Integumentary System - from crash course yt channel PDF

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Integumentary System - Composed of hair, nails, sweats, oil glands, and skin. Skin – protects the body against infection and extreme temperatures, maintains balance of fluids, and synthesizes Vitamin D for personal use. - Accounts for about 3-5 kilograms of body weight and if spread out, it would measure up to two square meters enough to cover a bed. - Made of stratified squamous epithelial tissue. - Biggest organ in the body. - Also plays a role in the excretion of waste.  Nerve endings allows you to sense the outside world.  Sweat glands and blood vessels help you maintain a proper temperature and communicate a whole range of stuff – from health to emotions - through blushing, flushing, and sweating.  The key to the integumentary system is layers. Layers of the Skin: 1. Epidermis – the only layer than can be seen by the naked eye. - bulk of epidermis is made up of cells called Keratinocytes – building blocks of the tough, fibrous, protein keratin that gives structure, durability, and waterproofing to the hair, nails, and outer skin; constantly dying and being replaced, you lose millions of them every day, enough to completely replace the epidermis every 4-6 weeks. Melanocyte – epidermal cell; spider-shaped cell that synthesizes melanin – the pigment that gives skin its color. Melanin – pigment produced by Melanocyte cells in the Epidermis; has two forms, producing pigments that range in color from reddish yellow to brownish black; main job is to protect us from the sun’s ultraviolet rays. Cellular extension – what affects the skin tone of the body; affect the amount of melanin they that contain. Langerhans Cell/Dendritic – kind of star-shaped, and like white blood cells and platelets; originate in bone marrow; once migrated to epidermis, their long, skinny tendrils run around the keratinocytes and spend much of their time ingesting the unwanted invaders that’re trying to sneak around the skin. Merkel Cells/Quartet – occur deep down the boundary between the epidermis and dermis, where they combine with nerve endings to create a sensory receptor for touch. Thick Skin – have more layers of epidermis than others; tougher stuff of the hands and the soles your feet, and consists of five epidermal layers. Thin Skin – covers everything else, with just four epidermal layers. Layers of Thick and Thin Skin: (Come - pneumonic) Stratum Corneum – “horny layer”; outermost and the roughest, made up of about 20 or 30 keratinocyte cells; the layer that is always being sloughed off and fed to dust mites, but while it’s in the place it offers basic protection from environmental threats. (Let’s - pneumonic) Stratum Lucidum – “clear layer”; holds two or three rows of clear, flat, dead keratinocytes that are only found in the thick skin of the palms and foot soles. (Get - pneumonic) Stratum Granulosum – “granular layer”; contains living keratinocytes that’re forming keratin like crazy; looks kind of grainy because those cells are getting compressed and flattened as they move up through the epidermal layers, maturing. * the deeper you go through the layers of epidermis, the younger the cells get. * regeneration happens in the lower layers, and new cells move up toward the surface, maturing all the way, where they eventually die and slough off from the surface of the skin. (Sun - pneumonic) Stratum Spinosum – “spiny layer”; cell regeneration, or mitosis is active; looks prickly when dehydrated for microscope slide preparation; they contain filaments that help them hold to each other. (Burned – pneumonic) Stratum Basale – “basal layer”; deepest, thinnest epidermal level; a single layer of columnar cells, but it’s like a cell factory where most of the new-cell production happens; connects the epidermis to the layer of skin below it, the dermis.

