Exam 3 Review - Skin, bone, axial skeleton on exam 3Chapter 5 – Integumentary system1. Integumentary System Basic Componentsa. Composed of: i. skin, hair, nails, and glands embedded in skin2. Skina. Skin is a giant sense organ – it is the largest oneb. Functionsi. Protection of underlying tissues and organs1. First defense against pathogens2. Impenetrable, bacteria can only get in if there is a cut of some sort3. Water resistant4. Immunity – may have enough macrophages to kill off pathogens that try to enterii. Excretions of salts, water, organic wastesiii. Maintenance of body temperature 1. Hypodermal regulation2. Sweat and Goose Bumpsiv. Production of melanin and keratinv. Synthesis of vitamin D31. Absorbs sunlight and synthesizes vi. Storage of lipidsvii. Detection of touch, pressure, pain, and temperature3. Skin Layersa. Epidermis – stratified squamous epitheliumi. Avascular – no blood vesselsii. Basement Membrane1. Bottom of epidermis. We are building up from the bottom.2. Melanocytes sit right on basement membranea. These synthesize a pigment called melanini. Deliver melanin to other layers of the epidermisb. Disperses the pigment throughout the skinc. Skin color differs based on how much melanin is released by the melanocyted. Located about the nucleus and are used to shield the nucleus from the suni. Tanning damages skinii. More melanin is produced to protect the nucleus from rays of the sune. Skin color depends on melanin production, not the number of melanocytesiii. Stratum basale1. Sits directly on the basement membrane. 2. Cells are constantly growing and dividing and producing daughter cells3. Contains keratinocytes – they are not yet keratin a. Just keep adding more, growing and growingb. Most plentiful kind of cell in epidermisc. Keratin is what eventually makes your skin tough and water tightd. Melanocytes are in this layer!!! e. Deepest layer  single cuboidal or columnar 4. Basal cells – germinate cells (stem cells)5. Merkel cells – hairless skin, respond to toch6. Melanocytes – contain pigment7. Epidermal ridges (finger prints)iv. Stratum spinosum1. As cells in the stratum basale age they start to enter the stratum spinosum layer2. This is a spiky looking shape 3. The keratinocytes are still alive, but not nearly as mitotically active as they used to be4. This is what creates the swirls in fingerprints5. Langerhans cells are found here (dendritic cells) 6. 8-10 layers of keratinocytes 7. Dendritic (Langerhans) cells active in immune response v. Stratum granulosum1. Older keratinocytes are in this layer. a. They are filling up with grains b. Get a granular dark appearance 2. The keratinocyte grains are precursors to keratin3. Cells get old and start dying – no longer making new cells4. Cells are filling up with keratin which is what causes them to die a. Too much keratin! vi. Stratum lucidum1. Thin clear zone only in thick skin! 2. Extra fifth layer vii. Stratum corneum1. Cells are filled with keratin and are dead – these are fully keratinized cells2. All cells are dead, as they get closer to the surface the keratinocytes let each other agoa. No longer hold on to each other – no more tight junctions 3. These will soon be dust4. There can be a minimally keratinized type of skina. Only occurs in places that need moisturei. Cavities that lead to inner body like mouth, ear, nose, vaginab. Dead cells aren’t sloughing off5. 15-30 layers of keratinocytes 6. Water resistant, shed every 2 weeksviii. Surface1. Cells fall off when they reach the surfaceix. Order of skin layers  corneum, lucidum, granulosum, spinosum, basalex. Hair follicles form when the layers of epidermis are modified and dig into the skin and the hair follicle then fills that empty space.1. No hair follicles in thick b. Dermis – connective tissue, partially loose and partially dense tissuei. Papillary layer1. Immediately underneath the epithelium 2. Areolar loose layer of connective tissue 3. It runs in a ridge, or hill type shape .ii. Reticular layer1. Underneath the papillary layer. 2. Mostly dense irregular connective tissue 3. Some reticular fibers and some elastic iii. Vascular – blood vessels and nerve fibersiv. Directly under the epidermis1. Tactile corpuscle – sensory nerve endinga. End immediately on the basement membrane b. Associated with the sense of touch 2. Merkel cells – sit right on top of tactile corpuscle a. Allow you to feel touch b. Merkel disk is when merkel cell sits on top of the sensory nerve endingv. Glands are in the dermis1. Sweat glands – used for thermoregulation – sudoriferous glanda. Most common are eccrine glands b. Some places only have apocrine glands i. not for thermoregulation ii. found in genital, groin, armpit regions 1. not used to release heat, they secrete a thicker fluid2. secrete when you are scared, sexually excited, or stressediii. don’t work until you hit pubertyc. Sebaceous gland – oili. Secrete oil into hair follicles d. Ceruminous glandi. In outer ear canal ii. Secretes cerumin 1. Ear wax 2. Helps flush out pathogens and bacteria vi. If you bleed when cut, you have cut down to the dermisc. Subcutaneous layer – hypodermis – not part of the skini. Located underneath the skin, made of adipose tissueii. Vascular – superficial region contains large arteries and veinsd. Hair Folliclesi. Hair1. Hair is seriously compressed keratinocytes 2. Hair doesn’t grow, what’s underneath the hair is what growsii. Hair bulb – small amount of tissue that contains actively dividing cells1. Little tiny piece of tissue and it’s called hair papillaa. Living part of hair follicle b. Produces keratin filled dead hair iii. To get rid of hair you have to kill the papillaiv. Most sebaceous glands coat the follicle, which is why hair is oilyv. A little muscle attaches about midshaft that contracts1. Attaches to edge of epithelium2. Called the arrector pili musclea. When this contracts it pulls the hair straight, this is why ourhair raises when you get cold4. Nailsa. Compressed keratinocytes – similar to hairb. Extend from a modified epidermis at your fingertips c. Has a root at the endd. Only a few mitotically active cells that cause it to grow, the rest is deade. Eponychiumi. Buildup of epidermal cells in a tough deposit where the nail comes outf. Hyponychium i. Under your nail at the very tip of itii. Tough epidermal