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Skin and Body Membranes

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1 Skin and Body Membranes
Chapter 4 Skin and Body Membranes

2 Body Membranes Cover surfaces, line body cavities, form protective sheets 2 groups – classified according to tissue

3 Epithelial membranes Aka covering and lining membranes
Do contain some connective tissue Considered simple organs (1) Cutaneous membrane – Skin Dry membrane

4 (2) Mucous membranes (mucosa)
Epithelium on top of lamina propria Lines any cavity w/ an exterior opening Wet (moist) membranes Continuously covered by secretions Ex. Respiratory, digestive, urinary, reproductive tracts Adapted for absorption or secretion

5 (3) Serous membranes (serosa)
Simple squamous epithelium on areolar tissue Line cavities closed to exterior Occur in pairs Parietal layer – wall of ventral body cavity Visceral layer – covers organs in the cavity

6 Serous fluid – btw layers – secreted by both layers
Allows organs to move w/out friction (heart,stomach) Name depends on location Abdominal cavity – peritoneum; lungs – pleura; heart - pericardium

7 Connective membranes Aka synovial membranes
Areolar tissue – no epithelial Line fibrous capsules around joints Smooth surface Secrete lubricating fluid

8 Line bursae (small sacs of connective tissue) and tendon sheaths
Cushion organs that move against each other

9 Integumentary System Cutaneous membrane
Aka integument – “covering” 2 layers – epidermis & dermis – usually very close Burns/friction may cause separation = blister Functions Insulates and cushions deeper organs Regulates body temp – capillaries, sweat glands Mini excretory system – urea, uric acid, salts, water released w/ sweat Synthesizes immunity proteins Synthesizes vitamin D Contains cutaneous receptors – touch, pressure, temp, pain

10 Epidermis Avascular Keratinocytes – majority of cells – produce keratin (tough, protective, waterproofing) May have up to 5 strata (layers)

11 (1) Stratum basale Deepest Best nourished via diffusion Aka stratum germinativum because they are continually dividing Daughter cells are pushed upward Contains melanocytes – produce melanin (pigment) Sunlight stimulates production Concentrated in 1 spot = freckles, moles

12 (2) Stratum spinosum (3) Stratum granulosum (4) Stratum lucidum
Dead – unable to get nutrients and oxygen Occurs in hairless, extra thick areas – palms, soles of feet (5) Stratum corneum 20-30 cell layers (3/4 of epidermis) Dead – completely filled w/ keratin Aka cornified cells (corno = horn) Rubbed/flakes off and is replaced by lower cells Cycle days


14 Dermis Hide – leathergoods
Strong, stretchy envelope that holds body together 2 layers (1) Papillary layer Upper dermal Dermal papillae – projections on superior surface Contain capillary loops which provide nutrients May have Meissner’s corpuscles – touch receptors Form ridges - fingerprints

15 (2) Reticular layer Deepest skin layer Contains blood vessels, sweat/oil glands, Pacinian corpuscles (pressure receptors) Both layers contain phagocytes that work to prevent bacteria from going deeper If blood supply is restricted = cell death = skin ulcers (bed sores) Ex. Decubitus ulcers – found in bedridden patients

16 Collagen fibers – provide toughness
Attract/bind water – keep skin hydrated Elastic fibers – give skin elasticity # of fibers decreases – allows wrinkles Blood vessels help maintain temp To release heat – vessels swell To conserve heat – vessels constrict, may bypass capillaries

17 Hypodermis Subcutaneous tissue – adipose tissue Not part of skin
Acts as an anchor, shock absorber, insulator

18 Skin Color 3 pigments Melanin – yellow, brown, black
Carotene – yellow-orange Oxygen-rich hemoglobin – red/pink Emotional stimuli or disease affect color Redness (erythema) Blushing, fever, inflammation, allergy

19 Pallor (blanching) – become pale
Anemia, low blood pressure, fear Jaundice (yellow cast) Liver disorder – bile deposited in tissues

20 Bruises (hematomas) Where blood has left vessels and clotted in tissue space May be vitamin C deficit or hemophilia

21 Cyanosis Bluish cast due to low oxygen Common in people with breathing disorders

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