Chapter 5 Study Skills: Key Terms
What is the integumentary system composed of?
Skin, hair, nails, and glands
What are the two distinct layers of the skin?
the epidermis and the dermis
composed of epithelial cells, the outermost protective shield of the body
Layer beneath the dermis; makes up the bulk of the skin, is a tough leathery layer composed mostly of dense connective tissue
Which of the two layers of the skin is vascularized?
The subcutaneous tissue just deep to the skin; AKA the superficial fascia
What are the functions of the hypodermis?
fat storage, anchoring the skin to the underlying structures, shock absorption, insulation
Keratin cells; produce keratin
Fibrous protein that gives the epidermis its protective properties
Spider-shaped epithelial cells that synthesize melanin; found in the deepest layer of the epidermis
Pigmentation produced by melanocytes; form a pigment shield that protects the nuclei of keratinocytes from the damaging effects of UV radiation in sunlight
Star-shaped cells that arise from bone marrow; AKA Langerhans Cells; ingest foreign substances, key activators of our immune systems
AKA Merkel Cells; Spiky, hemispheric cells present at the epidermal-dermal junction; each cell is intimately associated with a disclike sensory nerve ending, functions as a sensory receptor for touch
"Basal layer"; deepest epidermal layer, attached to the underlying dermis along a wavy borderline; AKA "Stratum Germinativum" due to the many mitotic nuclei pf young keratinocytes seen in this layer;
"Prickly Layer"; superficial to the Stratum Basale, several cell layers thick, contains a system of intermediate filaments, mainly tension-resisting bundles of pre-keratin filaments; keratinocytes in this layer appear to have spines, so they're called "prickle cells"
"Granular Layer"; thin layer superficial to the Stratum Spinosum, where the process of keratinization begins; lamellar granules contain water-resistant glycolipid which slows water loss across the epidermis
"Clear Layer"; visible only in thick skin; thin translucent band just superficial to the stratum granulosum; considered by some to be a subdivision of the Stratum Corneum
"Horny Layer"; consists of flattened, anucleate cells; accounts for up to three-quarters of the epidermal thickness; keratin and thickened plasma membranes protect the skin against abrasion and penetration, glycolipid between cells nearly waterproofs the layer
What are the two layers of the dermis?
Papillary and reticular
Thin, superficial layer of the dermis; areolar connective tissue that is heavily invested with small blood vessels and connective tissue; looseness of the connective tissue allows defense cells to wander freely
Peglike projections from the surface of the papillary layer of the dermis; indent the overlying dermis and lie atop larger mounds of skin in thick skin (dermal ridges)
Skin ridges formed by dermal ridges causing epidermal ridges; are assumed to enhance the gripping ability of the fingers and feet, contribute to our sense of touch by amplifying vibrations detected by the large lamellar corpuscles (receptors) in the dermis
Accounts for about eighty percent of the thickness of the dermis; coarse ,dense irregular connective tissue; contains pockets of adipose cells within its extracellular matrix and thick bundles of interlacing collagen fibers
Cleavage (Tension) Lines
Separations (less dense regions) of collagen fibers in the reticular layer of the dermis; run longitudinally in the skin of the head and limbs and in circular patterns around the neck and trunk
Why are cleavage lines important to surgeons?
Because when an incision is made parallel to these lines, the skin gapes less and heals more readily
Dermal folds that occur at or near joints, where the dermis is tightly secured to deeper structures; since the skin cannot slide easily to accommodate joint movement in such regions, the dermis folds and deep skin creases form (palms of our hands, wrists, fingers, soles, toes, etc.)
Polymer made of tyrosine amino acids that is the only pigment made in the skin; two forms range in color from reddish yellow to brownish black; found only in the deep layers of the epidermis
What is the only pigment made in the skin?
Yellow to orange pigment found in certain plant products; tends to accumulate in the stratum corneum and in fatty tissue of the hypodermis; can be converted to Vitamin A - essential for normal vision as well as epidermal health
oxygenated pigment in the red blood cells that shows as a pinkish hue in fair skin; especially visible in Caucasian skin because it only contains a small amount of melanin and the epidermis is transparent enough to allow hemoglobin's color to show through
"pili"; flexible strands produced by hair follicles that consist largely of dead, keratinized cells
What are the three concentric layers of keratinized cells in a hair?
the medulla, cortex, and cuticle
Central core of the hair, consists of large cells and air spaces; only part of the hair that contains soft keratin, is absent in fine hairs
Bulky layer of the hair surrounding medulla, consists of several layers of flattened cells
Outermost layer of the hair; formed from a single layer of cells overlapping one another like shingles on a roof; formation helps separate neighboring hairs so they do not mat; most heavily keratinized part of the hair; provides strength and helps keep the inner layers tightly compacted
What is hair pigment made of?
