Chapter 5: Integumentary
how does melanin work?
they cluster on the superficial side of keratinocytes between the incoming radiation and the cell nuclei, thus shielding the cell nuclei from UV rays which can damage DNA and cause cancer
what is the purpose of the projections present in the dermal papillae?
they increase the S.A. for exchange of gases, nutrients, and waste products between these layers, RECALL THAT EPIDERMIS IS AVASCULAR and thus RELIES on the diffusion of these materials from the underlying dermis
what is the purpose of the interdigitation observed in the dermal papillae?
they strengthen the dermal-epidermal junction and thus REDUCES BLISTER FORMATION
What types of cells are found in the dermis, and how does each contribute to the functions of skin?
Fibroblasts in the dermis produce the collagen and elastic fibers of the dermis. These fibers give the skin strength, resilience, and recoil properties; the macrophages, mast cells, and white blood cells function to fight infections; adipocytes store energy.
secretion of sebum is stimulated by:
HORMONES, especially androgens which skyrocket in production during puberty in both males and females
T/F The reticular layer is named for its networks of collagen fibers, the name does NOT imply any special abundance of reticular fibers.
TRUE
T/F In all but the darkest people, melanocytes respond to UVR by increasing the production of melanin and increasing its transfer to keratinocytes, the protective response we know as sun-tanning.
TRUE
T/F Keratinocytes produce antibiotics and enzymes that detoxify the harmful chemicals to which our skin is exposed.
TRUE
T/F Basal keratinocytes contain more melanin than do the melanocytes themselves.
TRUE, because melanin is produced in membrane-walled granules by melanocytes but shortly after the melanin is quickly transferred through the cell processes to nearby keratinocytes creating a build up there thus you'll most likely find the major bulk of melanin in basal keratinocytes
How does the keratin in hair and nails differ from the keratin in the epidermis?
The keratin in hair and nails is a hard keratin: it is tougher and more durable, and its cells do not flake off.
Which pigment causes the large variation in human skin color?
The large variation in skin color in humans is due to variation in the type and amount of melanin in the epidermal layer.
Melanocytes also secrete a variety of signaling molecules in response to.....
UV radiation that act to modulate the immune response in the skin, these signaling molecules influence the inflammatory response and may have other regulatory functions
the subcutaneous tissue thickens with...
WEIGHT GAIN, in women it first accumulates in the thighs and breasts and for men it first accumulates in the anterior abdomen as a "beer belly"
Clinical application- Cyanosis
When hemoglobin is poorly oxygenated, both the blood and the skin of Caucasians appear BLUE, a condition called cyanosis Skin often becomes cyanotic in people with heart failure or severe respiratory disorders. In dark-skinned people, the skin may be too dark to reveal the color of the underlying vessels, but cyanosis can be detected in the mucous membranes and nail beds.
stratum spinosum
several cell layers thick, the cells here contain thick bundles of intermediate filaments which consist of a tension-resisting protein pre-keratin and MITOSIS OCCURS HERE, BUT LESS OFTEN THAN IN THE BASAL LAYER
stratum spinosum definition from diagram
several layers of keratinocytes unified by DESMOSOMES, cells contain THICK bundles of intermediate filaments made of pre-keratin.
why does the plasma membrane in keratinocytes thicken?
so that they become MORE RESISTANT to destruction
mammary glands
specialized sweat glands highly modified to secrete milk.
what is the function of epidermal ridges?
increase friction, enhance the gripping ability of the hands and feet, interestingly enough the patterns of these ridges are genetically determined and UNIQUE TO EACH PERSON
stratum corneum
is the MOST superficial layer, 20-30 layers of DEAD cells represented only by flat membranous sacs filled with keratin. Glycolipids in extracellular space.
keratohyalin granules help form
keratin in the more superficial layers
epidermis
keratinized stratified squamous epithelium that contains 4 distinct types of cells: keratinocytes, melanocytes, tactile epithelial cells, and dendritic cells
deep dermal plexus
located between the subcutaneous tissue and the dermis, nourishes the subcutaneous tissue and the structures located within the deeper portions of the dermis
stem cells
located in a bulge in the superficial region of the external root sheath, give rise to the HAIR MATRIX CELLS and form the hair shaft as well as new epidermal cells
more superficial subpapillary plexus
located just below the dermal papillae, supplies the more superficial dermal structures, the dermal papillae, and the EPIDERMIS
functions of sebum include:
making our skin and hair oily, sebum collects dirt, softens and lubricates the hair and skin, prevents hair from becoming brittle, and keeps the epidermis from cracking
the 3 pigments that contribute to skin color are:
melanin, carotene, and hemoglobin
What type of tissue makes up (a) the papillary layer of the dermis, (b) the reticular layer of the dermis, and (c) the subcutaneous tissue?
