the integumentary system skin, hair, nails, and glands
TRANSCRIPT
The Integumentary System
Skin, Hair, Nails, and Glands
Do Now:
Calculate the weight of your skin: For average adult skin accounts for 7% of
body weight!
Thickness ranges from 1.5mm – 4.0mm Where on the body is it thickest?
Thinnest?
Integumentary Structure 2 Components:
Cutaneous Membrane Epidermis Dermis Hypodermis
aka subcutaneous layer Superficial fascia
Accessory Structures Hair Nails Exocrine Glands
Integumentary Function
Protection Temperature
maintenance Synthesis and
storage of nutrients Sensory reception Excretion and
secretion
Epidermis
Avascular & Keratinized Thick skin – 5 layers Thin skin – 4 layers New epidermis every 25-45 days Cells:
Keratinocytes (most cells) – produce keratin Tightly connected by desmosomes Callus – accelerated keratin formation
Melanocytes – (spider shaped) produce melanin Melanin taken in by keratinocytes Shields nucleus from UV
Merkel cells – sense skin curvature Langerhans’ cells – star shaped phagocytes
Layers of Epidermis
Layers (starting from basement membrane): Stratum Germinativum (Basale)
3 Intermediate layers Stratum Spinosum Stratum Granulosum Stratum Lucidum**
Stratum Corneum (superficial)
Stratum Germinativum (aka stratum basal)
Newly synthesized keratinocytes attached to basement by hemi-desmosomes
Forms ridge contours at interface of epidermal ridges and papillae of underlying dermis
Ridge contours are developmentally determined and visible in palmer, plantar, and digits
1 layer of Stem cells or germinative cells dominate the stratum germintivum Undergoing mitosis
10-25% melanocytes, some merkel cells Receives nourishment from dermis
Fingerprint Activity
Psoriasis
• Very common between 15-35
• Autoimmune disease
• increased rate of mitosis despite same rate of shedding
• Non-contagious
• Treated w/topically or phototherapy
Intermediate Strata Stratum Spinosum
spiny or prickly layer Newly synthesized
keratinocytes (several layers) Cells continue to divide Langerhans cells abundant
Stratum Granulosum 3-5 flattened grainy cell layers Stopped dividing, nuclei 7
organelles break down Produce keratin (durable,
water resistant protein) Produce glycolipids –reduces
water loss Stratum Lucidum
Thin layer clear layer Found in thick skin Densely
packed cells filled with keratin
Stratum Corneum Most Superficial layer ¾ of epidermis 20-30 layers of flat dead
keratinized or cornified cells
Held tightly together by desmosomes
Relatively dry (prevents microorganism growth)
Lasts about 2 weeks before shed Avg person sheds 40lbs of
skin in a lifetime!
Pigmentation:Skin Color
Melanin (yellow, brown or black pigment) Produced by melanocytes in epidermis Production increases in response to sun
exposure Prevents skin damage by absorbing UV
rays All humans have same number of
melanocytes Freckles & moles are areas of heavy melanin
production Carotene (orange-yellow pigment)
Converted to vitamin A for epithelial maintenance
Accumulates in stratum corneum Dermal Circulation
Oxygenated Hemoglobin - reddish tint Constricted blood vessels – pale Cyanosis – Sustained constriction bluish
color in Caucasian, only visible in nail beds of dark skin
What causes the appearance of wrinkled,
leathery skin?
Sun Exposure
UV stimulates production of vitamin D3
D3 is modified by liver and converted to calcitrol by kidneys
Calcitrol essential for absorption of calcium and phosphorus
Too much UV clumps elastin fibers causing leathery appearance
UV destroys folate needed for DNA synthesis Too much UV can also cause chromosomal
damage in stem cells of stratum germinativum causing skin cancer
Skin Cancer Most common form of cancer (and most preventable) Basal Cell Carcinoma – originates in stratum
germanitivum Squamous Cell Carcinomas – superficial layers Malignant Melanomas
Extremely dangerous Begins as a mole Melanocytes grow rapidly and metastasize through lymphatic
system
Know the ABCD rule!
