the skin
TRANSCRIPT
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The SKIN
Dr. Samar Asker
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The largest organ in the body
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ProtectionRegulation
ExcretionSynthesis
Receive sensation
Medico legal
functions
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Diagnose some diseases as : Measles anemia Jaundice chicken pox.
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Types of the skin Thick skin Palm, sole, tips of
Fingers& toes
Thin skinAll over the body
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Thick skinFormed ofepidermis & dermis.
The epidermis keratiniezed str.sq.epith formed of. Keratinocytes & non Keratinocytes
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The Keratinocytes::85% of cells of epidermis form keratin 5 layers .
1
2
345
•Basal layer together with Spinous layer are called malpighian layer
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Basal cell layer or Germinal l .LM:
• Single layer of columnar cells resting on clear wavy basement membrane . Have basal oval nucleus & basophilic Cytoplasm.
• The nuclei show mitotic figures for renewal which take place every 2-4 weeks mostly at night
.
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EM: • Cells are joined together
by “desmosomes” • to the basement
membrane by “hemidesmosomes”.
• Rich in ribosomes and polysomes
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•Melanocytes & Merkels cells are present in this layer.
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Spinous layer or Prickle cell l. LM:• 4-8 layers of polyhedral cells with
central and rounded nuclei.• They have spine-like processes
indicating sites of desmosomes as cells shrink during preparation.
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EM:•The cells are joined by “desmosomes” & have interdegitating cell membrane.
•The superficial cells contain membrane bound (coated) lamellar granules.
•Langerhans cells are present in this layer
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Granular layer LM: •Formed of 2-4 layers of spindle shaped cells with flat nuclei & basophilic granules .
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EM:2 types of granules -coated lamellar granules oval or rod shaped covered by membrane contain lamellar discs = lipid bilayer. They discharge their content to the intercellular spaces to form lipid sheets to act as cement & act as Barrier againest bacteria.
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Keratohyaline granules: large not covered by membrane form matrix which bind tonofilaments to form bundles
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Clear layer LM:1 layer of flattened cells with no nuclei “scales” which contain {eleidin granules} Keratohyaline eleidin granules).EM:No nucleus or organelles. Cells are joined by remnant of desmosomes contain packed filaments of eleidin = immature keratin imbedded in the matrix formed by the keratohyaline granules.
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Horny layer
LM : Many acidophilic layers or scales Of keratinized dead cellsEM: dead cells with no nuclei or organelles joined by remnant of desmosomes Filled with mature keratin filaments imbedded in the matrix
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Non Keratinocytes
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Melanocytes:Origin: ectodermalLM:• have pale rounded nuclei.
• long processes to transport their melanin to the adjacent cells .
• Give Dopa +ve reaction.
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EM: euchromatic nucleus
with prominant nucleolus
Character of protein forming cell i.e. many mito. rER & well developed GA
No desmosomes () keratinocytes but hemidesmosomes.
Function:Form tyrosinase enzyme
to form melanin which give the color of the skin
melanin granules protect the DNA from ultraviolet rays.
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Merkel’s cells:Origin: ectodermal
LM:Modified basal cells but slightly largerNaked sensory nerve fiber end in a disc like expansion under these cells
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EM:attached to the neighboring cells by desmosomes.Cytoplasm contains electron dense granules so may belong to ABUD cellsFunction:1. Mechanoreceptors for touch
& preasure.2. The content of the granules
is responsible for paracrine regulation of epidermal cells
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Langerhans Cells:Site:In the upper layer of stratum spinosum, representing 3-8% of the epidermal cells.Origin:MesodermalLM:• Branched cells between
cells of spinous layer.• Dark nucleus & pale
cytoplasm.
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EM:No desmosomes & no junction with keratinocytes.
1ry & 2ry lysosomesBirbeck granules= tennis racquet-shaped which contain hydrolytic enzymes.
Function:1. Phagocytic cells of the
skin2. Antigen presenting
cells
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The dermis
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Reticular layer Papillary layer
thicker & deeper thinner & superficial
dense fibrous C. T. loose C. T.Less cellular & vascular more cellular & vascular Krause and bulbs.Ruffini &Paciniancorpuscles.
Receptors: Meissner’s corpuscle
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Thin skin Thick skin The rest of the body Palm, sole, tips of
Fingers& toessite
ThinnerThinner
Thinner=1 AbsentThinner
ThickThickerThicker 2-4 LsPresentThick
EpidermisMalpighian L. Granular LClear layer
Horny layer
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Few irregular Regular , numerous, high Dermal papillae
Less numerous
present.
Sweat glands: more numerous.Hair follicles:Sebaceous glands: abcent Arrector pili muscle:.
Appendages
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Mitotic figures are common in the cells of :
a. Basal cell layer.
b. Spinous layer.
c. Horny layer.
d. Clear layer.
e. None of the above.
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The cells of granular layer contain :
a. Melanin pigments.
b. Carotene pigments.
c. Eleidin granules.
d. Basophilic keratohyaline granules.
e. Acidophilic keratohyaline granules.
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Berbick granules are present in : a. Melanophores.
b. Merkel's cells.
c. Langerhans cells.
d. Stratum lucidum.
e. Meissner's corpuscles
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1.Granular layer.
2.Horny layer.
3. Spinous layer.
4.Clear layer.
a. Squames condensed in
linear manner.
b. Wavy clear acidophilic
line.
c. Diamond-shaped cells.
d. Polyhedral cells.
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