(a) The papillary layer of the dermis is composed of loose areolar connective tissue. (b) The reticular layer is dense irregular connective tissue. (c) The subcutaneous tissue contains both loose areolar and adipose connective tissue.
explain different shaft projections and their consequential hair type formation:
(a) flat, ribbon-like in cross section= hair is kinky (b) oval in section= hair is wavy (c) perfectly round= hair is straight
stratum granulosum
1-5 layers of flattened cells, organelles deteriorating, cytoplasm full of lamellar granules (release lipids), and keratohyaline granules.
hair consists of 3 concentric layers of keratinized cells:
1. medulla: consists of large cells and air spaces, absent in fine hairs 2. cortex: surrounding the medulla, consists of several layers of flattened cells 3. cuticle: single layer of cells that overlap one another from below like shingles on a roof and the pattern is what helps keep neighboring hairs apart so that the hair does not mat
melanocytes
10-25% of the cells in the stratum basale, MAKE the dark skin pigment MELANIN which is made in membrane-walled granules and then transferred through the cell processes to nearby keratinocytes
Should a dark-skinned person living in the northern latitudes have concerns about vitamin D production? Why or why not?
A dark-skinned individual in northern latitudes would have concerns about vitamin D production. Greater amounts of melanin in darker skin reduces UV penetration. Because there is less sunlight in the winter months, dark skin produces less vitamin D than light skin.
stratum lucidum (clear layer)
ONLY IN THICK SKIN, thin translucent band that consists of a few rows of flat, dead keratinocytes
main function of sparse body hair in humans?
to sense things that lightly touch the skin, hair on scalp protects the head from direct sunlight and heat loss, eyelashes shield the eyes and nose hairs filter large particles such as insects and lint from inhaled air
lamellar granules contain
waterproofing glycolipids that are secreted into the extracellular space, and this GLYCOLIPID along with tight junctions between adjacent cells plays A MAJOR ROLE IN SLOWING WATER LOSS ACROSS THE EPIDERMIS
carotene
yellow-orange pigment, the body obtains from vegetable sources such as carrots and tomatoes and it tends to accumulate in the stratum corneum, of the epidermis and in the fat of the subcutaneous tissue
Apocrine glands become active in adolescence. Are these also the glands that cause acne?
Apocrine sweat glands do not cause acne. Acne is caused by sebaceous glands, which also become active at adolescence.
clinical application: freckles and moles NOTES
Both freckles and moles (nevi) are localized accumulations of melanin in the skin. In freckles, the increase in melanin is restricted to the basal layer of the epidermis. Freckles form as a result of repeated exposure to sunlight. Individuals with light complexions are more prone to freckle formation. Moles form when clusters of melanocytes are transformed into melanin-containing cells (nevus cells). These clusters are located in the basal layer of the epidermis and in the top layers of the dermis. Moles form shortly after birth and can appear anytime through young adulthood.
Which functions of skin are performed by cells located in the epidermis?
Cells in the epidermis function in protection (from UV radiation, water loss, chemicals, invading microorganisms, and scrapes and abrasions), production of vitamin D, and sensory reception.
stratum basale (basal layer)/ stratum germinativum
DEEPEST epidermal layer, is firmly attached to the underlying dermis along a wavy borderline
stratum basale
DEEPEST epidermal layer, one row of actively mitotic STEM cells, some newly formed cells become part of the more superficial layers. You tend to see occasional MELANOCYTES and DENDRITIC cells.
How do the dermal blood vessels regulate body temperature?
Dermal blood vessels dilate to release heat when the body is warm, and they constrict to prevent the loss of heat when the body is cold.
Which functions of skin are performed by eccrine glands?
Eccrine glands function in temperature regulation (sweat causes evaporative cooling) and excretion (sweat contains metabolic wastes, salts, and water).
Which type of tissue forms eccrine glands? (Look at the micrograph of the eccrine gland in Figure 5.8b).
Eccrine sweat glands, like most glands, are formed from cuboidal epithelium. In a micrograph, this epithelium may appear stratified because of the section.
