The skin Flashcards
Semester 1 year 1
What are the layers that make up skin?
-epidermis epithelial layer (uppermost)
-dermis
-hypodermis (not really skin) - areolar or adipose tissue bonds skin to underlying tissue
Describe the structure of the dermis
-thicker than epidermis
-has fibroblasts
-houses all of the accessory organs
-rich layer of blood + lymphatic vessels lying alongside it
-numerous nerve endings
What are fibroblasts?
Produce extracellular matrix proteins - mainly collagen
Describe the dermis at the epidermal boundary
-wavy boundary of finger like projections to increase connections
-tall dermal papillae facilitate nerve fibres reaching close to surface in sensitive areas
Describe the epidermis
-keratinised stratified squamous epithelium
-high degree of keratin
-highly layered (stratified) - layers have different functions, but work cohesively
-thin, flat cells
What are the 2 different skin types?
-thick skin - smooth + no hair (5 layers)
-thin skin - hair (4 layers)
Does the epidermis have blood vessels?
No - substances diffuse in from connective tissue
What are the 5 layers of the epidermis?
-stratum corneum
-stratum lucidum
-stratum granulosum
-stratum spinosum
-stratum basale
Describe the Stratum Basale (Germinativum)
-contain keratinocytes, which are mitotically active and touch the basement membrane
-contain melanocytes, which give skin colour
-have tactile/Merkel cells, which are connected to sensory nerves
Describe the Stratum Spinosum
-have several keratinocyte layers + is usually the thickest layer
-produce keratin filaments + keratinocytes are strongly linked by desmosomes
-tight junctions ensure water retention of skin
-dendritic cells present
Describe the Stratum Granulosum
-3-5 layers of flat keratinocytes
-post-mitotic, tight junction claudins
-contain dark-staining granules
-cells undergo apoptosis
-produce glycolipid-filled vesicles that form a waterproof barrier between stratum spinosum
Describe the Stratum Corneum
-cells are dead
-most superficial (don’t contain nuclei + contain lots of keratin)
-made of layers (stratum disjunction + stratum compactum)
-cornified envelopes
-resistant to abrasion, penetration + water loss
What are melanocytes?
Release melanin, which protects skin from UV damage
Describe nails as accessory structures
-derivatives of stratum corneum
-composed of dead scaly cells packed with ‘hard’ keratin fibres
-appearance indicates underlying health issues
Describe hair (pilus) as accessory structures
-filament of keratinised cells from follicle
-hair bulb grow around bud of vascular connective tissue (dermal papilla)
-3 layers (medulla, cortex, cuticle)
