Post on 01-Apr-2015
Chapter 4
Skin and Body Membranes
Body Membranes
• Cover surfaces, line body cavities, form protective sheets
• 2 groups – classified according to tissue
Epithelial membranes
• Aka covering and lining membranes
• Do contain some connective tissue
• Considered simple organs
• (1) Cutaneous membrane
– Skin
–Dry membrane
• (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
• (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
–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
Connective membranes
• Aka synovial membranes• Areolar tissue – no epithelial • Line fibrous capsules around joints
–Smooth surface–Secrete lubricating fluid
• Line bursae (small sacs of connective tissue) and tendon sheaths
• Cushion organs that move against each other
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
Epidermis• Avascular• Keratinocytes –
majority of cells – produce keratin (tough, protective, waterproofing)
• May have up to 5 strata (layers)
• (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
• (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 25-45 days
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
• (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
• 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
Hypodermis
• Subcutaneous tissue – adipose tissue
• Not part of skin
• Acts as an anchor, shock absorber, insulator
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
• Pallor (blanching) – become pale
– Anemia, low blood pressure, fear
• Jaundice (yellow cast)
– Liver disorder – bile deposited in tissues
• Bruises (hematomas)
– Where blood has left vessels and clotted in tissue space
– May be vitamin C deficit or hemophilia
• Cyanosis
–Bluish cast due to low oxygen
–Common in people with breathing disorders