T/F Spine-like extensions seen in keratinocytes residing in the skin's stratum spinosum exist in living cells.
FALSE, these spines do NOT exist in living cells, they are actually artifacts created during tissue preparation when the cells shrink while holding tight at their many desmosomes (the Velcro zippers)
Clinical Application: Acne NOTES
In some teenagers, so much sebum is produced that it cannot be ducted from the glands quickly enough. When a sebaceous gland becomes blocked by sebum, a whitehead appears on the skin surface. If the material oxidizes and dries, it darkens to form a blackhead (the dark color of a blackhead is not due to dirt). Blocked sebaceous glands are likely to be infected by bacteria, producing a pimple. The bacteria break down the sebum into irritating fatty acids. These acids, along with the bacterial products themselves, induce inflammation, especially when the entire infected mass bursts out of the follicle into the surrounding dermis. The acne that results can be mild or extremely severe, leading to permanent scarring. The treatment of acne addresses the different causal factors: increased sebum production and formation of whiteheads, inflammation, and bacterial infection. Topical medications such as benzoyl peroxide treat inflammatory acne; topical retinoids, derivatives from vitamin A, act to prevent the formation of whiteheads; and antibiotics destroy acne-causing bacteria. Often combinations of treatments are used for maximal results.
Tattoos NOTES
Lasers are now used for tattoo removal, but even this approach results in only moderate success. Lasers break the ink molecules into smaller particles to facilitate pickup and drainage by lymphatic vessels. Colored tattoos require the use of several different lasers that emit light at different frequencies to remove each of the different pigments. Interesting new work with mice indicates that the permanence of tattoos is a result of the ingestion of the tattoo ink by dermal macrophages, white blood cells that phagocytose foreign matter. It has been proposed that temporary inhibition of dermal macrophages during laser treatment may block the reingestion of tattoo ink by new macrophages and enhance lymphatic clearance of ink molecules from the dermis, thus resulting in better tattoo removal. Some, but not all, of the pigments used in tattoos have U.S. Food and Drug Administration approval for use on the skin surface; however, none are approved for intradermal use. Tattooing involves needles, bleeding, and risk of allergic reactions and bloodborne infectious diseases such as hepatitis transmitted either through needles or contaminated pigments. Even with the availability of laser removal techniques, it makes sense to consider the risks of getting a tattoo.
graying or whitening of hair results from a decrease in the production of....
MELANIN, the replacement of melanin is colorless air bubbles in the hair shaft
keratinocytes
MOST ABUNDANT epidermal cell, PRODUCE KERATIN which is a tough fibrous protein that gives the epidermis its protective properties, they also provide physical and mechanical protection
stratum corneum (horny layer)
MOST EXTERNAL part of the epidermis, is many cells thick and it is WHAT DEFINES thick skin from thin skin, the dead keratinocytes that compose this layer are flat sacs completely FILLED WITH KERATIN since all else disintegrated upon cell death
T/F Although dark-skinned people have a darker melanin, more granules, and more pigment in each melanocyte, they do NOT have more melanocytes in their skin.
TRUE
clinical application- skin's response to friction
Persistent friction (from a poorly fitting shoe, for example) causes a thickening of the epidermis called a callus. Short-term but severe friction (from using a hoe, for example) can cause a blister, the separation of the epidermis from the dermis by a fluid-filled pocket.
dendritic cells
STAR-shaped cells that are part of the immune system, they POLICE the outer body surface using receptor-mediated endocytosis to take up foreign proteins (antigens) that have invaded the epidermis THEN they leave the skin and travel to a nearby lymph node and initiate an immune response to all foreign cells that carry the antigen
thin skin
covers the rest of the body, only 4 strata present
Epithelial root sheath.
The epithelial root sheath is derived from the epidermis. It has two components: the EXTERNAL ROOT SHEATH, a direct continuation of the epidermis; and the INTERNAL ROOT SHEATH, which is derived from the matrix cells.
Name the five major functions of skin.
The five main functions of skin are protection, body temperature regulation, excretion, production of vitamin D, and sensory reception.
Glassy membrane.
The glassy membrane is at the junction of the fibrous sheath and the epithelial root sheath. It is in essence the basement membrane of the follicle epithelium.
Which layers of the epidermis contain living cells?
