A&P 5: The Integumentary System Flashcards
Integumentary system
skin & its derivatives (sweat/oil glands, hairs, nails) that make up a complex set of organs that serve several functions, mostly protective
Hypodermis
subcutaneous tissue just deep to the skin; technically not part of the skin, but shares some of its protective functions
Superficial fascia
another name for the hypodermis because it is superficial to the tough connective tissue wrapping of the skeletal muscles; consists mostly of adipose tissue
Epidermis
keratinized stratified squamous epithelium consisting of 4 distinct cell types & 4-5 distinct layers
Keratinocytes
chief role is to produce keratin
Keratin
fibrous protein that helps give the epidermis its protective properties
Melanocytes
spider-shaped epithelial cells that synthesize the pigment melanin; found in the deepest layer of the epidermis
Dendritic cells
star-shaped cells that arise from bone marrow and migrate to the epidermis
Langerhans cells
another name for Dendritic cells; named after a German anatomist; ingest foreign substances and are key activators of our immune system; their slender processes extend among the surrounding keratinocytes, forming a continuous network
Tactile (Merkel) cells
occasionally present at the epidermal-dermal junction; shaped like a spiky hemisphere, each of these is intimately associated with a disclike sensory nerve ending; functions as a sensory receptor for touch
Thick skin
covers areas subject to abrasion (palms, fingertips, soles of the feet); consists of 5 layers/strata - stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum
Stratum basale
deepest epidermal layer; attached to the underlying dermis along a wavy borderline; consists of a single row of stem cells, a continually renewing cell population, representing the youngest keratinocytes; many mitotic nuclei (rapid division of cells)
Stratum germinativum
another name for the stratum basale
Stratum spinosum
several cell layers thick; contain a weblike system of intermediate filaments, mainly tension-resisting bundles of pre-keratin filaments, which span their cytosol to attach to desmosomes; a prickly layer - kerationocytes appear to have spines
Stratum granulosum
a thin layer consisting of 4-6 cell layers in which a keratinocyte appearance changes drastically; process of keratinization begins
Keratinization
process of cells filling with the protein keratin
Stratum lucidum
clear layer; visible only in thick skin; a thin translucent band just above the stratum granulosum; considered by some to be a subdivision of the superficial stratum corneum, it consists of 2-3 rows of clear, flat, dead keratinocytes with indistinct boundaries
Stratum corneum
horny layer; flattened anucleate cells of the outermost epidermal layer; broad zone of 20-30 cell layers that accounts for up to 3/4 of the epidermal thickness
Dermis
2nd major skin region; strong, flexible connective tissue; “hide”; has a rich supply of nerve fibers, blood vessels and lymphatic vessels; major portion of hair follicles, oil/sweat glands reside here
Papillary layer
thin, superficial layer of areolar connective in which fine interlacing collagen and elastic fibers form a loosely woven mat that is heavily invested with small blood vessels; allows phagocytes & other defensive cells to wander freely, patrolling the area for bacteria that have breached the skin
Dermal papillae
peglike projections from the surface of the papillary layer, indenting the overlying epidermis; many contain papillary loops; others house free nerve endings & touch receptors (tactile/Meissner’s corpuscles)
Friction ridges
skin ridges assumed to enhance the gripping ability of the fingers and feet; also contribute to our sense of touch by amplifying vibrations detected by the large lamellar corpuscles (receptors) in the dermis
Reticular layer
80% of the thickness of the dermis; coarse, irregularly arranged, dense fibrous connective tissue; cutaneous plexus = network of blood vessels that nourishes this layer
Cleavage (tension) lines
less dense regions in between the thick bundles of interlacing collagen fibers; tend to run circularly around the trunk and longitudinally in the limbs
Flexure lines
dermal folds that occur at or near joints, where the dermis is tightly secured to deeper structures
Melanin
polymer made of tyrosine amino acids; two forms, ranging in color from reddish yellow to brownish black
Carotene
yellow to orange pigment found in certain plant products (carrots); tends to accumulate in the stratum corneum and in fatty tissue of the hypodermis; color is most obvious in the palms/soles (where the stratum corneum is the thickest); most intense when large amounts of foods rich in this in pigment are eaten; can be converted into vitamin A in the body (essential for normal vision and epidermal health)
Hemoglobin
oxygenated pigment in the red blood cells circulating through the dermal capillaries; pinkish hue of fair skin reflects the crimson color of this pigment
Skin appendages
hair, hair follicles, nails, sweat glands, and sebaceous (oil) glands
Hairs (pili)
flexible strands produced by hair follicles, consists largely of dead, keratinized cells
Cuticle
outermost part of the hair formed from a single layer of cells overlapping one another; helps separate hairs so it does not mat
Hair follicles
fold down from the epidermal surface into the dermis; in the scalp, may extend into the hypodermis
Hair bulb
the deep end of the follicle (4mm below the skin surface) expands to form this
Hair follicle receptor (root hair plexus)
knot of sensory nerve endings; wraps around each hair bulb; bending the hair stimulates these endings so hair acts as sensitive touch receptors
Peripheral connective tissue sheath
wall of a hair follicle composed of this fibrous sheath derived from the dermis
Epithelial root sheath
