Transcript Skin Anatomy & Physiology

Skin
Ram Mukkamala
Skin
• Largest organ completely covering the body continuous with
membranes lining body orifices .
• Average thickness:1-2mm,0.5mm on eyelids & 6mm on palms
& soles.
• pH-4 to 5.6
• Renewal of skin takes place in 28-50 days by shedding of outer
layer
Skin
Epidermis
Epidermis
• Stratum Corneum: 15 -20 layers of dead cells mechanical
protection and water proof. Thickening of corneal layer – Ichthyoses
• Stratum Lucidum: flat epithelial cells, homogenous translucent
appearance
• Stratum Granulosum: 2-5 layers of flattened rhomboid cells;
thinned or absent in Psoriasis
• Stratum Spinosum: spinous or prickle-cell layer
• Stratum basale: Usually one cell thick, 2-3 cell thick in glabrous skin
and hyperproliferative epidermis
Epidermis
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Melanocytes: large cells interspersed in basal layer
Langerhans cells: Antigen presenting cells
Merkel Cells: Nerve endings within epidermis
Other structures: Hair, sebaceous glands and ducts of sweat glands
Dermis
• Connective tissue layer made up of dense & stout collagen fibres,
fibroblasts and histocytes. Collagen fibres have elastic property and
capable of storing water.
• 2 layers in Dermis
• Superficial papillary layer : Projects into epidermis, Contain blood
vessels, lymphatic, and nerve fibres.
• Has some pigment containing cells called CHROMATOPHORE.
• The papilla are surrounded by rete ridges extending from the
epidermis.
Dermis
• Reticular layer : Made up of reticular and elastic fibres.
• These fibres are found around the hair bulbs, sweat glands and
sebaceous glands.
• This layer also contain mast cells, nerve endings, lymphatics,
epidermal appendages and fibroblasts.
• The hair follicles with hairs, nails, sweat glands and sebaceous
glands, even mammary glands are considered as appendages of the
skin.
• Below the Dermis – subcutaneous tissue helps in temperature
regulation
Glands of Skin
• Sebaceous glands: These are simple or branched alveolar glands situated
in the dermis of skin. Structure- Ovoid or spherical in shape, developed
from hair follicles and covered by connective tissue capsule. Secrete
Sebum which is formed by liquefaction of the alveolar cells.
• Sweat glands : There are 2 types of glands:
• Eccrine glands : Distributed throughout the body with exterior opening
through sweat pore. Temperature regulation.
• Apocrine glands : limited to areas like axilla, pubis, areola & umbilicus with
opening into hair follicle having thick & milky secretion. It starts
functioning only in puberty and had no role in temp. Regulation. It’s
secretion increases only in emotional conditions under hormonal control.
Have nerve supply by sympathetic adrenergic fibres.
Function
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Protective – physical and against UV rays
Sensory
Synthesis of Vitamin D
Temperature regulation
Thank you
Questions?