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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! . Where in the body is your skin the thinnest (~1.5mm)?. Lips Palmar region Lower eyelids Cervical region Popliteal region.

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The Integumentary System

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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!

Where in the body is your skin the thinnest (~1.5mm)?

  • Lips

  • Palmar region

  • Lower eyelids

  • Cervical region

  • Popliteal region

Where in the body is your skin the thickest (4mm)?

  • Calcaneal region

  • Abdominal region

  • Buccal region

  • Otic region

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


  • Avascular& Keratinized

  • Thick skin – 5 layers

  • Thin skin – 4 layers

  • New epidermis every 25-45 days

  • Cells:

    • Keratinocytes(90% cells) – produce keratin

      • Tightly connected by desmosomes

      • Callus – accelerated keratin formation

    • Melanocytes – (8% cells) spider shaped, produce melanin

      • Melanin taken in by keratinocytes

      • Shields nucleus from UV

    • Langerhans’ cells – star shaped phagocytes

    • Merkel cells – sense skin curvature

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 creating a strong bond, and increasing grip

  • Ridge contours are developmentally determined in 3rd month of fetal development 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

What is Psoriasis?

  • Autoimmune disease

  • Fungal infection

  • Increased rate of mitosis

  • Contagious

  • 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 (8-10 layers)

    • Cells continue to divide

    • Langerhans cells abundant

  • Stratum Granulosum

    • 3-5 flattened grainy cell layers

    • Stopped dividing, undergo apoptosis, nuclei & organelles break down

    • Produce keratin (durable, water resistant protein) becomes more apparent

    • Produce glycolipids –reduces water loss

  • Stratum Lucidum**

    • Thin tough clear layer

    • Found in thick skin

    • 4-6 layers of densely packed cells filled with keratin

Stratum Corneum

  • Most Superficial layer

  • ¾ of epidermis

  • 20-30 (up to 50) layers of flat dead keratinized or cornifiedcells

  • 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 wrinkled leathery skin?

  • Clumping of elastic fibers

  • Thymine dimers in DNA

  • Disruption of collagen fibers

  • 1&3

  • All of the above

What is the most common form of cancer?

  • Breast cancer

  • Lung cancer

  • Malignent melanomas

  • Basal Cell carcinoma

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, macrophages, mast cells

    • Dermal Papillae indent epidermis

    • Supports and nourishes epidermis

    • Capillaries and nerves

      • Meissnerscorpsucles – 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


  • 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:

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

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

    • Arrectorpilismooth muscle in dermis forces hair to stand up

Hair 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

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

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)

Write an analogy for our skin….

  • Human skin is like __________ because _______________.

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

  • Arrectorpili 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

  • ApocrineSweat 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

ID structure A

  • Sweat Gland

  • Sebaceous Gland

  • Epidermal Ridges

  • Adipocytes

  • Arrector Pilli muscle

  • PacinianCorpsucle

ID structure B

  • Hair Papilla

  • Sebaceous Gland

  • Hair shaft

  • Hair root

  • Arrector Pilli muscle

  • PacinianCorpsucle

ID structure C

  • Sweat Gland

  • Sebaceous Gland

  • Epidermal Ridges

  • Paciniancorpsucle

  • Hair Papilla

  • Hair shaft

  • Hair root

ID structure D

  • Merocrine Gland

  • Sebaceous Gland

  • Epidermal Ridges

  • Arrector Pilli muscle

  • PacinianCorpsucle

  • Apocrine Gland

ID structure E

  • Sweat Gland

  • Sebaceous Gland

  • Epidermal Ridges

  • Adipocytes

  • Arrector Pilli muscle

  • PacinianCorpsucle

ID structure F

  • Stratum basal

  • Stratum spinosum

  • Epidermal Ridges

  • Stratum lucidum

  • Stratum granulosum

  • Stratum corneum

ID structure G

  • PacinianCorpsucle

  • Merkels discs

  • Ruffinis endings

  • Free Nerve endings

  • Adipocytes

  • Meissnerscorpsucle

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

    Deeper 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


  • 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

Complete web showing how Integumentary system interconnected w/other organ systems!

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