Chapter 4 - Tissues (Histology)

Chapter 4 - Tissues (Histology) - KIN 216 Applied Human...

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Unformatted text preview: KIN 216 Applied Human Anatomy Chapter 4 Histological Classes and Subtypes Hist = tissue (Gr. Histos = web; French = to weave) Histology = the study of body's tissue 4 basic types (epithelial, connective, muscle, nervous) For each, KNOW Cell types and prominent organelles Matrix properties (mostly for connective tissue) Function and specialized structures for function Examples of locations within body Epithelial Tissue Usually is coverings, linings, exocrine glands (very little matrix) 2 kinds: membranous and glandular (names of subtypes indicate # of cell layers and shape of cells) Always have one free surface exposed to a body cavity, lumen (hollow portion of tube), or skin surface Functions Form coverings, linings of tubes and cavities Absorption, secretion, protection, filtering, ion transport Epithelial Tissue (2) Key characteristics Cellularity (i.e., lots of cells) Specialized contacts with other cells Polarity: One side exposed; unexposed side is bounded by basement membrane: binds epithelial tissue to underlying connective tissue (nourishes, provides support Avascular: no direct blood supply to epithelial tissue, THEREFORE it cannot be very thick because it relies on diffusion of nutrients from underlying connective tissue (only one cell layer thick or limited # of layers) Innervated: nerve endings are found in epithelial tissue Capable of RAPID regenerationneeded because of exposure to trauma, injury Commonly found in organelles in tissue: those that use O2 Special Characteristics Lateral surface features (NOT on exam) Cell junctions Tight Adherens Desmosomes Gap Basal surface feature Basal lamina: thin, non-cellular sheet made up of proteins, acts as filter and serves as scaffolding for new cell generation Apical Surface Features Microvilli Finger-like extensions of plasma membrane, moist surfaces Maximize surface area for nutrient transport/absorption Mucus Cilia Tail-like extensions that bend and move in coordinated waves Push mucus and other substances across epithelial surface Flagellum = extremely long cilium (sperm is only case) Membranous Epithelial Tissue Simple = one cell layer (all cells in layer have same shape); shape indicative of function Stratified = multiple layers (cell shapes can differ among layers); named according to apical layer (unbound side); protection Membranous Epithelial Tissue (2) Squamous = wide cells (more wide than tall); diffusion/filtration Cuboidal = same height and width (cubes); secretion/absorption Columnar = tall cells (more tall than wide); secretion/absorption Shape of nucleus matches cell type Simple Squamous Single layer of flat cells Occurs wherever items need to pass through quickly Slippery Specific types Endothelium Mesothelium Simple Cuboidal Single layer of cubelike cells Walls of small ducts of glands, tubules of kidneys Functions are the same as simple columnar Simple Columnar Single layer of tall cells Lines digestive tube (stomach to anal canal) Molecule movement Some have cilia: similar to a tail, assists with movement Pseudostratified Columnar Single layer but cells are different heights only the tall cells reach apical surface Secretion/absorption Similar to simple columnar Ex: respiratory tubes Stratified Squamous Many layers surface are squamous Lower levels are cuboidal or columnar Thickest; best protection epidermis of skin (special case = keratinized, chpt. 5) Stratified Cuboidal/Columnar Rare Ducts of glands Transitional Similar to stratified squamous and stratified cuboidal Specific to hollow urinary organs (bladder) Stretches to different cell layer thickness Glandular Epithelial Tissue Product is water-based fluid Secretion: process by which glands obtain substances from blood and transform them into product for discharge Protein made in rough ER, packaged by Golgi, released from cell by exocytosis Exocrine (external) or endocrine (internal) Unicellular or multicellular Commonly found organelles: rough ER, Golgi