integumentary system Flashcards
what does the integumentary system consist of
layered cutaneous membrane and associated appendages- hair, nails, oil glands and sweat glands
facts about the skin system
largest organ in the body, the main barrier between our body and external environment, always exposed to a wide variety of factors (chemicals, sunlight, temperature changes, weather), the outer layer is worn away and constantly replaced to always provide protection, the most extensive sensory gland because of the vast number of sensory receptors and nerves that respond to touch, pressure, temperature and pain
is skin supported by subcutaneous tissue
yes, which separates the skin from the underlying fascia
what are the 2 main layers of skin
epidermis- top layer made of stratified squamous epithelium
dermis- deep layer composed of connective tissue and contains blood vessels, lymph vessels and nerves, the hypodermis is the layer under the the dermis composed of adipose (fatty) CT
what are the functions of the skin
blood reservoir, excretion of excess and waste products, metabolism of vitamin D, protection, thermoregulation and sensory receptor
layers of the epidermis skin in order from top to deepest
stratum corneum, stratum granulosum, stratum spinosum, stratum basale
stratum corneum
most superficial layer, 20-30 layers of dead cells, flat membranous sacs filled with keratin. glycolipids in extracellular space
startum granulosum
typically 5 layers of flattened cells, organelles deteriorating, cytoplasm full of lamellar granules (release lipids) and keratohvaline granules
stratum spinosum
several layers of keratinocytes unified by desmosomes. cells contain thick bundles of intermediate filaments made of pre keratin
stratum basale
deepest epidermal layer, one row of actively mitotic stem cells, some newly formed cells become part of the more superficial layers. see occasional melanocytes and dendritic cells
what are the 4 cells in the epidermis and what layer of skin are they in
langerhans cells- digest foreign material/ activate immune system (stratum spinosum)
keratinocytes- toughens/ waterproofs skin, they do the metabolism of vitamin D, the most abundant cell and thet are continuously generated and replaced (stratum basale, spinosum, granulosum and corneum)
melanocytes- UV protection (stratum basale)
merkel cells/ discs- touch sensation (stratum basale)
what is stratum lucidum
thicker skin in feet or hands, it is placed below stratum corneum. made of 2-3 rows of clear, dead keratinocytes and helps to reduce friction between the epidermal layers
what are the 2 layers of the dermis
papillary layer- 20% and made of areolar CT- elasticity of the skin, contains dermal ridges and dermal papillae
reticular layer- 80% and made of dense regular CT- firmness of the skin, contains some adipose tissue, deep layer
skin appendages
sweat glands- temperature regulation, excretion of waste, merocrine glands.
hair- protection, filtering dust/ debris, touch detection, strands of hardened, dead keratinocytes.
nails- protection, tools, made of hardened keratinized cells and formed in the stratum corneum.
oil glands- lubrication, antibacterial, prevent water loss. is a holocrine gland so it bursts when its full and then is replaced
what are the 2 types of sweat glands
eccrine- found throughout the skin, open via pores at the surface. secrete regular swear
apocrine- only found in armpits and genital region. they open into a hair follicle and secrete sweat that has organic compounds in it e.g. proteins and lipids which have carbon in them which the bacteria on your body breaks down which is why it smells
what happens to the cells as they move up the skin layers
they are made in the deepest layer and as they go up the skin cells they flatten and mature and by the time they get to the stratum corneum they are dead as the epithelial layer has no blood supply
skin function- blood reservoir
5% of blood volume circulates within the dermis of the skin which can be shunted to other organs as necessary
skin function- excretion
water, salts and organic waste products are excreted in sweat, which is secreted onto the surface of the skin by sweat glands
skin function- metabolism
synthesises of vitamin D occurs within certain layers of the skin
skin function- protection
the skin is a thick, touch waterproof organ that forms a physical barrier from external environment, protecting against impact, abrasion, fluid loss and chemical attack. the PH of the skin is acidic which inhabits the growth of some bacteria and immune cells within the skin attack or destroy foreign microbes
skin function- thermoregulation
blood carries around heat of the body and when blood flows to the surface, heat can escape through the skin. when blood flow to the skin is reduced, heat within the body is conserved. heat loss occurs via evaporation of sweat from the skin. the hypodermis ( subcutaneous layer) which is made of adipose tissue, provides insulation against heat loss.
skin function- sensory reception
the body contains a variety of sensory nerve ending that detect touch, pressure, temp and pain stimuli and send information about those senses to the brain for interpretation
the dermis layer
is below the stratum basale, it is highly vascularised and contains numerous nerve endings. it contains invagination of the epidermis which create hair follicles, sweat glands and oil glands. it has 2 layers- papillary and reticular layers
what are dermal papillae
they are extensions of the dermis that push up against the stratum basale, causing epidermal ridges which sit in the dips between the dermal papillae, so the erpidermis and dermis meet along rising and falling line (undulating).
what are dermal ridges
the large mounds of dermal cells in the fingertips which cause large undulations in the entire epidermis, creating fingerprints that are typically unique to each other
what does the dermis do near joints
is it tightly secured to deeper structures where there would be increased tension on the skin when joints move. to accomodate joint movement, the dermis is thrown into deep folds which create creases in the skin that are easily seen in the epidermis. these creases are mostly visible on the hands, wrists, fingers, soles and toes
