Chapter 5
root
the portion of a hair deep to the shaft that penetrates into the dermis, and sometimes into the hypodermis
hemoglobin
Light-skinned individuals have little melanin in the epidermis, making their epidermis appear translucent with a skin color ranging from pink to red depending on the level of oxygen in the blood moving through capillaries in the dermis; the red color is due to ___________
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Mnemonic for the 5 layers of the epidermis
keratinocytes, Langerhans cells, melanocytes, tactile cells
What are the four principle types of cells in the epidermis? (alphabetical)
external root sheath
a downward continuation of the epidermis that makes up part of the hair follicle
hair matrix
a germinal layer of cells found in the bulb of each hair that is the site of cell division; the cells of this layer are responsible for the growth of existing hairs, and they produce new hairs when old hairs are shed
cuticle
a narrow band of epidermis that extends over the margin of the nail body
hair root plexus
a sensory nerve ending surrounding each hair follicle that is sensitive to touch; generates nerve impulses if the hair shaft is moved
keratin
a tough, fibrous protein that helps protect the skin and underlying tissues from abrasions, heat, microbes, and chemicals
carotene
a yellow-orange pigment that its stored in the stratum corneum and dermis after eating foods rich in the pigment (such as carrots and egg yolks)
melanin
a yellow-red or brown-black pigment that contributes to skin color and absorbs damaging ultraviolet light; once inside keratinocytes, this pigment shields the nuclear DNA from UV light
calcitriol
active form of vitamin D that is created starting with the activation of a precursor molecule in the skin by UV light
acne
an inflammation of sebaceous glands that usually begins at puberty when the sebaceous glands are stimulated by androgens
cutaneous membrane
another name for skin
keratinization
as keratinocytes are pushed toward the surface by the continuously dividing cells of the stratum basale, they receive fewer nutrients from the blood supply and eventually die; they also accumulate more and more keratin through this process
hair follicle
cavity surrounding the root of the hair which is made up of an external root sheath and an internal root sheath
tactile cells, Merkel cells
cells of the epidermis that are least numerous; they are located in the deepest layer of the epidermis, where they contact a nerve cell disc (of the same name) to function in detecting touch; (*may be called two names, give both)
keratinocytes
cells of the epidermis that are the most numerous and produce keratin; also produce lamellar granules, which release a waterproofing sealant that decreases water entry and loss
melanocytes
cells of the epidermis that have long, slender projections that extend between the keratinocytes and transfer melanin to them
Langerhans cells
cells of the epidermis that participate in immune response against microbes that invade the skin by helping other immune system cells recognize an invading microbe and destroy it
psoriasis
chronic skin disorder in which keratinocytes divide and move more quickly than normal from the stratum basale to the stratum corneum; normally the entire process takes about 4 weeks, but with this disorder the entire process can occur in 7-10 days
amount of melanin
differences in skin color are mainly due to the (amount of melanin/number of melanocytes)
lamellar granules
distinctive feature of keratinocytes of the stratum granulosum that release a lipid-rich secretion that is deposited in the spaces between cells of the superficial strata; the lipid-rich secretion acts as a water-repellant sealant
apocrine sweat glands
division of sudoriferous glands distributed mainly in the skin of the axilla, groin, areolae, and bearded regions of adult males whose secretion is the comprised with the addition of lipids and proteins; their secretory ducts open into hair follicles, and the secretory portion is located mostly in the hypodermis; when bacteria on the surface of the skin metabolizes the components of the secretions, an unpleasant odor arises; do not function until after puberty
eccrine sweat glands
division of sudoriferous glands distributed throughout the skin of most regions of the body whose secretion functions in regulating body temperature through evaporation
maturation phase
final stage of deep wound healing in which the scab sloughs off as the epidermis is restored to normal thickness
nevus
freckles and liver/age spots are accumulations of melanin; a ________, or mole, is a round, flat, or raised area that represents a benign localized overgrowth of melanocytes
pili