The stratum basale, stratum spinosum, and STRATUM GRANULOSUM are the epidermal layers containing living cells.
clinical application- the patch drug delivery system
The transdermal patch is designed so that drug molecules diffuse through the epidermis to the blood vessels in the dermal layer. A typical patch works well for small lipid-soluble molecules (for example, estrogen, nitroglycerin, and nicotine) that can make their way between epidermal cells. Other routes for drug delivery to the dermis are via penetration along a hair follicle or sweat gland. Patches are being developed to deliver larger molecules or molecules that are water soluble, such as insulin and vaccines. In one patch design, thin, hollow needles extend from the reservoir of the drug, through the epidermis, and down to the dermis, deep enough to deliver drugs to the subpapillary plexus but not so deep as to reach the nerve endings.
What is the meaning of the word roots epi-, sub-, cutaneous, and derm?
The word root epi means "over" or "above"; sub- means "below"; cutaneo and derm both refer to skin.
How does thick skin differ from thin skin in structure?
Thick skin contains an ADDITIONAL LAYER, the STRATUM LUCIDUM, and has a much thicker stratum corneum.
Peripheral connective tissue sheath (fibrous sheath).
This connective tissue sheath is derived from the dermis. It forms the external layer of the follicle wall.
the stratum basale consists of
a SINGLE ROW OF CELLS, mostly stem cells representing the youngest keratinocytes which divide rapidly and thus many mitotic nuclei are visible
dermal papilla (hair papilla), protrudes into each hair bulb and contains....
a knot of capillaries that deliver substances that stimulate hair growth and supply nutrients to the growing hair. If the hair papilla is destroyed by trauma, the follicle permanently stops producing hair.
the subcutaneous tissue is also...
an INSULATOR, because fat is a poor conductor of heat and it helps prevent heat loss from the body
Ceruminous glands
are modified apocrine glands in the lining of the external ear canal. Their product is a component of earwax.
when is cell death complete?
at the transition between the stratum granulosum and the stratum corneum
what protects the skin against abrasion and penetration?
both the keratin and the thickened plasma membranes of cells in the stratum corneum
nails
built-in modifications of the epidermis that help us pick up small objects and scratch the skin when it itches, composed of dead, keratinized cells
arrector pili
bundle of smooth muscle cells associated with each hair follicle, it runs from the superficial part of the dermis to the deep-lying hair follicle and when the pili is relaxed the hairs lie flat at an oblique angle whereas when the muscle contracts they stand up in response to cold or fear, creating dimples across the skin surface producing goose bumps.
holocrine secretion
central cells in the alveoli accumulate oily lipids until they become engorged and BURST apart, so whole cells essentially break apart to form the product
subcutaneous tissue/ hypodermis/ superficial fascia
consists of BOTH AREOLAR AND ADIPOSE CT, but adipose CT normally predominates. Besides storing fats, it anchors the skin to the underlying structures (mostly to muscles) and it does so loosely enough that skin can slide relatively freely over those structures
thick skin
covers the palms and soles, 5 strata present
clinical application- Decubitus Ulcer NOTES
decubitus ulcers= bedsores are a constant concern for patients who have impaired mobility who it affects? the bed-ridden elderly, wheel-chair bound individuals where? it usually occurs over a bony prominence, such as the hip, sacrum, or heel. **constant pressure from body weight causes a localized breakdown of the skin due to reduction in blood supply, and tissue death can occur within 2-3 hours consequences? without the protective covering of the epidermis, infectious agents can easily enter the body and cause serious and fatal complications
dermis
deep to epidermis, a fibrous connective tissue
reticular dermis
deeper, accounts for 80% of the thickness of the dermis and is DENSE IRREGULAR CT, the extracellular matrix contains THICK bundles of interlacing collagen and elastic fibers that run in many different planes BUT most actually run PARALLEL to the skin surface
what creates fingerprints, palm prints, and footprints?
dermal papillae lie atop larger mounds called dermal ridges, these elevate the overlying epidermis into epidermal ridges or friction ridges which create fingerprints, palm prints, and footprints
in light-skinned people the melanin is...
digested by lysosomes in cells a short distance above the basal layer
in dark-skinned people there is no....
digestion of melanin by lysosomes so the melanin stays occupying the keratinocytes throughout the epidermis
each nail has a....
