Skin Flashcards
What is the integumentary system
Skin + accessory structures
What are the functions of the integumentary system
Protection, excretion, temperature regulation, melanin and keratin production, vitamin D3 synthesis, lipid storage, detection
What are the cutaneous layers of the skin
Epidermis and dermis
What is the subcutaneous layer of the skin
Hypodermis
Describe the epidermis
Stratified barrier, mostly keratinocytes, no blood circulation
Describe the dermis
Protein fibres for strength, vascular (nourishes epidermis)
Describe the hypodermis
Adipose tissue
What is simple epithelia
A single layer of epithelial cells
What is stratified epithelia
Stacked layers of epithelial cells
What are the three types of epithelial cells
Squamous, cuboidal and columnar
What type of epithelia makes up the epidermis
Stratified squamous
What are the 5 layers of the epidermis
Stratum corneum, lucidum, granulosum, spinosum, basale
Describe the stratum corneum
Dead, dried out hard cells without nuclei or organelles. Abundance of keratin in this layer
Describe the stratum granulosum
Contains granules that promote dehydration of the cell, crosslinking of keratin fibre. Waxy material secreted into intercellular spaces.
Describe the stratum spinosum
Spinous, prickly cell layer. Intercellular bridges called desmosomes link cells together. Cells increasingly flattened as you move up. Contains dendritic cells
Which layer of the epidermis contains immune cells
Stratum spinosum
Describe the stratum lucidum
Thin, translucent layer made of keratinocytes becoming more flattened, present only in thick skin
Describe the stratum basale
Columnar, regenerative cells. As basal cells divide, daughter cell migrates up to replenish layer above
Where are desmosomes present in skin
Anchor adjacent cells in epidermis
Where are hemidesmosomes present in skin
Anchors stratum basale to dermis
How do the epidermis and dermis fit together
Dermal papillae and epidermal ridges
What is a dermal papilla
Projection from the dermis adjacent to the epidermal ridges. Increase SA and bind epidermis and dermis closely
What are the two layers of the dermis
Papillary layer, reticular layer
What is the papillary layer
Layer of the dermis, highly vascularised for nourishment
What is the reticular layer
Mesh like structure of collagen and elastin fibres for strength
What is a plexus
A network of blood vessels or nerves
What is the cutaneous plexus
Network of blood vessels present the junction of dermis/hypodermis. Supplies the hypodermis, deeper dermis, including capillaries for hair follicles and sweat glands
What is the subpapillary plexus
Branches from the cutaneous plexus, lies deep to papillary layer of dermis. Network of blood vessels providing oxygen and nutrients to the upper dermis and epidermis
What is the hypodermis
Not considered part of skin, dominated by adipocytes that produce subcutaneous fat which stores energy and provides insulation
What are the features of a first degree burn
Superficial, erythema (red/pink, dry, painful), usually no blisters, remains a water and bacterial barrier. Heals in 3-10 days
What are the features of a second degree burn
Epidermis + dermis, painful, moist, red, blistered. Heal is 1-2 weeks. Deeper may include whiteish, waxy looking areas, accessory structures may remain, may have some loss of sensation and scarring, usually heal in one month
What are the features of a third degree burn
Full thickness: extend into subcutaneous tissue, may involve muscle and bone. Can vary from waxy white to deep red or black. Hard, dry, leathery skin. No pain as sensory nerve endings are destroyed, may require skin grafting. Weeks to regenerate + scarring
What is hair made of
Dead, keratinised cells produced inside a hair follicle
What is the arrector pili muscle
Muscle which contracts to form goosebumps
What is the root hair plexus
Collection of sensory nerves at the base of each hair follicle for heightened sensation
What are sebaceous glands
Glands next to hair shafts which produce an oily secretion called sebum
What is the purpose of sebum
Nourishes hair shaft, moisturises skin, water repellent
What is an eccrine sweat gland
Found in most areas, pour watery secretions directly onto skin surface. Important in thermoregulation and excretion, some antibacterial action
What is an apocrine sweat gland
Found in specific areas (e.g armpit, groin), secrete sticky/oily and potentially odorous secretions. Influenced by hormones
What are the three types of receptors
Tactile, lamellar, bulbous
What are the functions of nails
Protection, sensation enhancement
How is skin affected by aging
