5 Chapter The Integumentary System
Skin and its accessory structures
structure function growth and repair development aging disorders
5-1
General Anatomy
A large organ composed of all 4 tissue types 22 square feet 1-2 mm thick Weight 10 lbs.
5-2
Overview
2 Major layers of skin
epidermis is epithelial tissue only dermis is layer of connective tissue, nerve & muscle
Subcutaneous tissue (subQ or hypodermis) is layer of adipose & areolar tissue
subQ = subcutaneous injection intradermal = within the skin layer
5-3
Overview of Epidermis
Stratified squamous epithelium Contains no blood vessels 4 types of cells 5 distinct strata (layers) of cells
5-4
Cell types of the Epidermis
Keratinocytes--90%
produce keratin
Melanocytes-----8 %
produces melanin pigment melanin transferred to other cells with long cell processes
Langerhan cells
from bone marrow provide immunity
Merkel cells
in deepest layer form touch receptor with 5-5 sensory neuron
Layers (Strata) of the Epidermis
Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum basale
5-6
Stratum Basale
Deepest single layer of cells Called stratum germinativum Combination of merkel cells, melanocytes, keratinocytes & stem cells that divide repeatedly Cells attached to each other & to basement membrane by desmosomes & hemidesmosomes
5-7
Stratum Spinosum
8 to 10 cell layers held together by desmosomes During slide preparation, cells shrink and look spiny Melanin taken in by phagocytosis from nearby melanocytes
5-8
Stratum Granulosum
3 - 5 layers of flat dying cells Show nuclear degeneration Contain dark-staining keratohyalin granules Contain lamellar granules that release lipid that repels water
5-9
Stratum Lucidum
Seen in thick skin on palms & soles of feet Three to five layers of clear, flat, dead cells Contains precursor of keratin
5-10
Stratum Corneum
25 to 30 layers of flat dead cells filled with keratin and surrounded by lipids Continuously shed Barrier to light, heat, water, chemicals & bacteria Friction stimulates callus formation
5-11
Keratinization & Epidermal Growth
Stem cells divide to produce keratinocytes As keratinocytes are pushed up towards the surface, they fill with keratin 4 week journey unless outer layers removed in abrasion Hormone EGF (epidermal growth factor) can speed up process Psoriasis = chronic skin disorder
cells shed in 7 to 10 days as flaky silvery scales abnormal keratin produced
5-12
Skin Grafts
New skin can not regenerate if stratum basale and its stem cells are destroyed Skin graft is covering of wound with piece of healthy skin
autograft from self isograft from twin autologous skin
transplantation of patients skin grown in culture
5-13
Dermis
Connective tissue layer composed of collagen & elastic fibers, fibroblasts, macrophages & fat cells Contains hair follicles, glands, nerves & blood vessels Major regions of dermis
papillary region reticular region
5-14
Papillary Region
Top 20% of dermis Composed of loose CT & elastic fibers Finger like projections called dermal papillae Functions
anchors epidermis to dermis contains capillaries that feed epidermis contains Meissner's corpuscles (touch) & free nerve endings (pain and temperature)
5-15
Reticular Region
Dense irregular connective tissue Contains interlacing collagen and elastic fibers Packed with oil glands, sweat gland ducts, fat & hair follicles Provides strength, extensibility & elasticity to skin
stretch marks are dermal tears from extreme stretching
Epidermal ridges form in fetus as epidermis conforms to dermal papillae
fingerprints are left by sweat glands open on ridges increase grip of hand 5-16
Skin Color Pigments (1)
Melanin produced in epidermis by melanocytes
same number of melanocytes in everyone, but differing amounts of pigment produced results vary from yellow to tan to black color melanocytes convert tyrosine to melanin
UV in sunlight increases melanin production
Clinical observations
freckles or liver spots = melanocytes in a patch albinism = inherited lack of tyrosinase; no pigment vitiligo = autoimmune loss of melanocytes in areas of the skin produces white patches 5-17
Skin Color Pigments (2)
Carotene in dermis
yellow-orange pigment (precursor of vitamin A) found in stratum corneum & dermis
Hemoglobin
red, oxygen-carrying pigment in blood cells if other pigments are not present, epidermis is translucent so pinkness will be evident
5-18
Skin Color as Diagnostic Clue
Jaundice
yellowish color to skin and whites of eyes buildup of yellow bilirubin in blood from liver disease
