Flashcards in Integumentary System (235 #5) Deck (42):
Layers of Skin
AKA - cutaneous membrane (2m sq and 5kg, 7% of body weight!)
1) epidermis - epithelial tissue, thin, nonvascular
2) Dermis - thicker, connective tissue, vascular
3) subcutaneous (subQ) or hypodermis, not considered part of the skin. Areolar and adipose tissues. Fibres from dermis attach to hypodermis, which attaches to fascia. Storage depot for fat, large blood vessels and Pacinian or lamellated corpuscles.
Layers of Epidermis
Keratinized stratified squamous epithelium containing:
1) keratinocytes - 90%
2) melanocytes - 8%
3) Langerhans cells - small fraction
4) Merkel cells - least amount
4) Lucidium (only thick skin)
THIN = 1,2,3,5
THICK = 1-5 higher friction (fingertips, soles, palms)
4-6 week cycle for replacement of cells from layer to layer.
arranged in 4-5 layers and produce keratin - tough fibrous protein that helps protext the skin and underlying tissues from abrasions, heat, microbes and chemicals. Also produce lamellar granules - release water-repellant sealant that decreases water entry and loss and inhibits entry of foreign materials
develop from ectoderm of developing embryo and produce melanin. Slender projections extend btwn keratinocytes and deliver melanin granules to them.
yellow-red or black-brown pigment that contributes to skin colour and absorbs UV light. Form a protective veil over the nucleus of keratinocytes to shield DNA.
AKA epidermal dendritic cells, arise from red bone marrow and migrate to epidermis. Immune responses to help other cells phagocytize microbes in skin, easily destroyed by UV.
detect touch sensations, part of efferent peripheral division.
single row of cuboidal or columnar keratinocytes. Some are stem cells that undergo mitosis to create new keratinocytes. Keratin intermediate filaments (tonofilaments) attach to desmosomes (attach within the layer and to stratum spinosum) and hemidesmosomes (attach to basement membrane. Also contains Merkel cells and melanocytes.
numerous keratinocytes in 8-10 layers, somewhat flattened, retain ability to divide. Produce coarser bundles of keratin than the basale layer. They develop thornlike spines when prepared for examination and the intermediate filaments at each projection attach into desmosomes. Provides both strength and flexibility. Langerhans cells and projections of melanocytes are also present.
3-5 layers of flattened keratinocytes undergoing apoptosis. Keratin filaments become more apparent. Darkly staining granules of keratohyalin, which assembles keratin intermediate filaments into keratin. Membrane-enclosed Lamellar granules fuse with plasma membrane and secrete lipid-rich secretion - water-repellant sealant, retards loss of water or entry of foreign materials in Granulosum, Lucidium and Corneum.
4-6 layers of flattened, clear dead keratinocytes that contain large amounts of keratin and thick plasma membranes.
25-30 layers of flattened dead keratinocytes, overlapping like skin of a snake. Constant exposure to friction may cause a CALLUS, or abnormal thickening of Corneum.
Epidermal Growth Factor (EGF)
hormonelike protein that affects the rate of cell division in the Basale
chronic disorder when keratinocytes divide and move too quickly from basale to corneum. Immature make abnormal keratin which forms flaky, silvery scales at the skin surface. Effective treatments suppress cell division, decrease the rate of cell growth or inhibit keratinization.
dense irregular connective tissue containing collagen and elastin - tensile strength and elastic recoil. Thicker than epidermis.
1) papillary region
2) reticular region
1/5 the thickeness - thin collagen & elastin fibres. Surface area increases due to dermal papillae - small nipple-shaped structures that project into epidermis - increases bond between dermis/epidermis in areas of high stress. Contain capillary loops (blood vessels) and Meissner corpuscles (touch) and free nerve endings (warmth, coolness, pain. tickling and itching).
attaches to subQ - bundles of thick collagen fibres arranged in a regular net-like pattern, scattered fibroblasts and macrophages + other wandering cells. Also includes some adipose and coarse elastic fibres.
