the skin Flashcards
what does the integumentary system consist of
-hair
- nails
-cutaneous glands (sweat, sebaceous filaments)
-skin is the largest organ (12-15% of body weight)
-barrier to external
-insight to internal health
what’s the structure of skin
-epidermis (uppermost- faces external world ) epithelia layer
-dermis
-hypodermis is the areolar or adipose tissue which binds skin to the underlying tissue- technically not part of the skin
what are fibroblasts and how do they produce ECM proteins
-found in dermis
-mainly collagen but can also be laminin/fibronectin forming elastic and reticular fibres
-2 zones which are papillary layer and reticular layer
what’s the papillary layer in fibroblasts
-papillary layer is thin and loose connective tissue region (areolar) used for mobility of leukocytes, mast and macrophage cells
what’s the reticular layer in the fibroblasts
-thick dense irregular connective tissue layer
-contains less cells and adipocyte clusters
what does the dermis contain which is useful for thermoregulation
-rich layer of blood and lymphatic vessels
why is there a high sensitivity in the dermis
-numerous nerve endings
what’s the dermal-epidermal boundary
-wavy boundary of finger like projections increasing connections e.g. dermal papillae(raised area) and epidermal ridges
-interdigitation prevalent which Is the epidermal and dermal layers going into the tissues of one another which increases surface area contact and stops the tissue from slipping away from one another
what do tall dermal papillae facilitate
-nerve fibres reaching close to the surface in highly sensitive areas
what is the epidermis
-keratinised stratified squamous epithelium
-very stratified (lots of layers)
-self-regenerative throughout life cycle 2-4 weeks
what are the stratified layers of epidermis
-stratum basale (base)
-stratum spinosum (spindly)
-stratum granulosum (granular in histology slide)
-stratum lucidum (translucent 2-3 extra layers in thick skin which protects from mechanical stress (eleidin)
-stratum corneum (most superficial because there iuds multiple layers)
what are the 2 different skin types in the epidermis
-thick skin (palms including fingertips, feet are smooth as they have no hair)- 5 layers
-thin skin (rest of body, 4 layers, non glabrous meaning it doesn’t have stratum lucidum
what does the lack of blood vessels in the epidermis mean
-diffusion occurs from underlying connective tissue
what does the stratum basale consist of
-keratinocytes- mitotically active and in touch with basement membrane- these produce cells which migrate upwards
-melanocytes which gives skin colour
-tactile/merkel cells which are connected to sensory nerves
what are melanocytes
-release melanin for UV absorption, antioxidant and radical scavenging, as well as protecting skin from the UV damage
-skin pigmentation: carotene pigments (orange-yellow) in subcutaneous fat and stratum corneum in the heels of the feet
-blood perfusion and O2 content
what are the two different types of pigments in melanocytes
-pheomelanin - red/yellow pigment
-eumelanin- brown/black pigment
what’s melanosomes
-the branching process
-phagocytosed (takes in the melanosomes) by keratinocytes which surround the nucleus
what’s the stratum spinosum
-several keratinocyte layers
-usually the thickest layer except in thick skin e.g. stratum corneum
-deepest cells mitotic, pushed upwards which cease to divide
-produce keratin filaments which are flat (more in upper layer)
-keratinocytes strongly linked by desmosome
-tight junctions ensure water retention of skin
-dendritic cells present
what’s stratum granulosum
-3-5 layers of flat keratinocytes
-high barrier function
-post-mitotic, tight junction claudins- used for barrier functions NB
-contain dark staining granules- bind to cytoskeleton (keratin precursors )
-cells undergo apoptosis
-produce glycolipid-filled vesicles (lamellar bodies/granules) which spread over cell surface creating a waterproof barrier between stratum spinosum
what’s the stratum corneum
-most superficial and its has a lot of proteins
–15-30 layers of flattened, dead, corneocytes/squames which are enucleated terminally differentiated dead keratinocytes
-contains stratum disjunctum and stratum compactum
-contaisn cornified envelope
-especially resistant to abrasion, penetration and water loss
what’s the stratum disjunctum
-beneath apical acid mantle and lipid barrier
-corneodesomosomes regulate desquamation
what’s stratum compactum
compact cells
what does the cornified envelope consist of
-keratins
-enclosed within insoluble amalgam of cross-linked protein
-surrounded by extracellular lipid envelope (fused lamellar bodies)
structure of nails
-derivatives of stratum corneum (flat in primates)
-composed of dead scaly cells densely packed with ‘hard’ keratin fibres
-new cells added by mitosis in the nail matrix
-appearance can indicate underlying health issues such as iron deficiency (flat or concave) and then long term hypoxemia- clubbed
-naisl grow faster I summer due to more heat therefore enzymes work faster
