Integumentary System and Bones
Integumentary System and Bones BIO 221
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This 6 page Study Guide was uploaded by Sara Ratti on Tuesday February 9, 2016. The Study Guide belongs to BIO 221 at Towson University taught by Professor Colleen Winters in Spring 2016. Since its upload, it has received 32 views.
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Date Created: 02/09/16
Chapter 5 Integumentary System Cutaneous Membrane Two components: epidermis (superficial epithelium) and dermis (underlying area of connective tissue) Accessory structures: hair, exocrine glands, and nails. Located in the dermis and protrude through epidermis. Integumentary Functions: protection of underlying tissues and organs, excretion of salts, water, and organic wastes, maintenance of normal body temperature, production of melanin (skin pigment) protects from UV radiation, production of Keratin- protects & serves as water repellent, synthesis of Vitamin D (converted to calcitriol for normal calcium metabolism), storage of lipids in adipocytes in the dermis & in adipose tissue in the hypodermis, detection of touch, pressure, pain, vibration, temperature, & relaying that info to nervous system, coordination of immune response to pathogens & cancers in the skin. The Dermis has an extensive network of blood vessels, sensory receptors to monitor touch, pressure, temperature, and pain (valuable information to the central nervous system-homeostasis) Epidermis: surface layer of the skin, protects the dermis, prevents water loss, entry of pathogens and synthesizes vitamin D. (sensory layer) Avascular (no blood vessels) Mircovilli: moves things through membranes (oxygen, nutrients, etc.) Cillia: moves things across membranes (fluids) Dermis: >Papillary Layer: nourishes and supports epidermis >Reticular Layer: has sensory receptors that detect, touch, pressure, pain, vibration, temperature. Blood vessels assist thermoregulation. Accessory Structures: >Hair Follicles: protects skull & provides delicate touch sensations on general body surface >Exocrine glands: assist in temperature regulation and waste excretion > Nails: protects & supports tips of fingers and toes. Keratinocytes: body’s most abundant epithelial cells-dominate epidermis. Cells form several layers or strata (epidermis is -stratified squamous epithelium-). Large amount of protein Keratin. Thin Skin: covers most of body surface Thick Skin: found on palms of hands and soles of feet *Thick & Thin skin refers to the thickness of the epidermis NOT cutaneous membrane. Epidermis Layers Stratum Basale: (stratum germinativum) Hemidesmosomes attach the cells of this layer to the basement membrane that separates the epidermis from Areolar tissue of the dermis. The Stratum Basale & dermis interlock, making a strong bond between epidermis & dermis Basal Cells: dominate stratum basale, are stem cells that divide to replace the more superficial keratinocytes that are shed at epithelial surface. Merkel Cells: scattered among SB, merkel cell with a sensory nerve terminal= Tactile disc: sensitive to touch and when compressed release chemicals to stimulate associated nerve ending. Melanocytes: brown skin tones result from the synthesis of these cells. These pigment cells are distributed throughout stratum basale Stratum Spinosum: each time a stem cell divides, one of the daughter cells is pushed superficial to the stratum basale into the stratum spinosum. Consists of 8-10 layers of keratinocytes bound together bound together by desmosomes. Stratum Spinosum= “spiny layer” the cells appear like miniature pincushions in standard histological sections. cells in SS take part in immune response- dendritic cells: stimulate defense against 1) micro-organisms that manage to penetrate superficial layers of the epidermis 2) superficial skin cancers Stratum Granulosum: “grainy layer” consists of 3-5 layers of keratinocytes derived from the stratum spinosum. By the time cells are pushed into this layer, they have stopped dividing & have started making large amounts of Keratin and Keratohyalin. When Keratin fibers accumulate, the cells grow thinner & flatter, their plasma membrane thickens and becomes less permeable. Keratinohyalin forms dense cytoplasmic granuales that promote dehydration of the cell as well as aggregation & cross-linking of Keratin fibers. Stratum Lucidum: thick skin of palms and soles, a glassy stratum (clear layer) covers the stratum granulosum. Cells are flat, densely packed, largely without organelles, and filled w/ keratin. Stratum Corneum: exposed surface of thin and thick skin. Has 15-30 layers of keratinized cells. Keraitinization/Cornification: the formation of protective, superficial layers of the cells filled with keratin. This process takes place on ALL exposed skin surfaces (except anterior surfaces of the eyes). The dead cells remain tightly interconnected by desmosomes. Connections are so tight keratinized cells shed in sheets (your dead skin sheds in sheets, sunburn peeling in large pieces). Insensible Perspiration: water from interstitial fluid slowly penetrates to the surface and evaporates into the surrounding air- Insensible b/c you cannot feel/see the water loss. Damage to the epidermis can increase the rate of this (connections break b/t superficial & deep layers so fluid accumulates in pockets (these are how blisters form). Xerosis is a skyrocketing version of this (excessively dry skin). Sensible Perspiration: produced by active sweat glands (sweating you can see & feel). Why do wrinkles form in the skin & why do we prune in long baths?: our fingertips shrink in water which is caused by blood vessels due to autonomic nervous system (ANS) which functions outside of our awareness & controls blood vessels. The Role of Epidermal Pigmentation Three components of pigmentation: Carotene, Melanin, Hemoglobin Carotene: an orange-yellow pigment that normally accumulates in epidermal cells. Most apparent in cells of the stratum corneum or light-skinned individuals, also accumulates in fatty tissues deep in the dermis and subcutaneous layer. (Found in a variety of orange vegetables, carrots). Carotene is converted to Vitamin A, which is required for both normal maintenance of epithelia & synthesis of photoreceptors pigments in the eye. Melanin: a pigment produced by melanocytes, pigment