Thins, sags/wrinkles due to reduced collagen, slower repair, drier, impaired cooling, less pigmentation
How does smoking affect skin aging
Damages collagen and elastin, linked with poor wound healing, acne, skin and oral cancers
Where are melanocytes located
Stratum basale (not shed). Density varies throughout body and time
What does the melanin pigment do
Absorbs UV light, protecting cells from damage
What do melanocytes do
Produce melanin pigment, transfer to epidermal cells by melanosomes (found throughout epidermis)
What is a mole
Cluster of melanocytes. Over proliferation can be caused by sun exposure
What is a freckle
Melanocytes overproducing melanosomes. Over production triggered by sun exposure
What is vitamin D essential for (UV exposure required for synthesis)
Calcium metabolism and strong bones
What happens when pigmentation does not match UV exposure
Highly pigmented people more susceptible to vitamin D deficiency, lowly pigmented people more susceptible to skin cancer
What is basal cell carcinoma
Relatively benign tumour, metastasis rare, originates in stratum basale
What is a malignant melanoma
Tumour originating in melanocytes, highly metastatic
The thickness of a melanoma highly correlates with
Mortality rate
What is a tattoo
Ink deposited onto dermal layer, captured inside immune cells/scar tissue
What tissue types is skin composed of
Epithelial, muscular, nervous, connective
What are free nerve endings
Small swellings at distal ends of axons (usually unmyelinated and small diameter), most common skin receptor (some cation channels, some chemically activated)
What do free nerve endings mostly respond to
Various painful, thermal and chemical stimuli, some movement and pressure, some itch, some wrap around hair follicles acting as light touch recepotrs which detect bending of hairs
What are tactile (merkel) discs
Free nerve endings located in deepest layer of epidermis
What do tactile (merkel) discs respond to
Touch and light pressure, texture, shape, edges, low frequency vibration (good at 2 point discrimination)
What are tactile (meissner) corpuscles
Receptors located in papillary layer of dermis, especially hairless skin. Encapsulated: spiralling/branching unmyelinated sensory terminals surrounded by modified Schwann cells and a thin oval fibrous connective tissue capsule. Deformation of capsule triggers AP
What do tactile (meissner) corpuscles respond to
Delicate (fine) or discriminative touch, light pressure, low frequency vibration (10-50 Hz)
What are lamellar (pacinian) corpuscles
Single sensory axon terminal lying within concentric layers of collagen fibres and specialised fibroblasts. Layers separated by gelatinous interstitial fluid. Fast adapting
What do lamellar (pacinian) corpuscles respond to
Deep pressure, vibration (250 Hz)
What are bulbous (ruffini) corpuscles
Nerve endings intertwined with core of collagen fibres continuous with those of surrounding dermis. Located in deep dermis and subcutaneous tissue
What do bulbous (ruffini) corpuscles respond to
Sustained deep pressure and stretching/distortion of the skin, slippage in fingers, proprioception (found in joints)
How is blood flow to the skin modulated
Smooth muscle in walls of vessels and precapillary spinchters innervated by sympathetic nerves (reduced SNS activation of α1 adrenergic receptors causes dilation of arteries, increased bloodflow)
What are α1 receptors
Activation of which causes vasoconstriction
What are the body’s primary mechanisms of heat transfer
Radiation, evaporation, convection, conduction
What is sympathetic cholinergic release of Ach onto GPCRS (G protein coupled receptors) enabled by
Eccrine glands innervated by the sympathetic nervous system
Where is the control centre for temperature regulation
Preoptic area of hypothalamus
How does the heat gain response work
Increased generation of body heat (non shivering and shivering thermogenesis), conservation of body heat (vasomotor centre decreases blood flow (shunting)), countercurrent exchange (warm blood leaving heart provides heat to cold blood returning to heart)
What is non shivering thermogenesis
Increased sympathetic nerve activity and circulating adrenaline and noradrenaline, increased cellular metabolism, uncoupling of oxidative phosphorylation (heat produced instead of ATP)
What is the effect of increased thyroxine (to increase body temperature)
Increases BMR
How do arector pili muscles aid in heat trapping
Traps insulating layer of air around body
What does the arrector pili muscle attach to
Hair follicle to upper dermis
What are potential complications of severe burns
Dehydration and hypovolemic shock, infection/sepsis, hypothermia
