Integumentary system Flashcards
Arrector pili
A microscopic band of smooth muscle that elevates the hair follicle
Contact inhibition
The cessation of cell division in cells that touch each other
Epidermis cells
Epidermal cells are
90% keratinocytes (keratin = tough fibrous protein that protects)
8% melanocytes (melanin = pigment that contributes to skin colour; eumelanin= brown/black, pheomelanin = reddish / yellow)
2% Langerhans cells; immune cells that are involved in skin ‘surveillance’
Fingerprints
Ridges formed during foetal development. Increase surface area and enhance grip by creating friction. Unique to each individual
Granulation tissues
Connective tissue that fills wound
Integumentary system, inc layers
Skin. Largest organ in the body. Covers external body & continues with mucous membranes internally, consists of 3 layers; epidermis, dermis, subcutaneous layer (adipose layer), contains accessory structures (glands, hair, nails)
Scar tissue
A mark on the skin or other body tissues where a wound, burn or sore has not healed completely and fibrous connective tissue has developed. Contains denser collagen fibres, fewer hairs, glands and nerve endings and blood vessels (whiter)
Two types of scar tissue:
1) Hypertrophic scar – stays within the boundary of the wound
2) Keloid scar – Takes up a larger space than the wound (normally raised)
Sensory nerve endings
3 types:
Meissner’s corpuscle; sensitive to light pressure
Pacinian corpuscle; sensitive to deep pressure
Free nerve ending; sensitive to pain & temperature
Skin colour;
Brown: Pigmentation due to varying degrees of melanin produced by melanocytes. People of different races have the same number of melanocytes but different amounts and types of melanin (eumelanin/ pheomelanin)
Pink: Colour due to level of blood circulation and oxyhaemoglobin
Natural Yellow: Colour caused by carotenes (pigment that gives egg yolk / carrots colour)
Yellow: Colour from pathology due to bilirubin.
Albinos are unable to synthesis melanin
Skin Functions
Functions; Protection, Thermoregulation (body temperature), Vit D production, Sensation, Absorption, Excretion
Skin functions; Protection
Against dehydration & external factors such as chemicals, toxins, trauma, light & microbes
Physical barrier - Closely packed keratinised cells & melanin
Sebum - Contains fatty acids which inhibit microbial growth
Sweat - Contains lysozymes, which are enzymes that break down bacteria
Nerve sensors - Induce protective reflexes
Desquamation - Shedding of the skin cells help remove microbes
Skin functions; Thermoregulation
Thermo = temperature
Normal body temp = 35.5 – 37.5 ‘C (98-100F). Heat is produced by liver, muscles & digestive organs. Adipose tissue = insulator. Heat loss by respiration through convection & evaporation (movement of heat through liquid / gases) Temperature control centres are the hypothalamus & medulla oblongata.
Thermoregulation occurs via activity of sweat glands (water evaporates off skin) & blood vessels (vasodilation/vasoconstriction). Both stimulated by ANS
Skin functions; Hyperthermia criteria
> 38.5’C. (Hyper = elevated)
When core temp. elevates above 38.5’C. Life threatening = 40’c, Death – 45’C.
Skin functions; Hypothermia criteria
<35’C. (Hypo = low). When core temperature drops below that required for normal metabolism & body functions. Death usually below 25’C
Skin functions: Vitamin D formation
UV light activates a Vitamin D precursor in the skin. The kidneys convert the precursor to calcitriol, which acts as a hormone to increase uptake of calcium & phosphorus (supporting bone density). Vitamin D is stored in the liver
Skin functions: Absorption
Substances absorbed through the skin:
Lipid-soluble molecules: (Vit. A, D, E, K, medications, essential oils, O2 & CO2)
Toxins: Acetone, carbon tetrachloride, lead & mercury, arsenic, poison oak & ivy, chemicals
Skin functions: Excretion
Substances excreted through the skin: Salt (sodium chloride), Water, Urea, Ammonia
Skin layers;
The skin consists of 3 main layers:
1) Epidermis (epi= above) The superficial (surface) layer of skin formed of tightly packed cells - epithelial tissue (keratised epithelium, a protective waterproof barrier). Replacement occurs 40 days.
2) Dermis; The middle layer of skin, formed of connective tissue. Also contains accessory structures – sweat glands, hair & sebaceous glands
3) Subcutaneous layer (sub = below): An insulating & protective layer of fatty tissue that connects the dermis to the deeper-lying muscle & bone
Epidermis layers
5 Layers =
1) Stratum corneum
2) Stratum lucidum
3) Stratum Granulosum
4) Stratum Spinosum
5) Stratum basale.
1st layer - stratum corneum
Outer layer (1st)
25-30 layers of flattened dead keratinocytes
Cytoplasm replaced by keratin
Are shed (desquamated)
2nd layer - stratum lucidum
3-5 layers of dead cells
Only present in thick skin
3rd layer - stratum Granulosum
3-5 layers of cells undergoing apoptosis (self-suicide) (1/2 living)
4th layer - Stratum Spinosum
8-10 layers of new (living) keratinocytes
5th layer - stratum basale
Single row dividing to form new keratinocytes
Skin layers: Dermis
The middle and thickest layer in skin, formed of connective tissue. Contains a matrix of collagen (strength) & elastic fibres (stretch & recoil).
Also includes accessory structures – sweat glands, hairs & erector pili muscles and sebaceous glands, arterioles & capillaries, lymph vessels & nerve endings and fibroblasts and immune cells.
Skin layers: Dermis; Hairs
Hairs are concentric columns of dead keratinised cells bonded together by proteins. Arrector pili connects the hair follicle to the dermis. When the hair is erect, it traps a layer of air next to the skin (part of thermoregulation)
Skin layers; Dermis; Sebaceous Glands
Secrete sebum - keeps hair soft, provides waterproofing for the skin & is anti-microbial. (Mainly on face, scalp, lips, eyelids, nipples, labial folds, glans penis)Skin layers; Dermis; Sebaceous Glands
Skin layers; Dermis; sweat (sudoriferous) glands
Consists of a gland, duct & a pore. Excretion of urea (waste). Body heat used to evaporate sweat – helps regulate body temperature, smell = bacteria breaking down substances in sweat such as fatty acids, excessive sweating leads to dehydration and sodium (NA+) depletion
Wound healing;
Deep wound
Affects dermis & subcutaneous layer. Three phases:
Inflammatory; migration of leukocytes to clean up microbes/foreign tissue, blood clot forms – scab, epithelial cells migrate to repair basement membrane
Proliferative: Granulation tissue formed with laying of collagen& blood vessels, extensive growth & repair of epithelial cells
Remodelling; 3 weeks – 6 months, scab off & scar tissue remains (fibrosis)
