Integumentary System

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Integumentary System

• Chapter 5 Vertebrate Anatomy

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5 Components of the Integumentary System

• Skin
• Sweat glands
• Oil glands
• Hair
• Nails

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Basics about skin

• Every square centimeter of human skin contains
• 70 cm of blood vessels
• 100 sweat glands
• 230 sensory receptors
• 55 cm of nerves
• 15 oil glands
• The surface area of the skin is about 2 square
  meters
• The skin weighs about 9 11 lbs.
• Though the term integument means covering,
  the skin is obviously much more than just this

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Skin is our primary barrier against

• Infection
• Heat loss
• Water loss

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Two Main Regions of the Skin

• Epidermis
• Made of epithelial tissue
• Outermost layer thin
• NOT vascular nutrients reach this layer via
  diffusion
• Dermis
• Underneath the dermis
• Makes up the bulk of the skin
• Lots of leathery connective tissue
• vascularized

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Two Main Regions of the Skin

• 3rd layer subcutaneous or hypodermis
• Not technically part of the skin
• Composed mostly of adipose tissue (fat)
• Protects
• Anchors skin to muscle
• Allows skin to slide freely over underlying
  structures
• Shock absorber and insulator

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Epidermis in Detail

• 4 different types of cells in epidermis
• Keratinocytes
• Melanocytes
• Merkel cells
• Langerhans cells

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Epidermis in Detail

• Keratinocytes
• Produce keratin
• Protein that gives epidermis its protective
  qualities
• Life of a keratinocyte
• Arise in the deepest part of the epidermis
• Pushed toward skin surface by production of new
  cells underneath
• By the time they reach the surface they are dead
  and scale-like
• Millions of keratinocytes rub off daily totally
  new epidermis every 25-45 days

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Epidermis in Detail

• Melanocytes
• Produce the pigment known as melanin
• Melanin molecules form a pigment shield that
  protects the nucleus from UV radiation
• A tan is your bodys effort to prevent you from
  getting skin cancer
• All races have the same number of melanocytes
• Differences in skin color are due to activity of
  these cells and/or how fast melanin breaks down
  once produced
• Click HERE for I Am Joes Melanocyte

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Epidermis in Detail

• Langerhans cells
• Help activate the immune system
• Shown at right
• Merkel cells
• Involved in forming sensory receptors that sense
  touch

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Layers of the Epidermis

• Thick skin of the palms, fingertips and soles of
  feet has 5 layers of epidermis
• Other skin has only 4 layers that are themselves
  thinner as well.

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Layers of the Epidermis

• Deepest Layer Stratum Basale
• Firmly attached to dermis underneath
• Youngest keratinocytes

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Layers of the Epidermis

• Stratum spinosum
• Next layer up from stratum basale
• Cells appear spiney

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Layers of the Epidermis

• Stratum granulosum
• Cells flatten as they pass through this layer
• Nuclei and organelles disintegrate
• Cells accumulate waterproofing granules
• The keratinocytes are toughening up in
  preparation of becoming the protective outer layer

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Layers of the Epidermis

• Above stratum granulosum, cells die
• They are too far away from dermal capillaries to
  receive adequate nourishment

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Layers of the Epidermis

• Stratum lucidum
• Only present in thick skin
• Thin translucent band above the stratum granulosum

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Layers of the Epidermis

• Stratum corneum
• 20-30 cell layers thick
• Keratin and thick cell membranes of these cells
  protect the skin against abrasion and penetration
• Glycolipids between the cells waterproof this
  layer
• Cornified or horny cells are the cell remnants
  of the stratum corneum
• These are familiar as dandruff
• The average person loses 40 lbs. of skin in a
  lifetime

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Dermis in Detail

• Strong flexible connective tissue layer
• Richly supplied with
• Nerve fibers
• Blood vessels
• Lymph vessels
• Major parts of hair follicles
• Major parts of oil glands
• Major parts of sweat glands

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Layers of the Dermis

• Two layers
• Papillary layer
• Reticular layer

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Layers of the Dermis

• Papillary layer
• Can lie atop dermal ridges
• Creates epidermal ridges that aid in gripping
  fingerprints

