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Skin complete Histology

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					Your God is only Allah, than Whom there is no other
God. He embraceth all things in His knowledge. TAHA, 98




                   ََ‫وسِ ع‬
                         َ                                        َّ ُ ُ ُ
                             ۚ‫إ َِّنما ٓ إِلَ ٰـهكم ٱَّلل ُ ٱلَّذِى ََل إِلَ ٰـه إِ ََّل هُو‬
                              َ           َ ٓ                                        َ
                                ً۬ ِ ٍ ۡ َ ُ
                             ‫ڪل َّ شىء ع ۡلما‬
• Histology of the
  Integumentary System
        INTEGUMENTARY SYSTEM
• SKIN
• Outer Body covering
   heaviest organ
• Accessory structures: hair, nails,
• glands, hooves, claws
                Functions of skin
Protection
Synthesizes vitamin D
with UV
Regulates body heat
Prevents unnecessary
water loss
Sensory reception
(nerve endings)
   Temperature sensor
   SECRETION & EXCRETION
– Mammary glands
– Sebaceous glands
– Sweat glands
CAMOUFLAGE
SPECIES & SEX RECOGNITION
FIGHTING STRUCTURES
                           Layers of Skin
• The epidermis and dermis.
   – EPIDERMIS
   – ORIGIN
   – constantly being regenerated.
   – Epithelial sheet
       • Distinct layers
Keratinized stratified squamous

keratinocytes + 3 other types cells:
melanocytes,
Langerhans (Dendritic) cells, and
Merkel cells (sensory receptors).
• Epidermal ridges or pegs
• Dermal Papilla
                         DERMIS
    – origin

       • Strong, flexible connective tissue.
• Cells
• Fiber type
•   Route of blood and nervous supply
•   temperature regulation
•   Two layers
•   Papillary
•   Reticular
                 *Dermal papillae
*Dermis layers
 Fingerprints, palmprints, footprints
Dermal Projections match epidermal "pegs"


 Pattern is genetically determined




   The dermis is the receptive site for the
   pigment of tattoos
                   STRATUM BASALE
• Deepest layer of the epidermis
• The single row of cells nearest the dermal boundary
• Germinal layer
   –   Source of KERATINO-CYTES
   –   A reserve layer in constant mitosis
   –   desmosomes.
   –   hemidesmosomes

• Contains MELANOCYTES as well as keratinocytes
                STRATUM SPINOSUM

Cells still alive and can divide if
necessary

Layer is 2-10 cells deep; varies
from place to place

“Prickle cell” appearance results
from attachments at desmosome.

Tonofilaments

NO cytoplasmic continuity
Lamellar granules
                  STRATUM
                GRANULOSUM
•   Third layer
•   Several layers of flattened cells
•   Non-membrane bounded Keratohyalin granules.
•   profilaggrin



• Filaggrin         Keratinization
• Lamellar granules(coating plasma lemma)
             STRATUM CORNEUM
• From Latin, cornus = “horn”
• Cells can no longer divide.

• Filling with keratin fibers and “keratohyaline granules”
   – -Appear clear
   – No nucleus No cytoplasmic organelles.


• Stratum Disjunctum
• No of layers varies among species and body
  regions.
“STRATUM DISJUNCTUM”
       • The outermost layer of the
         stratum corneum
       • Sloughing and desquamating
         dead cells




       • Large animals may lose up to 1
         kg per day of skin cells
       • “Dandruff” is produced here!
            STRATUM LUCIDUM

•   Not always present
•   Thick skin.
•   Hairless regions.
•   Clear lucent band
                       MELANOCYTES

• Source of MELANIN
• Stable population of cells
   – Little turnover
       • NOT part of keratinizing system
   – Less than 10% of the stratum basale
   – Of neural crest origin
   – Contains unique pathway with TYROSINASE
     MELANOCYTE


Extensive branching
processes
Produces melanin and
releases it in packets
Packets are engulfed by
keratinocytes:
“crinophagy”
Melanin carried up to
surface and lost in
sloughing

				
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Description: Skin complete Histology