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Anatomy and Physiology of the Skin

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Anatomy and Physiology of the Skin Skin appendages: Nails Anatomy Nail plate made up of dead keratinized cells of matrix. Nail bed is visible through nail plate. – PowerPoint PPT presentation

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Title: Anatomy and Physiology of the Skin


1
Anatomy and Physiology of the Skin
2
Structure of skin
  • Epidermis
  • Basement membrane (dermoepidermal junction)
  • Dermis
  • Subcutaneous fat
  • Epidermis Four layers (from outside inside)
  • Cornified layer
  • Granular layer
  • Spinous layer
  • Basal layer
  • Dermis contains
  • Collagen fibers
  • Elastic fibers
  • Ground substances
  • Blood vessels
  • Nerves.

3
  • Skin appendages
  • Hair follicle
  • Sebaceous gland
  • Arrector pili muscle
  • Eccrine sweat gland
  • Apocrine sweat glands
  • Nail

4
  • Dermatology deals with disorders of skin, hair,
    nails, and mucous membranes.
  • Structure
  • Epidermis (thinner outer layer of skin)
  • Dermis (thicker connective tissue layer)
  • Hypodermis (subcutaneous layer)

5
  • Dermatological disorder 10 -15 of primary
    care consultations
  • Skin is the largest organ in human body
  • Dermatological diseases can cause social and
    psychological problems, also it may affect
    ability to work (e.g. Chronic hand dermatitis.)
  • Skin is the gate of the body(might reflect
    systemic disease).

6
  • Physiology (function)
  • 1- Protection
  • - physical barrier that protects underlying
    tissues from injury, UV light and bacterial
    invasion.
  • - mechanical barrier and immunity
  • 2- Excretion
  • - sweat removes water and small amounts of
    salt, uric acid and ammonia from the body surface
  • 3- Synthesis of Vitamin D

7
  • 4- Regulation of body temperature
  • - high temperature or strenuous exercise sweat
    is evaporated from the skin surface to cool it
    down.
  • - vasodilation (increases blood flow)
    and vasoconstriction (decrease in blood flow)
    regulates body temp.
  • 5-Sensation
  • - nerve endings and receptor cells that detect
    stimuli to temp., pain, pressure and touch.

8
  • Epidermis
  • Basement membrane (dermoepidermal junction)
  • Dermis
  • Subcutaneous fat

9
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10
  • Stratum lucidum
  • Found in thick skin of palms and soles above
    granular layer

11
  • Epidermis Consist of several zones
  • Cornified layer (Stratum corneum )
  • Granular layer (Stratum granulosum)
  • Spinous layer (Stratum spinosum)
  • Basal layer (Stratum basale)
  • 7

12
  • Basal layer
  • Rest on the basement
  • membrane they divide
  • continuously and move
  • upwards.
  • Melanocytes are dendritic
  • cells lying between basal
  • cells in a ratio of 110 .
  • Melanocytes synthesize
  • melanin stored in
  • melanosomes.

13
  • Basal Cell layer
  • Melanosomes are
  • transferred to adjacent cells
  • forming the Epidermal
  • Melanin unit.
  • Small, unmelanized,
  • clumped melanosomes are
  • found in white skin
  • Large melanized, dispersed
  • melanosomes in dark skin

14
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15
  • The Spinous cell layer
  • Usually 5 -10 layers thick .
  • Adhere to each other by
  • desmosomes (complex
  • modification of the cell
  • membrane ).
  • Desmosomes appear like spines.

16
  • Granular Cell layer Diamond
  • shaped cells.
  • Cytoplasm is filled with
  • keratohyaline granules.
  • In thin skin it is 1 -3- cell layers and 10 cell
    layers in thick skin like palms and soles.

17
  • Stratum Corneum layer
  • The cells in this layer have no nucleous .
  • Cells have thick envelope
  • that resist chemicals.
  • Cells are held together by
  • desmosomes.
  • It is 25 cell layer .