producing cells. Two types: red-yellow form (pheomelanin) and a brown-black form (eumelanin). The melanocytes involved are located in the stratum basale , squeezed between or deep to the epithelial cells. Melanocytes manufacture both types of melanin from the amino acid tyrosine & package it into intracellular vesicles- melanosomes. Hemoglobin: Blood component of skin pigmentation Vitiligo and Albinism: skin pigment disorders that results from a lack of melanin. Albinism- no pigmentation at all. Vitiligo- patchy pigmentation (possibly an autoimmune disorder). Role of Dermal Circulation Blood contains red blood cells filled with the pigment Hemoglobin, which binds and transports oxygen in the blood stream. When bound to oxygen, hemoglobin is a bright red that gives capillaries in the dermis a reddish tint that is most apparent in light-skin individuals. Also, when the vessels are dilated it becomes more evident. Rise in temperature, exercising, etc. leads to the dilation of superficial blood vessels so the skin can act as a radiator and lose heat. Cyanosis: gives skin the bluish tint when blood circulation results due to fear, cold, cardiovascular or respiratory disorders. Hemoglobin releases oxygen and turns a much darker red in these conditions from the surface it looks blue. Jaundice: yellow tint of skin b/c the body is unable to excrete bile Tumors: affect the pituitary gland result in secretion of large amounts of melanocyte-stimulating hormone (MSH). Creates darkening of the skin- as if individual is a deep bronze tan. Addison’s disease: pituitary gland secretes large amounts of adrenocorticotropic hormone (ACTH) creates similar affect as tumors do (darkening skin). Sunlight causes epidermal cells to convert a steroid into Vitamin D(3) Epidermal cells convert vitamin D exposed to UV radiation into cholecalciferol. The liver converts cholecalciferol into an intermediate protein used by kidneys to synthesize the hormone, calcitriol, which is essential for the normal absorption of calcium and phosphorus in the small intestine. (Inadequate supply leads to impaired bone maintenance and growth). Sunlight Food Steroid compound- Cholecalciferol Dietary Cholecalciferol Liver- intermediate product Digestive Tract Kidney- Calcitriol Stimulation of calcium and PO4 ion absorption Rickets: disease caused by vitamin D deficiency, results in bending of abnormally week and flexible bones under the weight of the body. Epidermal growth factor has several effects on the epidermis and epithelial Epidermal Growth Factor (EGF): is one of the peptide growth factors. Promotes division of basal cells in the stratum basale and stratum spinosum Accelerating the production of keratin in the epidermal repair after injury Stimulating epidermal development and epidermal repaid after injury Stimulating synthetic activity and secretion by epithelial glands The dermis is the tissue layer that supports the epidermis The dermis has two major components 1) superficial papillary layer 2) deeper reticular tissue Papillary Layer: consists of areolar tissue. Contains capillaries, lymphatic vessels, and sensory neurons that supply the surface of the skin. (dermal papillae project between the epidermal ridges). Reticular Layer: lies deep to the papillary layer. Consists of an interwoven meshwork of dense irregular connective tissue containing both collagen and elastic fibers. Bundles of collagen extend superficially beyond the reticular layer to blend into those of the papillary layer, boundary of the 2 layers is indistinct. Dermatitis: an inflammation of the skin that primarily involves the papillary layer. The inflammation typically begins in a part of the skin exposed to infection or irritated by chemicals, radiation, or mechanical stimuli. Sometimes no discomfort or it may itch like poison ivy. Dermal Strength and Elasticity Collagen Fibers: very strong and resist stretching but easily bent or twisted. Elastic Fibers: permit stretching and then recoil to their original length. Elastic fibers allow flexibility and collagen fibers limit the flexibility to prevent damage to the tissue. Hypodermis connects the dermis to underlying tissue Hypodermis:/Subcutaneous Layer lies deep to the dermis. No distinct boundary between dermis b/c the connective tissue fibers of the reticular layer are extensively interwoven with those of the hypodermis. Elastic. Makes up 80% of all body fat-remaining fat is visceral fat around visceral ograns. Venous circulation region contains a lot of blood, and much of this volume will shift to the general circulation of these veins (skin is a blood reservoir) Hair is composed of keratinized dead cells that have been pushed to the surface Accessories of Integumentary system: hair follicles, sebaceous and sweat glands- originate from the epidermis. Hairs: project above the surface of the skin almost everywhere, except over sides and sole of feet, palms of hands, sides of fingers, and toes, lips, and portions of external genetelia. Terminal Hair: head hair, arm, facial hair Vellus Hair: “peach fuzz” Root hair plexus: of sensory nerves surrounds the base of each hair follicle. You can feel the movement of the shaft of a single hair. Arrector Pilli: bundle of smooth muscle forms this muscle. Extends from the papillary layer of the dermis to the connective tissue sheath surrounding hair follicle. Muscle contracts which pulls the hair forcing it to stand erect caused by emotional states- fear, rage, response to cold “goosebumps” Sebaceous Glands Oil glands that are holocrine glands that discharge oily lipid secretion into hair follicles. They produce large quantities of lipids as they mature. Release lipids through holocrine secretion: process that involves the rupture of the secretory cells. Sebaceous glands that communicate w/ a single hair follicle share a duct and thus are classified as simple branched alveolar glands. Lipids released from the gland cells enter the lumen (passageway) of the gland, the arrector pili muscles that erect the hair then contract, squeezing the sebaceous gland forcing the lipids into the hair follicle onto the surface. Secreted lipid product= sebum. Sebaceous Follicles: large sebaceous glands that are not associated w/ hair follicles. Instead their ducts discharge sebum directly to epidermis.
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