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Layers of the Dermis

• Reticular layer
• 80 of dermis
• Lots of collagen fibers
• Give strength and resiliency prevents most jabs
  from entering dermis
• Also elastin fibers
• Provide stretch/recoil

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Clinical Aspects of Dermis

• Stretch marks
• Silvery white scars caused by dermal tears
• Blisters
• Epidermis and dermis become separated by a fluid
  filled pocket

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Skin Color

• Only pigment MADE in the skin that contributes to
  skin color is melanin
• Melanocytes of dark-skinned people produce more
  and darker melanin that those of light-skinned
  people
• Local accumulations of melanin freckles and
  pigmented moles

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Skin Color

• Melanocytes become more active upon exposure to
  sun
• Purpose of melanin is to protect DNA from UV
  radiation
• Initial signal for speed up of melanin production
  is increased rate of repair of photo-damaged DNA!

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Skin Color

• 3 effects of excessive sun exposure
• Clumping of elastin fibers leathery skin
• Depression of immune system
• Alter DNA Cancer

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Skin Color

• Some chemicals can make people especially
  sensitive to light photosensitivity
• Antibiotics
• Antihistamines
• Perfumes
• Detergents
• May cause itchy, blistery lesions then peeling
  in sheets

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Skin Color

• Other pigments that color the skin (but are not
  MADE in the skin)
• Carotene
• Yellow/orange
• Accumulates in stratum corneum
• Hemoglobin
• Pigment in blood

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Skin Color

• Jaundice
• Excess bile pigments (bilirubin) accumulate in
  the blood and deposit in body tissues
• Yellow

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Skin Color

• Bruises
• Black and blue marks indicate blood escaped from
  circulation and clotted beneath the skin
• Hematoma

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Appendages of the Skin

• Hair follicles
• Hair
• Nails
• Sweat glands
• Sebaceous glands

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Sweat Glands

• Found almost everywhere on the skin
• 2.5 million sweat glands on a person
• There are two types of sweat glands
• Eccrine
• Apocrine

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Sweat Glands - Eccrine

• Most abundant on palms, soles of feet and
  forehead
• The pore of the gland is on the skins surface
• Composition of Sweat
• pH of sweat ranges from 4 to 6
• 99 water
• Some salts
• Vitamin C
• Antibodies
• Traces of metabolic wastes
• Urea, uric acid, ammonia
• Lactic acid attracts mosquitoes

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Sweat Glands - Eccrine

• Major role of sweat assist in thermoregulation
  control of body temperature
• Heat induced sweating begins on the forehead
• Cold sweat begins on the palms, soles of feet,
  armpits

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Sweat Glands - Apocrine

• Location
• Axillary (armpit) and genital areas
• Empty into hair follicles
• Begin to function at puberty
• NO role in thermoregulation
• Seen as analogous to sexual scent glands in other
  animals
• Composition of apocrine sweat
• True sweat PLUS fatty substances and proteins a
  viscous and milky substance
• Secretion of apocrine glands is initially
  odorless
• It is the breakdown of the organic compounds by
  bacteria that causes odor

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Sweat Glands - Apocrine
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Other Glands highly modified sweat glands

• Ceruminous glands
• Lining of the external ear canal
• Secrete wax
• Deters insects and blocks entry of foreign
  material
• Mammary glands
• Specialized glands that secrete milk in mammals

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Sebaceous Glands

• Found everywhere on the skin EXCEPT palms and
  soles of feet
• Largest on the face, neck and upper chest
• Secrete sebum
• Glands become active at puberty

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Clinical Aspects of Sebaceous Glands

• If a sebaceous gland becomes blocked we observe a
  whitehead
• If the material in the white head becomes
  oxidized, it darkens and results in a blackhead
• The inflammation of sebaceous glands accompanied
  by pimples is known as acne
• Usually caused by a bacterial infection

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Sebaceous Glands

• Function of Sebum
• Softens and lubricates hair and skin
• Slows water loss
• Kills bacteria
• Sebum is usually secreted into a hair follicle