* the ultraviolet radiation in sunlight can damage the epidermis, causing elastic fibers to clump up. 2. Dermis – below the Epidermis; where most of the work that skin does gets done like sweating, and circulating blood, and feeling everything everywhere all the time; got loads of collagen and elastin fibers, which help make the skin strong and elastic; full of capillaries and boos vessels; houses the nerve fibers that register sensations like temperature, pressure, and pain, as well as parts of hair follicles and oil and sweat glands with the ducts that lead up to the surface of the skin. Layers of the Dermis: Papillary Layer – upper layer; composed of a thin sheet of areolar connective tissue that’s riddled with little peg-like projections called Dermal Papillae – pretty neat because in the thick skin of the hand and feet, these tiny protrusions form unique friction ridges that press up through the epidermis to help our fingers and feet grip surfaces. Reticular Layer – deeper and thicker that makes up 80% of your dermis, made up of dense irregular connective tissue; all of the dynamic parts contained within the dermis like the nerve fibers and capillaries are distributed between both its layers. 3. Hypodermis/Subcutis – bottom part, composed mostly of adipose connective tissue or fatty tissue; most basal layer; provides insulation, energy storage, shock absorption, and helps anchor the skin; it is where most of the body fat hangs out. Corpuscles - Cutaneous Sensory Receptors – receives stimuli from the outside environment and send them to the brain; register all of the different sensations that you associate with touch. Tactile Corpuscles – what make you constantly aware of the tag that’s scratching at the back of your neck Lamellar Corpuscles – register the sense of pressure, like when someone puts their hand on your shoulder  Hair follicles have receptors, which is why you can feel a slight breeze on your skin or through your hair.  About 5% of the entire blood volume is retained in the skin at any given time.  Both blood and sweat glands work together to perform a key function: regulating the body temperature.  Even without exercise, the body oozes out about half a liter of sweat per day, in an effort to keep you at a comfortable temperature, noticeable sweat called insensible perspiration. Cyanosis – blue skin; in Caucasian people may indicate heart failure, poor circulation, or severe respiratory issues. That’s because blood that’s been depleted of oxygen turns darker in color, and when seen through the tissue of lips or skin, it can look bluish. Jaundice – yellowing of the skin; usually signifies liver disorder, as yellow bile starts accumulating in the blood stream. Erythema – reddened skin; could indicate a fever, inflammation, or allergy – all of these conditions cause blood vessels to expand and more blood to flow to the skin.  The bones require Vitamin D to keep producing new bone cells, and it’s the only vitamin that the body can actually produce on its own. Your skin cells contain a molecule that converts to vitamin D when it comes in contact with UV light. From the skin, the vitamin heads through your bloodstream to your liver and kidneys where it truly becomes activated D, also called calcitriol, which is circulated to all the bones of your body Skin appendages – hairs, nails, sweat, sebaceous, or oil glands which can be fascinating as well as frustrating in its own way.  All of your hairs, or pili, are basically just flexible strands of dead keratin protein cells, like your fingernails. Cuticle – outermost layer of dead cells; like it’s made of overlapping roof shingles. Two main regions of hair being plucked 1. Shaft – where the keratinization is complete 2. Root – the part inside the follicle where keratinization is still happening Parts of the Nail 1. Nail Body 2. Nail Bed 3. Root of Nail Lunule – “little moon”; little white crescent at the base of the nail; the active nail matrix where grow originates.  You’ve got up to three million tiny sudoriferous, or sweat glands distributed throughout your body. These guys secrete your salty, watery sweat, and they come in two types: eccrine and apocrine.

Two type of Sweat Glands/Sudoriferous 1. Eccrine Sweat Glands – more abundant – they’re in the palms, forehead, and in the soles of the feet; simple coiled tubes that start in the dermis, extend through a duct, and open into a pore on the surface of the skin. 2. Apocrine Sweat Glands – you only have about 2000 of these, and they start cookin’ around puberty, emptying into the hair follicles around the armpits and groin; secrete a kind of deluxe sweat, with fats and proteins in it; more vicious and sometimes yellowish in color; when bacteria on the skin get a hold of this sweat, it gets odorific, creating what we generically call body odor. Mammary Glands - secrete milk in lactating people, and ceruminous glands, the ones that make your cerumen, or earwax, are two other types of modified apocrine sweat glands. Sebaceous/Oil Glands – found everywhere but the thick skin in the palms and foot soles; their ducts are smaller on the limbs, but pretty big on the face, neck, and upper chest; most of this secrete their sebum, an oily substance, into hair follicles where it can travel to the surface of the skin; while they cause wicked pimples, their primary goal is to soften and lubricate your skin and hair, and help slow water loss from the skin in dry environments.   ...