뒤로Anatomy & Physiology: Tissues and Histology
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Histology is the study of tissues by fixing, slicing thin, staining, and viewing specimens under a microscope to examine cells and tissues microscopically.
Cells form tissues through selective cell-cell adhesion and recognition systems that make similar cells preferentially adhere to one another, allowing dissociated cells to reassemble into organized tissues.
The four basic tissue types are epithelial, connective, muscular, and nervous tissues.
Epithelial tissue functions in protection, absorption, filtration, excretion, secretion, and reception (sensory).
Epithelial cells exhibit polarity, specialized contacts, are supported by connective tissue, avascular but innervated, and have a high capacity to regenerate.
Polarity means epithelial cells have a top (apical) surface exposed to the body surface or cavity and a bottom (basal) surface attached to the basal lamina.
Cells are connected laterally by tight junctions and/or desmosomes forming continuous sheets.
The basement membrane is a structure made of two laminas (basal and reticular) that links epithelial tissue to underlying connective tissue and resists stretching forces.
Epithelial tissue lacks blood vessels and relies on diffusion from underlying connective tissue for nutrients but is innervated by nerve fibers.
By cell shape (squamous, cuboidal, columnar), number of layers (simple or stratified), and surface specializations (ciliated, keratinized).
Single layer of flat cells allowing diffusion or filtration; found in kidney glomeruli, lung air sacs, and lining of heart and blood vessels.
Single layer of cube-shaped cells; functions in secretion and absorption; located in kidney tubules, ducts, and ovaries.
Single layer of tall cells; involved in secretion and absorption; often has cilia or microvilli; found in digestive tract, gall bladder, bronchi, and uterine tubes.
Single layer of cells of varying heights that appear stratified; functions in mucus secretion and movement; found in upper respiratory tract and ducts of large glands.
Multiple layers of flat cells; provides protection against abrasion; keratinized type strengthens cells; found in skin epidermis, mouth, esophagus, and vagina.
Stratified epithelium with dome-shaped surface cells; allows stretching; lines ureters, bladder, and parts of urethra.
Endocrine glands have no ducts and secrete hormones into blood; exocrine glands have ducts and secrete onto body surfaces or cavities.
Single cells like mucous and goblet cells that produce mucin, which dissolves in water to form mucus for protection and lubrication.
By duct structure (simple or compound) and secretory unit shape (tubular, alveolar, or tubuloalveolar), and mode of secretion (merocrine, holocrine, apocrine).
Merocrine: secretion by exocytosis; holocrine: cell ruptures releasing contents; apocrine: apex of cell pinches off releasing secretion.
Connective tissue is abundant tissue with an extracellular matrix; functions include binding, support, protection, insulation, and transport.
The ECM consists of ground substance (gel-like with interstitial fluid, adhesion proteins, proteoglycans) and fibers (collagen, elastic, reticular).
Fibroblasts (produce fibers and ground substance), macrophages (immune defense), lymphocytes (antibody production), mast cells (histamine secretion), and adipocytes (fat storage).
Loose connective tissue: areolar, adipose, reticular; dense connective tissue: dense regular, dense irregular, elastic.
Loose connective tissue with fibroblasts and collagen fibers; supports and binds tissues; found under epithelia and around organs.
Loose connective tissue rich in adipocytes for fat storage; functions in shock absorption, insulation, and energy storage; located under skin and around organs.
Hyaline: most abundant, found at bone ends and respiratory tract; elastic: more elastic fibers, found in ears and epiglottis; fibrocartilage: very strong, found in intervertebral discs and knee.
Bone is a hard connective tissue with collagen and calcium salts; cells are osteoblasts and osteocytes; arranged in osteons; highly vascularized and supports the body.
Blood is a liquid connective tissue with cells suspended in plasma; functions in transport of nutrients, wastes, gases, and immune responses.
Skeletal muscle: voluntary, striated, multinucleated; cardiac muscle: involuntary, striated, branched; smooth muscle: involuntary, non-striated, spindle-shaped.
Neurons transmit electrical signals; glial cells support, insulate, and protect neurons.
Cutaneous (skin), mucous (lines cavities open to exterior), serous (lines closed cavities), and synovial (lines joints).
1. Inflammation: blood vessels dilate and clot forms. 2. Organization: clot replaced by granulation tissue, epithelium regenerates. 3. Regeneration and fibrosis: scab detaches, tissue matures, scar forms.
Epithelial tissues, bone, most connective tissue proper (except dense regular), and blood-forming tissue regenerate well.
Smooth muscle and dense regular connective tissue have moderate capacity; cardiac muscle and nervous tissue of brain and spinal cord have virtually no capacity.