SKIN

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SKIN

• Cutaneous membrane
• Integumentary system

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INTEGUMENTARY SYSTEM

• Means covering
• Consists of Skin, sweat glands, oil glands, hairs
  and nails

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SKIN

• Basic Functions
• To protect
• To insulate
• To cushion
• The skin protects deeper tissues from
• Mechanical damage
• Chemical damage
• Bacterial damage
• Ultraviolet radiation (damaging effects of
  sunlight)
• Thermal (heat or cold) damage
• Desiccation (drying out)
• Aids in body heat loss or heat retention
  (controlled by the nervous system)
• Aids in excretion of urea and uric acid
• Synthesizes vitamin D

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STRUCTURE OF THE SKIN 2 kinds of tissue

• 1 EPIDERMIS- (stratified squamous)
  KERATINOCYTES cells which produce KERATIN-
  fibrous protein that makes the skin become hard
  and tough
• 2 DERMIS- dense connective tissue firmly
  connected to epidermis, but can separate and form
  a blister-

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STRUCTURE OF THE SKIN

• SUBCUTANEOUS TISSUE (HYPODERMIS)- not
  considered skin- adipose tissue that anchors skin
  to surrounding organs

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EPIDERMIS

• 5 LAYERS CALLED STRATA- all layers are avascular-
  has no blood supply

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EPIDERMIS

• STRATUM BASALE- single bottom layer of epidermis-
  columnar in shape- receive the most
  nourishment-constantly undergoing cell division
  with all the new daughter cells pushed upwards

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EPIDERMIS

• STRATUM SPINOSUM-spiny layer of cuboidal cells-
  nuclei appear dark- first signs of cell death

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EPIDERMIS

• STRATUM GRANULOSUM- partially flattened cells
  whose cytoplasm contains small granular proteins
  that are in the process of turning into keratin-
  nucleus begins to disappear

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EPIDERMIS

• STRATUM LUCIDUM clear layer- 3 to 4 rows of
  cells that are flattened and now dead- keratin
  formation continues
• is only where the skin is hairless and extra
  thick, palm of the hands and soles of the feet

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EPIDERMIS

• STRATUM CORNEUM-most superficial layer- 20-50
  cells thick accounts for 75 of the skins
  thickness
• slowly rubs and flakes off and is replaced by
  cells produced by the division of the deeper
  stratum basale cells. Every 25 to 45 days we have
  a new epidermis.

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KERATINOCYTES

• Keratin is found the stratum corneum and is a
  tough protein that provides a durable overcoat
  for the body, protecting the deeper cells from
  the hostile external environment. It also
  protects them from water loss and helps the body
  resist biological, chemical, and physical assault

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MELANOCYTES

• Melanin is a pigment that ranges in color from
  yellow to brown to black and is mainly found in
  the stratum basale. Sunlight stimulates the
  melanocytes to produce melanin, tanning occurs.
  The stratum basale cells phagocytize the pigment,
  accumulating it within them. The melanin forms a
  protective pigment umbrella over the nuclei
  that shields their genetic material from the
  damaging effects UV RAYS. Freckles and moles are
  seen where melanin is concentrated in one spot

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DERMIS

• The dermis is a strong, stretchy envelope that
  helps to hold the body together
• Contains collagen and elastic fibers
• Collagen- provides toughness, also attracts and
  binds to water to keep skin hydrated
• Elastic- provides elasticity
• It varies in thickness, thick on the palms of the
  hand and soles of the feet, but quite thin on the
  eye lids
• Consists of two regions
• 1. PAPILLARY LAYER- upper region
• 2. RETICULAR LAYER- lower region

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DERMIS

• PAPILLARY LAYER (upper)-contains dermal
  papillae
• DERMAL PAPILLAE- uneven fingerlike projections
  from its superior surface (fingerprints)- these
  projections can house many things
• Capillary Loops-
• Free nerve endings (pain receptors)
• Meissners corpuscles- (touch receptors)

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DERMIS
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DERMAL PAPILLAE can house many things

• 1. Capillary Loops- which can increase /
  decrease blood flow to skin
• 2. Free nerve endings (pain receptors) some
  receptors detect hot or cold.
• 3. Meissners corpuscles- (touch receptors)

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DERMIS

• RETICULAR LAYER (deep)-
• Contains
• 1. BLOOD VESSELS
• 2. SUDORIFEROUS GLANDS-(sweat) (2 types)
• 3. SEBACEOUS GLANDS- (oil)
• 4. PACINIAN CORPUSCLES- deep pressure receptors

