Here's an easy mnemonic to remember the layers of the epidermis and some other fun facts.
The Epidermis consists of 5 layers (From base to top)
- Stratum basale
- Stratum spinosum
- Stratum granulosum
- Stratum lucidum
- Stratum corneum
Bottom to Top:
Stratum Basale (as it is the basal layer) :
These cells multiply and produce the keratinocytes which move up the layers.
Melanocytes are present in this layer which produce melanosome (melanin packed in granules) and ship them to the keratinocytes in other layers through their dendrites.
Stratum Spinosum / prickle cell layer (contains desmosomal bridges which look like spines.) :
Connected to each other by the aforementioned desmosomal bridges.
Stratum Granulosum (contain keratohyaline granules) :
Diamond shaped cells.
Granules contain protein filaggrin (filament aggregation) which is responsible for the aggregation of keratin filaments.
Present only in palms and soles.
Stratum Corneum (horny layer) :
Most superficial layer.
Cells are fully keratinised and end up as anucleate dead cells which later desquamate.
Basale, spinosum and granulosum together are called as the living layer.
Corneum is called as the dead layer.
Dermis consists of the superficial papillary dermis and the deep reticular dermis.
Skin is the largest organ in the body.
Keratin is synthesised in the Spinosum layers but accumulates in the granulosum layer.
The migration of cells from basal layer to desquamation is known as the Turn over Time which is normally 4-5 weeks.
Merkel cells(sensory end organ) present in the basal layer are responsible for the touch sensation.
P.S. The image has been taken from another site.