DSF Histo of Skin Flashcards
3 layers of skin
Epidermis
Dermis
Hypodermis (subcutis)
Epidermis
Keratinized stratified squamous epithelium
Dermis
Papillary and Reticular
Loose irregular and dense irregular CT
Hypodermis (subcutis)
Loose CT
Shock absorption, insulation, energy reservoir
Thick skin
Soles and palms Thick layer of epidermis Only eccrine glands, no other appendages Highly innervated for exquisite sensory discrimination *Have Stratum lucidum
4 cell layers of epidermis (5 in thick skin)
Stratum basale Stratum spinosum Stratum granulosum Stratum lucidum Stratum corneum
4 cell types w/in the epidermal cell layers
Keratinocytes
Melanocytes
Langerhans cells
Merkel cells
Keratinocytes
Ectodermally-derived cells
Protection from mechanical forces, UV light, water barrier
Specialized apoptosis involved in maturation
Contain majority of skin’s melanin
Melanocytes
Produce melanin (oxidation of Tyr (tyrosinase key), released in melanosomes)
Found in stratum basale
Origin: neural crest
Langerhans cells
Stratum spinosum
Immune cells of epithelium - can migrate
Lymphocytes, mast cells, macrophages
Dendritic cells (APCs) - adaptive immunity
Derived from bone marrow stem cells (mesoderm)
NO pigment or keratin, can be identified in TEM by folded nuclei
Birbeck granules
Merkel cells
Mechanoreceptor cells of epithelium (SB of epidermis)
Also found along basement membrane of hair follicles
Form Merkel corpuscle along w/ underlying nerve processes
Likely neural crest origin
Intimately associated w/ a nerve fiber
Stratum basale
Single cuboidal/low columnar layer, attached to BL by hemidesmosomes
Proliferative
Beginning of keratin synthesis - few keratin filaments
Continuous w/ basal layer of appendages
Stains blue due to lots of free ribosomes
Vitamin D production
Melanin present above nucleus (to protect DNA)
Stratum spinosum
Stratified and non-uniform
Vitamin D production
“Spinous” processes: cytoplasmic projections/desmosomal attachments
Near basal layer: Proliferative capability, keratin synthesis
Near surface: flatter, larger, more TFs, start of water barrier formation
Keratohyalin granules
Stratum granulosum
Contain filaggrin and trichohyalin - involved in aggregation of keratin filaments into tonofibrils (TFs)
Stratum granulosum
1-3 layers thick No proliferation Even more keratin filaments bundled into TFs Lamellar bodies released Keratohyalin granules Cells undergo apoptosis
Stratum corneum
Dead cells (no nuclei/organelles) Keratin matrix Coated w/ water barrier Subject to exfoliation/desquamation *SL in thick skin similar