The Integumentary System Flashcards
(30 cards)
Classes of body membranes
• Lines or covers portions of internal or external body surface
• Consists of:
– Epithelium
– Connective tissue support
• Specific classes:
– Mucous membrane: mucus cells, moist
– Serous membrane: visceral and parietal layer
• Pleura, pericardium and peritoneum
– Synovial membrane: no true epithelial layer
– Cutaneous membrane
Cutaneous membrane: skin
• Covers body surface, thick and waterproof
• Epithelium (epidermis) and connective tissue support (dermis)
Skin functions
• Protection: 1st line of defense!
– Attack, water gain, water
loss (dehydration),
environment, UV radiation
• Elimination (release) of
substance via glands
• Thermoregulation
• Melanin production
• Keratin production
• Makes vitamin D3
• Lipid and blood storage
• Sensory perception, relay to NS
• Communication
The Integumentary System
• Contains largest organ - the skin!
– “the integument”
• Skin: Cutaneous membrane
– Epidermis: epithelial tissue
– Dermis: connective tissue
• Skin accessories: glands, nails, hair
– Originates from epithelium
– In dermis, penetrates epidermis
• Subcutaneous layer: hypodermis
– Not part of integument
– Superficial fascia: anchors to muscle
(mostly), bone
– Areolar, adipose (1/2 body
fat!…liposuction)
– Rich blood supply: subcutaneous/
hypodermal injections
The Epidermis
• Avascular stratified squamous epithelium- no bleeding when damaged!
– Layered, 4 cell types
– Basement membrane separates from dermis
– Not as thick as dermis, nutrition and O2 via diffusion
– Basal surface (dividing cells) - more metabolic demands
– Apical surface- exposed surface, dead cells fall off and are replaced
The 4 cells
of the
epidermis
Keratinocytes: majority, Melanocytes, Merkel (tactile) cells, Dendritic (Langerhans) cells: immune response
Keratinocytes: majority
– Make keratin protein
– Desmosomes
between cells – very
strong connections!!
– Protection: resists
mechanical stress
and H20 loss
– Mitotically active
cells at basal surface
– Replacement of dead
cells at apical surface
• New epidermis
monthly!
Melanocytes
– Produce melanin: brown/black – orange/red pigment
– Skin color, UV absorption, DNA protection
Merkel (tactile) cells
– Sensitive to touch, communicate with nerve ending (disc) about touch, shape,
patterns
Dendritic (Langerhans) cells: immune response
– Phagocytes, starts immune response (vs. invaders, epidermal cancer cells)
The epidermis structure
• Keratinocytes in layers of skin at
various life cycle development
• Basal surface
– Mitosis - birth of keratinocytes
– Hemidesmosomes connect to
extracellular matrix of dermis
• Move towards apical surface
– Connected by desmosomes
– Keratinization – make keratin
– Resistance/protection vs.
mechanical stress and
waterproofing
– Cells die – due to keratin and
distance from nutrients, O2
• Apical surface – groups of dead
keratinocytes are shed and replaced
Melanin and UV
protection
• Melanin produced
by melanocytes
transferred to
keratinocytes
– Concentrated
peri-nuclear
• Protect DNA
– Melanin
synthesis ↑
with UV
exposure
Epidermal variation: Skin color
Pigments:
• Melanin: two forms
– Melanocytes synthesize
– Transferred to keratinocytes
– All have melanocytes, melanin
type/amount, stability varies
– Freckles, moles, vitiligo,
albinism
• RBC Hemoglobin in dermis blood
– Red tint visible through skin
• Carotene accumulation from diet
– Can be converted to vitamin A
– Excess collects in superficial
epithelium and fat of
dermis/subcutaneous layer
Skin cancer
• Basal cell carcinoma: 80%, most common
– Sun exposure increases risk
– Slow-growing, surgical removal
treatment
• Squamous cell carcinoma: 2nd most
common
– Sun exposure increases risk
– Grows faster, can metastasize
– But early detection surgical removal
treats
• Melanoma: 2-3%, most dangerous!
– ↑ division of melanocytes
– Sun exposure increases risk
– Very metastatic, most difficult to treat
– Early detection key!
Epidermal function: Vitamin D3
• UV radiation (10-15 mins/ 2x week):
– Epidermal cells produce cholecalciferol (vitamin D3)
– Kidneys eventually make calcitriol (active form
vitamin D3)
• Aids calcium /phosphorus absorption in GI tract
• Insufficient vitamin D3: Rickets
The dermis
• Your “hide” under
epithelium
• Connective tissue with
collagen (strong) and
elastic (stretchy) protein
fibers
• Little cell division…Tattoos?
• Good blood/nerve supply
• Epidermal accessory
structures rooted
• “Dermatitis”
• Two tissue components
– Superficial papillary
layer
– Deeper reticular layer
The dermis: the papillary layer
• Thin, superficial, monitored by phagocytes
• Dermal papilla: projections of dermis ↑ surface area
– Interlock tight with epidermis
– Support epidermis with blood supply
– Sensory (nerve) receptors
The dermis: the reticular layer
• Major part of dermis, epithelial accessory structures anchored
• Large collagen fiber bundles and elastic fibers: strength and stress
resistance in many directions
– Striae (stretch marks): dermal tearing, fibers overstretched
• Sensory (nerve) receptors
Dermal
features
• Cleavage or tension lines
– Indicate overall direction of collagen fiber bundles in reticular layer
– Knowledge of lines important for surgeons when making incisions to
enhance healing
The dermis: innervation
• Nerve supply (innervation)
controls:
– Blood flow: can redirect as
necessary
– Gland secretions
review
• Different sensory receptors:
– Sense light touch, deep
pressure, vibration, pain,
other
Burns
• Most immediate threat: infection!, loss of body fluids and dehydration
• Degrees of burns based on severity and ability to heal
– First degree: epidermis, no blisters, no scars
– Second degree: epidermis and part dermis, blisters, possible scarring
– Third degree: all epidermis, dermis and deeper tissues; not usually
painful at first, fluids and skin grafts often needed, significant scarring
Epithelial wound healing
• Epithelial wound healing: expect bleeding??
– Epithelial cells migrate, contact inhibition, cell division
Deep
wound
healing
• Bleeding!
• Blood clotting
• Cleaning of
wound:
inflammation
• Migration of
epithelial cells
• Scar tissue
forms
• Blood vessels
regrow
• Epithelium
regenerates
Integumentary accessory structures
• Hair, nails: harder keratin than epidermis
• Sebaceous and sweat glands
• Forms from embryonic epidermis that folds into dermis
• Located in dermis: penetrate through epidermal skin surface
