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.

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The Integumentary System

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The integumentary system

The Integumentary System

Skin, Hair, Nails, and Glands

Do now

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

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

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

  • Calcaneal region

  • Abdominal region

  • Buccal region

  • Otic region

Integumentary structure

Integumentary Structure

  • 2 Components:

    • Cutaneous Membrane

      • Epidermis

      • Dermis

      • Hypodermis

        • aka subcutaneous layer

        • Superficial fascia

    • Accessory Structures

      • Hair

      • Nails

      • Exocrine Glands

Integumentary function

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 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

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

Fingerprint Activity

What is psoriasis

What is Psoriasis?

  • Autoimmune disease

  • Fungal infection

  • Increased rate of mitosis

  • Contagious

The integumentary system

  • 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

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

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

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

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

What is the most common form of cancer?

  • Breast cancer

  • Lung cancer

  • Malignent melanomas

  • Basal Cell carcinoma

Sun exposure

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

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

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 “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

Cutis hyperelastica

Mechanoreceptors of skin

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

Sensory Homunculus

What causes a decubitus ulcer or bed sore

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

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

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

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

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

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

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

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

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

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

Write an analogy for our skin….

  • Human skin is like __________ because _______________.

What are comedones

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

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

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

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

Slides of Scalp vs. Palm

Id structure a

ID structure A

  • Sweat Gland

  • Sebaceous Gland

  • Epidermal Ridges

  • Adipocytes

  • Arrector Pilli muscle

  • PacinianCorpsucle

Id structure b

ID structure B

  • Hair Papilla

  • Sebaceous Gland

  • Hair shaft

  • Hair root

  • Arrector Pilli muscle

  • PacinianCorpsucle

Id structure c

ID structure C

  • Sweat Gland

  • Sebaceous Gland

  • Epidermal Ridges

  • Paciniancorpsucle

  • Hair Papilla

  • Hair shaft

  • Hair root

Id structure d

ID structure D

  • Merocrine Gland

  • Sebaceous Gland

  • Epidermal Ridges

  • Arrector Pilli muscle

  • PacinianCorpsucle

  • Apocrine Gland

Id structure e

ID structure E

  • Sweat Gland

  • Sebaceous Gland

  • Epidermal Ridges

  • Adipocytes

  • Arrector Pilli muscle

  • PacinianCorpsucle

Id structure f

ID structure F

  • Stratum basal

  • Stratum spinosum

  • Epidermal Ridges

  • Stratum lucidum

  • Stratum granulosum

  • Stratum corneum

Id structure g

ID structure G

  • PacinianCorpsucle

  • Merkels discs

  • Ruffinis endings

  • Free Nerve endings

  • Adipocytes

  • Meissnerscorpsucle

Injury and repair of skin

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

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

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