Exocrine Glands Secrete onto body surfaces or into cavities (multicellular have ducts) Local activity Unicellular Only important example: goblet cell Epithelial lining of intestines, respiratory tubes, between columnar cells Produce mucin: glycoprotein that dissolves in water = product of mucin and water is mucus Multicellular Exocrine Glands 2 parts: duct and secretory unit (secretory epithelium) Most are surrounded by connective tissue Classified by duct structure: simple or compound (branches) AND secretory unit: tubular or alveolar (spherical sacs) tubuloalveolar also exist Endocrine Glands Ductless Secrete into tissue fluid Produce hormones, which travel through bloodstream to target organs Connective Tissue (CT) Most complex class Major functions: Bind and support other tissues in body Protection and nourishment (maintenance of other tissues) Highly vascular (except for cartilage) MOST can regenerate but slower than epithelial More matrix than cells (cells NOT tightly packed) Immune function (circulating WBCs) Most storage occurs in CT 3 types of protein fibers (collagen, reticular, elastic) Common features of MOST CT subclasses Major CT Classes Defined by matrix properties Embryonic (mesenchyme): jelly-like substance, cells undifferentiated (blasts) CT proper: matrix is ground substance (soft, flexible) Cartilage: matrix is firmer than CT proper but still flexible Bone: rigid matrix (inorganic- mineral salts and organic- collagen) Vascular: fluid matrix (plasma) WHY classified as CT? Function is to nourish other tissues, originates from same type of cells as CT (in bone) Embryonic (Mesenchyme) All CT types originate from this (mesenchyme = undifferentiated tissue) Has jelly-like matrix Usually develops into some type of tissue somewhere, but doesn't always differentiate Some continues to develop into and through adulthood in order to repair/ replace damaged CT CT Proper Most complex- has many subtypes and two subclasses (loose and dense) Forms stoma (supportive framework) of organs Common features: Matrix = ground substance Cells = mostly fibroblasts (fibro = fibers, which are proteins- common organelles are ribosomes, ER, Golgi) The fibers give structural support and strength to matrix and produce 3 types of fibers: Collagenous Elastic Reticular The subclasses are identified by: Consistency of ground matrix Type and arrangement of the 3 fiber types Subclasses of CT Proper Loose Areolar Adipose Reticular Irregular Regular Elastic Dense Areolar (Loose) Most widespread type of CT proper Location is hypodermis (deepest skin layer), fascia (surrounding muscles), surrounding nerves, blood vessels Loosely arranged fibers, widely spaced cells; has all 3 types of protein fibers Lots of open spaces with no cells or fibers Functions: cushioning, support and binding, defense against infection, nourishment of surrounding tissue- also repair of damaged tissue GOOD blood supply, highly vascular Cells are mostly fibroblasts (produce protein fibers), some mast cells: react to injury- produce heparin, which is anticoagulant- also produce histamine, which is vasodilator Common organelle: lysosomes- many macrophages: engage in phagocytosis, eat damaged cells Adipose (Loose) Lots of cells- few fibers, little matrix Cell type is adipocytes (arise from fibroblasts) Adipocytes have FEW organelles (some mitochondria, few ribosomes/rough ER/Golgi)mostly smooth ER, nucleus pushed to side VERY vascular! Functions: Energy fuel storage Thermal insulation Padding for protection Throughout body in hypodermis (subcutaneous) and around kidneys, heart, joints, bone marrow Location: Typical adipose tissue is white, but there is another type that is brown (produces heat, consumes nutrients) in babies Reticular (Loose) Gives rise to vascular tissue Matrix: softer, more jellylike Fibers: reticular fibers only, form network Cells: reticulocytes specialized for phagocytosis Function: degrade worn out cell parts Organelles: lysosomes, peroxisomes Location: bone marrow, lymph nodes, spleen, liver Irregular (Dense) Thicker collagen fibers than loose tissue Fibers run in different