1) blood vessels
3) hair follicles
4) sebaceous glands
5) sudoriferous glands
striae (stretch marks)
skin is stretched too much and lateral bonding btwn collagen fibres is disrupted, so small dermal blood vessels rupture. Eventually turn from red to silvery (scar tissue).
produced during 3rd month of fetal dev, downward projections of epidermis into the dermis between the dermal papillae - increase surface area for grip, create strong bond btwn dermis & epidermis in areas of high stress, surface area allows for more touch (Meissner) receptors for tactile sensitivity. Sweat pores on top of ridges form FINGERPRINTS (dermatoglyphics). Unique for every person.
Tension Lines (Lines of Cleavage)
indicate predominant direction of underlying collagen fibres - they tend to orient more in one direction due to natural tension resulting from bony projections, muscles and movement of joints.
With hemoglobin & carote ne, impart variety of colours to skin. Tyrosine + Tyrosinase in melanosomes = Pheomelanin (yellow-red) and Eumelanin (brown - black), number is about the same for everyone - difference is due to amount of pigment the melanocytes produce and tx to keratinocytes. Exposure to UV increases melanin production.
inherited inability to produce melanin - problems with vision and overexposure to sunlight.
the partial or complete loss of melanocytes from patches of skin
stored in corneum and fatty areas of dermis and subQ - precursor to vit A (used in vision pigment synthesis)
Hair - Pili
present everywhere except palm, palmar surface of fingers, soles, plantar surfaces of toes.
1) protect from injury and sun's rays
2) protect (eyes, ears, nose) from foreign particles
3) touch receptors of hair root follicles are activated when a hair is moved slightly
Anatomy of a Hair
1) shaft - superficial portion that projects above skin surface
2) root - portion deep to shaft and into dermis, sometimes subQ
THREE concentric layers of cells:
1) medulla - heavily pigmented
2) cortex - elongated cells
3) cuticle (outside, keratinized)
surrounds root of hair, epithelial root sheath is made up of:
1) external - downward continuation of the epidermis
2) internal - produced by the matrix and forms a cellular tubular sheath of epithelium btwn external RS and hair
BULB contains nipple-shaped indentation, papilla of the hair - areolar connective tissue and many blood vessels. Also contains hair matrix - germinal layer of cells arising from stratum basale.
dermis around root sheath = dermal sheath - arector pili extends from it to the superficial dermis of the skin. GOOSEBUMPS when muscle is contracted.
Root Hair Plexus
dendrites of neurons sensitive to touch. Generate nerve impulses if hairs are moved.
1) growth - cells of hair matrix divide, new cells added to base of hair root (2-6 yrs)
2) regression - cells of hair matrix stop dividing, follicle atrophies and hair stops growing (2-3 weeks)
3) resting (3 months)
85% of hair is in growth stage, visible hair is dead but portions of it's root are still alive. 70-100 hairs fall out a day.
Types of Hair
1) lanugo - fine non-pigmented downy hairs on fetus
2) terminal hairs - long coarse heavily pigmented hairs
3) vellus hairs - short, fine, pales hairs.
simple, branched, acinar glands connected to hair follicles. Absent in palms and soles. Secrete sebum = mixture of triglycerides, cholesterol, proteins and inorganic salts. Coats surface of hairs to keep from drying/brittle and prevents evaporation of water from skin, keeps skin soft and inihibits growth of some bacteria.
Eccrine Sudoriferous Glands
1) simple, coiled tubular glands throughout most of skin, esp forehead, palms and soles
2) secretory portion in deep dermis or upper subQ
3) duct on surface of epidermis
4) perspiration = water, Na+, Cl-, urea, uric acid, ammonia, amino acids, glucose and lactic acid
5) regulates body temp, waste removal, stimulated during emotional stress
6) onset of function is soon after birth
Apocrine Sudoriferous Glands
Exocytotic secretion is odorless until mixes with bacteria on skin. Is milky and yellowish.
