The Integumentary System

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The Integumentary System
2
Introduction

• An organ consists of a group of tissues that
  performs a specific function.
• The tissues comprising the skin are the
  epithelium of the epidermis and the connective
  tissues of the dermis.
• A system is a group of organs working together
  toward common goals.
• The organs that make up the integumentary system
  are the skin and its derivatives, such as hair,
  nails, glands and nerve endings many
  interrelated factors (nutrition, hygiene,
  circulation, age, immunity, genetic traits,
  psychological traits, psychological state and
  drug use) affect both appearance and health of
  the skin.

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Skin

• The skin is one of the largest organs of the
  body.
• Dermatology is the medical specialty that deals
  with diagnosing and treating skin disorders.
• Structurally, skin consists of two principal
  parts the epidermis (the outer, thinner portion
  composed of epithelium) and the inner or thicker
  dermis which is composed of connective tissue.
  It overlies the subcutaneous or SubQ layer. This
  is also called the superficial fascia or
  hypodermis.

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Functions of the Skin

• Regulation of body temperature
• Protection
• Sensation
• Excretion
• Immunity
• Blood Reservoir
• Synthesis of Vitamin D

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Epidermis

• The epidermis is composed of stratified squamous
  epithelium and contains four principal types of
  cells keratinocytes, melanocytes, Langerhans
  cells and Merkel cells.
• Four or five (soles or palms) distinct layers
  form the epidermis.

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Epidermis

• The layers of the epidermis (from deepest to most
  superficial) are stratum basale (also known as
  the stratum germinitivum), stratum spinosum,
  stratum granulosum, stratum lucidum (which is
  only in the palms and soles) and the stratum
  corneum.

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Epidermis

• The basale layer undergoes continuous cell
  division and produces all other layers.
• The cells in the multiple layers of the stratum
  corneum are continuously shed and replaced by the
  cells from the deeper strata.
• Keratinization replacement of cell contents with
  the protein keratin, occurs as the cells move to
  the skin surface over 2 to 4 weeks.

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Epidermis

• Epidermal Growth Factor or EGF is a hormone that
  stimulates growth of epithelial and epidermal
  cells during tissue development repair and
  renewal.

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Dermis

• The dermis is composed of connective tissue
  containing collagen and elastic fibers. It has
  two regions papillary and reticular layers.

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Papillary Layer

• The papillary layer is areolar connective tissue
  containing fine elastic fibers, dermal papillae
  and corpuscles of touch or Meissners corpuscles.

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Reticular Layer

• The reticular layer is irregular connective
  containing collagen and elastic fibers, adipose
  tissue, hair follicles, nerve, sebaceous (oil)
  glands and ducts of sudoriferous (sweat) glands
• Strength, extensibility and elasticity are
  provided to the skin by the combination of
  collagen and elastin fibers.
• Lamellated or Pacinian corpuscles found in the
  subcutaneous layer (hypodermis or superficial
  fascia) are sensitive to pressure.
• Lines of cleavage (tension lines) indicate the
  direction of collagen fibers bundles in the
  dermis and are considered in making surgical
  incisions.

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Skin Color

• The wide variety of colors in skin are due to
  three pigments melanin, carotene and hemoglobin
  (in blood capillaries) in the dermis.
• The color of skin and mucous membranes can
  provide clues for diagnosing certain problems
  such as cyanosis, jaundice and erythema.

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Skin Color

• Epidermal ridges increase friction for better
  grasping ability and provide for the basis of
  fingerprints and footprints. The ridges
  typically reflect contours of the underlying
  dermis.

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Skin Grafts

• When the germinal portion of the epidermis is
  destroyed, new skin cannot regenerate without a
  skin graft. The most successful type of skin
  graft comes from the individual himself or from
  an identical twin.
• Another type of self donation is autologous skin
  transplantation in which sheets of skin are grown
  in the laboratory from a small amount of the
  patients epidermis, synthetic materials may be
  used to simulate dermis and epidermis while this
  skin is being grown.

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Epidermal Derivatives

• Epidermal derivatives are structures developed
  from the embryonic epidermis.
• Examples of epidermal derivatives are hair, skin
  glands (sebaceous, sudoriferous and ceruminous)
  and nails.

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Hair

• Hairs or pili are epidermal growths that function
  in protection and reduction in heat loss.
• Hair consists of a shaft above the surface, a
  root that penetrates the dermis and subcutaneous
  layer and a hair follicle.
• Associated with hairs are sebaceous (oil) glands,
  arrectores pilorum muscles and root plexuses in a
  cyclic pattern.
• The color of hair is primarily due to melanin.
• Hormonesparticularly androgenscan stimulate
  hair growth in both males and females or somehow
  inhibit it in genetically predisposed males (male
  pattern baldness). Drug treatment can
  occasionally stimulate regrowth of some lost hair.

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Glands

• Sebaceous (oil) glands are usually connected to
  hair follicles they are absent in the palms and
  soles.
• Sebaceous glands produce sebum which moistens
  hairs, waterproofs and softens the skin.
• Enlarged sebaceous glands may produce blackheads,
  pimples and boils.

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Sudoriferous Glands

• Sudoriferous glands or sweat glands are divided
  into apocrine and eccrine types.
• Eccrine Sweat Glands have an extensive
  distribution, their ducts terminate at pores at
  the surfaces of the epidermis.
• Apocrine Limited in distribution to the skin of
  the axilla, pubis, and areolae their ducts open
  into the hair follicles. Sudoriferous glands
  produce perspiration (sweat) which assists in
  maintaining proper body temperature and also
  carries small amounts of washes to the surface.

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Ceruminous Glands

• Ceruminous glands are modified sudoriferous
  glands that produce a waxy substance called
  cerumen. The are found in the external auditory
  meatus (ear canal).

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Nails

• Nails are hard keratinized epidermal cells over
  the dorsal surfaces of the terminal portions of
  the fingers and toes.
• The principal parts of a nail are body, free
  edge, root, luncuna, eponychium and matrix.
• Cell division of the matrix cells produce new
  nails.
• Functionally, nails help in grasping and
  manipulating small objects in various ways and
  provide protection against trauma to the ends of
  the digits.

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Skin and Homeostasis

• Epidermal Wound Healing wounds are repaired by
  enlargement and migration of basal cells, contact
  inhibition and division of migrating and
  stationary basal cells.