BIOL 2P93 Lecture Notes - Histology, Hair, Subcutaneous Tissue

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Outline of Lecture 21 (05-07 A; Hubbard)
Skin Histology
Epidermis
- Epidermal ridge: projects into dermis for epidermis-dermis attachment, prominent in thick skin
- Four layers (superficial to deep)
- Stratum corneum: cornified dead cells
- Stratum granulosum: apoptotic cells and exocytosis of lamellar bodies
- Stratum spinosum: nonproliferative, desmosomes keep cells attached to each other
- Stratum basale: proliferating cells, hemidesmosomes attach to dermis
- Melanocytes: cells with clear cytoplasm and prominent nuclei that transfer melanin to
keratinocytes
- Merkel cell: touch receptors
- Langerhans’ cell: immune protection in spinous layer
- No intrinsic blood supply to epidermis; nutrients diffuse from plexus III
Dermis
- Dermal papillae: projects into epidermis for epidermis-dermis attachment, prominent in thick
skin
- Sandwhiched by capillary plexi III (superficially) and II (deeply)
- Meissner’s corpuscle: touch receptor, found in dermal papillae, laminated appearance
- Pacinian corpuscle: pressure/vibration receptor, found deeper in dermis, onion-like appearance
- Pilosebaceous unit: only found on hairy skin!
- Hair follicle: hair bulb found in dermis or hypodermis, but cells actually derive from epidermis
- Sebaceous gland: secretes sebum into hair shaft which is open to outside environment
- Arrector pili: muscular contraction causes hair to stand on end
Hypodermis
- Hypodermis contains much fat
- Sandwhiched by capillary plexi II (superficially) and I (deeply)
- Eccrine gland: sweat gland originating in hypodermis, duct can be traced through dermis and
epidermis as it travels to surface
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