Cyanotic
bluish color to nail beds and skin hemoglobin depleted of oxygen looks purple-blue
Erythema
redness of skin due to enlargement of capillaries in dermis during inflammation, infection, allergy or burns
5-19
Accessory Structures of Skin
Epidermal derivatives Cells sink inward during development to form:
hair oil glands sweat glands nails
5-20
Structure of Hair
Shaft -- visible
medulla, cortex & cuticle CS round in straight hair CS oval in wavy hair
Root -- below the surface Follicle surrounds root
external root sheath internal root sheath base of follicle is bulb
blood vessels germinal cell layer
5-21
Hair Related Structures
Arrector pili smooth muscle in dermis contracts with cold or fear. forms goosebumps as hair is pulled vertically
Hair root plexus
detect hair movement
5-22
Hair Growth
Growth cycle = growth stage & resting stage Growth stage
lasts for 2 to 6 years matrix cells at base of hair root producing length
Resting stage
lasts for 3 months matrix cells inactive & follicle atrophies
Old hair falls out as growth stage begins again
normal hair loss is 70 to 100 hairs per day
5-23
Hair Color
Result of melanin produced in melanocytes in hair bulb Dark hair contains true melanin Blond and red hair contain melanin with iron and sulfur added Graying hair is result of decline in melanin production White hair has air bubbles in the medullary shaft
5-24
Functions of Hair
Prevents heat loss
Decreases sunburn Eyelashes help protect eyes Touch receptors (hair root plexus) senses light touch
5-25
Glands of the Skin
Specialized exocrine glands found in dermis Sebaceous (oil) glands Sudiferous (sweat) glands Ceruminous (wax) glands Mammary (milk) glands
5-26
Sebaceous (oil) glands
Secretory portion in the dermis Most open onto hair shafts Sebum
combination of cholesterol, proteins, fats & salts keeps hair and skin from soft & pliable inhibits growth of bacteria & fungi(ringworm)
Acne
bacterial inflammation of glands secretions stimulated by hormones at puberty5-27
Sudoriferous (sweat) glands
Eccrine (sweat) glands
most areas of skin secretory portion in dermis with duct to surface regulate body temperature with Apocrine perspiration
(sweat) glands
armpit and pubic region secretory portion in dermis with duct that opens onto hair follicle secretions more viscous
5-28
Ceruminous glands
Modified sweat glands produce waxy secretion in ear canal Cerumen contains secretions of oil and wax glands Helps form barrier for entrance of foreign bodies Impacted cerumen may reduce hearing
5-29
Nails
Tightly packed, keratinized cells Nail body is pink due to underlying capillaries Lunula appears white due to thickened stratum basale in that area Cuticle (eponychium) is stratum corneum Nail matrix deep to the nail root is the region from which the nail growth occurs Growth is 1mm per week--faster in summer & on most-used hand
5-30
Structure of Nails
Tightly packed keratinized cells Nail body
visible portion pink due to underlying capillaries free edge appears white
Nail root
buried under skin layers lunula is white due to thickened stratum basale
Eponychium (cuticle)
stratum corneum layer
5-31
Nail Growth
Nail matrix below nail root produces growth Cells transformed into tightly packed keratinized cells 1 mm per week
5-32
Types of Skin
Thin skin
covers most of body thin epidermis (.1 to .15 mm.) that lacks stratum lucidum lacks epidermal ridges, has fewer sweat glands and sensory receptors
Thick skin
only on palms and soles thick epidermis (.6 to 4.5 mm.) with distinct stratum lucidum & thick stratum corneum lacks hair follicles and sebaceous glands 5-33
General Functions of the Skin
Regulation of body temperature Protection as physical barrier Sensory receptors Excretion and absorption Synthesis of vitamin
5-34
Thermoregulation
Releasing of sweat onto the skin
perspiration & its evaporation lowers body temperature
Adjusting flow of blood to the body surface
in moderate exercise, more blood brought to surface helps lower temperature with extreme exercise, blood is shunted to muscles and body temperature rises
Shivering and constriction of surface vessels
raise internal body temperature as needed
5-35
Protection
Physical, chemical and biological barrier
tight cell junctions prevent bacterial invasion lipids released retard evaporation pigment protects somewhat against UV light langerhans cells alert immune system
5-36
Cutaneous Sensations
Touch, temperature, pressure, vibration, tickling and some pain sensations arise from the skin.