Melanocytes at the base of the hair follicles, transferred to the cortical cells
What extra pigment is included to color red hair?
What causes gray/white hair?
When melanin production decreases and air bubbles replace melanin in the hair shaft
Fold down from the epidermal surface into the dermis; may extend to the hypodermis in the scalp; deep end of the follicle expands to form a hair bulb
Deep end of the hair follicle; hair follicle receptor wrapped around each hair bulb
Hair Follicle Receptor (Root Hair Plexus)
Knot of sensory nerve endings that wraps around the hair bulb, allowing the hair to act as a sensitive touch receptor
What signals hair to grow?
The hair papilla, a bit of dermal tissue that protrudes into the hair bulb and contains a knot of capillaries that supply nutrients to the hair and signal it to grow
Which structure causes hair to stand on end due to temperature extremes or strong emotion? What is this phenomenon called?
Arrector Pili Muscle, Piloerection
What are the two classifications hair?
Vellus and terminal
Body hair of children and adult females; pale, fine hairs
Longer, coarser hair of the eyebrows and the scalp; may also be darker
What factors influence hair growth and density?
Nutrition, hormones; conditions that increase local dermal blood flow (chronic physical irritation or inflammation) may enhance local hair growth
Excessive hairiness that is thought to result from an adrenal gland or ovarian tumor that secretes abnormally large amounts of androgens
What does the average hair growth cycle consist of?
Active growth phase (weeks to years) followed by a regressive phase
What happens during the regressive phase of the hair growth cycle?
Hair matrix cells die; follicle base/hair bulb shrivel somewhat, which drags the hair papilla upward to the region of the follicle that doesn't regress; follicle then enters a resting phase of one to three months, after which the cycling part of the follicle regenerates and the matrix proliferates to form a new hair to replace the old one that has fallen out or will be pushed out
Male Pattern Baldness
Genetically determined, sex-influenced condition thought to be caused by a delayed-action gene that changes the response of hair follicles to dihydrotestosterone and shortens the follicle growth cycles so much that many hairs never even emerge from follicles before shedding
What factors can cause hair loss?
Factors that upset the normal balance between hair loss and replacement; high fever, surgery, severe emotional trauma, certain drugs (i.e. chemotherapy drugs), Protein-deficient diets, lactation
Rare condition in which the immune system attacks the follicles and hair falls out in patches
What factors cause hair loss to be permanent?
Any factors that eliminate the follicles (severe burns, excessive radiation, etc.)
Clear, protective covering on the dorsal surface of the distal part of a finger or toe; useful as tools to help pick up small objects or scratch an itch; contain hard keratin
Thickened, proximal portion of the nail bed; responsible for nail growth
Why do nails normally appear pink?
Rich bed of capillaries in the underlying dermis
Skin folds that overlap the proximal and lateral borders of the nail
Proximal nail fold that projects onto the nail body
Thickened region beneath the free edge of the nail where dirt and debris tend to accumulate (informally called the "quick")
Sweat Glands (Sudoriferous Glands)
Glands that are distributed over the entire skin surface except the nipples and parts of the external genitalia; up to 3 million per person
What are the two types of sweat gland?
Eccrine Sweat Glands and Apocrine Sweat Glands
Eccrine (Merocrine) Sweat Glands
Most numerous; particularly abundant on the palms, soles of the feet, and forehead; simple, coiled, tubular gland; secretion is a hyptonic filtrate of the blood released by exocytosis, 99 percent water with some salts, vit C, antibodies, dermcidin, metabolic waste; regulated by the sympathetic division of the autonomic nervous system to prevent overheating of the body
Apocrine Sweat Glands
Largely confined to the axillary and anogenital regions; release product same as eccrine glands; basis of body odor; precise function is not yet known; thought to be the human equivalent of animals' sexual scent glands
Modified apocrine glands found in the lining of the external ear canal; forms earwax
Specialized sweat glands that secrete milk
Sebaceous (Oil) Glands
Simple branched alveolar glands found all over the body except in the thick skin of the palms and the soles; secrete sebum mostly into hair follicles and eventually to the skin surface; when duct is blocked, it forms white or blackheads, active inflammation of the glands causes acne
Oily substance constituted of accumulated lipids and cell fragments
What are the main functions of the skin and its derivatives?
