Soriano Notes~Chapter 5~Anatomy & Physiology

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SKIN MAJOR LAYERS (3)

Back 1

(Integument)

1~Epidermis –Outermost superficial region

2~Dermis –Middle region

3~Hypodermis (superficial fascia) –Deepest region

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EPIDERMIS

Back 2

~Made of keratinized stratified squamous epithelium, has 4 cell types & 4-5 layers

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*CELLS OF EPIDERMIS (4)

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1~Keratinocytes – Produce fibrous protein keratin

2~Melanocytes –Produce brown pigment melanin

3~Langerhans’ cells –Epidermal macrophages that help activate immune system

4~Merkel cells –Fx as touch receptors in association w sensory nerve endings

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*LAYERS OF EPIDERMIS (5)

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1~Stratum Basale (Basal Layer)

2~Stratum Spinosum (Prickly Layer)

3~Stratum Granulosum (Granular Layer)

4~Stratum Lucidum (Clear Layer)

5~Stratum Corneum (Horny Layer)

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*STRATUM BASALE OF EPIDERMIS

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(Basal Layer)

~Deepest epidermal layer firmly attached to dermis

~Consists of a single row of youngest keratinocytes

~Cells undergo rapid division, hence its alternate name, stratum germinativum

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*STRATUM SPINOSUM OF EPIDERMIS

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(Prickly Layer)

~Cells contain a weblike system of intermediate filaments attached to desmosomes

~Melanin granules & Langerhans’ cells are abundant in this layer

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*STRATUM GRANULOSUM OF EPIDERMIS

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(Granular Layer)

~Thin; 3-5 cell layers

~Drastic changes in keratinocyte appearance b/c Keratohyaline & lamellated granules accumulate in cells

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*STRATUM LUCIDUM OF EPIDERMIS"

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(Clear Layer)

~Thin, transparent band

~Consists of a few rows of flat, dead keratinocytes

~Present only in thick skin

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*STRATUM CORNEUM & Fx (3) OF EPIDERMIS

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(Horny Layer)

~Outermost layer of keratinized cells

~Accounts for 3 quarters of epidermal thickness

~Fx include: a~Waterproofing b~Protection from abrasion & penetration
c~Rendering body relatively insensitive to biological, chemical & physical assaults

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*DERMIS & LAYERS (2)

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~Strong, flexible connective tissue

~Cell types include fibroblasts, macrophages & occasionally mast cells & white blood cells

~Composed of 2 layers: a~Papillary
b~Reticular

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*PAPILLARY LAYER OF DERMIS

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~Areolar connective tissue w collagen & elastic fibers

~Its superior surface contains peglike projections called dermal papillae which contain capillary loops, Meissner’s corpuscles & free nerve endings

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*RETICULAR LAYER OF DERMIS

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~80% of skins thickness

~Collagen fibers in this layer add strength & resiliency to skin while elastin fibers provide stretch-recoil properties

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HYPODERMIS

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~Subcutaneous layer composed of adipose & areolar connective tissue

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SKIN COLOR PIGMENTS (3)

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1~Melanin –Yellow->reddish-brown->black pigment, responsible for dark skin colors...Freckles & pigmented moles result from local accumulations of melanin

2~Carotene –Yellow->orange pigment, most obvious in palms & soles

3~Hemoglobin –Reddish pigment responsible for pinkish hue

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SWEAT GLANDS (4)

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1~Eccrine sweat glands –Found in palms, soles of feet & forehead

2~Apocrine sweat glands –Found in axillary & anogenital areas prevent overheating

3~Ceruminous glands –Modified apocrine glands in external ear canal that secrete cerumen

4~Mammary glands –Specialized sweat glands that secrete milk

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SEBACEOUS GLANDS

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~Simple alveolar glands that soften skin by secreting oily sebum when stimulated by hormones

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HAIR

Back 17

~Filamentous strands(shaft-pigmented by melanocytes at base of hair) of dead keratinized cells produced by hair follicles where root is embedded in skin

~Contains hard keratin which is tougher & more durable than soft keratin of skin

~Consists of a core called medulla, a cortex & an outermost cuticle

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HAIR Fx (3)

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1~Helping to maintain warmth

2~Alerting body to presence of insects on skin

3~Guarding scalp against physical trauma, heat loss & sunlight

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HAIR FOLLICLE

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~Root sheath extending from epidermal surface into dermis

