Question

Scavenger cells of alveoli is called as
A.Melanophage
B.Monocyte/macrophage
C.Dust cell
D.Microglial cell

Answer 1

Hint: Scavenger cells work by engulfing foreign substances that get into lungs .It can be bacteria, dust, blood cells from injury and carbon particles. These are present on the internal luminal surfaces of the alveoli, the alveolar ducts, and the bronchioles.

Complete answer:
1.The alveoli represent the ultimate structural and physiological units of lung. Alveoli provide great surface area (like villi of intestine in mammals) for gaseous exchange by diffusion.
2.The wall of alveoli consists of two types of alveolar epithelial cells. Type-I alveolar cells (pneumocytes) are unusually thin and delicate squamous epithelial cells that form 90% of the alveolar surface. Type-II alveolar cells (pneumocytes), also called septal cells, are fewer in number, scattered among the squamous cells.
3.Alveolar wall also possesses alveolar macrophages or scavenger cells are also called dust cells, these roaming phagocytes ingesting fine dust particles and other debris like blood cells from injury, bacteria, carbon particles, etc.
4.Whereas Melanophage are macrophages which contain melanin and are present in pigmented skin lesions .
5.Monocytes/macrophages are agranulated white blood cells. Monocytes are phagocytic means they engulf any foreign particle present in the bloodstream.
6.Microglial cells are also types of macrophage cells which are found in the central nervous system. They help in removing damaged neurons and infections by macrophages and are important for maintaining the health of the CNS.

Hence the correct answer is OPTION(D)

Note: The total number of alveoli present in human lungs has been estimated to be approximately 300 million, exposing a surface area of nearly 70 m. In adult man, the surface area of skin is around 1.6 m only. So the surface of alveoli of lungs is more than 40 times the skin.