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Ch. 5: Integumentary

Integumentary System

Functions of the Integumentary System -Protects against hazard environmental hazards -Helps regulate body temperature -Provides sensory information -Support from keratin fibers
Define Epidermis The outermost epithelium of the cutaneous membrane. Consists of stratified squamous epithelium. Avascular. Dominated by keratinocytes.
Cells of the Epidermidis -Keratinocytes -Melanocytes -Langerhans Cells -Merkel Cells -Basal Cells
Keratinocytes Most abundant epithelial cells. Form several layers and contain large amounts of keratin. Low Metabolic rate, close to now blood vessels/avascular.
Thin Skin vs. Thick Skin Thin covers most of the body, contains 4 strata. Thick covers palms and feet soles, contains 5 strata (5th layer=stratum lucidum), thick outer layer (strata corneum).
Melanocytes Melanin pigement-producing cells squeezed within the bottom strata of epithelium. Skin pigmentation differences dependent on how synthetically active these cells are.
Langerhans Cells Immune-responsive cells within the skin. Stimulate defense against microorganisms that manage to penetrate the superficial layers of the epidermis and superficial skin cancers.
Merkel Cells Receptive cells that convey sensory signals in the skin.
Basal Cells Cells that actively divide and add new cells. High metabolic activity, rich in blood vessels. (bottom, while keratinocytes are at top and opposite).
5 Strata of Epidermis(superficial-->deep)...(keratin producing-->metabolically active) 1. Stratum Corneum 2. Stratum Lucidum (thick skin only) 3. Stratum Granulosum 4. Stratum Spinosum 5. Stratum Germinativum
Stratum Corneum Most superficial layer. 15-30 layers of dead cells represented by flat membraneous sacs filled with keratin. Water resistant.
Insensible vs. Sensible Perspiration Insensible=when water from interstitial fluids slowly penetrates the surface to be evaporated into the surrounding air(causes the loss of ~1 pint of water/day). Sensible=through active sweat glands
Stratum Lucidum Found ONLY in thick skin, just deep to stratum corneum. Covers the stratum granulosum with flattened, densely packed, organelle-free, keratin filled cells.
Stratum Granulosum "Grainy layer". The layer superficial to the stratum spinosum. 3-5 layers of keratinocytes, organelles deteriorating, cytoplasm full of lemellated granules (release lipids) and keratohyline granules. Most cells have stopped dividing.
Keratohyalin Forms dense cytoplasmic granule that promote cell dehydration as well as aggregation and cross-linking of the keratin fibers. (keratin glue)
Stratum Spinosum 8-10 layers of keratinocytes bound together by desmosomes. Look spiny b/c keratinocyte cytoplasms are shrunk, desmosomes still in tact. Contains Langerhans cells. Cells contain thick bundles of intermediate filaments made of pre-keratin.
Stratum Germinativum AKA stratum basale. Deepest stratum. One row of active stem cells. Some newly formed cells become part of superficial layers. Interlocks with papillae of the dermis with epidermal ridges. Dominated by basal cells, contain merkel cells and melanocytes
Epidermal Ridges + Dermal Papillae Hilly surfaces that interlock and connect the epidermis and dermis. Strength of attachment is proportional to the surface area of the basal lamina (between the ridges and papillae), the deeper the folds, the larger the surface area.
Epidermal Pigmentation Carotene and Melanin
Carotene Orange-yellow pigment found in epidermal cells and fatty tissues.
Melanin A brown, yellow-brown, or black pigment made by melanocytes of the stratum germinativum. Pigment transfer temporarily colors keratinocytes.
Melanosomes Intracellular vesicles that contain melanin (manufactured from tyrosine). Melanosomes are larger in dark-skinned people, thus pigmentation is darker and more persistent. Act as sun/UV block for cell nuclei.
Rickets The bending/weakening of bones from vitamin D3 deficiency.
Vitamin D3 Synthesis from Sunlight When exposed to sun, deeper epidermal cells convert a steroid into cholecalciferol (Vit D3) which the liver converts into a product which the kidneys use to make calcitriol which is essential for calcium and phospherous absorption by the small intestine.
Roles of Epidermal Growth Factor (EGF) -Promoting divisions of stem cells in the strata basale & spinosum -accelerating production of keratin in differentiating keratinocytes -stimulating epidermal development&repair after injury -stimulating synthetic activity & secretion by epithelial gla
Dermis Lies between the epidermis and hypodermis. Organized in papillary layer and reticular layer.
Papillary Layer Rich in areolar tissue. Contains the capillaries, lymphatics, and sensory neurons that supply the surface of the skin. Interconnects with epidermis via papillae-epidermal ridge connection.
Reticular Layer Deep to the papillary layer. Consists of an interwoven meshwork of dense irregular connective tissue containing collagen (blend into papillary layer and subcutaneous layer) and elastin.
Stretch Marks Come from the stretching of elastin fibers past their maximum elastic limits.
Lines of Cleavage Patterns of collagen and elastin fiber bundles that are oriented to resist the forces applied to skin during normal movement. Used by surgeons to determine how to make incisions (parallel to the lines of cleavage) to promote quicker, scar-free healing.
Dermal Blood Supply From the cutaneous plexus and papillary plexus
Cutaneous Plexus Networks supplied by arteries, formed in the subcutaneous layer along its border with the reticular layer of the dermis.