inner wall of a hair follicle, derived mainly from an invagination of the epidermis; has external and internal parts, thins as it approaches the hair bulb so only a single layer of epithelial cells covers the papilla
Hair matrix
actively dividing area of the hair bulb that produces the hair; originates in a region called the hair bulge located a fraction of a mm above the hair bulb
Arrector pili
bundle of smooth muscle cells associated with each hair follicle; attached in such a way that its contraction pulls the hair follicle upright and dimples the skin surface to produce goose bumps; contractions force sebum out of hair follicles to the skin surface, where it acts as a skin lubricant
Vellus hair
body hair of children and adult females
Terminal hair
coarser, longer hair of the eyebrows and scalp, which may also be darker than vellus hair
Hirsutism
excessive hairiness; may result from an adrenal gland or ovarian tumor that secretes abnormally large amounts of androgens
Alopecia
baldness
Male pattern baldness
most common type of true/frank baldness; genetically-determined, sex-influenced condition
Nail
scalelike modification of the epidermis that forms a clear protective covering on the dorsal surface of the distal part of a finger or toe; useful as tools to pick up small objects or to scratch
Nail matrix
thickened proximal portion of the nail bed; responsible for nail growth
Nail folds
proximal and lateral borders of the nail are overlapped by these skin folds
Cuticle (eponychium)
proximal nail projects onto the nail body as this
Hyponychium
thickened region beneath the free edge of the nail where dirt and debris tend to accumulate; “quick”; secures the free edge of the nail plate at the fingertip
Sweat glands (sudoriferous glands)
distributed over the entire skin surface except the nipples and parts of the external genitalia; up to 3 million per person
Eccrine sweat glands
AKA merocrine sweat glands; numerous; particularly abundant on the palms, soles of the feet, and forehead; each is a simple, coiled, tubular gland; secretory part lies coiled in the dermis; the duct extends to open in a funnel-shaped pore at the skin surface
Apocrine sweat glands
approximately 2000; largely confined to the axillary and anogenital areas; merocrine glands which release their product by exocytosis; larger than the other type of sweat glands; lie deeper in the dermis or even in the hypodermis; ducts empty into hair follicles; viscous, sometimes with a milky/yellowish color; secretion is odorless but when bacteria on the skin decompose its organic molecules, it takes on a musky, unpleasant odor
Ceruminous glands
modified apocrine glands found in the lining of the external ear canal; secretion mixes with sebum produced by nearby sebaceous glands to form a sticky, bitter substance (earwax), which is thought to deter insects and block entry of foreign material
Mammary glands
specialized sweat glands that secrete milk
Sebaceous glands (oil glands)
simple branched aveolar glands that are found all over the body except in the thick skin of the palms and soles; small on the body trunk and limbs, but quite large on the face, neck, and upper chest
Sebum
oily substance secreted by sebaceous glands; functionally called holocrine glands
Acid mantle
low pH of skin secretions retards the multiplication of skin’s bacteria
Cutaneous sensory receptors
skin is richly supplied with these, which are actually part of the nervous system; classified as exteroceptors because they respond to stimuli arising outside the body
Basal cell carcinoma
least malignant and most common type of skin cancer (80% of cases); stratum basale cells proliferate, invading the dermis and hypodermis; lesions appear most often on sun-exposed areas of the face that appear as shiny, dome-shaped nodules that later develop a central ulcer with a pearly, beaded edge; relatively slow-growing; metastasis seldom occurs before it is noticed; full cure by surgical excision in 99% of cases
Squamous cell carcinoma
second most common skin cancer; arises from the keratinocytes of the stratum spinosum; lesion appears as a scaly reddened papule that arises most often on the head (scalp, ears, lower lip) and hands; tends to grow rapidly and metastasize if not removed; chance of complete cure good if caught early and removed
Melanoma
cancer of melanocytes; most dangerous skin cancer; highly metastic, resistant to chemotherapy; accounts for 2-3% of skin cancers; can begin wherever there is a pigment; most appear spontaneously (1/3 from preexisting moles); metastasizes rapidly to surrounding lymph and blood vessels
ABCD Rule
rule for recognizing melanoma: asymmetry, border irregularity, color, diameter; sometimes E added (elevation above the skin surface)
Burn
tissue damage inflicted by intense heat, electricity, radiation, or certain chemicals, all of which denature cell proteins and kill cells in affected areas
Rule of nines
approximating method that divides the body into 11 areas, each accounting for 9% of total body area, plus an additional area surrounding the genitals for 1% of body surface area
First-degree burns
burn in which only the epidermis is damaged; symptoms include localized redness, swelling, and pain; tend to heal in 2-3 days without special attention; sunburn is an example
Second-degree burns
injure the epidermis and the upper region of the dermis; symptoms mimic those of 1st degree burns, but blisters also appear; burned area is red and painful, but skin regeneration occurs with little or no scarring within 3-4 weeks if care is taken to prevent infection; along with 1st degree burns = partial-thickness burns
Third-degree burns
involve the entire thickness of the skin; burned area appears gray-white, cherry red, or blackened; initially there is little or no edema; nerve endings have been destroyed, so the burned area is not painful; skin might eventually regenerate but skin grafting is advised
Dermatitis
skin inflammation