Protection, body temperature regulation, cutaneous sensation, metabolic functions, blood reservoir, excretion
What are the three types of protective barriers in the skin?
Chemical, physical, and biological
What are some of the chemical barriers in the skin?
Skin secretions (dermcidin, bacterial substances in sebum, etc.), melanin
Low pH of skin secretions which retards the multiplication of bacteria on the skin surface
What are some of the substances that do penetrate the skin in limited substances?
Lipid-soluble substances (oxygen, carbon dioxide, fat-soluble vitamins (A, D, E, K) and steroids), oleoresins of certain plants, organic solvents (acetone, dry-cleaning fluid, paint-thinner, etc.), Salts of heavy metals (lead, mercury, etc.), selected drugs, drug agents called penetration enhancers, which help ferry other drugs into the body
What is mostly responsible for the physical impenetrability of the skin?
Multiple layers of dead, flat cells surrounded by water-resistant glycolipids, which blocks most diffusion of water and water-soluble substances between cells
What are some of the biological barriers in the skin?
Dendritic cells of the epidermis, macrophages in the dermis, DNA itself
What is the role of macrophages in the skin for protection?
Dermal macrophages dispose of viruses and bacteria that manage to penetrate the epidermis
What is the role of DNA in the skin for protection?
Electrons in DNA molecules absorb UV radiation and transfer it to the atomic nuclei, which heat up and vibrate, which dissipates to surrounding water molecules; in short, it converts potentially destructive radiation into harmless heat
How does the skin aid in temperature regulation when body temp is too high?
The nervous system stimulates dermal blood vessels to dilate and the sweat glands increase their secretory activity to produce sensible (visible) perspiration; when the perspiration evaporates from the body, it dissipates the heat and effectively cools the body
How does the skin aid in temperature regulation when body temp is too low?
Dermal blood vessels constrict, which causes the warm blood to bypass skin temporarily and allows skin temperature to drop, slowing passive heat loss from the body and conserving body heat
Cutaneous Sensory Receptors
Parts of the nervous system richly present in the skin that allow for cutaneous sensation in the skin
What kind(s) of metabolic functions does the skin perform?
Vitamin D synthesis using sunlight, and therefore inadvertently calcium metabolism; epidermis makes chemical conversions that supplement those of the liver; skin cells make several biologically important proteins
How does the skin act as a blood reservoir?
Dermal vascular supply can hold about five percent of the body's entire blood volume, which is supplied to other body organs when they need a greater blood supply
How does the skin aid in excretion?
Skin eliminates limited amounts of nitrogen wastes (ammonia, urea, and uric acid) through sweat; profuse sweating is an important avenue for water and salt loss
Basal Cell Carcinoma
Least malignant, most common skin cancer; manifests in stratum basale cells and causes lesions on the skin
Squamous Cell Carcinoma
Second most common skin cancer; arises from the keratinocytes of the stratum spinosum; lesions appear as scaly red papules
Most dangerous, most metastatic skin cancer, most resistant to chemotherapy; least common; can begin wherever there is pigment; appears as a spreading brown to black patch
What is the ABCDE Rule for Melanoma Recognition?
Asymmetry, Border Irregularity, Color, Diameter, Evolution
Tissue damage inflicted by intense heat, electricity, radiation, or certain chemicals, all of which denature cell proteins and kill cells in the affected areas
What is the immediate threat to life resulting from severe burns?
Catastrophic loss of body fluids containing proteins and electrolytes, which leads to dehydration and electrolyte imbalance and later renal failure and circulatory shock
Rule of Nines
Method of estimation of the percentage of body surface that is affected by burns; divides the body into 11 areas, each accounting for 9 percent of the total body area (additional one percent is the genitalia
First Degree Burns
Only the epidermis is damaged; symptoms include localized redness, swelling, and pain
Second Degree Burns
Injure the epidermis and the upper region of the dermis; symptoms mimic first-degree symptoms, with the addition of blisters
Third degree burns
Full-thickness burns; burned area appears gray-white, cherry red, or blackened, little to no edema initially, no pain since nerve endings have been destroyed
How are third-degree burns usually treated?
Scaling and various kinds of skin inflammation that become more common as a person ages