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Tissues
Groups of cells that are similar in structure and function
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organs
A part of the body formed of two or more tissues and adapted to carry out a specfic function
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histology
the study of tissues
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epithelial tissue (epithelium)
covers surfaces; covers external body surface, lines it cavities and tubules, and generally marks off our insides from our outsides.
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characteristics of epithelial tissues
- polarity- membranes always have one free surface (apical surface), typically significally differenct from basal surface.
- cellularity and specialized contacts- cells fit closely together
- supported by connective tissues- adhesive basement membrane (basal lamina) connective tissue (reticular lamina)
- avascularity- no blood supply of their own, diffusion of nutrients from the underlying connective tissue
- regeneration-if well nurished, cells can reginerate themselves
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2 criteria of epithelia
- simple-one layer of cells attached to the basement membrane
- stratified-2 or more layers of cells
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types of epithelial tissues
- squamous (scalelike)
- cuboidal (cubelike)
- columnar (column-shaped)
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pseudostratified epithelium
cells vary in height and the nuclei lie at different levels above the basement membrane, gives the false appearance of being stratified
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Transitional epithelium
stratified squamous epithelium of rounded or plump cells with the ability to slide over one another to allow the organ to be stretched-found in urinary systme subjected to periodic distention (bladder).
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endocrine glands
ductless glands, secrete hormones
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exocrine glands
retain their ducts, secretions empty through ducts, internal and external ...sweat and oil glands, liver, pancreas
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simple squamous epithelium
- single layer of flattened cells with disc-shaped central nuclei and sparse cytoplasm- simplest of the epithelia
- function- allows passage of materials by diffusion and filtration in sites where protection is not important; secretes lubricating substances in serosae
- found in kidney glomeruli, air sacs of lungs, lining of heart, blood vessels, lymphatic vessels, lining of ventral body cavity (serosae)
- Cells touching cells-no space between cells
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simple cuboidal epithelium
- single layer of cubelike cells with large spherical central nuclei
- function-secretion and absorption
- location-kidney tubules, ducts and secretory portions of small glands, ovary surface
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simple columnar epithelium
- single layer of tall cells with round to oval nuclei, some cells bear cilia, layer may contain mucus-secreting unicellular glands (goblet cells)
- function-absorption and secretion of mucus, enzymes and other substances;ciliated type propels muicus by ciliary action
- location- nonciliated type lines most of the digestive tract (stomach to anal canal), gallbladder, and excretory ducts of some glands; ciliated variety lines small bronchi, uterine tubes and some regions of the uterus
- Goblet cells have mucus in them
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stratified squamous epithelium
- thick membrane composed of several cell layers-
- function-protects underlying tissues in areas subjected to abrasion
- location-nonkeratinized type forms the moist linings of the esophagus, mouth and vagina; keratinized variety forms the epidermis of the skin, a dry membrane
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connective tissue
found in all parts of the body as discrete structures or as part of various body organs, the most abundant and widely distributed of the tissue types. functions- protect, support and bind together other tissues
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bone (osseous tissue)
protect and support other body tissues and organs
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dense connective tissue
ligaments and tendons- bind the bones together or bind skeletal muscles to bones
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areolar connective tissue
soft packaging material that cushions and protects body organs
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adipose
fat tissue provides insulation for the body tissues and a source of stored food
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hematopoietic tissue
blood forming tissue replenishes the body's supply of red blood cells
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characteristics of connective tissue
- rich supply of blood vessesl (with some exceptions)
- composed of many types of cells
- great deal of noncellular, nonliving material (matirx) between the cells of connective tissue
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extracellular matrix
nonliving material between the cells- distinguishes connective tissue from all other tissues-primarily responsible for strength associated with connective tissue
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ground substance
- component of matrix- composed chiefly of interstitial fluid, cell adhesion proteins and proteoglycans; liquid, semisolid, gel-like or very hard (glue)
- the fibers which provide support, include collagen (white), elastic (yellow), and reticular (fine collagen) - collagen fibers are most abundant
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connective tissue proper: loose connective tissue, areolar
- gel-like matrix witha ll three fiber types; cells:fibroblasts, macrophages, mast cells, and some white blood cells
- function- wraps and cushions organs, plays important role in inflammation, holds and conveys tissue fluid
- location-widely distributed under epithelia of body; forms lamina propria of mucous membranes, packages organs, surrounds capillaries
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connective tissue proper: loose connective tissue, adipose
- matrix as in areolar, but very sparse; closely packed adipocytes (fat) nucleus pushed to the sideby large fat droplet
- function- provides reserve fuel, insulates against heat loss, supports and protects organs
- locatations-under skin, around kidneys and eyeballs, within abdomen, in breasts
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connective tissue proper: dense connective tissue, dense regular
- primarily parallel collagen fibers, a few elastin fibers; major cell type is the fibroblast
- function- attaches muscles to bones or to muscles, attaches bones to bones, withstands great tensile stress when pulling force is applied in one direction
- locatation-tendons, most ligaments, aponeuroses
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connective tissue proper:dense connective tissue, dense irregular
- primarily irregularly arranged collagen biers, some elastic fibers, major cell type is the fibroblast
- function-able to withstand tension exerted in many directions, provides structural strength
- location-dermis of the skin, submucosa of digestive tract, fibrous capsules of organs and joints
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cartilage: hyaline
- amorphous but firm matrix; collagen fibers form an imperceptible network; chrondroblsts produce the matrix and when mature lie in lacunae
- function-support and reinforces has resilient cushioning properties, resists compressive stress
- location-forms most of the embryonic skeleton, covers the ends of long bones in joint cavities, forms costal cartilages of the ribs; cartilages of the nose, trachea and larynx
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cartilage:elastic
- similar to hyaline cartilage, but more elsastic fibers in matrix
- function-maintains the shape of a structure while allowing great flexibility
- location-supports the external ear, epiglottis
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cartilage: fibrocartilage
- matrix similar to but less firm than that in hyaline cartilage, thick collagen fibers predominate
- function-tensile stenght with the ability to absorb compressive shock
- location-intervertebral discs, pubic symphysis, discs of knee joint
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mast cells
large, darkly staining granules in its cytoplasm
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nervous tissue
- 2 major cell populations-
- neuroglia-special supporting cells that protect support and insulate themore delicate neurons
- neurons- highly specialized to receive stimuli, and to conduct waves of excitation, or impulses to all parts fot the body
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muscle tissue
highly specialized to contract and produce most types of body movement
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skeletal muscle
the meat or flesh, attached to the skeleton
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cardiac muscle
found only in the heart, involuntary muscle control
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smooth muscle
also called visceral muscle, found mainly in the walls of hollow organs- no striations are visible the uninucleate smooth muscle cells are spindle shaped
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