1) simple, coiled tubular glands throughout armpits, groin, areolae, clitoris, labia minora, bearded regions of face
2) secretory portion in deep dermis or upper subQ
3) duct on hair follicle
4) perspiration = LIPIDS & PROTEINS, water, Na+, Cl-, urea, uric acid, ammonia, amino acids, glucose and lactic acid
5) stimulated during emotional stress and sexual excitement
6) onset of function is puberty
1) simple, coiled tubular glands throughout external auditory canal
2) secretory portion is subQ
3) duct on surface of ear canal or into sebaceous glands
4) secretion = cerumen
5) stops foreign bodies and insects into ear canal
6) onset of function is soon after birth
2) blood reservoir (8-10%)
4) cutaneous sensations
5) excretion and absorption (transdermal drug administration)
6) synthesis of vit D
Epidermal Wound Healing
abrasions & minor burns. Basal cells of the epidermis break contact with the basement membrane, cells enlarge and migrate across the wound until they meet in the middle, stopping due to CONTACT INHIBITION. EGF stimulates basal stem cells to divide and replace relocated ones.
Deep Wound Healing
injury extends to dermis and subQ.
1) inflammatory phase - blood clot forms in wound and unites the edges. Inflammation helps eliminate microbes, foreign material and dying tissue. Vasodilation help deliver phagocytic WBCs (neutrophils) and mesenchymal cells which develop into fibroblasts.
2) migratory phase - clot becomes scab, epithelial cells migrate beneath scab to bridge wound. Granulation tissue fills the wound, blood vessels regrow and fibroblasts create collagen and glycoproteins.
3) proliferative phase - extensive growth of epithelial cells, etc.
4) maturation phase - scab sloughs off once epidermis restored.
process of scar tissue formation. When scar remains inside boundaries of original wound = hypertrophic scar. When beyond = keloid scar. Scar tissue has more densely arranged collagen fibres, decreased elasticity and fewer blood vessels, hairs, skin glands or sensory structures.
1) epidermis develops from ectoderm. First layer is basal layer, divides and forms periderm. Continually sloughed off and mix with sebaceous secretions to form vernix caseosa. In 1st trimester, Langerhans cells leave red bone marrow and migrate to epidermis, then Merkel cells.
2) dermis arises from mesoderm, gives rise to mesenchyme which differentiates into fibroblasts.
3) hair follicles start of downgrowths of the basal layer (hair buds) and become bulbs - cells in the centre become the matrix cells. by month 5, lanugo is present.
4) sebaceous glands start as outgrowths of hair follicles at 4 months
5) sudoriferous glands are derived from the hair buds.
6) nails appear at 10 weeks starting as thick layer of epithelium - at 9th month the keratinized nails actually reach the tops of the nail bed.
tightly packed hard dead keratinized epidermal cells:
1) nail body - visible portion, like corneum and are harder cells, not shed. layer of epithelium below and deeper dermis.
2) free edge - hanging over edge of finger, white due to lack of underlying capillaries
3) nail root - buried in fold of skin.
4) lunula - white moon - thicker epithelial region
5) hyponychium - anchors nail to fingertip at distal edge
6) eponychium or cuticle - narrow band of epidermis adheres to lateral border of nail wall (corneum)
7) nail matrix - deep to nail root, divide mitotically to produce new cells.
Effects of Aging
1) collagen fibers in the dermis begin to decrease in number, stiffen, break apart
2) elastic fibres lose elasticity, thicken and fray (hastened by smoking)
3) fibroblasts decrease in number = increased wrinkling
4) Langerhans cells dwindle in #, macrophages are less effective = decrease immune response
5) size of sebaceous glands decreases = dry broken skin susceptible to infection.
6) sweat diminishes = likelihood of heat stroke increases.
7) decrease in # of functioning melanocytes = grey hear and atypical skin pigmentation.
8) hair follicles stop producing = hair loss
9) increase in size of some melanocytes = age spots
10) subQ adipose is lost
skin heals more slowly and poorly.