GENERAL HISTOLOGY

Detailed explanation-1: -Simple squamous epithelium lines air sac or alveoli. These squamous epithelial cells are permeable and allow the oxygen from the air to enter the blood in the capillaries of the lung, So, the correct answer is option ‘Squamous epithelium’.

Detailed explanation-2: -Alveoli are separated from one another by thin alveolar walls (interalveolar septa). Each alveolus is lined by simple squamous epithelium, exceedingly thin to facilitate diffusion of oxygen while still forming an epithelial barrier between the outside air and the internal body fluids.

Detailed explanation-3: -Alveoli are the site of gas exchange in the lungs. Because rapid diffusion of gases is necessary between the capillaries and the alveoli, a very thin epithelial layer is needed. As a result, alveoli use simple squamous epithelium so that gases can easily diffuses to and from the bloodstream.

Detailed explanation-4: -The alveolus is composed of alveolar epithelial type 1 cells, alveolar epithelial type 2 cells and capillary cells. Type 1 cells are large, squamous epithelial cells that cover  95% of the alveolar surface area.

Detailed explanation-5: -Alveolar Epithelial Cells Most of the alveolar surface is covered by simple squamous cells known as type I pneumocytes (Figure 1-9). These cells have a small nucleus with highly branched cytoplasmic processes covering 4000 to 5000 µm2.