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Hair and Hair Follicles

• Function of hair in MOST mammals is to keep warm
• The main function of OUR hair is to sense insects
  on the skin
• Hair on the scalp protects against
• Heat loss
• Physical trauma
• sunlight
• Other hair
• Eyelashes shield eyes
• Nose hairs filter large particles from inhaled air

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Structure of Hair

• Hair is made of keratinized cells
• Shaft part of the hair that projects from the
  skin
• Outermost layer cuticle
• When cuticle wears away, split ends result
  the inner keratin fibers fray
• Hair type determined by shape of shaft
• Flat and ribbon like shaft results in curly/kinky
  hair
• Round shaft results in straight hair
• Root part of the hair that is embedded in the
  skin
• When melanocytes at the base of hair follicles
  decrease their production of melanin, gray/white
  hair results

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Hair Shaft
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Structure of the Hair Follicle

• Deep end of the follicle is expanded and forms
  the hair bulb
• Root hair plexus
• Sensory nerve endings wrapped around the hair
  bulb
• Allow hairs to act as touch receptors
• Papilla
• Carries capillaries (and thus nutrients) to the
  hair bulb

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Structure of the Hair Follicle

• Arrector pili
• Tiny muscles
• When they contract they pull the hair upright
• Results in goose bumps
• Used in other mammals for heat retention
• fluffing of fur traps air and air is a good
  insulator
• Virtually useless in humans

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Distrubution, Types and Growth of Hair

• 100,000 hairs on an average scalp
• 30,000 in an average beard
• Male sex hormones called androgens (testosterone
  in particular) stimulates hair growth in both
  sexes
• Average rate of hair growth per week is 2mm
• About 90 hairs lost per day
• Eyebrows are shorter because life of hair
  follicle is less

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Distrubution, Types and Growth of Hair

• Hair thinning and baldness
• Rate of hair growth declines in 40s
• Atrophy of hair follicles
• Hairs are not replaced as fast as they are shed
• Male pattern baldness
• Genetically determined
• Gene switches on that changes the way hair
  follicles responds to testosterone

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Nails

• Scale-like modifications of the epidermis
• Protect ends of fingers or toes
• Correspond to hoofs and claws
• Useful as tools
• Lots of keratin

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Nails

• Nail bed under the nail
• Nail matrix
• Responsible for growth
• Visible as the lunula

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Functions of the Integumentary System

• Protection
• Provides 3 barriers
• Chemical barrier
• Low pH inhibits bacterial growth
• Bactericidal substances in sebum inhibits bact.
  growth
• Melanin protects against UV light
• Physical barrier
• Helps prevent foreign objects from penetrating
  skin
• Waterproofed so that water and solutes may
  neither entor nor LEAVE the body
• Biological barrier
• Cells like Langerhans cells are active, living
  elements of the immune system

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Functions of the Integumentary System

• Body Temperature Regulation
• Sweat glands constantly secrete small amounts of
  sweat
• Rise in body temp causes dermal blood vessels to
  dilate sweat glands are stimulated
• Up to 12 liters of water can be lost in one day
• Cold external environment causes dermal blood
  vessels to constrict
• Causes the warm blood to bypass the skin and the
  cold environment temporarily

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Functions of the Integumentary System

• Cutaneous Sensation many different types of
  sensory receptors sense different types of touch
• Meissners corpuscles sense carress, feel of
  clothing
• Pacinian receptors sense bumps, deep pressure
• Root hair plexus senses wind blowing hair tug
  on hair
• Bare nerve endings - pain

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Functions of the Integumentary System

• Metabolic functions
• Vitamin D is made only when sunlight strikes the
  skin

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Functions of the Integumentary System

• Blood reservoir
• Skin holds 5 of the bodys blood supply
• Blood can be shunted from the skin to other
  organs (ex. Working muscles, stomach, etc.) as
  needed
• Why you may feel cold after eating

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Functions of the Integumentary System

• Excretion
• Water, salt and nitrogenous wastes are all
  excreted through the skin in some amount

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Homeostatic Imbalances of the Skin

• Over 1000 different skin conditions exist
• Most are caused by
• Bacterial infection
• Viral infection
• Yeast infection

