L5 - Respiratory Anatomy & Physiology

Question 1

What is respiration?

Answer 1

The exchange of gases between the tissues of the body and the external environment.
It involves 2 gases: oxygen and carbon dioxide

Question 2

Other functions of the respiratory system

Answer 2

• Enables speech, singing, and other vocalisations
• Route for water loss + heat elimination
• Enhances venous return
• Helps maintain normal acid-base balance
• Defends against inhaled foreign matter
• Nose serves as the organ of smell

Question 3

What are the two zones in the respiratory structure?

Answer 3

Conducting zone & Respiratory zone

Question 4

What does the conducting zone consist of?

Answer 4

Larynx – Trachea – Bronchi (left and right) – Terminal Bronchioles

Characteristics:
* Tough, non-muscular tube
* Rings of cartilage - prevent collapse

Question 5

Small bronchioles in the conducting zone of lungs

Answer 5

• Extensive branching pattern
• No cartilage to hold them open
• Walls - smooth muscle innervated by ANS
• Sensitive to certain hormones and local chemicals

Question 6

What does the respiratory zone consist of?

Answer 6

• Respiratory bronchioles
• Alveoli (air sacs)

Question 7

What does the respiratory epithelia (around the alveoli) consist of ? (hint: 5 components)

Answer 7

• Type 1 alveolar cells - small epithelial cells (no cilia) where gas exchange occurs
• Type 2 alveolar cells - secrete surfactants which reduces surface tension (facilitates lung expansion)
• Columnar epithelial cells - ciliated (mucous barrier defence against pathogens + foreign matter)
• Goblet cells - secretes mucous (mucous barrier defence against pathogens + foreign matter)
• Macrophages - remove foreign material from alveoli, preventing infection

Question 8

Parasympathetic innervation of the lungs

Answer 8

• DIRECT innervations of the smooth muscle in the bronchioles via the vagus nerve
• ACh acts on the muscarinic M3 receptors
• Opening of calcium ion channels
• Effect —-> CONTRACTION

Question 9

Sympathetic innervation of the lungs

Answer 9

• INDIRECT innervation
• On pre-ganglionic nerves – noradrenaline binds to alpha2-adrenoceptors
• On smooth muscle of bronchioles - adrenaline (released from adrenal medulla) binds to beta2-adrenoceptors
• Reduction in release of ACh

-Effect —-> RELAXATION

Question 10

Blood supply to the alveoli

Answer 10

• Tracheal arteries (from thyroid arteries) and veins
• Pulmonary artery - (from heart) deoxygenated blood supply to get oxygenated — then back to heart via pulmonary vein

Question 11

What causes the ease of breathing?

Answer 11

• Properties of the lung tissues - compliance and elasticity
• Surfactant secreted from Type II alveolar cells
• Pleural membranes - fluid surrounding lungs

Question 12

What is compliance in terms of pulmonary elasticity?

Answer 12

• Ease with which the lungs can expand and contract in response to changes in pressure
• High lung compliance = lungs can expand and contract easily
• Low lung compliance = lungs are stiff and resistant to changes in pressure

Question 13

What is elastic recoil in terms of pulmonary elasticity?

Answer 13

• The tendency of an elastic structure to oppose stretching or distortion.
  (tendency to deflate following inflation)

Question 14

How are lungs held open?

Answer 14

• Positive trans pulmonary pressure
  (P-tp)
• Surfactants - reduce surface tension in alveoli

Question 15

What is the role of the surfactants in the lungs?

Answer 15

• Made of phospholipid (lipophilic)
• Moisture (H2O) in airways causes surface tension within alveolus due to H-bonding – causes inward pressure and thus alveoli reduces its compliance (cannot expand a lot during inspiration) – ultimately collapse of alveoli
• Surfactant in between water molecules - reduces H-bonding, hence reduces surface tension
• Prevents lung collapse
• Prevents too much expansion