Do Now: What are Stretch Marks?
Damage to the dermis (collagen & elastin fibers) due to rapid stretching of the skin due to rapid growth or weight gain
Appear reddish- purple at first then fade to a lighter color over time
Tend to occur in regions of the body where fat is stored
Hormonal changes, genetics, and diet can all affect development of stretch marks
Dermis “hide” Dermis – contains network of blood
vessels, lymph vessels, and nerve fibers Papillary Layer (thin superficial)
Loose connective tissue fibroblasts., macrphages, mast cells
Dermal Papillae indent epidermis Supports and nourishes epidermis Capillaries and nerves
Meissners corpsucles – touch receptors Reticular Layer (80% of dermis)
Meshwork of dense irregular connective tissue
Elastic fibers provide stretch & recoil Collagen fibers provide rigidity & strength BV, sweat and oil glands Phagocytes
Striae – stretch marks Blisters
Cutis hyperelastica
Mechanoreceptors of Skin
Merkel’s disk Skin Curvature
Meissner Corpuscle Light Touch
Free Nerve Endings Pain Chemicals
Ruffini’s ending Heat Stretch
Pacinian Corpuscle Deep Pressure Vibrations
Sensory Homunculus
What causes a decubitus ulcer or bed sore?
Caused by an interruption of blood supply to a tissue causing necrosis. These develop in patients that have been bed ridden for long periods of time. They are caused by the weight of the body on the skin overlying a bony area compressing the blood supply.
Do Now: List & describe layers of the Integument
Epidermis Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum germanitivum (Basale)
Dermis Papillary Layer Reticular Layer
Hypodermis
Subcutaneous Layer Not actually part of integument, blurred boundary Anchors skin to muscles, but loosely so it can slide Loose connective tissue with many adipocytes Fat distribution changes as grow and mature
(shock absorption & insulation) Females thighs & breasts Males abdomen “beer belly”
Contains no vital organs and few capillaries Subcutaneous injection useful method of
administering drugs with hypodermic needle
Accessory Structures: Hair and Hair Follicles
2.5 million hairs on human body!! Hair Growth Cycle
Hair grows for 2-5 years about .3mm per day then pushed to surface to be shed for new cycle to begin (scalp 6-10 yr cycle, eyebrows 3-4 months)
Function Protect scalp from UV, cushion head, and
insulate skull Prevent entry of foreign particles in nostrils, ears,
and eyes Respond to stress or cold (arrector pili smooth
muscle in dermis forces hair to stand up) Structure
Walls of follicle contain cells of epidermis Hair Papilla – peg of connective tissue
containing capillaries and nerves, cell division occurs
Hair Root – anchors hair in to skin Hair Shaft – 3 layers of dead keratinized cells Medulla – core of hair (soft keratin)
Absent in fine hair Cortex – surrounds medulla (hard keratin) Cuticle – surface single layer made of
overlapping shingles of cells
Hair Texture
Oval – silky & wavy Flat & ribbonlike – curly Round – straight
Conditioners – smooth out rough cuticles making it shiny
Split ends – cuticle wears away at ends
Hair Types: Cuticle
Coronal Crown like (stacked paper cups) Small rodents & bats
Spinous Petal or triangular shaped Mink, cats and seals
Imbricate Flattened, overlapping scales Humans and other animals
Medulla Fragmentary (trace) Discontinuous (broken) Continuous
Cortex Human pigment granules distributed by cuticle (except red-hair) Cattle, dogs and some humans have ovoid bodies
Human Hairs vs. Animals
Consistent color & pigmentation throughout shaft (see banding in animals)
Animal pigmentation is centrally located Humans 2 types of hair:
Vellus hair – fine body hair Terminal hair – coarser, darker hair (increased testosterone
increases growth)
Hair Color
Genetically determined by type and amount of pigment produced by melanocytes Brown – true melanin Blond - sulfur Red - iron Gray - Pigment
production decreases White air bubbles within
hair shaft
Do Now: What is alopecia?
