Arrange the following layers of epidermis from surface to deep layer - CorneocytesMerkel cellsMelanocytesLangerhans cells
(A) Corneocytes>merkel cell>melanocytes>langerhans cells (B) Merkel cells>corneocytes>melanocytes>langerhans cells (C) Melanocytes >merkel cells>corneocytes>langerhans cells (D) corneocytes>>langerhans cells>melanocytes > merkel cells
(D) Ans. DThe epidermis is composed of 4 or 5 layers, depending on the region of skin being considered.Those layers in descending order are:Cornified layer (stratum corneum)Composed of 10 to 30 layers of polyhedral, anucleated corneocytes (final step of keratinocyte differentiation), with the palms and soles having the most layers.Clear/translucent layer (stratum lucidum, only in palms and soles)This narrow layer is found only on the palms and soles. The epidermis of these two areas is known as "thick skin" because with this extra layer, the skin has 5 epidermal layers instead of 4Granular layer (stratum granulosum)Keratinocytes lose their nuclei and their cytoplasm appears granular. Lipids, contained into those keratinocytes within lamellar bodies, are released into the extracellular space through exocytosis to form a lipid barrier. Those polar lipids are then conveed into non-polar lipids and arranged parallel to the cell surface.Spinous layer (stratum spinosum)Keratinocytes become connected through desmosomes and sta produce lamellar bodies, from within the Golgi, enriched in polar lipids, glycosphingolipids, free sterols, phospholipids and catabolic enzymes.Langerhans cells, immunologically active cells, are located in the middle of this layer.Basal/germinal layer (stratum basale/germinativum).Composed mainly of proliferating and non-proliferating keratinocytes, attached to the basement membrane by hemidesmosomes.Melanocytes are present, connected to numerous keratinocytes in this and other strata through dendrites.Merkel cells are also found in the stratum basale with large numbers in touch-sensitive sites such as the fingeips and lips.