Basic histopathology of skin
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The document summarizes the histology of skin. It describes the three main layers of the skin - epidermis, dermis and subcutis. The epidermis is composed of keratinocytes and contains melanocytes and Langerhans cells. It has multiple layers with different functions. The dermis lies below the epidermis and contains blood vessels, nerves, hair follicles and glands. The subcutis is the deepest layer composed of loose connective tissue and fat. There are regional variations in the thickness and components of the different skin layers.
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Basic histopathology of skin
- 1. Basics of Histopathology Of Skin
- 3. Epidermis • Most superficial layer of the skin • Composed of multiple layers of keratin containing epithelial cells = keratinocytes with Melanocytes, merkel cells, and Langerhans dispersed throughout • Major functions: – Maintenance of fluid and electrolyte balance – Protection from ultraviolet light – Sensory and immune function
- 4. Epidermis : Layers Stratum Corneum Stratum Granulosum Stratum Spinosum Stratum Basale Stratum Lucidum Thin Skin Thick Skin Rete ridge
- 5. Differences between thin & thick skin Thin Skin • Palms of hands and soles of feet = acral skin • 5 layers thick stratum corneum with increased granular layer • More sensory receptors • Lack sebaceous glands and increased eccrine glands • No hair follicles Thick Skin • Entire body except thick skin areas. • Less than 5 layers of stratum corneum with no stratum lucidum • Hair follicles present except lips, labia minora, and glans penis
- 6. Epidermis Desmosome = Intercellular Bridges
- 7. Epidermis: Melanocytes Melanocytes: clearish cells in basal layer with dark nuclei ; ratio of 1: 10. Langerhans’s Cells: dendritic cells of the epidermis. Sit in the mid-spinous. Not visible by light microscopy.
- 8. Dermal-Epidermal Junction • Connects the epidermis and dermis • It is composed of proteins which provide a firm connection – Hemidesmosome: connects basal keratinocytes to basement membrane – Basement membrane • Lamina lucida = collagen types XVII, XIII, laminin 5 & 6 • Lamina densa = collagen type VII – Anchoring fibrils attach the basement membrane to the dermis hooking on to collagen VII and collagen I.
- 9. Basement Membrane Lamina Lucida Lamina Densa Basal layer keratinocytes of epidermis Basement Membrane Hemidesmosomes Collagen type XVII, XIII Laminins 5 & 6 Collagen Type VII Anchoring Fibrils Dermis Collagen type I
- 10. Dermis • Everything below the dermal epidermal junction / basement membrane – Connective tissue layer with contains blood vessels, nerves, sensory receptors, adnexal structures - Two layers • Papillary dermis = includes the dermal papilla which project into the epidermis -Capillaries, free nerve endings and encapsulated sensory receptors called Meissner’s corpuscles. • Reticular dermis = area between the papillary dermis and subcutis
- 13. Dermal Appendages Hair Follicle Pilar Muscle Sebaceous Glands Eccrine Glands
- 14. Sebaceous Glands • Usually associated with hair follicles • Simple branched acinar glands – Several acini that empty into single duct • Holocrine secretion • Empty “sebum” into hair follicle
- 15. Hair Follicle Outer Root Sheath Inner Root Sheath Hair Cuticle Hair Medulla Hair Cortex cross section (above the level of the bulb) Papilla Bulb Matrix Connective Tissue Sheath
- 16. Eccrine Glands • Merocrine sweat glands • Release to adjust body temperature • Three cell types – Dark cells: pyramid shaped with secretory granules line lumen of tubule – Clear cells: located toward basement membrane – Myoepithelial cells: spindle shaped contractile cells
- 17. Apocrine Glands • Apocrine glands – Similar to eccrine glands but larger lumens and ducts empty onto superficial regions of hair follicle – Release product by shedding of part of cytoplasm = apocrine snouting – Influenced by hormones (sexual scent glands) – Only found on axilla, areola, perianal and genital area
- 18. Subcutis Pacinian Corpuscle • Subcutis – Area deep to the dermis – Includes the hypodermis • Loose connective tissue containing adipose tissue, nerves, sensory receptors, arteries and veins • Provides a flexible attachment to the underlying muscle and fascia Hair bulb in the subcutis of the scalp. Adipocytes
- 19. Mucosal epithelium:- • 2 layers- 1. Surface-stratified squamous epithelium- 2. Deeper-lamina propria- fibrous connective tissue- type I and lll collagen & elastin fibres. Stratified squamous epithelium:- 1. keratinized-masticatory mucosa- dorsum of toungue, hard palate & attached gingiva. 2. Nonkeratinized- lining mucosa-buccal, labial,alveolar mucosa.
- 20. Regional variation of the skin:- • Palms and soles - thickened & compact stratum corneum with stratum lucidum, numerous eccrine glands & no pilosebaceous units. • Trunk – significantly thicker reticular dermis. • Scalp – numerous terminal hair follicles, with most bulbs in the subcutis. • Face- prominent sebaceous glands in vellus hairs.
- 21. • Eyelid- epidermis is thin (2-3 layers thick). • Modified apocrine glands (Moll’s gland) & vellus hairs are seen in the dermis. • Smooth muscle fibres – numerous in dermis of areola, nipple, also seen in dartos layer in foreskin & scrotum. • Skin biopsy from legs (adults)- prominent thick walled blood vessels –gravity and stasis.
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