Skeletal Muscle Tissue Special note for Nervous and Muscular Tissues IMPORTANT Excitability of all living cells in nervous and muscle Electrical charge difference voltage that occurs across the plasma membrane is the basis of their excitation They respond quickly to stimulus by means of changes in membrane potential MUSCLES change in result in contraction and shortening of the cell NERVOUS changes result in rapid transmission of signals to other cells Skeletal remember is striated and voluntary There are striations long threadlike cells called muscle fibers there are multiple nuclei s per muscle fiber cell The striations can be alternating dark and light bands Located most attach to bone But they are in the tongue eyelids and facial muscles Body movements facial expression breathing speech swallowing Cardiac muscle Tissue Myocytes and Cardiocytes are shorter branched and notched at the ends One centrally located nucleus per fiber cell Intercalated discs join cardiocytes end to end and provide electrical and mechanical connection Striated and INVOLUNTARY Located in the HEART Remember striated but involuntary Pumping of the blood under involuntary control Smooth Muscle Tissue Do not confuse with Dense regular because they look similar Remember hints It is not striated and is involuntary Short cells over lapping each other one nucleus per cell and are centrally located Located in VISCERAL muscle Forms layers of digestive track respiratory and urinary tract think smooth and propels contents through an organ regulates diameter of blood vessels Functions in swallowing contractions of the stomach labor contractions control of blood pressure and flow Under involuntary control Layers from top to bottom Strata of the Epidermis layers of the epidermis Layers from top to bottom 1 Stratum Corneum up to 30 layers of dead keratinized cells remember epidermis skin and there is dead cells in Keratinized stratified squamous Skin This layer is the first layer below skin epidermis 2 Stratum Lucidum Seen ONLY in thick skin and is superficial to Granulosum above it Keratinocytes are densely packed 3 Stratum Granulosum 3 5 layers of flat keratinized granules 4 Stratum Spinosum Biggest area remember Produce more and more keratin filaments which cause cell to flatten higher up flatter cells appear DENDRITIC cells found here consist of several layers of keratinocytes deepest cells capable of mitosis 5 Stratum Basale Single layer of cuboidal to low columnar stem cells and keratinocytes resting on basement membrane This is the deepest part Melanocytes and tactile cells are scattered around stem cells divide here Mitosis Give rise to Keratinocytes that migrate toward skin surface replace lost epidermal cells Slide of Skin Epidermis is keratinized stratified squamous epithelium it is skin Keratinized it will have a layer that looks smooth like with no cells and that is the dead cells of the skin that flake off Look for the dead squamous cells They provide a touch barrier protect the skin from microorganisms and eventually fall off the epidermis renews itself about 5 6 weeks Located in the epidermis palms soles Below will be a dense irregular connective tissue reticular layer in the dermis Cells of the epidermis stem cells undifferentiated that divide and give rise to keratinocytes keratinocytes major epidermal cells synthesizing keratin melanocytes synthesize the brown to black pigment melanin tactile cells receptor for touch Dendritic cells stand guard against toxins defense system for the skin Keratin is thick in the epidermis dead cells at the surface packed with tough protein called keratin Lamellar paciniian corpuscle slide Note Onion shape layer appearance It is a PRESSURE receptor they sense pressure located in the dermis Ex When you lean against a wall or feel a vibration Tactile Meissner Corpuscle Slide Touch receptor located in the upper portion of the dermis allow for a very light touch stimuli Note the difference in shape on the slides from these 2 types of receptors Diagram of Hair in a Follicle and a slide of Hair in a Follicle Hair and nails are mostly composed of dead keratinized cells hard keratin makes up hair and nails Pilus another name for hair pili Hair slender filament of keratinized cells that grows from an oblique tube in the skin Hair is found everywhere except palms soles ventral lateral sides of fingers and toes called Hair Follicle lips nipples parts of genitals Hair is divisible into 3 zones in length Bulb A swelling at the base where hair originates in dermis or hypodermis only living hair cells are in or near bulb Root remainder of the hair in the follicle Shaft portion above the skin surface More important info Dermal Papilla Bud of vascular connective tissue encased by bulb and provides the hair its sole source of nutrient Hair Matrix Region of mitotically active cells above the papilla Hair s GROWTH 3 layers of hair in cross section from inside out Medulla core of loosely arranged cells and air spaces Cortex bulk of hair several layers of elongated keratinized cells Cuticle multiple layers of very thin scaly cells when hair is pulled out this comes out with it More Info about the HAIR end and widens into a bulge Epithelial root sheath Extension of epidermis lies right after hair root it s toward deep Connective tissue root sheath Derived from the dermis surrounds epithelial root sheath Hair receptors Nerve fibers that entwine each follicle and respond o hair movement Pioerector Muscle Arrector Pilli Bundles of smooth muscle cells extends from dermal collagen to connective tissue root sheath and responsible for Goosebumps Hair Growth hints 1 Anagen Growth stage 6 8 years 90 of scalp follicles at any given time stem cells multiply think growth and travel downward pushing dermal papilla deeper into the skin forming epidermal root sheath new hair grows up the follicle alongside of an old club hair from last cycle 2 Catagen Degeneration stage 2 3 weeks Mitosis stops club hair easily pulled out 3 Telogen Resting stage 1 3 months when papilla reaches the bulb no growth or degeneration Look at hair cycle picture on page 189 Fingernail Diagram and Functions Fingernails and toenails clear hard derivatives of stratum corneum composed of very thin dead packed with keratin NAIL PLATE hard part of the nail o Free Edge Overhangs the fingertip o Nail Body Visible attached part of the nail o Nail root Extends proximally underlying skin Nails o Nail fold surrounding skin rising a bit above