Papillary Plexus Branching small artery network formed upon reaching the papillary layer of the dermis
Contusion AKA bruises. Caused by the rupturing of dermal blood vessels, which leak blood into the dermis.
Mechanoreceptors in the skin Tactile (Meissner's) Corpuscles and Lamellated (Pacinian) Corpuscles
Tactile vs. Lamellated Corpuscles Tactile=nerve receptors sensitive to light touch, located in the dermal papillae. Lamellated=nerve receptors sensative to deep pressure and vibration, located in the reticular layer.
Hypodermis Layer of skin deep to dermis. Stabilizes position of skin relative to underlying tissues, while permitting independent movement of the layers. Site for subcutaneous injection (lower layer). Contains adipose tissue (redistributed w/ age).
Layers of Hypodermis Top/superficial=blood rich bottom/deep=poor in blood vessels, site of medical injections
Hairs Rises from the dermis, comes out through epidermis almost everywhere besides the sides and soles of feet, palms, sides of fingers and toes, lips, and parts of external genitalia.
Hair Follicles Organs that produce nonliving hair. Wrapped in dense connective tissue sheath. Root hair plexus at each base for sensory reception.
Functions of Hair & Follicles All=sensory receptors Head=Protect scalp from UV radiation, cushion light impact to head, and insulates the skull. Nose+Ear=help prevent entry of foreign particles and insects. Eyebrows=keep sweat out of eyes
Arrector Pili Bundle of smooth muscle cells form this muscle. Contract to stand up root hairs (goosebumps).
Hair Root Portion that anchors hair into the skin. Begins at base (hair bulb) and extends distally to point at which internal organization of the hair is complete, about 1/2 way to skin surface.
Hair Shaft The part of hair that we see on the surface that extends from the 1/2 way point to the skin surface to the exposed hair tip.
Hair Production Begins at base where a mass of epithelial cells forms a cap called the hair bulb that surrounds a small hair papilla. Superficial cells of the hair bulb produce the hair as they form a layer called the hair matrix which contain basal cells that divide.
Hair Papilla A peg of connective tissue containing capillaries and nerves.
Hair Matrix Layer formed by superficial cells of the hair bulb. Basal cells near center divide and produce daughter cells near center. Closest to center=medulla/core. Farther from the center=cortex. Edges of the hair matrix form the cuticle, at the surface of hair
Soft vs. Hard Keratin Soft=in the medulla, is thinner and more flexible. Hard=thick layers in the cuticle, give hair its stiffness.
Internal Root Sheath Surrounds hair root and deeper portion of the shaft. Produced by cells at the periphery of the hair matrix. Disintegrate quickly. Doesnt extend the entire follicle length.
External Root Sheath Extends from the skin surface to the hair matrix in longitudinal section. Over most of that distance has all the cell layers found in the superficial epidermis. Resembles stratum basale cells where it joins the hair matrix.
Glassy Membrane A thickened clear layer wrapped in a dense connective tissue sheath. In contact with the surrounding connective tissues of the dermis.
Club Hair Inactive hair at the end of the growth cycle. Follicle is smaller and connections with the hair matrix breaks down. Shed and pushed to the surface when another cycle begins (every 2-5 years).
Types of Hair Vellus and Terminal
Vellus Hairs Fine "peach fuzz" [~velvet]. Present at armpits, pubic area, and limbs until puberty.
Terminal Hairs Heavy, more deeply pigmented, and sometimes curly hair. Found on head, eyebrows, eyelashes, and replace vellus hairs after puberty.
Hair Color Dependent on pigment produced by melanocytes at the hair papilla. Different forms of melanin. White hair=lack of pigment+air bubbles in medulla of hair shaft. Dyes color, but weaken cuticles. Conditioners counteract this affect.
Sebaceous Glands AKA oil glands. Holocrine glands that discharge an oily lipid secretion (sebum) into hair follicles. Those that communicate with a single follicle and share a duct=simple branched alveolar glands.
Sebum The secreted lipid product from sebaceous glands. A mix of tricylglycerides, cholesterol, proteins, and electrolytes. Inhibits bacteria growth, lubricates&protects shaft keratin, and conditions surrounding skin.
Sebaceous Follicles Large sebaceous glands NOT associated with hair follicles. Located on the face, back, chest, nipples, and external genitalia. Active during the last few months of fetal development forming a protective surface layer w/shed epidermal cells.
Seborrheic Dermatitis Inflammation around abnormally active sebaceous glands, usually of scalp. Common cause of dandruff in adults.
Sudoriferous Glands Sweat Glands. 2 types are apocrine and merocrine (eccrine).
Apocrine Sweat Glands Secrete their products into *hair follicles* beginning after puberty. Produce a sticky, cloudy, and potentially smelly secretion. NOT ACTUALLY APOCRINE-type GLAND. IS ALSO MEROCRINE!
Merocrine/Eccrine Sweat Glands Discharge their secretions directly onto the *surface of the skin*. More numerous, widely distributed, smaller than apocrine. Found especially on palms and soles. Called sensible perspiration.
Sweat: Composition 99% water, also contains some electrolytes (mostly NaCl), organic nutrients, antibiotic peptide (dermicidin), and waste products.
Sweat: Functions -Cooling the skin surface -Excreting water and electrolytes (and many metabolized drugs) -Providing protection from environmental hazards (dilutes chemicals and discourages microbe growth by either flushing them preventing adhering or antibiotic action.
Created by: 725585579
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