Everything in the body is composed of four basic tissues 1 epithelium covers body surfaces lines body cavities creates the internal external linings of organs makes up glands 2 nervous allows internal communication 3 muscle BODY TISSUES Pg 1 a skeletal b cardiac in the heart only c smooth composing all other hollow organs 4 connective there are many types to be covered in detail shortly NERVOUS Neuron The main cell is the neuron support cells are called neuroglia 6 types more on those in detail in another chapter 1 soma aka perikaryon cell body 2 dendrite a short cell process that takes a nerve impulse toward a cell body there may be one or many many many 3 axon a long cell process that takes the nerve impulse away from the soma there will always be only one branches off the axon are called axon collaterals MUSCLE allows movement produces heat offers protection stabilizes joints 1 skeletal looks striated acts voluntarily 2 cardiac also looks striated but acts involuntarily 3 smooth also acts involuntarily but doesn t look striated SKELETAL voluntary striated Skeletal muscle cells are called muscle fibers myofibers myo muscle skeletal muscle cells are elongated cylinders with the nucleus sometimes many of them usually pushed to one side under a microscope you ll see alternating bands of different proteins creating the striations these will be covered in detail in a few weeks CARDIAC involuntary striated Cardiac muscle cells called myocytes are also striated but not elongated they are short and branching and are connected to one another by an intercalated disc which serves two purposes a structural linkage to anchor cells together so the constant beating of the heart doesn t pull them apart b electrical linkage for passage of an electrical impulse from cell to cell SMOOTH involuntary nonstriated There are no striations and each cell has only one nucleus Smooth muscle is found in the walls of hollow organs blood vessels esophagus stomach intestines uterus vagina penis You have no voluntary control over it or cardiac muscle ALL MUSCLE TYPES ARE HIGHLY VASCULAR EPITHELIAL Epithleial tissue comes in different shapes and different classifications for different purposes it covers body surfaces it lines body cavities it lines organs internally and externally heart internal lining endocardium external pericardium blood vessels internal lining endothelium it composes glands squamous flat cuboidal squarish columnar elongated transitional an odd shape more to come pg 2 CLASSIFICATIONS SHAPES Functions simple one layer of cells stratified more than one layer 2 20 or more protection the more stratified an epithelium is the more protection it offers control absorption and filtration less stratification enables better absorption or filtration excretion secretion sensory reception skin epithelium has nerve endings spread throughout it which do the actual sensory reception CHARACTERISTICS Epithelial cells are lined up very close with one another with very little space between them Epithelial cells have polarity o North pole the top of the cell apical surface is exposed to the outer surface such as skin is exposed to air or a gland is open to its duct modifications include cilia long mobile hairs that sweep in one direction microvilli short stationary projections that create more surface area for absorption o South Pole the bottom of the cell basal surface the cell sits on a basement membrane proteins secreted by the cell it is too thin to see even with a microscope this membrane acts as a selective filter to allow or disallow diffusion of substances into the cell The basement membrane then is supported by or on a bed of connective tissue usually areolar tissue Epithelial tissue is innervated but avascular blood filters through the underlying connective tissue and Epithelial cells are highly regenerative constant abuse causes the top layer of cells to be rubbed off and diffuses through the basement membrane they must be replaced SPECIFIC TYPES OF TISSUE SIMPLE EPITHELIA made of only one layer of cells good for absorption filtration or secretion The different shapes are squamous cuboidal columnar or transitional 1 squamous flat squashed squa for squamous and squashed cells best for rapid diffusion or some secretion such as serous fluid pg 3 found in the alveoli of lungs capillaries serosa linings and kidney tubules endothelium friction reducing lining in lymphatic and blood vessels endocardium friction reducing lining in the heart mesothelium found in the serosa of organs in the ventral cavity 2 cuboidal cube shaped best for absorption better than squamous for secretion sometimes it has microvilli short stationary projections off the cell which increase a cell s surface area to improve absorption such as in the brush border of the kidney tubules or small intestine sometimes it has cilia long mucus covered moving projections off the cell that sweep substances in one direction such as found in the bronchioles of the lung called the mucociliary escalator most often found in glands mammary thyroid salivary ovaries kidney 3 columnar elongated shape best for secretion mucus some absorption often has a microvilli brush border of the digestive tract b cilia in the trachea of the respiratory tract also in the fallopian tubes may also have goblet cells unicellular gland cells interspaced with the epithelium that secrete mucus onto the apical surface microvilli cilia 4 pseudostratified columnar good for the same as simple columnar this tissue looks stratified but is actually only one layer thick ciliated found in the respiratory tree as part of the mucociliary escalator nonciliated found in parts of the male urethra ducts of small glands STRATIFIED EPITHELIA Squamous and transitional are the only commonly found stratified epithelia stratified cuboidal and columnar are rare On stratified tissue the base cell layer is usually cuboidal or columnar the apical surface can be any shape naming of the tissue is according to the shape of the TOP LAYER of cells 1 squamous the most common stratified tissue used mainly for protection found in areas subject to abrasion skin mouth rectum vagina it makes up body coverings of areas of the body open to the outside 2 types keratinized found only in the skin extending briefly into the gums the top cell layer is composed of dead cells keratin is a protein that protects from dehydration nonkeratinized all other places the top layer is not composed of dead cells Flaking or