5.5: Key Terms
- Page ID
- 108211
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| Words (or words that have the same definition) | The definition is case sensitive | (Optional) Image to display with the definition [Not displayed in Glossary, only in pop-up on pages] | (Optional) Caption for Image | (Optional) External or Internal Link | (Optional) Source for Definition |
|---|---|---|---|---|---|
| (Eg. "Genetic, Hereditary, DNA ...") | (Eg. "Relating to genes or heredity") |  | The infamous double helix | https://bio.libretexts.org/ | CC-BY-SA; Delmar Larsen |
| Word(s) | Definition | Image | Caption | Link | Source |
|---|---|---|---|---|---|
| acne | skin condition due to infected sebaceous glands | ||||
| albinism | genetic disorder that affects the skin, in which there is no melanin production | ||||
| anagen | active phase of the hair growth cycle | ||||
| apocrine sweat gland | type of sweat gland that is associated with hair follicles in the armpits and genital regions | ||||
| arrector pili | smooth muscle that is activated in response to external stimuli that pull on hair follicles and make the hair “stand up” | ||||
| 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 | ||||
| basal cell carcinoma | cancer that originates from basal cells in the epidermis of the skin | ||||
| bedsore | sore on the skin that develops when regions of the body start necrotizing due to constant pressure and lack of blood supply; also called decubitis ulcers | ||||
| callus | thickened area of skin that arises due to constant abrasion | ||||
| catagen | transitional phase marking the end of the anagen phase of the hair growth cycle | ||||
| corn | type of callus that is named for its shape and the elliptical motion of the abrasive force | ||||
| cortex | in hair, the second or middle layer of keratinocytes originating from the hair matrix, as seen in a cross-section of the hair bulb | ||||
| cuticle | in hair, the outermost layer of keratinocytes originating from the hair matrix, as seen in a cross-section of the hair bulb | ||||
| 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 | ||||
| desmosome | structure that forms an impermeable junction between cells | ||||
| eccrine sweat gland | type of sweat gland that is common throughout the skin surface; it produces a hypotonic sweat for thermoregulation | ||||
| eczema | skin condition due to an allergic reaction, which resembles a rash | ||||
| elastin fibers | fibers made of the protein elastin that increase the elasticity of the dermis | ||||
| eleiden | clear protein-bound lipid found in the stratum lucidum that is derived from keratohyalin and helps to prevent water loss | ||||
| epidermis | outermost tissue layer of the skin | ||||
| eponychium | nail fold that meets the proximal end of the nail body, also called the cuticle | ||||
| external root sheath | outer layer of the hair follicle that is an extension of the epidermis, which encloses the hair root | ||||
| first-degree burn | superficial burn that injures only the epidermis | ||||
| fourth-degree burn | burn in which full thickness of the skin and underlying muscle and bone is damaged | ||||
| glassy membrane | layer of connective tissue that surrounds the base of the hair follicle, connecting it to the dermis | ||||
| hair | keratinous filament growing out of the epidermis | ||||
| hair bulb | structure at the base of the hair root that surrounds the dermal papilla | ||||
| hair follicle | cavity or sac from which hair originates | ||||
| hair matrix | layer of basal cells from which a strand of hair grows | ||||
| hair papilla | mass of connective tissue, blood capillaries, and nerve endings at the base of the hair follicle | ||||
| hair root | part of hair that is below the epidermis anchored to the follicle | ||||
| hair shaft | part of hair that is above the epidermis but is not anchored to the follicle | ||||
| hypodermis | connective tissue connecting the integument to the underlying bone and muscle | ||||
| hyponychium | thickened layer of stratum corneum that lies below the free edge of the nail | ||||
| integumentary system | skin and its accessory structures | ||||
| internal root sheath | innermost layer of keratinocytes in the hair follicle that surround the hair root up to the hair shaft | ||||
| keloid | type of scar that has layers raised above the skin surface | ||||
| 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 | ||||
| lunula | basal part of the nail body that consists of a crescent-shaped layer of thick epithelium | ||||
| medulla | in hair, the innermost layer of keratinocytes originating from the hair matrix | ||||
| Meissner corpuscle | (also, tactile corpuscle) receptor in the skin that responds to light touch | ||||
| 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 | ||||
| melanoma | type of skin cancer that originates from the melanocytes of the skin | ||||
| 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 | ||||
| metastasis | spread of cancer cells from a source to other parts of the body | ||||
| nail bed | layer of epidermis upon which the nail body forms | ||||
| nail body | main keratinous plate that forms the nail | ||||
| nail cuticle | fold of epithelium that extends over the nail bed, also called the eponychium | ||||
| nail fold | fold of epithelium at that extend over the sides of the nail body, holding it in place | ||||
| nail root | part of the nail that is lodged deep in the epidermis from which the nail grows | ||||
| Pacinian corpuscle | (also, lamellated corpuscle) receptor in the skin that responds to vibration | ||||
| 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 | ||||
| rickets | disease in children caused by vitamin D deficiency, which leads to the weakening of bones | ||||
| scar | collagen-rich skin formed after the process of wound healing that is different from normal skin | ||||
| sebaceous gland | type of oil gland found in the dermis all over the body and helps to lubricate and waterproof the skin and hair by secreting sebum | ||||
| sebum | oily substance that is composed of a mixture of lipids that lubricates the skin and hair | ||||
| second-degree burn | partial-thickness burn that injures the epidermis and a portion of the dermis | ||||
| squamous cell carcinoma | type of skin cancer that originates from the stratum spinosum of the epidermis | ||||
| 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 | ||||
| stretch mark | mark formed on the skin due to a sudden growth spurt and expansion of the dermis beyond its elastic limits | ||||
| sudoriferous gland | sweat gland | ||||
| telogen | resting phase of the hair growth cycle initiated with catagen and terminated by the beginning of a new anagen phase of hair growth | ||||
| third-degree burn | burn that penetrates and destroys the full thickness of the skin (epidermis and dermis) | ||||
| vitamin D | compound that aids absorption of calcium and phosphates in the intestine to improve bone health | ||||
| 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 |