Respiratory: Physiology - Anatomy, structure and functional interface of the respiratory system Flashcards
By what process does O2 and CO2 exchange occur?
Simple diffusion
What is the thickness and total surface area of the blood-gas barrier? How many alveoli are there?
0.2-0.3 µm thin
TSA 50-100m2
~500 million alveoli
What is the volume of the anatomic dead space?
150ml
What are the conducting airways?
Airways that do not participate in gas exchange
Includes trachea, left and right main bronchus, segmental bronchi, down to terminal bronchioles
Describe the change in structure from proximal to distal conducting airways
Proximal airways: ciliated columnar epithelium with cartilaginous walls
Distal airways: mostly smooth muscle
What is the volume of the respiratory zone at rest?
2.5-3L
What is an acinus?
Unit distant to terminal bronchiole (includes respiratory bronchiole, alveolar ducts and sacs)
How does movement of gas occur in the conducting vs the respiratory zone?
Conducting zone: movement via flow down pressure gradient
Respiratory zone: cross-sectional area increases and therefore forward velocity of gas decreases, movement occurs predominantly via diffusion
Describe the passage of the pulmonary arteries and veins in the lungs
Initially pulmonary arteries, veins and bronchi all run together
Towards periphery of lung, pulmonary veins move away to pass between lobules whilst pulmonary arteries and bronchi continue down the centre of lobules as “bronchovascular bundle”
What is the diameter and wall thickness of the pulmonary capillaries?
Diameter 7-10µm (just large enough for an RBC)
Thickness <0.3µm
How long do RBCs spend traversing the pulmonary capillaries? How many alveoli do they cross in this time?
0.75secs traversing pulmonary capillary, crossing 2-3 alveoli over this time
Describe the dual blood supply of the lung
Pulmonary circulation: responsible for gas exchange
Bronchial circulation: blood supply to conducting airways, lung can function without it (as in post-transplant)
What is the role of surfactant and which cells produce it?
Produced by type II pneumocytes
Reduces surface tension in the alveolar to increase stability (prevent collapse)
Describe how inhaled particles are filtered by the respiratory system
Large particles filtered by the nose
Smaller particles filtered by the mucociliary escalator in the conducting airways
Particles depositing in the alveolar are removed by macrophages
