The Integumentary System

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Chapter 5

• The Integumentary System
• J.F. Thompson, Ph.D. J.R. Schiller, Ph.D. G.
  Pitts, Ph.D.

2
The Skin - General

• Epithelial and connective tissues working
  together for specific purposes
• The largest organ of the body
• 1.5 - 2 square meters
• 4 - 5 kg
• Variable thickness 1.5 mm to 4 mm

3
Skin Physiology - Many Functions

• Regulation of body temperature insulator,
  radiator
• Protection a physical barrier and for water
  conservation
• Sensation - varied sensory nerve endings
• Communication to other humans by
  signals/expressions and by touch
• Excretion (in sweat) - H2O, salts, small organic
  compounds (a minor contribution to excretion)
• Immunity certain phagocytes in the epidermis
  are important from the immune system for defense
• The dermis is a significant blood reservoir
• Synthesis of Vitamin D for calcium absorption

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The Architecture of the Skin

• 2 Principal portions
• Epidermis - epithelium
• Dermis areolar dense irregular connective
  tissue
• Hypodermis
• beneath the dermis
• the subcutaneous layer next to
• adipose layer or
• muscle or
• bone

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The Epidermis

• Stratified Squamous Epithelium
• 4 cell types
• Keratinocytes - 90
• filled with keratin (protein)
• waterproof barrier
• Melanocytes - 8
• produce melanin (pigment)
• pass melanin to keratinocytes
• Langerhans cells
• phagocytes (from immune system)
• easily damaged by UV light
• Merkel cells
• in deepest layer of hairless skin
• sensory transduction - touch

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Epidermal Cell Layers

• Stratum basale
• A single layer of cuboidal/columnar cells
• Stem cells, melanocytes, Merkel cells
• Stem cells ? keratinocytes, mitosis pushes the
  other layers to the top
• Stratum spinosum
• 8 to 10 layers of closely packed cells
• Cell junctions - spot desmosomes
• Langerhans cells

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Epidermal Cell Layers

• Stratum granulosum
• 3-5 layers of flattened, with keratohyaline
  granules
• beginning breakdown of nucleus, cell death
  initiated
• Stratum lucidum
• only in thick skin (palms, feet)
• 3-5 layers of clear, flat dead cells with keratin
• Stratum corneum
• 20-30 layers of flattened, dead, keratin-filled
  cells
• continuously shed and replaced
• 2-4 weeks for each cell to form and to move from
  the stratum basale to the surface

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Epidermal Histology

• Stratum Corneum
• Stratum Granulosum
• Stratum Spinosum
• Stratum Basale

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The Dermis - General

• Variable thickness - thicker on palms and soles
  thicker on dorsal surfaces rather than on
  ventral thicker on lateral surfaces than on
  medial surfaces
• Few cells present - fibroblasts, macrophages,
  adipocytes
• Matrix thick with many protein fibers collagen,
  elastin, reticular
• The location for blood vessels, nerves and
  sensory receptors, glands, hair follicles

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Dermis - Structure

• Papillary region (layer) - outer layer - 20
• Areolar connective tissue, elastic fibers
• Dermal papillae mound-like projections to
  increase the surface area for nutrition from
  capillaries
• Some papillae contain Meissner's corpuscles (for
  light touch)

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Dermis Structure (cont.)

• Reticular region - 80
• Dense, irregular connective tissue
• Collagen, elastic fibers in a network surrounding
  the various cells
• Fibers give strength, elasticity, extensibility
• Tears in reticular region - "stretch marks -
  long straight red or white streaks

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Three Skin Pigments - Melanin

• Melanin - yellow to black
• Made by melanocytes
• Common in mucous membranes, penis, nipples,
  areolas, face, extremities
• The number of melanocytes is similar in all races
  but the amount and type of melanin produced and
  distributed to the keratinocytes varies
• Freckles, livers spots - melanocyte clusters
• Melanin is synthesized from tyrosine (amino acid)
• UV radiation increases enzyme activity (negative
  feedback)
• Melanin production protects the body against UV
  radiation

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3 Skin Pigments - Carotene HgB

• Carotene - yellow-orange pigment in the dermis
• Gives egg yolks, carrots, their color
• Used in the synthesis of a vision pigment
• Persons of Asian extraction have carotene in
  their stratum corneum, in the fatty areas of the
  dermis and in their subcutaneous layers
• Hemoglobin because the skin is translucent
• Caucasian skin tinted red to pink depending on
  dermal capillary blood flow

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Skin Color

• Skin color
• Blood is bright red when carrying oxygen, dark
  red/purple when deoxygenated the skin appears to
  have a blue or green or purple tinge depending on
  the individual
• The relative color of skin and exposed mucous
  membranes can give clues to a persons
  oxygenation status

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Skin Color Clinical Terminology

• Erythema
• skin redness
• exercise, embarrassment, high blood pressure,
  certain drugs, inflammation, etc.
• Pallor
• pale
• cold temperatures, stress or anemia
• Cyanosis
• bluish, no oxygen
• babies not breathing, heavy smokers/emphysema

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Skin Color Clinical Terminology

• Jaundice
• yellow/orange
• after internal hemorrhage
• liver problems disturbing the breakdown removal
  of RBC's
• Bronzing
• Metallic appearance of skin
• Addisons disease hypofunction of adrenal cortex
• Black and blue marks, bruises (contusions)