hairs; on the scalp, they protect the head from injury and the sun's UV rays; eyebrows and eyelashes protect the eyes from foreign particles, just as hair in the nose and external ear canal protect those structures; also functions in sensing light touch; each hair is composed of columns of dead, keratinized epidermal cells bonded together by extracellular proteins
stratum spinosum
layer of the epidermis arranged in 8-10 layers of many sided keratinocytes fitting closely together; keratinocytes of this layer shrink and pull apart when prepared for microscopic examination, so they appear to be covered in spines (hence the name); Langerhans cells and melanocytes are also found in this layer; (labelled D in the image)
stratum basale
layer of the epidermis composed of a single row of cuboidal or columnar keratinocytes; some cells in this layer are stem cells; melanocytes and tactile cells are scattered among the keratinocytes of this layer as well; (labelled E in the image)
stratum corneum
layer of the epidermis consisting of 25-30 layers of flattened, dead keratinocytes that are continuously shed and replaced by cells from the deeper strata; its multiple layers of dead cells help to protect deeper layers from injury and microbial invasion; (labelled A in the image)
stratum lucidum
layer of the epidermis present only in thick skin of the fingerprints, palms, and soles; it consists of 4-6 layers of flattened clear, dead keratinocytes that contain large amounts of keratin and thickened plasma membranes; (labelled B in the image)
stratum granulosum
layer of the epidermis that consists of 3-5 layers of flattened keratinocytes; marks the transition between the deeper, metabolically active strata and the dead cells of the more superficial strata; distinctive presence of lamellar granules within the keratinocytes; (labelled C in the image)
ceruminous glands
modified sweat glands in the external ear that produce a waxy secretion
pacinian corpuscles
nerve endings found in the hypodermis (and sometimes the dermis) that are sensitive to pressure
papilla
nipple-shaped indentation on the bulb of the hair follicle that contains many blood vessels that nourish the growing hair follicle
sebaceous glands
oil glands; these are connected to hair follicles (with few exceptions); the secreting portion lies in the dermis and usually opens into the hair follicle
thick skin
one of two major types of skin that is primarily due to a increased number of layers in the stratum corneum; this skin does not contain hair or sebaceous glands, but does have more numerous sweat glands, and denser sensory receptors
bulb
onion-shaped structure at the base of each hair follicle that houses the papilla of the hair; also contains a germinal layer of cells called the hair matrix, the site of cell division
medulla
the pigment of hair is found in which layer of hair cells
pallor
paleness of the skin that may occur in conditions such as shock or anemia
free edge
part of the nail body that may extend past the distal end of the finger or toe; appears white because there are no underlying capillaries
nails
plates of tightly packed, hard, keratinized epidermal cells that form a clear, solid covering over the dorsal surfaces of the distal portions of the fingers and toes
fibrosis
process of scar tissue formation; scar tissue differs from normal skin tissue in that its collagen fibers are more densely arranged, it has less elasticity, fewer blood vessels, and may not contain the same number of hairs, skin glands, or sensory structures
internal root sheath
produced by the hair matrix and forms a tubular sheath of epithelium between the external root sheath and the hair
erythema
redness of the skin that is caused by engorgement with blood capillaries in the dermis due to skin injury, exposure to heat, infection, inflammation, or allergic reactions
sebum
sebaceous glands secrete this oily substance, a mixture of triglycerides, cholesterol, proteins, and inorganic salts; coats the surface of hairs and helps keep them from drying; also prevents excessive evaporation of water from the skin, keeping it soft and pliable; inhibits growth of some bacteria
Meissner corpuscles
sensory receptors found in the dermal papillary region that are sensitive to touch
free nerve endings
sensory receptors found in the dermal papillary region that initiate signals that produce sensations of warmth, coolness, pain, tickling, and itching
subungal
situated or occurring under a fingernail or toenail
arrector pili
smooth muscle cell bundle that extends from the superficial dermis of the skin to the dermal root sheath around around the hair follicle; autonomic nerve endings stimulate these muscles to contract (pulling the hair perpendicular to the skin surface) under certain conditions; this action also causes goosebumps
sudoriferous glands
sweat glands; release perspiration into hair follicles or onto the skin surface through pores
integumentary system
system composed of the skin, hair, nails, and skin glands
