal pleura - closest to ribs
- Visceral pleura - closest to lung
(thin, moist layer allows lung to slide smoothly)
Which area separates the lungs and what does it contain?
• Mediastinum • Contains: - trachea - oesophagus - heart - great arteries/veins/nerves/lymphs
What surfaces are the lungs made up of?
- Costal surface - convex surface facing ribs
- Mediastinal surface - moulded to mediastinum
- Inferior surface - concave moulded to diaphragm
Where is the apex of the lung located?
- Projects 2-3cm above clavicle
* Within root of neck
What is the difference between the PO2 in the air and blood in the alveoli?
• PO2 air > blood
Air = 100mmHg, blood = 40mmHg
Describe the anatomy of the diaphragm
- Attached to costal margin
- Centre of dome bulges up
- Pressure difference between pleural and abdominal cavities
How does the diaphragm change during inspiration?
• Contraction of diaphragm - pulls costal margin down • Contraction of intercostal muscles - pulls ribs up and out • Pleural cavities expand - increase volume - decreased pleural pressure • Air drawn in - increased lung volume • Lowest part of lung expands into costo-diaphragmatic recess
Which nerves supply the diaphragm?
- Phrenic nerves
* C3, C4, C5
Outline the blood circulation from the vena cava, towards the lungs and back to the heart
- Vena cava
- Right atrium
- Tricuspid valve
- Right ventricle
- Pulmonary valve (semi-lunar)
- Pulmonary artery
- Pulmonary circuit
- Alveoli
- Pulmonary Vein
- Left atrium
- Mitral valve
- Left ventricle
- Aortic valve (semi-lunar)
- Aorta
(low resistance to accommodate entire CO)