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Skin Pathologies

• Basal cell carcinoma
• From stratum basale
• Least malignant - 99 full cure
• Squamous cell carcinoma
• From stratum spinosum
• Prognosis is good if removed early
• Melanoma
• Melanocyte cancer
• Highly metastatic
• Resistant to chemotherapy
• ABCD Rule
• Asymmetry
• Border irregularity
• Color several present
• Diameter greater than 6 mm

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Skin Pigments Melanin Pathologies
albino
vitiligo

• Albinism - inability to produce melanin cannot
  breakdown tyrosine, no melanin, inborn error of
  metabolism recessive trait
• Vitiligo - partial/complete loss of melanocytes
  from skin patches

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Skin Grafts

• Sometimes when the is skin severely damaged, it
  cannot regenerate itself
• Success is dependent on the site of origin of the
  transplanted tissue
• autograft
• from the same person
• donated from a different site
• can be tissue cultured first
• isograft - identical twins
• homograft - skin from another human
• heterograft - skin from an animal

Autograft to knee
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Epidermal Derivatives Hair Pili

• Hair functions
• Protection
• increase surface area for evaporative heat loss
• increased length (scalp) for sunburn and
  heatstroke
• eyebrows, eyelashes - insects, foreign particles
• nostril hair same
• ear hair - same
• Mechanical dry lubricant for limb movements
• Secondary sexual characteristic to attract mates
• Touch receptors respond to changes in position
• Rate of growth replacement affected by many
  things heredity, diet, illness, fever, blood
  loss, surgery, drugs, chemotherapy

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Hair Anatomy

• Shaft
• medulla - inner layer
• cortex - middle layer, pigments, air spaces
• cuticle - outermost layer, hard keratin
• Root
• similar to shaft, but in skin
• Follicle - surrounds root
• Sheath - supports shaft root
• Bulb - enlarged layered structure at base where
  hair is generated
• papilla - areolar connective tissue, blood
  vessels supply nutrients
• matrix - germination layer of papilla (stratum
  basale) builds hair shaft
• Sebaceous glands release oil
• Arrector Pili smooth muscle

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Hair Follicle
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Hair Color

• Brown, black
• melanin deposited
• into the shaft
• Red, blond variants
• of melanin with iron
• sulfur in the molecule
• Grey some loss of melanocytes reduces melanin
  deposition
• White - air bubbles accumulate in the cortex

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Hair and Hormones

• Testosterone
• Secretion increases at puberty
• Male pattern of hair growth and distribution
  begins
• Hirsutism
• Excess testosterone production, tumor or hormonal
  imbalance
• Excess hair production in females or pre-pubertal
  males

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Hair and Hormones

• Male pattern baldness
• Genetic predisposition sex-linked trait
  testosterone inhibits scalp hair growth in these
  individuals
• Finasteride (Propecia) - anti-testosterone agent
• Must be taken for remainder of life
• Minoxidil (Rogaine)
• Anti-hypertensive medicine
• Widens blood vessels, increases blood flow
• Topically (daily) promotes growth in people with
  reduced hair growth (not much but some) but not
  in truly bald individuals

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Male Pattern Baldness
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Sebaceous (Oil) Glands

• Connected to hair follicles located in the
  dermis
• Most secrete directly into follicles some
  directly onto the skin
• Gland shape differs depending on location
• Holocrine gland
• Secrete sebum (oil)
• fats, cholesterol, proteins, inorganic salts
• keeps hair from drying
• prevents water evaporation from skin
• keeps skin soft, supple
• inhibits growth of many bacteria

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Sudoriferous (Sweat) Glands

• Sweat a plasma filtrate consisting of water,
  salts, urea, uric acid, amino acids, ammonia,
  sugar, lactic acid, ascorbic acid, and pheromones
• pH between 4 and 6
• Salty and acidic solution inhibits most bacterial
  growth
• Maintain body temperature, but insignificant for
  waste removal
• Two types
• Eccrine sweat glands
• Most abundant (millions), especially on the palms
  and soles and the forehead
• Apocrine sweat glands
• Less abundant, confined mostly to axillary and
  anogenital regions and the areolae of the breast

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Eccrine Sweat Glands

• Lifetime performance influenced by environmental
  experience in infancy
• Secretory portion located in the dermis

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Apocrine Sweat Glands

• Secretory portion is located in the dermis or the
  subcutaneous region secrete into hair follicles
• Secrete more during emotional stress, sexual
  arousal
• A merocrine process

http//faculty.une.edu/com/abell/histo/histolab3g.
htm
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Modified Sudoriferous (Sweat) Glands

• Two types of modified sweat glands
• Ceruminous glands protect against ectoparasites
  (bugs)
• Produce a bitter waxy secretion (cerumen)
• Open into the external auditory meatus (ear
  canal) or into local sebaceous glands
• Mammary glands highly specialized for milk
  production
• Hormonally regulated by estrogens, prolactin, and
  oxytocin

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Cystic Fibrosis (CF)

• Patients have an autosomal recessive inborn error
  of metabolism
• Altered chloride transport which alters the
  characteristics of most glandular secretions
• Detected in infants with a simple chloride sweat
  test CF babies have elevated sweat chloride
  values
• Primarily affects the respiratory and digestive
  systems with thick clogging secretions
• Average lifespan approximately 30 years
• 1/3900 newborns ? 3/100 adults are carriers

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Nails

• Tightly packed cells with hard keratin
• Nail matrix - under root of nail
• Site of nail growth
• Transforms normal skin cells into nail cells
  which push forward
• 1mm/week in fingers slower in toes
• The longer the finger the greater the growth rate

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End Chapter 5