~In Dermis a knot of sensory nerve endings (a root hair plexus) wraps around each hair bulb

~Bending a hair stimulates these endings, hence our hairs act as sensitive touch receptors

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TYPES OF HAIR (2)

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1~Vellus -Pale, fine body hair found in children & adult female

2~Terminal -Coarse, long hair of eyebrows, scalp, axillary & pubic regions

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TYPES OF HAIR THINNING & BALDNESS

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1~Alopecia –Hair thinning in both sexes

2~True, or frank, baldness:
a~Genetically determined & sex-influenced condition
b~Male pattern baldness –Caused by follicular response to DHT

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STRUCTURE OF NAIL

Back 22

~Scalelike modification of epidermis on distal, dorsal surface of fingers & toes

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*Fx OF INTEGUMENTARY SYSTEM (6)

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1~Protection –Chem, phys & mechanical barrier
2~Body temp reg~[Dilation (cooling) & constriction (warming) of dermal vessels] & Increasing sweat gland secretions to cool body
3~Cutaneous sensation–Exoreceptors sense touch & pain
4~Metabolic fx–Synthesis of vitamin D in dermal blood vessels
5~Blood reservoir –5% of blood volume
6~Excretion –Nitrogenous wastes are eliminated in sweat

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*SKIN CANCER & TYPES (3)

Back 24

~Most skin tumors are benign & do not metastasize

~A crucial risk factor for nonmelanoma skin cancers is disabling of p53 gene

~Newly developed skin lotions can fix damaged DNA ~3 major types of skin cancer are:
1~Basal cell carcinoma
2~Squamous cell carcinoma
3~Melanoma

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BASAL CELL CARCINOMA

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~Least malignant & most common skin cancer

~Stratum basale cells proliferate & invade dermis & hypodermis

~Slow growing & do not often metastasize buy can be cured by surgical excision in 99% of cases

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SQUAMOUS CELL CARCINOMA

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~Arises most often on scalp, ears & lower lip from keratinocytes of stratum spinosum

~Grows rapidly & metastasizes if not removed but prognosis is good if treated by radiation therapy or removed surgically

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MELANOMA ARE DANGEROUS BECAUSE (2)

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~Cancer of melanocytes is most dangerous type of skin cancer because it is:
1)Highly metastatic
2)Resistant to chemotherapy

~Treated by wide surgical excision accompanied by immunotherapy but chance of survival is poor if lesion is over 4 mm thick

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*BURN CLASSIFICATIONS

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1~1st-degree –Only epidermis is damaged~Symptoms include localized redness, swelling & pain
2~2nd-degree –Epidermis & upper regions of dermis are damaged~Symptoms mimic first degree burns, but blisters also appear
3~3rd-degree –Entire thickness of skin damaged~Burned area is gray-white, cherry red, or black; there is no initial edema or pain (since nerve endings are destroyed)

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RULE OF NINES & CONSIDERED CRITICAL IF (3)

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~Estimates severity of burns~Burns considered critical if:
a~Over 25% of body has second-degree burns
b~Over 10% of body has third-degree burns
c~There are third-degree burns on face, hands or feet

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DEVELOPMENTAL SPECTS OF INTEGUMENT: FETAL

Back 30

~Epidermis develops from ectoderm

~Dermis & hypodermis develop from mesoderm

~Lanugo –Downy coat of delicate hairs covering fetus

~Vernix caseosa –Substance produced by sebaceous glands that protects skin of fetus in amnion

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DEVELOPMENTAL ASPECTS OF INTEGUMENT: ADOLESCENT-ADULT

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~Skin & hair become oilier & acne may appear

~Skin shows effects of cumulative environmental assaults around age 30~Scaling & dermatitis become more common

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DEVELOPMENTAL ASPECTS OF INTEGUMENT: OLD AGE

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~Epidermal replacement of cells slows & skin becomes thinner, dry & itchy

~Subcutaneous fat layer diminishes, leading to intolerance of cold

~Decreased elasticity & loss of subcutaneous tissue leads to wrinkles

~Decreased numbers of melanocytes & Langerhans’ cells increase risk of skin cancer

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MELANOMA CHARACTERISTICS (4)

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a~Asymmetry;2 sides of pigmented area do not match
b~Border is irregular & exhibits indentations
c~Color is black, brown, tan & sometimes red or blue
d~Diameter is larger than 6 mm (size of a pencil eraser)