BSC 215 Lecture Notes - Lecture 9: Mitosis, Stratum Basale, Stratum Spinosum
8 Jun 2018
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The Epidermis
The epidermis consists of keratinized stratified squamous epithelium. Four cell types are present:
• Keratinocytes produce keratin, a protein that hardens and waterproofs
the skin. Mature keratinocytes at the skin surface are dead and filled
almost entirely with keratin.
• Melanocytes produce melanin, a pigment that protects cells from
ultraviolet radiation. Melanin from the melanocytes is transferred to
the keratinocytes.
• Langerhans cells are phagocytic macrophages that interact with white
blood cells during an immune response.
• Merkel cells occur deep in the epidermis at the epidermal‐dermal
boundary. They form Merkel discs, which, in association with nerve
endings, serve a sensory function.
There are several layers making up the epidermis. “Thick skin,” found on the
palms of the hands and soles of the feet, consists of five layers while “thin
skin” consists of only four layers. Below is a list of all five layers:
1. The stratum corneum contains many layers of dead, anucleate keratinocytes
completely filled with keratin. The outermost layers are constantly shed.
2. The stratum lucidum contains two to three layers of anucleate cells. This
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Document Summary
The epidermis consists of keratinized stratified squamous epithelium. Four cell types are present: keratinocytes produce keratin, a protein that hardens and waterproofs the skin. Mature keratinocytes at the skin surface are dead and filled almost entirely with keratin: melanocytes produce melanin, a pigment that protects cells from ultraviolet radiation. Melanin from the melanocytes is transferred to the keratinocytes: langerhans cells are phagocytic macrophages that interact with white blood cells during an immune response, merkel cells occur deep in the epidermis at the epidermal dermal boundary. They form merkel discs, which, in association with nerve endings, serve a sensory function. There are several layers making up the epidermis. Thick skin, found on the palms of the hands and soles of the feet, consists of five layers while thin skin consists of only four layers. Below is a list of all five layers: the stratum corneum contains many layers of dead, anucleate keratinocytes completely filled with keratin.
