Chapter 5 Flashcards
(107 cards)
rintegumentary system
organ system made up of skin, sweat, oil glands, hairs and nails. made of cutaneous membrane and accessory structures.
epidermis
region of skin, composed of keratinized stratified squamous epithelium, the outermost protective shield of the body. provides a barrier against bacteria as well as chemical and mechanical injuries
made of 4 distinct cell types (keratinocytes, melanocytesm dendritic cells and tactile cells)
and 5 types of layers (stratum basale, stratum spinosum, stratum granulosum, stratum lucidum and stratum croneum)
dermis
region of skin. made up organs and vessels. makes up the bulk of the skin. it is a tough layer made up of dense fibrous connective tissue. has a rich supply of nerve fibers, blood vessels and lymphatic vessels. 2 layers: papillary layer and reticular layer
hypodermis
subcataneous tissue located just below the dermis. not part of the skin. consists of adipose tissue and areolar connective tissues. it anchors the skin to the muscles and acts as a shock absorber and an insulator that reduces heat loss. also called superficial fascia. allows skin to move easily over the underlying muscles because of the loose connective tissue
keratinocytes
most common cell of the epidermis. produce keratin (fibrous protein that gives epidermis its protective properties and reduces water loss at the skin surface). arise from stratum basale layer. these undergo constant mitosis. these are dead when they reach the skin surface and milions of these rub off everyday. we get a new epidermis every 25-45 days
melanocytes
a cell of the epidermis. synthesize the pigment melanin. melanin accumulate on the superficial side of the keratinocyte nucleus and forms a pigment shield that protects the nucleus from UV radiation
dendritic cells
epidermis cell (a type of macrophage). arise from bone marrow and migrate to the epidermis. they ingest foreign substances and activate our immune system. kind of phagocyte. also called Langerhans cells. represent a link between the integumentary and the lymphoid systems. most abundant in stratum spinosum. engulf antigens and then present fragments of them to their own surfaces, where they can be recognized by T cells
tactile cells or merkel cells
epidermis cell. functions as a sensory receptor for touch
thick skin
refers only to epidermis. covers areas subject to abrasion (palms, fintertips, soles of feet). have 5 layers (from deep to superficial): stratum basale, stratum spinosum, stratum granulosum, stratum lucidum and stratum corneum.
(stratum lucidum is absent in thin skin)
stratum basale also called stratum germinativum
deepest epidermal layer. attached to underlying dermis. consists of a single row of stem cells that form keratinocytes. melanocytes are here too. undergoes constant mitosis to replace cells lost by abrasion. journey from this layer to surface is 25-45 days
stratum spinosum
layer of epidermis. several layers of keratinocytes unified by desosomes. contain thick intermediate filaments and dendritic cells
stratum granulosum
layer of epidermis. consists of 4 to 6 cell layers. process of keratinization begins (this is when cells fill up with the protein keratin). cells flatten and organelles deteriorate. the cytoplasm is full of keratohyalin granules and lamellar granules. plasma membrane of cells here thicken. cells above these are too far from dermis (which has nutrients) so cells above this die
stratum lucidum
epidermis layer located just above stratum granulosum. consistes of 2 or 3 layers dead keratinocytes
stratum corneum
outermostepidrmal layer. 20 to 30 cell layers thick. accounts for 75% of epidermal thickness. keratin and thick plasma membraneof the cells here protect the skin from abrasion and penetration. protects deep cells from external environment.
papillary layer
layer of dermis made of areolar connective tissue. connective tissue with defensive cells like phagocytes. has dermal papillae that indent the overlying epidermis. papillae cause skin ridges called friction ridges that enhance gripping ability in hands and feet and also contribute to our sense of touch. layer of the skin that contains the blood vessels and nerves that are closest to the surface of the skin
reticular layer
deeper layer of dermis. accounts for 80% of the thickness of the dermis and tension lines in skin. irregular dense fibrous connective tissue (strong). extracellular matrix includes adipose cells and thick bundles of collagen fibers. separations betweenthese bundles form cleavage lines (externally invisible and run longitudinally).
flexure lines
skin markings caused by dermal folds that occur at or near joints where the dermis is tightly secured. this skin cannot slide easily to accommodate joint movement so creases form
melanin
pigment that contributes to skin color. synthesized from melanocytes. this protects the DNA of skin cells from UV radiation by absorbing the sun rays (natural sunscreen). differences in skin color depend on the kind and amount of this made. produced in the skin
carotene
pigment that contributes to skin color. yellow/orange pigmant found in plants (carrots). accumulates in stratum corneum and can cause skin color change when eaten a lot. this can also be converted to vitamin A, which is essential for vision.
hemoglobin
pigment that contributes to skin color. oxygenated pigment in RBC’s that causes a pinkish hue of fair skin. white people have little melanin so this color shows through the skin easily
skin
made up for epidermis (superficial region), dermis (middle region) and hypodermis (deepest region and technically not a part of skin).
hair
flexible strands of dead keratinized cells. contains hard keratin. major regions include medulla(only part with soft keratin), cortex and outermost cuticle. pigment is melanin. functions include alerting the body to presence of incets on the skin and guarding the scalp against physical trauma, heat loss and sunlight
hair follicle
extends from epidermis into dermis to form hair. includes hair bulb (expanded deep end), outermost sheath is connective tissue sheath. has a hair follicle receptor (root hair plexus) that is a sensory nerve ending around each hair bulb and it stimulated by bending hair (acts as touch receptrs). attached to arrector pili
arrectior pili
smooth muscle in dermis attached to hair follicles. when it contracts it pulls the hair follicle upright and dimples the skin to produce goose bumps. most important role is to force sebum out of the hair follicle to the skin surface