Skin Anatomy: Epidermis and Dermis

Skin Structure

• The skin consists of two main layers: the epidermis (superficial epithelial layer) and the dermis (deep underlying connective tissue layer)
• The skin rests on the hypodermis, a connective tissue rich in adipose tissue

Cells of Epidermis

• Keratinocytes: most abundant type, found in the epidermis
• Melanocytes: found scattered in the stratum basale, produce melanin pigment
• Langerhans cells: found in the stratum spinosum, have a role in immune response
• Merkels cells: found among keratinocytes in the stratum basale, function as mechanoreceptors

Layers of Epidermis

• Stratum germinativum (basal layer): single layer of cuboidal to columnar cells, rests on basement membrane
• Stratum spinosum (prickle cell layer): several layers of polyhedral cells
• Stratum granulosum: 3-5 layers of cells that become flattened as they are pushed upward, accumulate granules of two types
• Stratum lucidum (clear layer): 3-5 layers of flattened cells
• Stratum corneum (cornified layer): dead, scale-like cells

Melanocytes

• Produce melanin pigment, which is transferred to adjacent keratinocytes
• Melanin synthesis depends on the presence of tyrosinase enzyme located in melanosomes, formed in the RER and packed in Golgi

Langerhans Cells

• Located in the stratum spinosum, contain specific rod-like inclusions called Birbeck granules
• Function as antigen-presenting cells, phagocytose foreign antigens, process and present them on their surface to T-lymphocytes

Merkel Cells

• Originate from the neural crest, located among keratinocytes in the stratum basale
• Function as mechanoreceptors, associated with unmyelinated sensory nerve fibers

Dermis

• Consists of two layers: an outer papillary layer and an inner reticular layer containing thick collagen bundles
• Most of the nerve supply and all the vascular supply is found in the dermis and hypodermis

Sweat Glands

• Eccrine glands: simple coiled tubular glands, found all over the body, most numerous in the palms and soles
• Apocrine glands: simple coiled tubular glands, found in the axilla and pubic regions

Sebum Production

• Sebum is secreted by sebaceous glands, which open into the upper part of the hair follicle
• Sebum has bacteriostatic, fungistatic properties, and softens the stratum corneum

Learn about the layers and cells of the epidermis and dermis, including keratinocytes, melanocytes, and more. Explore the structure and function of the skin's outer and underlying layers.