Which of the following is labile cell -

Ans. is 'd' i.e., Surface epithelium o When a cell proliferates, it pass through a cell cycle,o Cell cycle has a series of phases : -* Gtphase-Rest phase (Presynthetic phase)* Sphase-Synthetic phase in which synthesis of DNA takes place.* Gphase-Resting phase (Postsynthetic or postmitotic phase).* Mphase-Mitotic phase in which mitosis takes place. # Go phase-When cell is not proliferating, it remains in quiescent phase (Go).Based on their proliferative capacity, cells are divided into1. Labile cells (Continouslv dividing cells) or intermitotic cells.o Have capacity to proliferate and regenerate.o Have very short Go and almost always remain in cell cycle. Example are : -Surface epithelium (stratified squamous) of skin, oral cavity, vagina and cervix.Lining mucosa of all excretory ducts of glands (Salivary gland, pancreas, biliary duct).Columinar epithelium of GIT and uterus.Transitional epithelium of the urinary tract.Bone marrow cells and hematopoietic cells.Basal cells of epithelia.2. Stable or quiescent or reversible postimitotic cells,.o Have limited capacity to proliferate and regenerate.o Ramain in Go phase of cell cycle but can enter in G1 phase when stimulated i.e., they usually remain quiescent, but proliferate in response to stimuli. Example are -Parenchymal cells of liver, kidney and pancreas.Mesenchymal cells, e.g., fibroblast and smooth muscles.Vascular endotheliumOsteoblast, chondroblastResting lymphocytes and other leukocytes.3. Permanent or nondividing or irreversible postmitotic cells.o Cannot divide and regenerate.o These cells are nondividing and have left the cell cycle, i.e., they do not belong to any phase of cell cycle. Example are -NeuronsCardiac muscleSkeletal muscle