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The Integumentary System. Chapter 5. Cool Skin Facts:. Surface Area = 1.2-2.2 sq.m (1/2 white board) Weight = 4-5 kg (8-9lbs) 7% of body weight Thickness – 1.5-4.0 mm Millions rub off each day- New epidermis every 25-45 days. Two Regions. Epidermis. Composed of epithelial tissue - PowerPoint PPT Presentation
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The Integumentary SystemChapter 5
Cool Skin Facts:Surface Area = 1.2-2.2 sq.m(1/2 white board)
Weight = 4-5 kg (8-9lbs)7% of body weight
Thickness – 1.5-4.0 mmMillions rub off each day- New epidermis every 25-45 days
Two Regions
Epidermis
Dermis
Composed of epithelial tissue Outermost layer Non-vascular Keratinized stratified squamous
epithelium
Composed of fibrous connective tissue Underlying layer vascularized
Cells of the epidermis Keratinocytes- produce keratin, tightly
connected by desmosomes, continuous mitosis Melanocytes-pigment called melanin(protects
from UV), spider-shaped cells, found in deepest layer of epidermis
Merkel cells-shaped like spikey hemisphere, Merkel disc has sensory function
Langerhans cells -made on bone marrow, macrophages
Layers of Epidermis Stratum Basale- ( Basal Layer) bottom,
attached to dermis, youngest keratinocytes, 10-25% are melanocytes
Stratum Spinosum (Prickly Layer) intermediate filaments resist tension attach to desmosomes, keratinocytes appear spiny
Stratum Granulosum (Grandular layer) 3-5 layers thick, keratinocytes flatten, accumulate keratohyaline and lamellated granules
Epidermis layers cont. Stratum Lucidum (clear layer)- thin,
translucent, dead keratinocytes Stratum Corneum (Horny Layer)- 20-30
layers thick, ¾ of epidermal thickness, 40 lbs shed in lifetime
DermisPapillary and Reticular Layers
Papillary Thin, blood vessel rich, areolar
connective, collagen and elastin fibers, loosely woven
Dermal papillae- indent overlying epidermis, touch receptors(Meissner’s corpuscles), fingerprints
Reticular Layer 80% of thickness of dermal layer Dense irregular connective tissue Extra cellular matrix contains thick
bundles of interlacing collagen fibers, form cleavage, tension and lines in the skin, flexure lines (at joints)
Skin Pigments Melanin-
› Protects from UV› All have same
number only make different amounts
Carotene-› Yellow to orange› Accumulates in fatty
tissue and stratum corneum (soles of feet and palms)
› *Hemoglobin (found in Red blood cells) can give reddish hue
Skin color signs of diseases Redness (erythema)- embarrassment,
fever, hypertension, inflammation, allergy
Pallor (pale)- fear, anger, stress, anemia, low blood pressure
Jaundice (yellow)- liver disorder, bile pigments accumulate in body tissues, bilirubin secreted by liver cells as component of bile
Skin diseases continued…. Bronzing-Addison’s disease,
hypofunction of adrenal cortex Black and blue marks- hematomas
(bruise)
Appendages of the skin Nails Sweat glands (sudiferous glands) pH 4-6
› Eccrine (merocrine)-palms, soles of feet, forehead
› Apocrine gland- hair follicles, body odor, musky, unknown function
› Other- ceruminous glands (ear wax)› Mammary glands- milk
Sebaceous glands (oil) Hair
Sebaceous Oil glands Found everywhere except palms, soles
of feet Holocrine gland Sebum- oily Soften and lubricates hair Bactericidal action Seborrhea – “cradle cap”
Nails Hard Keratin
http://www.thaimedicalnews.com/wp-content/uploads/healthy-finger-nails-diagram.gif
Hairs and Hair Follicles Sense insects before they sting Head hair protects against UV, heat
loss, physical trauma Eye lashes- shield eyes Nose hairs- filter large particles like lint
and insects
Structure of Hair Pili-”hairs” consist of largely dead,
keratinized cells. Hard keratin-tough and durable,
individual cells do not flake off Soft Keratin- found in typical epidermal
cells
3 Concentric Layers of the Hair
Medulla- core, large cells and air spaces, not found in fine hairs
Cortex- bulky layer surrounding medulla,
several layers of flattened cells Cuticle-single layer of cells, overlaps on
another like shingles *Red heads have trichosiderin- iron-
containing pigment
Hair Follicle Structure
Types of Hair Vellus Pale, fine Females and
children
Terminal Coarser Scalp and eyebrows Androgen
stimulates
Hair Growth Facts Hirsutism- excessive
hairiness, caused by excessive androgens
2.5 mm/week Lose about 90
hairs/day
Growth cycle› Active (anagen)› Regressive
( catagen)› Resting phase
(telogen)
Hair thinning and Baldness Alopecia- hair
thinning or baldness Drug induced Excessive vitamin A Chemotherapy Burns Radiation Alopecia areata-
autoimmune
Male Pattern Baldness
Minoxidil treatment