18
  • Basement Membrane (BM)
  • Pink homogenous area between epidermis and
    dermis .
  • Consists of number of
  • proteins like BP antigens, collagen 4
  • The site of attack injury
  • in blistering diseases.

19
Skin Structure
  • Components of BM
  • Lamina lucida thin clear amorphous space
  • Lamina densa an electron dense area containig
    type4 collagen
  • Anchoring fibrils anchors epidermis to dermis
    ,type 7 collagen

20
Skin Structure
  • Dermis is divided into
  • Papillary dermis .
  • Reticular dermis
  • Consists of
  • Collagen fibers Provides strength .
  • Elastic Fibers
  • Provides elasticity,
  • protection against shearing
  • forces.

21
Skin Structure
  • Ground substance
  • Binds water and maintains
  • the skin turgor.
  • Blood vessels
  • To nourish the overlying
  • epidermis.

22
Skin Structure
  • The function of dermis
  • It provides nourishment to the epidermis and
    interact with it during wound repair.
  • It gives the skin its strength elasticity, and
    softness.

23
Skin structure
  • Subcutaneous Fat
  • Composed of lipocytes

24
Skin Structure
  • Skin Appendages include
  • Eccrine/ apocrine sweat
  • glands.
  • Sebaceous glands.
  • Hair Follicles.
  • Nails

25
Skin appendages
  • Eccrine sweat glands
  • Tubular structures open
  • freely on the skin not
  • attached to hair follicles.
  • Under the influence of
  • cholinergic stimuli.

26
Skin appendages
  • Eccrine sweat glands
  • Present everywhere except
  • the vermilion border nail
  • beds labia minora glans
  • Abundant in palms soles.

27
Skin appendages
  • Apocrine glands
  • Present in the axillae
  • anogenital area modified
  • glands in the external ear
  • canal the eye lids(molls
  • glands ) and areolae.

28
  • Sebaceous glands
  • Attached to hair follicles or open freely.
  • Present in the scalp forehead face upper
    chest except palms and soles.
  • Under the control of androgens.
  • Ectopic glands in the mucous
  • membrane are called fordyce spots.

29
  • Sebaceous glands.
  • Present in the areola as
  • Motgomerys tubercles in the
  • eye lids as Meibomian glands.

30
Skin appendages
  • Hair follicles
  • The hair follicle with its
  • attached sebaceous gland
  • form the Pilosebaceous
  • Unit.
  • Structure
  • Infundibulum Region between skin surface and
    sebaceous gland.

31
Skin Appendages
  • Isthmus begin at sebaceous
  • glands and end at bulge (site of
  • insertion of arrector pilli
  • muscle)
  • Hair bulb envelopes the dermal papilla

32
Skin Appendages
  • Arrector pili is smooth muscle located in the
    dermis and is attached to the side of the hair
    shaft.
  • - Cold and emotions will contract muscle and
    pull hair in vertical position.

33
Skin Appendages
  • Hair shaft has
  • Cuticle
  • Cortex contain pigment cells
  • Medulla found only in terminal hair

34
Skin appendages
  • Nails Anatomy
  • Nail plate made up of dead keratinized cells of
    matrix.
  • Nail bed is visible through nail plate.
  • Nail matrix lies above the midportion of distal
    phalanx

35
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36
Skin appendages
  • The lunula is the visible part of the matrix
  • Proximal nail fold can be
  • altered in connective tissue
  • Fingernails grow 3 mm/m
  • Toenails grow 1 mm/m

37
Cornification (keratinization)
  • Occur in the cytoplasm of epidermal
    keratinocytes during their terminal
    differantiation into dead horny
    cell(corneocyte)

38
Cornification (keratinization)
  • The total process takes
  • approximately 2 months.
  • It involves the formation of keratin
    polypeptides.
  • Abnormalities in this process leads to roughness
    and scaling of the skin e g psoriasis.

39
Skin immune system
  • Langerhans cells interact with keratinocytes,
    which secrete a number of immunoregulating
    cytokines, and T-cells forming the skin immune
    system.

40
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