integumentary system

The integumentary system- comprised of the skin, hair, and nails

skin- largest organ of the body, made up of the epidermis, dermis, and hypodermis

epidermis- outer layer, made of stratified squamous epithelium, avascular (no direct blood flow), recieves nutrients from the basement membrane

four layers of the epidermis- stratum corneum, stratum granulosum, stratum spinosum, and stratum basale

stratum basale- bottom layer of the epidermis, adhered to the basement membrane, constantly dividing to rebuild the skin

30 days- time for a cell to move from the stratum basale to the stratum corneum. remains for another 2 weeks until it is removed

epidermal ridges- formed by the stratum basale, also called fingerprints, are unique to each person and consistent through life

cells found in the epidermis- keratinocytes, Langerhans cells, fibroblast cells, melanocytes, and Merkel cells

melanocytes- produce the pigment melanin

Langerhans cells- act as a first lie of defense, identifying microorganisms before reaching the bloodstream

Merkel cells- sensory receptor that responds to light tough

keratinocytes- produce keratin, a tough substance

fibroblast cells- produce collagen which adheres the epidermis cells together and give the skin elasticity

dermis- middle layer, contains sweat glands, oil glands, and sensory organs, has a high water content

papillary region- superficial layer of the dermis, contains collagen fibers and elastic fibers

reticular region- deep layer of the dermis, contains collagen fibers and elastic fibers, contains the skins main blood supply

contusion- a bruise, damage of a blood vessel in the skin

hypodermis- inner layer, also called subcutaneous, made of mostly fat cells (adipocytes), anchors the dermis to a layer of fat cells

purpose of fat- insulate and regulate body temperature

skin cells- absorb ultraviolet light to produce vitamin D, contains sensory receptors and glands for protection from pathogenic microorganisms and temp changes

lymphatic system- protects the body is foreign objects and microbes that get into the body due to integumentary system damage

merkels cells and meissners corpuscles- mechanoreceptors that detect sensory info by way of light touch and vibration

nociceptors- detect pain, like from a pin prick

pacinian corpuscles- detect mechanical sensory info based on pressure applied to the skin

thermoreceptors- detect hot and cold

exocrine glands- release secretions through a duct into an epithelial surface or lining

multicellular glands- set within epithelial tissue and release contents through a duct to the surface

sebaceous glands- (oil glands) produce sebum to keep the hair and skin from drying out and inhibits the growth of harmful microorganisms

sweat glands- (sudoriferous glands) produce sweat in almost every part of the skin

dermatome- a region of skin innervated by one sensory nerve, sends sensory nerves to the spinal nerve, then the spinal cord, then other the brain for processing

hair- made up of dead epidermal cells that have been converted to keratin

hair root- begins at the hair bulb which has a blood and nervous supply in the dermis

shaft- extends through the epidermis to the outside

arrector pili muscle- a smooth muscle on each hair follicle that contracts when the body is cold or experiences emotional responses

nails- composed of dead epidermal cells that have been converted to keratin

nail body- visible portion of the nail, covering the epidermis called the nail bed

cuticle- the stratum corneum of the epidermis that extends from the nail root, covering some of the visible portion of the nail

lunula- visible portion of the nail bed near the nail root

tissues- cells that come together, comprised of cells and a matrix

matrix- (extracellular material) made up of ground substance, protein, and collagen

clot- blood platelets accumulate at the damage site to form a mesh like substance and prevent blood loss

mast cells- release histamine to dilate blood vessels to bring more blood and nutrients to the damage site, initiate an inflammatory response

macrophages- engulf and destroy disease-causing pathogens

fibroblasts- secrete new collagen in the shape of the old tissue to support the tissue matrix until new cells are developed

scar- an overgrowth of the fibrous connective tissue that cannot be fully replaced, caused when the wound is too deep, some of the original function is lost

first degree burn- only damage the epidermis, becomes dry, red, and painful, eg: sunburn

second degree burn- damages the epidermis and some of the dermis, turns red and forms blister, is painful and swollen due to damage to the sensory organs in the dermis

third degree burn- damage the epidermis, dermis, and possibly the subcutaneous layer, typically becomes white and possible “charred”, extremely painful

fourth degree burn- damages the epidermis, dermis, hypodermis, and some of the tissue such as a muscle or bone, no sensation due to destroyed nerve endings, may require a skin graft