Station 4

Question 1

What are the two main cell types of the alveoli, and their functions?

Answer 1

Type II Alveolar cells (pneumocytes) - produce and secrete surfactant which reduces surface tension in the alveoli, especially at lower lung volumes when it is spread thickest

Type I Alveolar (pneumocytes) - comprise the ‘thin’ portion of the alvolar wall. Very thin squamous cell, that comprises the alveolar part of the respiratory membrane.

Question 2

What other cell might you see associated with the alveolar surface? What is its function?

Answer 2

Alveolar Dust Cell - resident macrophage of the alveoli - immune function (phagocytic)

Question 3

What are the knob-like structures at the entry to each alveolus? What is their function?

Answer 3

Smooth muscle knobs, covered by epithelial cells - mainly clara cells.

They contract in response to PSNS stimulation

Question 4

What layers constitute the respiratory membrane?

Answer 4

The squamous epithelial cell of the capillary, the fused basement membrane, the Type I alveolar cell

Question 5

What is the significance of the ‘thin’ and ;thick’ portions of the alveolar walls?

Answer 5

Thin = part of the respiratory membrane. Gas diffusion.

Thick = house connective tissue, lymphatics

Question 6

What structures comprise the inter-alveolar septum?

Answer 6

Elastic and collaged fibers

Macrophages

Lymphocytes

Mast Cells

Capillaries

Question 7

Of the two main types of cells found in the alveoli, what are their relative numbers vs their contribution to the surface area of the alveolus?

Answer 7

Type I pneumocytes = 40% of cells, but comprise ~90% of the alveolar wall

Type II pneumocytes = 60% of cells, but comprise ~10-15% of the alveolar wall

Question 8

When is sufficient surfactant produced?

Answer 8

35 weeks

Question 9

What are the alveolar pores of Kohn?

Answer 9

Pores/openings between adjacent alveoli. Provide colateral air circulation to alveoli when there are upstream airway blockages.