Skin (lectures 1 to 3) Flashcards
Name for skin accessories and function
Integumentary system
Roles of integumentary sytstem
-Protects underlying tissues and organs from abrasions, fluid loss, chemicals etc.
-Excretes salts, water, and organic wastes using glands
-Temperature regulation by insulation or evaporative cooling
-Produces melanin: protects underlying tissues against UV
-Produces keratin: Protection against abrasions & water repellent
-Synthesize Vitamin D3 (steroid) converted to calcitriol (hormone important for normal calcium metabolism)
-Lipid storage in adipocytes, some in dermis and mostly in adipose tissue in hypodermis
-Detect touch, temperature, pain, and pressure stimuli and relay information to nervous system
The primary layers of skin
Epidermis, dermis, hypodermis
Epidermis
-Stratified barrier, mostly keratinocytes, no blood circulation (avascular)
-Cutaneous layer
Dermis
-Protein fibres for strength, vascular (nourishes epidermis), not shed
-Cutaneous layer.
-Papillary layer and reticular layer
-Situated below the epidermis &
anchors via hemidesmosomes
Hypodermis
-Adipose tissue
-Subcutaneous layer (not considered part of the
skin)
-Dominated by adipocytes that produce subcutaneous fat
-Subcutaneous fat stores energy & provides insulation
-Common site of injections using hypodermic needles
What tissue type is predominant in epidermis?
Epithelial tissue (covers exposed surfaces, lines internal passageways and chambers, forms secretory glands)
Types of epithelia
-Simple (single) epithelia (squamous, cuboidal, columnar)
-Stratified (layered) epithelia (squamous, cuboidal, columnar)
What type of epithelia makes up the majority of the epidermis?
Stratified squamous epithelia
Layers of the epidermis
-Stratum corneum (spiky layer)
-Stratum granulosum (granular layer)
-Stratum spinosum (spinous or prickly cell layer)
-Stratum basale (basal layer)
Stratum corneum
(spiky layer), dead, dried-out hard cells
without nuclei, easily flakes off & can be
completely removed
Stratum granulosum
(granular layer), contain granules that promote
dehydration of the cell, crosslinking of keratin fibre, waxy material is secreted into the
intercellular spaces
Stratum spinosum
(spinous or prickly cell layer), intercellular bridges (desmosomes) link cells together, cells become increasingly flattened as they move upward, contains dendritic (immune) cells
Stratum basale
(basal layer), columnar regenerative cells, as basal cell divides, daughter cell migrates upwards to replenish layer above
Desmosomes function in skin
Anchors adjacent/neighboring cells in epidermis
Hemidesmosomes function in skin
Anchors stratum basale to the dermis
Stratum lucidum
extra layer, only in thick skin
Thick skin
Palms of hands and soles of feet, no hair, extra epidermal layer (Stratum lucidum)
Dermal papillae
Projections from dermis adjacent to epidermal
ridges, both increase surface area and bind
epidermis and dermis closely
Reticular Layer of dermis
-Mesh like structure of collagen and elastin fibres (for strength)
-Both papillary and reticular layers contain blood vessels, lymphatics, sensory nerve fibres and accessory structures
Papillary Layer of dermis
-Consists of highly vascularised tissues (for nourishment).
-Both papillary and reticular layers contain blood vessels, lymphatics, sensory nerve fibres and accessory structures
Plexuses of the Dermis
Cutaneous Plexus and Subpapillary Plexus
Cutaneous Plexus
- Network of blood vessels present at junction of dermis/hypodermis.
- Supplies hypodermis, deeper dermis, including capillaries for hair follicles and sweat glands
-Plexus=network of blood vessels or nerves
Subpapillary Plexus
- Branches from cutaneous plexus
- Lies deep to papillary layer of dermis
- Network of blood vessels providing O2
and nutrients to upper dermis and epidermis
-Plexus=network of blood vessels or nerves
First degree burns
-Superficial (outer layers of epidermis)
-Red/pink, dry, painful (Erythema)
-Usually no blisters (mild sunburn)
-Skin remains a water and bacterial barrier
-Usually heals 3-10 days
Second degree burns
Normal 2nd degree burns:
-Epidermis and varying amounts of dermis
-Painful, moist, red and blistered
-Usually heal in approx. 1-2 weeks (needs good dressings)
Deeper 2nd degree burns:
-May include whiteish, waxy looking areas
-Hair follicles, sweat glands may remain intact
-Usually heal in 1 month
-May have some loss of sensation and scarring
Third degree burns
Full thickness burns (extend into subcutaneous tissue and may involve muscle and bone
-Varied color from waxy white through to deep red or black
-Hard, dry and leathery skin
-No pain in these areas as sensory nerve endings
destroyed
-May require skin grafting
-Weeks to regenerate and scarring
What cell dominates the hypodermis?
Adipocytes
Accessory structures
Hair, nails, sweat glands, receptors
Hair
All over body except palms, soles and lips
-Made of dead, keratinized cells
produced inside hair follicle
-Hair shaft projects from follicle
Consists of: Arrector pili muscle, root hair plexus, sebaceous glands
Arrector pili muscle
Contraction produces goosebumps, improves
insulation
Root hair plexus
Collection of sensory nerves at base of each
hair follicle, heightened sensation