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SUDORIFEROUS GLANDS-

• Two types
• ECCRINE GLANDS more numerous and produce sweat-
• SWEAT contains
• 1. water
• 2. sodium chloride
• 3. vitamin C
• 4. metabolic waste (ammonia, urea)
• 5. lactic acid (attracts mosquitos)

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SUDORIFEROUS GLANDS-
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FUNCTIONS OF SWEAT

1. Evaporation of sweat off the skins surface gives
   cooling effect
2. Acidic (pH of 4-6) inhibits bacteria growth

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SUDORIFEROUS GLANDS-

• APOCRINE GLANDS- found only in the armpit and
  genital areas
• SECRETION contains fatty acids and proteins
  (yellowish or milky color)
• The secretion is odorless but bacteria can grow
  from it giving off an unpleasant odor.

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SEBACEOUS GLANDS (oil glands)

• Typically located near hair follicle and dump
  secretions (SEBUM) there.
• SEBUM- lubricant that keeps skin soft and moist.
  Keeps hair from becoming brittle. Also contains
  chemicals to kill bacteria.

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SEBACEOUS GLANDS (oil glands)

• If a sebaceous gland becomes blocked a WHITEHEAD
  APPEARS
• If that material oxidizes and dries then a
  BLACKHEAD FORMS

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SKIN COLOR

• 3 pigments contribute
• 1. MELANIN in the epidermis (amounts and types)
• 2. CAROTENE- (orange-yellow pigment found in
  carrots)- found in the stratum corneum and
  subcutaneous tissue
• 3. Amount of OXYGEN bound to hemoglobin of Red
  blood Cells- when poorly oxygenated skin appear
  blue called CYANOSIS

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HAIR

• Is a flexible outgrowth of dead (KERATINIZED)
  epithelial cells
• In earlier humans hair provided insulation in
  cold weather
• It has a few minor protective functions
• Guarding the head against bumps
• Shields the eye (eyelashes)
• Helps to keep foreign particles out of the
  respiratory tract (nose hairs)
• Has 3 layers
• Medullainner most
• Cortexmiddle bulky area
• Cuticleoutermost, single layer

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LAYERS OF HAIR

• The MEDULLA is a honeycomb structure of keratin
  and air spaces

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LAYERS OF HAIR

• The CORTEX gives flexibility and tensile strength
  to hair and contains melanin (giving hair its
  color). Without melanin, the partly hollow hair
  appears grey.

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LAYERS OF HAIR

• The CUTICLE is made from 6 to 11 layers of
  overlapping semi-transparent scales (which make
  the hair waterproof and allow it to be
  stretched). Someone with thick, course hair will
  have more overlapping layers of cuticles that
  someone with fine hair.

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HAIR

• Shaft is the part exposed above the skin
• Root is the part below the surface surrounded by
  the hair follicle
• Arrector Pilli Muscles are the smooth muscle
  cells which are attached to dermal tissue and
  follicle which can contract and produce goose
  bumps. Its purpose is to keep warm. (Hair
  follicles are always at an angle and the arrector
  pilli muscles reduce that angle)
• Hair Bulb Matrix is the area at the (inferior)
  end of the root where cell stratum basale
  epithelial cells rapidly divides promoting hair
  growth (1 mm every 3 days)
• Melanocytes are located in the stratum basale
  layer which give your hair its color

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HAIR
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HAIR BULB MATRIX (growth zone)

• Consists of
• 1. PAPILLA- well vascularized connective tissue
  that goes up into the hair bulb
• 2. STRATUM BASALE- one layer of cells around
  Papilla- where hair growth occurs

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HAIR BULB MATRIX
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Nails

• A scalelike modification of the epidermis that
  corresponds to hoofs or claws
• Nearly colorless except they look pink due to
  rich blood supply in the dermis beneath

• Three parts of the nail
• 1. Bodyarea that is visible
• 2. Free Edgearea that overhangs the digit
• 3. Rootarea covered by nail folds, embedded in
  the skin

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Nails

• Nail Folds are the overlapping skin of the nail
• CUTICLE is the thick proximal nail fold

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Nails

• Nail Matrix is the area responsible for nail
  growth
• As the nail cells are produced by the matrix,
  they become heavily keratinized and die

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BURNS

• BURN- tissue damage and cell death caused by
  intense heat, electricity, UV radiation, or
  chemicals
• 2 LIFE THREATENING PROBLEMS RESULT
• 1. Loss of fluids- ( proteins and electrolytes)
  Leads to dehydration, circulatory shock, kidney
  shutdown
• 2. Infection - bacteria or fungi infecting
  deeper unprotected tissues

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SEVERITY OF BURNS

• FIRST DEGREE BURNS- only epidermis is damaged-
  temporary discomfort. (most sunburns)

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SEVERITY OF BURNS

• SECOND DEGREE BURNS- injury to epidermis and
  upper region of dermis- Blisters will appear- but
  skin will regenerate

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THIRD DEGREE BURNS

• Third degree burns destroy all three layers of
  the skin. Regeneration of the skin is impossible
  because blood vessels have been destroyed. The
  good news is that Nerve endings have also been
  destroyed. NO PAIN!!! YEAH!

