Question Video: Describing the Major Cells That Line the Alveoli | Nagwa Question Video: Describing the Major Cells That Line the Alveoli | Nagwa

Question Video: Describing the Major Cells That Line the Alveoli Biology • First Year of Secondary School

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Fill in the blank. The walls of the alveoli in the lungs are made of a very thin epithelium to facilitate gas exchange. This epithelium is mostly composed of _ cells.

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Video Transcript

Fill in the blank. The walls of the alveoli in the lungs are made of a very thin epithelium to facilitate gas exchange. This epithelium is mostly composed of blank cells. (A) Simple squamous, (B) stratified squamous, (C) simple columnar, or (D) stratified columnar.

An epithelium is a type of tissue which lines many surfaces of the body and is involved in protection, absorption, and secretion. Epithelial tissues are made up of epithelial cells, of which there are three types. These are squamous, columnar, and cuboidal. Each of these cell types can be either simple or stratified. Simple just means they are arranged in a single layer of cells, and stratified means they are in two or more layers of cells. Squamous cells are thin, flat cells which can appear polygonal when viewed from above. Columnar cells are, as the name suggests, column-shaped and elongated cells which are taller than they are wide. And cuboidal cells are cube-shaped cells which appear square in cross section.

We’re told in the question that the epithelium which lines the walls of the alveoli is very thin. This is so there is a short diffusion pathway for the efficient exchange of oxygen and carbon dioxide between the alveoli and the surrounding blood capillaries. To achieve this, the alveoli are lined with a single layer of cells. And this layer is composed of the thinnest, flattest epithelial cell type, squamous cells.

We can now correctly fill in the blank with answer option (A). This epithelium is mostly composed of simple squamous cells.

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