Hairs not replaced as fast as they are shed, begins anteriorly and progresses posteriorly
Male pattern baldness – sex linked trait by delayed action gene that when turned on changes response to testosterone Until recently, only cure inhibits
testosterone production
What are comedones? Acne is caused by blocked sebaceous duct, forming a
sebum plug Affects over 85% of adolescents and young adults. Secretions accumulate causing inflammation and possible
bacteria infection Blackheads – open comedones, melanin oxidizes turning
black Whiteheads – closed comedones Hormonal changes can cause increased oil production Try not to squeeze, scratch, pick, or rub the pimples.
Although it might be tempting to do this, it can lead to skin infections and scarring.
Accessory Organs: Nails
Protect exposed finger tips and limit distortion when exposed to mechanical stress
Tools – pick up or scratch itch Free Edge Nail body – dead keratinized cells
Nail bed – epidermis covered by nail body
Nail root – anchors nail body Nail matrix – nail growth occurs
Cuticle – portion of stratum corneum extending over nail
Lunula – pale crescent (area of obscured blood vessels)
Accessory Structures: Sebaceous Glands Holocrine oil glands Arrector pili muscle contracts squeezes the sebaceous gland forcing
oily secretion out Sebum (oily secretion) lubricates hair and skin and inhibits bacteria
growth, slows water loss from skin Glands are sensitive to androgens (sex hormones)
Cradle Cap – overactive sebaceous glands
Accessory Structures: Sudoriferous (sweat) Glands
About 3 million per person! Merocrine (eccrine) Sweat Glands
Secreted directly onto surface of skin via exocytosis
99% water w/electrolytes, vitamin C, antibodies, metabolic wastes and drugs, pH of 4-6
Cools surface of skin and lowers body temp Too much perspiration may lead to dehydration Flushes microorganisms from surface
Apocrine Sweat Glands sweat glands that secrete products into hair
follicles in armpits, nipples, and groin Sticky, cloudy secretion released at puberty Odorous as bacteria break it down as food
Slides of Scalp vs. Palm
Injury and Repair of Skin
Inflammatory response – triggered by mast cells increase blood flow to area Scab (fibrin proteins) forms at surface to restrict entry of microorganisms Cells divide rapidly to replace missing cells Macrophages and phagocytes clear debris and patrol area for pathogens Animation: http://www.youtube.com/watch?v=QHzHc9E8kTw&feature=relatedDeeper wounds Scar tissue – lots of collagen fibers and few blood vessels
Fetuses don’t scar Keloid – thickened area of scar tissue with shiny smooth surface (tend to form in
adults with dark skin) Damaged hair follicles, sebaceous and sweat glands, muscle cells and nerves
are rarely repaired Burns
1st degree – kills superficial epidermal cells, injures papillary dermis 2nd degree – kills epidermis and possible some dermis, injures reticular dermis 3rd degree – kills all epidermal and dermal cells, injures hypodermis and deeper
tissues Skin Gun: http://www.youtube.com/watch?v=eXO_ApjKPaI
Aging Epidermis thins as stem cell activity decreases
increasing skin injuries and infections Number of macrophages and other immune system
cells decreases Decline in vitamin D3 production reduces calcium and
phosphorus absorption weakening muscles and bones Melanocyte activity decreases causing increases
sensitivity to sun Gland activity decreases causing dry scaly skin Follicles decrease function creating thin light hair Elastic fibers decrease resulting in wrinkling Reduced blood supply to dermis – less
thermoregulation Repairs are slow…6-8 weeks
Write an analogy for our skin….
Human skin is like __________ because _______________.
Complete web showing how
Integumentary system
interconnected w/other organ
systems!
Integumentary System
Skeletal System
Muscular
System
Nervous System
Endocrine
SystemCardiovascular System
Lymphatic
System
Respiratory
System
Digestive
System
Urinary System
Reproductive
System
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