L1: Functional Anatomy Of The Conducting And Exchanging Portion Of The Respiratory System

Question 1

Main function of respiratory system

Answer 1

1. Conduction of air (nasal cavity to bronchioles)
2. Gas exchange between air and blood (respiratory bronchioles to alveoli)
3. Pulmonary ventilation (thoracic wall, diaphragm and pleura)

Question 2

Conducting pathway and Exchange pathway

Answer 2

Conducting:
Upper: Nasal cavities —> Paranasal sinuses —> Pharynx (nasopharynx, oropharynx, laryngopharynx/hypopharynx) —>
Lower: Larynx —> Trachea —> Bronchi —> Bronchioles —> Terminal bronchioles

• all contains bone and cartilage (prevent collapse and provide elasticity)
• mucus warm, moist (by evaporation of water) and cleanse the air (trap debris)
• lined by ***respiratory epithelium (ciliated pseudostratified columnar epithelium with goblet cell)

Exchange: Respiratory bronchioles —> Alveoli

Question 3

Components of alveoli

Answer 3

1. Type 1 pneumocyte
   - simple squamous epithelium with tight junction
   - flattened with large surface area
2. Type 2 pneumocyte (cuboidal cell)
   - secrete surfactant (from lamellar bodies within the cell) —> reduce surface tension —> prevent collapse
3. Dust cell
   - macrophage
   - move from capillary to alveolar space
   - move up bronchial tree to larynx —> carried by cilia —> swallowed / expectorated with mucus
4. Pulmonary interstitium
   - CT stroma, elastic fibre to help recoil
5. Capillary
   - convoluted course

(External) alveolar air space —> surfactant —> Type 1 pneumocyte —> fused BM (endothelial + pneumocyte) —> endothelial cells (Internal)

Question 4

Structure of nose

Answer 4

1. Dorsum
2. Tip
3. Wings/Alae
4. Nostrils
5. Septum/columella (visible part)
6. Nasal hair / vibryssess
7. Nasal cavity
   - nasal concha (superior, middle, inferior) + meatus
   —> create turbulent flow to increase likelihood of air contacting mucosal surface
   —> increase surface area
   - nasal septum (increase surface area)
   - choana (beat mucus —> nasopharynx —> swallow)
8. Paranasal sinuses (create turbulent flow, resonating chamber for voice production)
   - Frontal
   - Ethmoid
   - Maxillary
   - Sphenoid

Question 5

Structure of trachea

Answer 5

• anterior wall: 15-20 C-shaped hyaline cartilage (posterior wall devoid of cartilage)
• posterior wall: elastic ligamentous membrane with trachealis muscle (smooth muscle) —> contract to move air rapidly to expel mucus/foreign objects

Question 6

Level of carina

Answer 6

• T4-T5
• sternal angle
• tracheal bifurcation (very sensitive to mechanical stimulation)
• attachment to 2nd rib

Question 7

Bronchus

Answer 7

Left: narrower, horizontal, longer
Right: wider, vertical, shorter (短小精悍)

Question 8

Changes in bronchial tree

Answer 8

Hyaline cartilage, goblet cell, glands: stops before terminal bronchioles

Ciliated cells: stops in respiratory bronchioles

Smooth muscle: stops in alveolar duct

Epithelium + elastic fibre: throughout

Question 9

Blood supply to lungs

Answer 9

Bronchial artery and vein

Pulmonary artery and vein

Question 10

Pharyngeal lymphoid ring

Answer 10

1. Pharyngeal tonsil / Adenoid (located on the roof of the nasopharynx, under the sphenoid bone)
2. Tubal tonsils x2 (on each side, where each auditory tube opens into the nasopharynx)
3. Palatine tonsils x2 (common tonsils, located in the oropharynx)
4. Lingual tonsil (located on the back part of the tongue)

Question 11

Structure of larynx

Answer 11

• connected by membranes and muscles to hyoid bone

Divided into 3 parts:

• Vestibule
• Ventricle (space between false and true vocal folds)
• Infraglottic cavity

1. Thyroid cartilage (anterior)
2. Cricoid cartilage (anterior)
3. Arytenoid cartilage (posterior)
4. Corniculate cartilage (posterior)
5. Vocal cord
6. Epiglottis
7. Glottis (space between true vocal folds)