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					  Chapter 4:
    Integumentary System
What is it?
 The skin and its derivatives (sweat and oil
 glands, hair and nails) serve a number of
 functions, mostly protective.
Skin Structure

                 Figure 4.4
                Skin Structure
• Epidermis – outer layer
   – Stratified squamous
   – Often keratinized
     (hardened by keratin)
• Dermis
   – Dense connective tissue

                                 Figure 4.3
•   16% of your total body weight
•   First line of defense against microorganisms
•   Irradiated by sunlight
•   1.5-2 M squared in area
•   There are 2 major components: 1)
    cutaneous membrane (skin) and 2)
    accessory structures (nails, hair and
    exocrine glands).
• Or cornification, is the formation of
  protective , superficial layers of cells filled
  w/ keratin.
   Functions of SKIN or
 Subcutaneous Membrane
1. Protection- of underlying tissues and organs
   from fluid loss, abrasion and impact and
   chemical attack and microbial infection.
2. Excretion- of salts, water and organic wastes
   and by integumentary glands.
3. Maintenance- of body temperature…via
   evaporation or insulation( Keratin)
4. Synthesis of Vitamin D3, a steroid, a hormone
   necessary for normal calcium absorption.
5. Detection of touch, pressure, pain…general
   senses that are relayed to the central nervous
        SKIN: 2 TISSUES
• 1. Epidermis- Contains either 4 or 5 layers
  depending on if THIN or THICK skin.
• THIN: covers most of body ( 4 layers)(.08mm)
• THICK: soles of feet, palms of hands (.5mm) (5
  layers here.
• Stratum: 1. germantivum(basale) 2. spinosum,
  3.granulosum, 4. Lucidum (only in thick skin),
  and 5.corneum.
• Example: Stratum germativum (basale)for 1st
Dermis:Components &
1) Papillary Layer- Consists of Areolar
   Tissue. Contains capillaries, lymphatics, and
   sensory neurons that supply the surface of the
   skin. Projections: Dermal Papillae.
2) Reticular Layer- deep to the PL,
    Contains blood vessels, deep pressure receptors
   called* Pacinian corpuscles and Macrophages.
   Also tissue : consists of interwoven layer of
   connective tissue; containing collagen and
   elastin fibers. Appendage structures extend into
• Thicker than epidermis
• Contains connective tissue; elastic fibers,
  collagen, nervous tissue, smooth muscle and
  blood;receptors and glands are found here.
• A basement membrane separates the
  epidermis from dermis.
The Dermis
Papillary layer
• loosely woven fibers
• rich blood supply
• irregular surface (fingerprints)
 Reticular layer
• dense irregular CT
• cleavage lines
• less scarring
• flexure lines—less sliding
Layers of Epidermis
          Layers of Epidermis

•   Stratum basale (germinativum)
•   Stratum spinosum (prickly layer)
•   Stratum granulosum (granular)
•   Stratum lucidum (clear layer)
•   Stratum corneum (horny layer)
Cell and Layers of the Epidermis
         Stratum Basale

• Single layer cells on basement membrane
• Cell types in this layer
  – keratinocytes
     • undergo mitosis to replace epidermis
  – melanocytes
     • distribute melanin through cell processes
     • melanin picked up by keratinocytes
  – merkel cells are touch receptors
     • form Merkel disc
• Pigment (melanin) produced by
• Color is yellow to brown to black
• Melanocytes are mostly in the stratum
• Amount of melanin produced depends upon
  genetics and exposure to sunlight
• These are found mostly
  in the stratum basale
• Everyone has the same
  number of melanocytes.
• The darker skin a
  person has depends on
  how much melanin a
  particular melanocyte
  produces and the size of
  the granules. This is
  determined by one’s
• UV rays can stimulate
  additional melanin
Here’s How it Works
      Melanocyte Stimulation
• Melanocytes deeper in the epidermis are
  stimulated to produce new melanin
  granules. These new granules are
  transferred to keratinocytes in the upper cell
  layers of the skin. These granules become
  positioned in the outer portions of the cells
  above the cell nuclei, thus providing
  additional protection.
If Melanocytes on Bottom,
How Does Skin Get Tan on

• Melanocytes have extensions that transfer
  the granules to surface cells by a process
  known as Cyocrine Secretion.
    Stratum Spinosum
• Contain special white blood cells from the
  lymphatic system. Help protect body from
   Statum Grandulosum
• Produces lipid-filled vesicles that
  release a glycolipid by exocytosis
  to waterproof the skin
       Statum Lucidum
• Thin translucent zone seen only in
  thick skin ( palms and soles of

• Cells have no nucleus or organelles
        Stratum Corneum
•   The most superficial layer of epidermis
•   20- 30 layers thick
•   Cornified, ABSOLUTELY dead
•   ABSOLUTELY flattened
•   These take up 75% of the epidermis.
•   They exfoliate continuously.
   Appendage Structures
Cutaneous Glands- the EXOCRINE glands,
   including sweat and sebaceous glands.
• Both of these glands are formed in epidermis and
   pushed down during development and remain
   almost entirely in dermis.
• Sebaceous- OIL glands. Usually empty into
   hair follicle, sometimes directly skin.
---SEBUM=oil and skin cells, germicide.
   Pacinian Receptors
• Named after
• Theses are sensory
  receptors that detect
Pacinian Receptor
More Than One Kind….
     Sebaceous (Oil) Glands
Secrete oil or sebum
Everywhere except palms, soles
Usually secretes into hair follicle
Lubricates hair and skin
• softens dead cells--pliability
• slows water loss
• bactericidal
Stimulated by hormones
 Sebaceous           Sweat
    glands           gland
with hair follicle
   • sss