collagen, elastic
the combination of these two fibers in the reticular region provides the skin with strength, extensibility (ability to stretch), and elasticity (ability to return to original shape after stretching)
cerumen
the combined secretion of the ceruminous and sebaceous glands is the yellowish material that provides a sticky barrier that impedes the entrance of foreign bodies in the external auditory canal; also waterproofs the canal and prevents bacteria ad fungi from entering cells
dermis
the deeper, thicker, vascular portion of the skin which is composed of dense, irregular connective tissue containing a woven network of collagen and elastic fibers that provide great tensile strength
dermal root sheath
the dermis surrounding the hair follicle (external and internal root sheaths) and therefore the hair root
inflammatory phase
the initial phase of deep wound healing in which bleeding produces a blood clot in the wound, loosely uniting the wound edges; this is followed by a response that helps eliminate microbes, foreign material, and dying tissue; the permeability and diameter of local blood vessels is increased enhancing delivery of white blood cells and mesenchymal cells (which develop into fibroblasts)
skin
the largest organ in the body in both surface area and weight; structurally consists of two principle parts: the dermis and the epidermis
nail matrix
the proximal portion of the epithelium deep to the nail root where cells divide to produce new nail cells
nail root
the proximal portion of the nail that is buried in a fold of skin
migratory phase
the second phase of deep wound healing which the blood clot becomes a scab, and epithelial cells migrate beneath the scab to bridge the wound; deep to the epithelial cell bridge, fibroblasts migrate into the wound area and begin synthesizing collagen fibers and glycoproteins to become scar tissue, and damaged blood vessels begin to regrow
medulla, cortex, cuticle
the shaft and root of hair both consist of three concentric layers of hair cells; give the three layers in order from innermost to outermost
shaft
the superficial portion of a hair that projects from the surface of the skin
epidermis
the superficial, thinner, avascular portion of the skin which is composed of keratinized stratified squamous epithelial tissue
granulation tissue
the tissue filling a deep wound during the migratory phase of healing
nail body
the visible portion of the nail; most appears pink because of blood flowing through underlying capillaries
lunula
the whitish, crescent-shaped proximal end of the nail body
epidermal ridges
these are the series of ridges and grooves present on the surfaces of palms, fingers, soles, and toes; they project downward from the epidermis into the dermis between the dermal papillae, and form an extremely strong bond to resist lateral forces that attempt to separate the epidermis from the dermis; they also increase the surface area of the epidermis, thus increasing grip by increasing friction; ducts of sweat glands open at the tops of these and form fingerprints
dermal papillae
these small, nipple-shaped projections into the undersurface of the epidermis that greatly increase the surface area of the dermis papillary region; they contain capillary loops and sensory receptors (Meissner corpuscles and free nerve endings)
proliferative phase
third phase of deep wound healing characterized by extensive growth of epithelial cells beneath the scab
reticular region
this division of the dermis is attached to the hypodermis (subQ) and contains bundles of thick collagen fibers, some elastic fibers, scattered fibroblasts, adipose cells, and various wandering cells (such as macrophages); blood vessels, nerves, hair follicles, sebaceous glands, and sudoriferous glands occupy the spaces between fibers
papillary region
this division of the dermis makes up about one fifth of the total dermis; it contains thin collagen and fine elastic fibers, and has a surface area greatly increased by dermal papillae
jaundice
this is due to the buildup of the yellow pigment bilirubin in the skin, giving the skin and sclera of eyes a yellowish appearance
subcutaneous layer
this layer that is deep to the skin consists of areolar and adipose tissues; also called the hypodermis; serves as a storage depot for fat and contains large blood vessels that supply the skin
epidermal growth factor
when an epidermal wound occurs, surrounding stratum basale cells break contact with the basement membrane and migrate into the wounded area; then this hormone stimulates the basal stem cells to divide and replace the ones that have moved into the wound
cyanotic
when blood is not picking up an adequate amount of oxygen from the lungs, as in someone who has stopped breathing, the mucous membranes, nail beds, and skin appear bluish or __________
