The Integumentary System

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• The Integumentary System

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• Introduction
• Organs are body structures composed of two or
  more different tissues.
• The skin and its accessory organs make up the
  integumentary system.

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• Skin and Its Tissues
• The skin is a large organ responsible for
• temperature regulation
• protection of underlying tissues
• Slowing the rate of water loss
• housing sensory receptors
• synthesizing certain chemicals
• excreting wastes

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• The skin consists of an outer epidermis and a
  dermis, connected to underlying tissue by the
  subcutaneous layer (hypodermis).

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• Epidermis
• The epidermis is made up of stratified squamous
  epithelium and lacks blood vessels.
• The layer of reproducing cells (the stratum
  basale), which lies at the base of the epidermis,
  is well-nourished by blood vessels from the
  deeper dermal layer.

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• Cells are pushed outward as new cells are
  formed, and become keratinized as they die.
• Layers of the Epidermis
• Stratum corneum
• Stratum lucidum
• Stratum granulosum
• Stratum spinosum
• stratum basale

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• Skin Color
• Specialized cells in the epidermis called
  melanocytes produce melanin, a dark pigment that
  provides skin color.
• Differences in skin color result from differing
  amounts of melanin and in the size of melanin
  granules.
• The amount of melanin
  produced is affected by
  genetics and
  environmental factors.

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• Dermis
• The dermis binds the epidermis to underlying
  tissues.
• It consists of dense connective tissue with tough
  collagen and elastic fibers within a gel-like
  ground substance.

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• Dermal blood vessels carry nutrients to upper
  layers of skin and help to regulate temperature.
• The dermis also contains nerve fibers, sensory
  fibers, hair follicles, sebaceous glands, and
  sweat glands.

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Fingerprints
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• Subcutaneous Layer
• The subcutaneous layer (hypodermis) is composed
  of loose connective tissue and insulating adipose
  tissue.
• It binds the skin to underlying organs and
  contains the major blood vessels that supply the
  skin.

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• Accessory Organs of the Skin
• Hair Follicles
• Hair can be found in nearly all regions of the
  skin.
• Hairs develop from cells at the base of the hair
  follicle, an area of the lower epidermis that
  dips down into the dermis.
• As new cells are formed, old cells are pushed
  outward, become keratinized, and die forming the
  hair shaft.

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• Hair color is determined by genetics melanin
  from melanocytes is responsible for most hair
  colors red hair contains an additional pigment.
• A bundle of smooth muscle cells, called the
  arrector pili muscle, attaches to each hair
  follicle. These muscles cause goose bumps when
  cold or frightened.

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• Sebaceous Glands
• Associated with hair follicles and secrete an
  oily substance that waterproofs and moisturizes
  the hair shafts.

Nails Nails consist of stratified squamous
epithelial cells overlying the nail bed. As new
cells are produced, older ones are pushed
outward and become keratinized.
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Nails Continued
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• Sweat Glands
• Each gland consists of a tiny tube that
  originates as a ball shaped coil lined with sweat
  secreting epithelial cells.
• Cells respond to body temperature and stress
• Modified Sweat Glands
• Modified sweat glands, called secrete wax in the
  ear canal.
• Mammary glands, another modified type of sweat
  glands, secrete milk.

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Specialized skin glands

• Scent Glands
• Specific type of sweat gland
• Found near hair follicles
• Axillary genital regions
• Develop at puberty

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• Regulation of Body Temperature
• The skin plays a key role in the homeostatic
  mechanism that regulates body temperature.
• Response to increased body temperature
• Heat from cellular metabolism or the environment
  is transferred to the blood and carried to the
  hypothalamus of the brain.
• The hypothalamus signals the dermal blood vessels
  to dilate and sweat glands to secrete.
• Increased blood flow to the skin and evaporation
  of sweat results in a release of heat from the
  body.

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• Response to decreased body temperature
• Hypothalamus detects decrease in body temperature
• Hypothalamus stimulates dermal blood vessels to
  constrict and sweat glands to remain inactive.
• Decreased blood flow to the skin and lack of
  sweat reduce amount of heat loss.
• Skeletal muscles may also be stimulated
  (shivering) which increases cellular metabolism
  and thus, heat production.

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• Healing of Wounds and Burns
• The bodys initial response to skin trauma is
  inflammation.
• Inflammation-
• The dilation of blood vessels in affected area
  become more permeable, fluids leave the blood
  vessels and enter the damaged tissues. This
  provides the tissues with increased nutrients and
  oxygen necessary for healing.

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• Healing the wound
• Shallow wounds are healed as epithelial cells
  along the margin of the wound divide more rapidly
  than usual and fill the gap.
• Wounds that affect the dermis /or hypodermis
  result in a blood clot and scab that cover and
  protect the underlying tissues. Fibroblasts form
  collagenous fibers that bind the edges of the
  wound together.

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Skin cancer

• Squamous cell carcinoma
• Basal cell carcinoma
• Common, slow growing form of skin cancer,
  usually linked to over exposure to sun, usually
  curable
• Melanoma
• develop in melanocytes, lesion becomes dangerous
  when it spreads downward into deeper layers,
  survival rate low once this type of growth
  occurs.

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