5-37
Excretion and Absorption
Only a minor role is played by the skin 400 mL of water evaporates from it daily Small amounts salt, CO2, ammonia and urea are excreted Lipid soluble substances can be absorbed through the skin
vitamins A, D, E and K, Oxygen and CO2 acetone and dry-cleaning fluid, lead, mercury, arsenic, poisons in poison ivy and oak
5-38
Transdermal Drug Administration
Method by which drugs in a patch enter the body Drug absorption most rapid in areas where skin is thin (scrotum, face and scalp) Examples
nitroglycerin (prevention of chest pain from coronary artery disease) scopolamine ( motion sickness) estradiol (estrogen replacement therapy) nicotine (stop smoking alternative)
5-39
Synthesis of Vitamin D
Sunlight activates a precursor to vitamin D Enzymes in the liver and kidneys transform that molecule into calcitriol (most active form of vitamin D) Necessary vitamin for absorption of calcium from food in the gastrointestinal tract
5-40
Epidermal Wound Healing
Abrasion or minor burn Basal cells migrate across the wound Contact inhibition with other cells stops migration Epidermal growth factor stimulates cell division Full thickness of epidermis results from further cell division
5-41
If an injury reaches dermis, healing occurs in 4 phases
inflammatory phase has clot unite wound edges and WBCs arrive from dilated and more permeable blood vessels migratory phase begins the regrowth of epithelial cells and the formation of scar tissue by the fibroblasts proliferative phase is a completion of tissue formation maturation phase sees the scab fall off
Deep Wound Healing
Scar formation
hypertrophic scar remains within the boundaries of the original wound keloid scar extends into previously normal tissue
collagen fibers are very dense and fewer blood vessels are present so the tissue is lighter in color
5-42
Phases of Deep Wound Healing
Which phases have been left out of this illustration?
5-43
Development of the Skin
Epidermis develops from ectodermal germ layer Dermis develops from mesodermal germ layer
at 8 weeks, fetal "skin" is simple cuboidal epithelium nails begin to form at 10 weeks, but do not reach the fingertip until the 9th month dermis forms from mesoderm by 11 weeks by 16 weeks, all layers of the epidermis are present oil and sweat glands form in 4th and 5th month by 6th months, delicate fetal hair (lanugo) has formed
Slippery coating of oil and sloughed off skin 5-44 called vernix caseosa is present at birth
Age Related Structural Changes
Collagen fibers decrease in number & stiffen Elastic fibers become less elastic Fibroblasts decrease in number Langerhans cells and macrophages decrease in number and become less-efficient phagocytes Oil glands shrink and the skin becomes dry Walls of blood vessels in dermis thicken so decreased nutrient availability leads to thinner skin as subcutaneous fat is lost
5-45
Photodamage
Ultraviolet light (UVA and UVB) both damage the skin Acute overexposure causes sunburn DNA damage in epidermal cells can lead to skin cancer UVA produces oxygen free radicals that damage collagen and elastic fibers and lead to wrinkling of the skin
5-46
Skin Cancer
1 million cases diagnosed per year 3 common forms of skin cancer
basal cell carcinoma (rarely metastasize) squamous cell carcinoma (may metastasize) malignant melanomas (metastasize rapidly)
most common cancer in young women arise from melanocytes ----life threatening key to treatment is early detection watch for changes in symmetry, border, color and size risks factors include-- skin color, sun exposure, family history, age and immunological status 5-47
Burns
Destruction of proteins of the skin
chemicals, electricity, heat
Problems that result
shock due to water, plasma and plasma protein loss circulatory & kidney problems from loss of plasma bacterial infection
5-48
Types of Burns
First-degree
only epidermis (sunburn)
Second-degree burn
destroys entire epidermis & part of dermis fluid-filled blisters separate epidermis & dermis epidermal derivatives are not damaged heals without grafting in 3 to 4 weeks & may scar
Third-degree or full-thickness
destroy epidermis, dermis & epidermal derivatives damaged area is numb due to loss of sensory nerves
5-49
Pressure Sores
Decubitus ulcers Caused by constant deficiency of blood flow to tissue Areas affected is skin over bony prominence in bedridden patients Preventable with proper care
5-50