The document provides an overview of the anatomy and physiology of skin. It discusses the structure of skin, which consists of two main layers - the epidermis and dermis. The epidermis contains 5 layers (from superficial to deep): stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and stratum basale. The dermis lies beneath and contains two layers - the papillary layer and reticular layer. It also describes the blood supply, skin appendages like hair follicles and glands, and main functions of the skin like providing a barrier and sensing.

1. ANATOMY AND
PHYSIOLOGY OF SKIN
BY DR. D.N.S.SAI KUMAR (1ST YEAR POSTGRADUATE)
UNDER GUIDANCE OF
-DR. P.MYTHILI M.S
-DR. B.VANAJA RATNA KUMARI M.S
-DR. M.RAVI CHANDRA M.S
-DR. S.V.RAMANA M.S
-DR.S.VENKATA NAIDU M.S

2. -INTRODUCTION
-STRUCTURE OF THE SKIN
-LAYERS OF EPIDERMIS AND DERMIS
-APPENDAGES OF SKIN
-FUNCTIONS OF THE SKIN

3. INTRODUCTION
 The skin also known as cutaneous membrane or integument
 It is largest sensory organ in terms of both surface area and weight
 In adults skin covers an area of 2 sq.mts(22 sq.ft) , weighs about 4.5
to 5 kgs and constitutes16% of the body weight
 Its continuous with mucous membrane of body orifices
 Average thickness is 1 to 2 mm , Eyelids -0.5 mm , Palms and Soles
-6mm

4. STRUCTURE OF THE SKIN
 Skin+ its appendages = integumentary system
 Structurally the skin consists of two layers
 EPIDERMIS
 DERMIS These layers have different
. FUNCTIONS
.HISTOLOGICAL APPEARANCE
.EMBRYOLOGICAL ORIGIN
- HYPODERMIS
Beneath these two layers a layer of loose connective tissue , the hypodermis or subcutis is found
which binds skin to underlying structures
Its equivalent to superficial fascia

7. Layers of epidermis
 Epidermis is composed of stratified squamous keratinised
epithelium
 Its avascular and further subdivided into 5 layers
 From superficial to deep the layers of epidermis are
 1.STRATUM CORNEUM
 2.STRATUN LUCIDUM (only in palms and soles)
 3.STRATUM GRANULOSUM
 4.STRATUM SPINOSUM
 5.STRATUM BASALE ( STRATUM GERMINATIVUM )

8. STRATUM CORNEUM
 25 TO 30 layers thick
 Made up of dead Keratinocytes
 Barrier to light, heat, water, chemicals and
bacteria
 Lamellar granules in this layer makes it
water repellent
 Epidermal turn over time ranges about 52-
75 days

9. STRATUM LUCIDUM
 Smooth, translucent layer of the epidermis
 It is found only in the thick skin of the palms,
soles, and digits
 Composed of dead keratinocytes
 These cells are densely packed with eleiden,
derived from keratohyalin
 Eleiden gives transparent (i.e., lucid) appearance
and provides a barrier to water.

10. STRATUM GRANULOSUM
 Transition zone between metabolically active cell layers and dead
cell layers
 Cells progressively flattened and undergo apoptosis
 Presence of basophilic keratohyaline granules
 TONOFILAMENTS+ KHG = KERATIN
 Presence of Lamellar bodies (Odland bodies) makes it water
resistant

11. STRATUM SPINOSUM (prickle cell layer)
-It is spiny in appearance due to the protruding
cell processes that join the cells via desmosome
-Polyhedral cells with prominent nucleoli
-Synthesize the intermediate filament :
cytokeratin
-Cytokeratin aggregates to form tonofilaments
which give resistance to abrasion
-Langerhans cell functions as a macrophage of
stratum spinosum

12. STRATUM BASALE ( STRATUM GERMINATIVUM )
-The cells in the stratum basale bond to the dermis via intertwining collagen
-The stratum basale is a single layer of cells primarily made of basal cells
-A basal cell is a cuboidal-shaped stem cell that is a precursor of the keratinocytes
of the epidermis
-It contains two other cell types, merkel cell a touch receptor especially abundant
in hands and feet
-The second is a melanocyte, a cell that produces the pigment melanin
-Melanin gives hair and skin its color, and also helps protect the living cells of the
epidermis from ultraviolet (UV) radiation damage.

13.  In a growing fetus,
fingerprints form where the
cells of the stratum basale
meet the papillae of the
underlying dermal layer
(papillary layer), resulting in
the formation of the ridges on
your fingers that you
recognize as fingerprints.
Fingerprints are unique to
each individual and are used
for forensic analyses because
the patterns do not change
with the growth and aging
processes

17. LAYERS OF DERMIS
-The dermis might be considered the “core”
of the integumentary system (derma- =
“skin”), as distinct from the epidermis (epi- =
“upon” or “over”) and hypodermis (hypo- =
“below”)
-Overall thickness of skin depends on
thickness of dermis
-It has two components —the papillary layer
and the reticular layer.
-Mainly consists of collagen and elastic
fibres

18. -Responsible for tone and texture of
the skin
-Neurovascular structures and skin
appendages are found in dermis
 The collagen and elastic fibres are
not randomly oriented but form
regular lines of tension in skin
called LANGERS LINES
 Skin incisions made parallel to
langers lines heal with least
scarring

19. BLOOD SUPPLY OF THE SKIN
ARTERIES form two plexuses
One at the junction of papillary
and reticular layer (subpapillary
plexus) and other at the junction
of dermis and hypodermis (
cutaneous plexus)
VEINS form two three plexuses -2
in same position as for arterial
and other in the middle of dermis

20. Appendages OF SKIN
 These are developed as a result of downgrowth of epidermis of skin
towards dermis and hypodermis
 It includes
1.Hair follicle: gives rise to hair
2. Sebaceous gland
3.Eccrine sweat gland
4.Apocrine sweat gland
5.Nail

24. FUNCTIONS OF SKIN
BARRIER
DRUG ABSORPTION
IMMUNOLOGIC FUNCTIONS
HEMOSTASIS
SENSORY INFORMATION
ENDOCRINE FUNCTIONS
EXCRETORY FUNCTIONS