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THIRD DEGREE BURNS

• Burned areas appear gray-white or blackened
• Skin transplants are necessary

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SKIN CANCER

• -Skin Cancer is the single most common cancer in
  humans.
• -Although most skin tumors are benign and to not
  spread to other body organs, some can be
  malignant or cancerous.
• -Single biggest risk factor is overexposure to
  the sun
• - Other risk factors include skin infections,
  chemicals, or physical trauma

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BASAL CELL CARCINOMA-

• most common and least malignant type of skin
  cancer.
• Stratum Basale cells are altered to where they
  no longer distinguish the boundary of epidermis
  and dermis. New dividing cells are pushed in all
  directions including into the dermis and
  subcutaneous layers.
• - appears as a dome shaped nodule that develops a
  central ulcer with a pearly beaded edge
• - 99 curable if cancer is surgically removed.

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SQUAMOUS CELL CARCINOMA-

• arises from the stratum spinosum
• - appears as a small rounded elevation that is
  red and scaly which gradually forms a shallow
  ulcer with a firm raised border
• - appears most often on the scalp, ears, back of
  the hand, and lower lip.
• - can become malignant and invade adjacent lymph
  nodes if not removed.

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MALIGNANT MELANOMA-

• cancer of the melanocytes- occurs wherever there
  are pigment.
• - accounts for only 5 of cancers
• - develop spontaneously or from pigmented moles
• -rapidly spread and attack surrounding lymph and
  blood vessels
• -chance for survival 50

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When should you worry about a mole being
cancerous?

• FOLLOW THE ABCD RULE (pg 111)-
• Asymmetry,
• Border irregularity (lesion is not smooth but has
  indentions),
• Color (blacks, browns, tans, blues and reds)
• Diameter (more than 6 mm)

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BURNS- RULES OF 9

• RULE of NINES- body is divided into 11 areas
  that each account for 9
• Example- 4.5 front of arm, 4.5 back of arm,
  front of leg 9, back of leg 9
•  

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BURNS

• Burns are considered critical if
• 1. Over 25 of the body has second degree burns
• 2. Over 10 of the body has third degree burn
• 3. There are third degree burns of the face,
  hands, or feet

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How does the skin react to Heat or cold?

• HEAT
• 1. Nerves in dermal papillae send signals to
  brain (hypothalamus) of temp. change
• 2. Capillaries are opened up completely to allow
  blood to RADIATE out heat
• 3. ECCRINE GLANDS are activated to allow sweat
  evaporation to cool the body.

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If body gets too HOT

• HEAT EXHAUSTION or HEAT STROKE can occur

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How does the skin react to Heat or cold?

• COLD
• 1. Nerves in dermal papillae send signals to
  brain (hypothalamus) of temp. change
• 2. VASOCONSTRICTION of blood vessels and vascular
  shunts redirect blood away from the capillaries
  (surface)
• 3. Keeps blood near the core for warmth
• 4. ARRECTOR PILI MUSCLES contract to form an
  extra layer of insulation
• 5. If body temperature is still too low the
  SHIVERING occurs to produce more heat.

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If the body gets too cold

• FROSTBITE or HYPOTHERMIA can set in .

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The AGING of SKIN

• As Adults get older-
• Amount of SUBCUTANEOUS TISSUE decreases (less
  insulation)
• Amount of OIL decreases (drier, itchier)
• Layers of skin become thinner
• Loss of collagen and elastin fibers
• More susceptible to cold, bruising, and other
  types of injuries

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Other problems with aging skin

• Loss of elasticity and subcutaneous tissue causes
  skin to SAG (Example- bags under the eyes, jowls
  begin to sag)
• MAJOR CAUSES- exposure to sun, dehydration, poor
  nutrition, poor sleeping habits
• Loss of hair follicles-- ALOPECIA- thinning of
  the hair
• MALE PATTERN BALDNESS- caused by loss of
  testosterone

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