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Homeostatic Imbalances of the Skin

• Burns
• More than 2 million Americans are treated for
  burns each year.
• 12,000 die
• Most immediate threat to life in severe burns
• Catastrophic loss of body fluids

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Skin Cancer

• Most tumors that arise on the skin are benign and
  do not metastasize
• They do not spread
• Example a wart caused by a virus
• Some skin tumors are malignant
• Cancerous
• Invade other body areas

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Skin Cancer

• Important risk factor in nonmelanoma skin cancer
  is over exposure to sunlight (UV radiation)
• UV radiation appears to damage a tumor suppressor
  gene, thus allowing a tumor to begin and grow

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Basal Cell Carcinoma

• Least malignant skin cancer
• Most common skin cancer
• Slow growing
• Full cure in 99 of cases
• Excision

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Squamous Cell Carcinoma

• Appears as a scaly red bump
• Often found on scalp, ears, hands, lower lip
• Grows rapidly if not removed metastasizes to
  lymph nodes
• Cure rate is good if caught early and removed
• Surgery and radiation

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Malignant Melanoma

• Most dangerous skin cancer
• Melanocytes become cancerous
• 5 of skin cancers are of this type
• About 1/3 appear from pigmented moles
• First appears as a spreading black/brown patch.
  Metastasizes rapidly to surrounding lymph and
  blood vessels
• Survival rate is 50

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ABCDE Rule for Recognizing Malignant Melanoma

• A Assymetry
• B Border irregularity
• C Color
• D Diameter Larger than 6mm
• E - Elevation

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Related Clinical Terms

• Albinism
• Inherited
• Melanocytes do not make melanin
• Skin is pink
• Hair is pale/white

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Related Clinical Terms

• Boil
• Inflammation of hair follicles and sebaceous
  glands
• Infection spread to dermis
• Area of inflammed tissue gradually forms a
  pus-filled swelling that is painful to touch

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Related Clinical Terms

• Callus
• Gross thickening of the epidermis caused by
  persistent friction

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Related Clinical Terms

• Cold Sore
• Caused by herpes simplex infection
• Virus localizes in a cutataneous nerve
• Remains dormant until activated by some stressor
  like emotional upset, fever or UV radiation

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Related Clinical Terms

• Contact dermatitis
• Itching
• Redness
• Caused by exposure of skin to chemicals

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Related Clinical Terms

• Decubitus
• Bedsores
• Caused by continuous pressure

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Related Clinical Terms

• Port Wine Stain
• Most noticeable of birth marks
• Deep red blotches resulting from an abnormally
  dense network of blood vessels beneath the skin
  surface

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Related Clinical Terms

• Psoriasis
• Chronic
• Reddened epidermal lesions covered with dry
  silvery scales
• May be disfiguring
• Cause unknown
• Autoimmune attack suspected

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Related Clinical Terms

• Ringworm
• Highly contagious fungal infection
• May or may not be ring-shaped
• Fungi feed on dead skin and wastes in sweat
• Athletes foot is one

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Related Clinical Terms

• Rosacea
• Redness of face accompanied by rash-like lesions
• Due to vasodilation of facial blood vessels
• Sudden facial flushing that rapidly disappears,
  though each episode lasts longer
• Can be brought on by exercise, hot fluids,
  alcohol
• Can lead to mats of swollen veins and pustule
  clusters if untreated
• Cause unknown bacterial infection suspected

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Related Clinical Terms

• Vitiligo
• Most common skin pigment disorder
• Loss of melanocytes
• Uneven dispersal of melanin
• Unpigmented skin regions surrounded by pigmented
  areas
• Autoimmune cause suspected

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More on Burns

• Degrees of Burns
• 1st degree burn
• Only produce redness
• Least severe

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More on Burns

• 2nd degree burn
• Produce blisters
• Moderately severe

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More on Burns

• Degrees of Burns
• 3rd degree burn
• Most severe
• Tissue destroyed down to the level of muscle
  and/or bone
• Requires skin grafts to repair
• Greatest Dangers
• Initially
• Loss of body fluids
• May lead to shock and organ failure
• Later
• infection

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Degrees of Burns