The Integumentary System

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The Integumentary System
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Functions

• Protection- from abrasions, uv light,
  microorganisms and dehydration
• Sensation- has sensory receptors that can detect
  heat, cold, touch . Pressure and pain
• Vitamin D Production when exposed to the sun
  (uv light ) the skin produces a molecule that can
  be transformed into vitamin D
• Temperature regulation- is controlled by
  regulating the blood flow through the skin and
  the activity of the sweat glands.
• Excretion- small amounts of wastes are lost
  through the skin and in gland secretions

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Layers of Skin

• Epidermis layers of epithelial tissue that rests
  on the dermis
• Dermis- dense connective tissue 10-20 times
  thicker than the epidermis and provides most of
  the structural of the skin
• Beneath the Skin
  Layers
• Hypodermis-the foundation upon which the skin
  rests , it attaches to the underlying bone and
  muscle and supplies it with blood vessels and
  nerves. It is also known as subcutaneous tissue
  and is really loose connective tissue that
  contains half the bodies stored fat ( adipose ).

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Epidermis

• Stratified squamous epithelium
• In the deepest layers, cells are constantly being
  produced by mitosis
• As new cells are being produced, they push the
  older cells to the surface where they slough or
  flake off
• They result from the process of keratinization-
  cells of the stratum basale change shape and
  chemical composition as a result of being filled
  with a protein called keratin. As keratinization
  proceeds the cells die and produce an outer layer
  of dead cells that resist abrasions and forms a
  permeability barrier.

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Epidermal Layers

• Stratum Corneum
• Stratum Intermedia
• Stratum Basale

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Stratrum Corneum

• is the most superficial of the epidermis.
• It consists of dead squamous cells filled with
  the hard protein called keratin.
• These cells are also surrounded by lipids that
  prevent the loss of water
• Composed of 25 or more layers of dead squamous
  cells joined by desmosomes, eventually desmosomes
  break apart and the cells slough off
• \

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Stratum Basale

• Stratam basale
• Stratum basale-deepest layer which consists
  of cuboidal or columnar cells that undergo
  mitotic divisions about every 19 days. One
  daughter cell becomes a new statum basale cell
  and can divide again. The other cell is pushed
  toward the surface, a journey that takes place
  about 40-56 days. As cells move to the surface,
  changes in the cells produce intermediate strata.

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Layers of Epidermis
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Dermis

• Dense collagenous connective tissue contains
  fibroblasts, fat cells an macrophages
• Nerves, hair follicles , smooth muscle , glands
  and lymphatic vessels extend into the dermis, but
  there are fewer fat cells and blood vessels than
  the hypodermis
• Collagen and elastic fibers are responsible for
  its structural strength
• The upper part has projections called a dermal
  papillae, which contain nutrient blood vessels
  that supply the overlying epidermis

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Dermis
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Hypodermis
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Skin Color

• Melanocytes cells which produce melanin.
  Melanin production is determined genetically but
  can be modified by hormones and uv light .
• - Other factors that can affect skin color
• Carotene
• Scattering of light by collagen
• Amount of Blood Flow

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Melanocytes
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Accessory Skin Structures

• Hair
• Muscles
• Glands
• Nails

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Hair

• common to all mammals
• found everywhere except palms, soles, lips,
  and distal segments of skin and toes
• Parts
• shaft- protrudes above the surface
• root and hair bulb below the surface
• Shaft
• hard cortex surrounded by a cuticle
• softer center medulla
• Hair follicle
• extension of the epidermis deep into the dermis,
  can serve as a source of new epithelial cells

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Hair
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Hair Growth

• Growth Stage-epithelial cells within thestratum
  basale divide and keratinize. Hair grows longer
  because these cells are added to the base
• eyelashes grow for 30 days and rest for
  1O5days
• scalp hairs grow for 3 years and rest for 1-2
  years
• Rest Stage- growth stops and hair is held in the
  folicle

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Muscles

• Associated with each hair follicle are smooth
  muscle cells Known as the ARRECTOR PILI- cause
  hair on end or goose flesh.

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Glands

• Types of Exocrine Glands
• Sebaceous- simple branched and acinar, connected
  by a duct to the hair follicle. They produce
  sebum, an oily white substance that lubricates
  the skin
• Sweat Glands- two types
• Merocrine- simple coiled tubular, almost
  everywhere, secrete water and a few salts
• Apocrine-simple , coiled tubular glands
  that produce a thick secretion rich in organic
  substances
• under the influence of hormones
  during puberty
• secretions odorless but when
  hit bacteria become body odor

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Exocrine Glands of the Skin
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Nails

• Nail a thin plate consisting of dead layers of
  dead stratum corneum that contain keratin
• nail body
• nail root
• Eponychium or cuticle is stratum corneum that
  extends onto nail body
• Nail Matrix
• Nail root distal to matrix
• Nail bed- under nail , distal to matrix
• Laluna part of the matrix that can be seen
  through the nail body as the white crescent
• Nails grow continually, no resting phase

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Nail
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Physiology of the Integumentary System

• Prevention of water loss due to lipids that act
  as a barrier
• Prevention of microorganisms from entering
• Protection from abrasion due to the overlying
  stratified squamous
• Melanin absorbs uv light and protects underlying
  structures from its damaging effects
• Hair is an insulator, eyebrows keep sweat out of
  the eye, hairs in nose prevent dust entry.
• Nails for defense

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Sensation

• Sensation-
• receptors in the epidermis and dermis that can
  detect pain, heat cold and pressure and movement
  of hair

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Vitamin D Production

• when exposed to the sun a precursor molecule of
  Vitamin D is formed
• It then proceed to the liver and then the kidney
  fro modification to its active form
• Vitamin D is need for the uptake of Clcium and
  phosphorous by the intestines so they can be used
  for normal bone and muscle function

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Temperature Regulation

• Normal body temperature is 37C Or 98F
• Body temperature is extremely important because
  it the rate of chemical reactions are controlled
  by this, fro example the action of enzymes
• Blood vessels in the dermis will either dilate or
  vasoconstrict to meet homeostasis

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• Cleavage lines
• Bacterial Viral and Fungal Infections
• Burns
• Skin Cancer

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Body temperature
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Excretion

• Removal of waste products from the body
• sweat, salt water and wastes such as urea,
  uric acid and ammonia

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Degrees of Burns

• Partial Thickness
• first degree
• second degree
• Full thickness
• third degree

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Types of Skin Cancer

• Basal Cell
• Squamous Cell
• Melanoma