Integumentary System Body Membranes • Body membranes cover surfaces, line body cavities, and form protective sheets over organs • Two major groups: – Epithelial membranes – cutaneous (skin), mucous, and serous membranes – Connective tissue membranes – synovial membranes Epithelial Membranes • Epithelial membranes – covering and lining membranes • Contain an epithelial sheet, but it is always combined with a connective tissue layer • 2 tissues = These membranes are actually simple organs Cutaneous Membrane = Skin • Its superficial epidermis is composed of keratinizing stratified squamous epithelium. • Underlying dermis is mostly dense (fibrous) connective tissue. • Exposed to air = dry membrane Mucous Membrane = Mucosa Varied types Stratified squamous epithelium in mouth, esophagus Simple columnar epithelium in digestive tract • Composed of epithelium resting on loose connective tissue called lamina propria. • Lines all body cavities that open to exterior • Wet membranes bathed in secretions or urine • Adapted for absorption or secretion Serous membrane = serosa • Simple squamous epithelium resting on areolar connective tissue • Line body cavities that are closed to exterior • Occur in pairs: – Parietal layer lines the wall of the ventral cavity – Visceral layer covers the outside of those organs • Layers separated by serous fluid, which allows organs to slide without friction (heart, stomach) Serosa • Serosa lining the abdominal cavity and covering its organs = peritoneum • Membrane surrounding lungs = pleura • Membrane around the heart = pericardium Synovial Membranes • Composed of soft areolar connective tissue and contain no epithelial cells. • Line the fibrous capsules surrounding joints and tendon sheaths • Secrete lubricating fluid to cushion organs during muscle activity Tattoos • Tattoos are made by using a needle to deposit pigment in the dermis. • Risk of Hepatitis C is about 15x higher in people who have tattoos… Cutaneous Membrane = Skin • Skin and its glands (sweat, oil), along with hair and nails, make up the integumentary system • Integument (covering): – keeps water and other molecules in the body – Insulates and cushions body organs – Protects body from mechanical (bumps), chemical (acids and bases), thermal (heat and cold), UV (solar radiation), and bacteria damage. • Uppermost layer of skin is full of keratin and is cornified (hardened) to help prevent H2O loss. Capillary Network in Skin • Capillary network and sweat glands regulate heat loss • Urea, salts, and water are lost as sweat • Manufactures proteins important to immunity and synthesizes Vitamin D (sunlight converts cholesterol in skin into vitamin D). • Cutaneous sensory receptors are located in skin – sense pain, pressure, temperature, touch Skin Structure • Tissues in skin: • Epidermis – stratified squamous epithelium, keratinizing (can become hard) • Dermis – dense connective tissue • Subcutaneous layer (hypodermis) – below dermis, adipose tissue, anchors skin to organs. Skin Structure • Subcutaneous layer – shock absorber and insulation from extreme T changes • Thicker in women than in men (adipose tissue) Epidermis • Five layers / strata: – Stratum Corneum – Stratum Lucidum – Stratum Granulosum – Stratum Spinosum – Stratum Basale • Epidermis is avascular (no blood supply) – Ex: shaving is cutting off cells w/ no blood (usually) Stratum Basale • Most cells of epidermis are keratinocytes (keratin cells) which produce keratin • Keratin –protein that makes epidermis tough • Deepest layer of epidermis / closest to dermis • Daughter cells pushed upward into superficial layers Epidermis • Stratum basale constantly undergoing mitosis, a.k.a. stratum geminativum • New cells become increasingly flatter and full of keratin • Stratum Spinosum – cuboidal cells • Stratum granulosum – cells granular Epidermis • As new cells die they form the stratum lucidum • This layer is only present where skin is hairless and thick (palms of hands, soles of feet) • Stratum corneum – ¾ of epidermal thickness • Cornified or horny (cornu = horny) cells, completely keratinized Melanin • Melanin is a pigment that ranges from yellow to brown to black • Produced by melanocytes, found in stratum basale. • Everyone has same number of melanocytes • Complexion determined by quantity of melanin produced • Heredity – genes specific for melanin production; mutant genes can cause lack of melanin Albinism • Albinism results when genetic changes result in a lack of pigment (melanin) production • Can have eye problems (light scattering, optic nerve problems) Dermis = your hide • Two major regions – Papillary – upper dermal region • Dermal papillae (papill=nipple) – house pain receptors, send nutrients to epidermis, form fingerprints – Reticular – deepest skin layer • Contains blood vessels, sweat and oil glands, and pressure receptors (Pacinian corpuscles) • Collagen (toughness) and elastic (stretch when growing) fibers found in dermis • Many receptors for nervous system Skin Appendages • Cutaneous glands – exocrine. Release secretions to skin surface via ducts. – Sebaceous (oil) glands – often open into hair follicles. Everywhere but palms and soles. • Secrete sebum – oil that keeps skin soft and kills bacteria. Increased amount in adolescence Acne = infection of sebaceous gland • When sebaceous gland’s duct is blocked by sebum, a whitehead appears on skin surface • If the material accumulates and dries it darkens to form a blackhead. Sweat Glands • Sweat (Sudoriferous) Glands – more than 2.5 million per person. Two types: – Eccrine glands – most numerous, all over body. Produce sweat (water plus salts and vitamins) • Sweat is acidic (pH 4-6) so inhibits growth of bacteria – Apocrine glands – confined to armpits and genital areas of the body. Secrete fatty acids and proteins • Function unclear but activated during stress, pain, sex Hair • Millions of hairs • Minor protection: – Head bumps – Eyelashes – Nose hairs • Early humans – provided insulation from cold weather Hair • • • • • Produced by hair follicle Flexible epithelial structure Root in follicle Shaft projects from skin Matrix (growth zone) of hair bulb at end of follicle • Pigment made by melanocytes Nails • Scale-like modification of epidermis • Free edge • Body (visible portion) • Mostly nonliving keratinized cells