distal free edge, nail plate (visible attached part) and a root (the proximal part embedded in the skin) and it rests on a bed of epidermis called the nail bed which contains the deeper layers of the epidermis since the nail itself corresponds to the superficial keratinized layers
tactile epithelial cells (Merkel cells)
distributed SPARSELY among the keratinocytes, each is intimately associated with a disc-like sensory nerve ending and functions as a RECEPTOR FOR TOUCH
sweat glands (sudoriferous glands) types include:
eccrine and apocrine glands
how do stretch marks form?
extreme stretching of the skin, as occurs in obesity and pregnancy, can tear the collagen in the dermis and such dermal tearing results in the silvery white scars that we know as "stretch marks"
hypodermis/ subcutaneous tissue
fatty layer composed of loose areolar connective tissue and adipose tissue, not considered part of the skin it is part of the integument and contributes to many of the skin's functions
hematoma
general term for a clotted mass of escaped blood anywhere in the body
melanin
most important pigment, made from an amino acid called tyrosine and ranges from yellow to reddish to brown to black, it passes from melanocytes to keratinocytes in the basal layer (stratum basale) of the epidermis and VARIATIONS IN SKIN COLOR result from differences in both the AMOUNT AND TYPE of melanin being produced by the melanocytes
apocrine sweat glands
mostly confined to the axillary, anal, and genital areas, they are LARGER and their ducts open into hair follicles, essentially they produce a special kind of sweat that consists of fatty substances and proteins
skin appendages include:
nails, hair, hair follicles, sebaceous (oil) glands, and sweat glands which all derive from the epithelial cells of the epidermis, and they ALL EXTEND INTO THE DERMIS
the dermis is richly supplied with...
nerve fibers and BLOOD VESSELS which consist of two vascular plexuses (network of converging and diverging vessels)
granular layer is composed of
pre-keratin intermediate filaments, keratohyalin granules, and lamellar granules
hard keratin
predominates in hair and nails
primary functions of the skin are:
protection, body temperature regulation, excretion, production of vitamin D, and sensory reception
how does the epidermis acquire nutrients?
relies on the capillaries in the underlying connective tissue, the dermis, for its nutrients
cleavage lines
represent separations between underlying collagen fiber bundles in the reticular dermis run CIRCULARLY around the trunk and LONGITUDINALLY in the limbs surgical incisions PARALLEL TO CLEAVAGE LINES HEAL BETTER than those made across them
dermis is a
strong, flexible region of connective tissue and the second major of the skin, typically containing cells of any connective tissue proper: fibroblasts, macrophages, mast cells, and scattered white blood cells. Fiber types: collagen, elastic, and reticular are also typical.
papillary dermis
superficial 20%, contains AREOLAR CT composed of very THIN collagen and elastic fibers and it also includes the dermal papillae which are finger-like projections that extend into the overlying epidermis
dermal blood vessels perform a critical role in...
temperature regulation, holding 5% of all the blood in the body due to their extensive nature the nerves stimulate these vessels to constrict, shutting more blood into the general circulation when it is cold and the internal organs need MORE HEAT, versus when it is very hot the dermal vessels SWELL WITH BLOOD, cooling the body down by radiating heat AWAY from it
the nail matrix is...
the actively growing part of the nail, the matrix is SO THICK that the pink dermis cannot show through it and instead we see the white crescent moon (lunule) under the nail's proximal region
eccrine sweat glands
the bulk pf sweat glands, most abundant on the palms, soles, and forehead, the secretory base lies in the deep dermis and subcutaneous tissue, and the duct runs superficially to open at the skin surface through a funnel-shaped pore
which layer of cells are the ones in stratum lucidum awfully identical to?
the cells in the stratum corneum
which part is the most heavily keratinized in hair?
the cuticle, providing strength and keeping inner layers tightly compacted.
the two regions of the dermis are:
the papillary dermis and reticular dermis
hemoglobin
the pink hue of Caucasian skin reflects the crimson color of oxygenated hemoglobin, in the capillaries of the dermis. B/c caucasian skin contains little melanin, the epidermis is nearly transparent and allows the color of blood to show through
hair has two chief parts and they are:
the root and the shaft (what projects above the skin surface)
sebaceous glands
the skin's oil glands, occur over the entire body except on the palms and soles and are simply alveolar glands with several alveoli opening into a single duct and produce SEBUM
what is the largest of ALL organs?
the skin, accounting for about 7% of total body weight
how do we leave fingerprints behind?
there are sweat pores open along the crests of the friction ridges, thus fingerprints are essentially "sweat films"