 Sebaceous           Eccrine glands , that
    glands           is SUDORIFEROUS
                     or SWEAT GLAND
  associated         empties onto Skin
with hair follicle
     Apendages (cont.)
• Sweat Glands- Eccrine and Apocrine
• Eccrine- more numerous, ubiquitious, used to
  regulate body temperature.Empty onto skin.
• Apocrine- found auxillary, and pubic areas only.
  Develop during puberty under influence of
  testosterone. Contain protein and fat. Do not
  regulate body temp. Activated by stress and sexual
  foreplay. Empty onto hair follicle.. usually.
Apocrine Vs. Eccrine Glands
  What Did You Say???
• Ceruminous glands- This are
  modified (eccrine) sweat glands in the
  passageway of the external ear. Their
  secretions combine w/ sebaceous glands
  forming CERUMEN….or earwax.
  Together w/ tiny hairs traps foreign
        Subcutaneous Layer
• Located under the dermis
• Mostly adipose
• Functions
   – energy reservoir
   – thermal insulation
• Hypodermic injections
   – highly vascular
 Common Cancers: Skin Cancer
• Risk factors
   – Exposure to UV light
• Detection and treatment
   – Types: basal and squamous cell carcinomas (95% of
     skin cancers), melanoma is most dangerous
   – Melanoma: asymmetry, border irregularity, color
     change, diameter greater than ¼ inch
   – Surgical removal
   – Early detection: 96% survival 5 years out
                 Skin Cancer
• Skin cancer is the most common type of cancer in
  humans. Cause is unknown, but most important
  risk factor is over exposure to UV light. Frequent
  irritation to skin by infections, chemicals or
  physical trauma seem to be a predisposing. Also
  Risk factors: living at high altitudes, fair skinned
  people, having a lot of moles, a family history of
  the disease and if you had one or more severe
  sunburns as a child
       Skin Cancer: RFs
• over exposure to UV light.
• Frequent irritation to skin by infections, chemicals or
  physical trauma
• living at high altitudes,
• fair skinned people,
• having a lot of moles
• family history of the disease
• one or more severe sunburns as a child
         Skin Cancer: 3 Types
• Basal – arise from the layer stratum basale. Least
  malignant, most common. Cannot form keratin (
  soft). Looks like a mound. No boundary between
  epidemis and dermis.
• Squamous – arise from statum spinosum.
  Characterized by pearly beaded edge. These will
  metastasize into the lymph nodules if left
  untreated and can be lethal.
• Melanoma- rarest but most deadly. Develops
  from pigmented moles. 5% survival rate.
    ABCD Test For
  A – Asymmetrical; the two sides of the
pigmented spot do not match.

  B- BORDERS-irregular boarders; not
smooth with indentations apparent

  C-   COLOR- pigment contains areas of
different colors

  D- DIAMETER- larger than ¼ inch
• Hot water, sunlight, radiation, electric shock or acids
  and bases
• Death from fluid loss and infection
• Degrees of burns
   – 1st-degree = only the epidermis (red, painful and edema)
   – 2nd-degree = epidermis and part of dermis (blistered)
      • epidermis regenerates from hair follicles and sweat glands
   – 3rd-degree = epidermis, dermis and more is destroyed
      • often requires grafts or fibrosis and disfigurement may occur
• Treatment – IV nutrition and fluid replacement,
  debridement and infection control
Figure 6.12aa
Figure 6.12ab
Figure 6.12ba
Figure 6.12bb
Figure 6.12ca
Figure 6.12cb
Hair and Hair Follicles
HAIR STRUCTURE ( flexible epithelial
• contains a MATRIX- the growth zone ..a zone of
  stratum basale, hair bulb at inferior end of follicle.
  (ACTIVELY DIVIDING Epithelial Cells—alive)
• Root- Part of hair enclosed in follicle—now
  keratinized and dead
• Shaft- Hair part that projects from surface of the
  scalp or skin.
          Hair Follicle
• Composed of:
• Inner Epidermal Sheath ( epithelial tissue)
• Outer DERMAL Connective Tissue
• Nipple-like PAPILLA (provides blood
  supply to matrix in hair bulb)
• Arrector pili ( small bands of smooth
  muscle) that connect follicle to dermal
  tissue. ---goose bumps.
           HAIR FOLLICLE
The part of the hair covered by the follicle is
 called the ROOT.

Hair exposed is called the SHAFT.

Hair is formed from STRATUM BASALE
 Cells in GROWTH ZONE of MATRIX of
 HAIR BULB. This is nurished by
 DERMAL Papilla .
• SOFT KERATIN in the Medulla

• HARD KERATIN in the Cortex and Cuticle
• Hardest and Outermost is the CUTICLE
     Associated Hair Structures
• Hair follicle
   – Dermal and epidermal sheath
     surround hair root
• Arrector pilli ( when erect
  pull hair straight and causes
  “goose bumps”)
   – Smooth muscle
• Sebaceous gland
• Sweat gland

                                   Figure 4.7a

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