6.14: Glossary

Key Terms and Definitions

• Albinism - genetic disorder that affects the skin, in which there is no melanin production
• Basal cell - type of stem cell found in the stratum basale and in the hair matrix that continually undergoes cell division, producing the keratinocytes of the epidermis
• Dermal papilla - (plural = dermal papillae) extension of the papillary layer of the dermis that increases surface contact between the epidermis and dermis
• Dermis - layer of skin between the epidermis and hypodermis, composed mainly of connective tissue and containing blood vessels, hair follicles, sweat glands, and other structures
• Elastin fibers - fibers made of the protein elastin that increase the elasticity of the dermis
• Epidermis - outermost tissue layer of the skin
• Hypodermis - connective tissue connecting the integument to the underlying bone and muscle
• Integumentary system - skin, hair, nail and its accessory structures
• Keratin - type of structural protein that gives skin, hair, and nails its hard, water-resistant properties
• Keratinocyte - cell that produces keratin and is the most predominant type of cell found in the epidermis
• Keratohyalin - granulated protein found in the stratum granulosum
• Langerhans cell - specialized dendritic cell found in the stratum spinosum that functions as a macrophage
• Melanin - pigment that determines the color of hair and skin
• Melanocyte - cell found in the stratum basale of the epidermis that produces the pigment melanin
• Melanosome - intercellular vesicle that transfers melanin from melanocytes into keratinocytes of the epidermis
• Merkel cell - receptor cell in the stratum basale of the epidermis that responds to the sense of touch
• Papillary layer - superficial layer of the dermis, made of loose, areolar connective tissue
• Reticular layer - deeper layer of the dermis; it has a reticulated appearance due to the presence of abundant collagen and elastin fibers
• Stratum basale - deepest layer of the epidermis, made of epidermal stem cells
• Stratum corneum - most superficial layer of the epidermis
• Stratum granulosum - layer of the epidermis superficial to the stratum spinosum
• Stratum lucidum - layer of the epidermis between the stratum granulosum and stratum corneum, found only in thick skin covering the palms, soles of the feet, and digits
• Stratum spinosum - layer of the epidermis superficial to the stratum basale, characterized by the presence of desmosomes
• Vitiligo - skin condition in which melanocytes in certain areas lose the ability to produce melanin, possibly due an autoimmune reaction that leads to loss of color in patches