Question

Choose the components that make up the respiratory membrane
I. Type I cells of alveolar epithelium
II. Type II cells of alveolar epithelium
III. Basement membrane
IV. Lumen of blood capillaries
V. Endothelial cells of blood capillaries

• A. I, III ,V
• B. I, II, IV
• C. II, III, IV
• D. II, IV, V

Answer 1

The correct option is A I, III ,V

Respiratory membrane is a thin membrane which allows exchange of gases. It consists of type I cells of alveolar epithelium which are 1 cell thick made up of squamous epithelial cells. This is in contact with the wall of blood capillaries which are also 1 cell thick. Together the alveolar wall, capillary wall and the basement membrane in between form the respiratory membrane.
Type I cells of alveoli are known as pneumocytes. They make up 95% of the alveoli and are made up of simple squamous epithelium that allow quick diffusion of gases.
Type II cells of the alveoli prepare a surface active reagent (pulmonary surfactant) that prevents the lungs from collapsing, called lecithin.