planes- or different layers run in different directions Cells and matrix are same as areolar Function: Protection from stretching Dermis of skin, surrounds kidneys, lymph nodes, bone Location Regular (Dense) Lots of collagen positioned in same direction Function: provide strong support and flexibility Relatively poorly vascularized compared to other types, so it's slow to heal Cells: fibroblasts Location: tendons, ligaments, fascia, sclera of eye, dermis of skin Common organelles: those affiliated with protein- ribosomes, ER, Golgi Elastic (Dense) Mostly the same as Regular (Dense) Elastin fibers in irregular arrangement Stretches but returns to original size Found in large artery walls, larynx, trachea, bronchi Cartilage Matrix = lots of fibers and proteoglycans (type of fiber with protein and CHO, very complex and takes a long time to build themthis is why it takes cartilage a long time to heal) and water Cells = chondrocytes Blood supply = limited (another reason it's slow to heal) also no nerves Functions: protection, cushioning, shock absorption (resist compression) Location: nose, ears, trachea, joints Types of Cartilage Hyaline (Gr. Hyalos = glass) Looks like frosted glass (THIN fibers) Matrix = fairly soft and flexible- weakest type of cartilage BUT most abundant Surrounded by a capsule of dense fibrous CT Perichondrium = outer layer around cartilage (but not at articular surfaces of bones) Function: framework, structure EX: ribs attached to sternum by costal cartilage, which is hyaline Types of Cartilage (2) Fibrocartilage Lots of cartilage, little matrix- densely packed fibers (TOUGH- strongest type of cartilage) Doesn't have perichondrium Chondrocytes are arranged in rows with collagen fibers in between Function: structure, framework, compression resistance (protection) is main function Location: between joints EX: symphysis pubis, intervertebral disks, menisci Types of Cartilage (3) Elastic cartilage Similar to hyaline but has elastin fibers Stronger than CT proper Location: external ear, eustachian tube (ear to throat), epiglottis, larynx Function: stretch/strength, repeated bending Bone Cells: osteoblasts (build and mature into osteocytes) osteoclasts (break down, remodel bone) Matrix: rigid due to deposit of mineral salts (calcium, phosphorus), also lots of collagen (provides some flexibility) Vascularity: HIGH, very metabolically active (remodeling, hemopoiesis) Subtypes of bone tissue Cancellous (aka trabecular, spongy, medullary) is where hemopoiesis occurs found on inside lining- spongy structural unit = trabeculum location = inner cavity of long bones (medullary cavity) softer, more vascular, lots of empty spaces Compact (aka dense, cortical) hard and dense, lots of mineral salts location: outer layer structural unit = osteon, has central canal with concentric rings Vascular Atypical CT (no binding or support) Why is vascular tissue classified as CT? Origin is fibroblasts (made in bone marrow), function is nutrient delivery Develops from mesenchyme Has cells and matrix Cells: blood cells (leukocytes-WBCs, erythrocytes-RBCs, thrombocytes-platelets) Matrix: fluid (plasma) Coverings and Linings Membranes that cover areas in the body made up of an epithelial sheet and underlying layer of CT proper Cutaneous: skin (dry membrane) Mucous: lines organs that open to outside of body (moist) many (but not all) secrete mucus Lamina propria: loose CT Serous: lines cavities Simple squamous epithelial layer on top of areolar CT serous fluid Muscle Tissue Cells: myocytes (long, thin fibers) that contain myofilaments Sarcolemma = cytolemma of muscle cell Sarcoplasm = cytoplasm of muscle cell Sarcoplasmic reticulum = ER of muscle cell Matrix: very little (densely packed cells) Vascularity: HIGH (due to how high metabolic rate needs to get) Function: contraction, movement 3 types: skeletal, cardiac, smooth Skeletal Muscle Multinucleated High metabolic rate (lots of mitochondria) Highly vascular Lots of fibrous proteins Striations (regular alignment of actin, myosin) Connected to bone by tendons Function: movement of skeleton, posture ("voluntary" control) Sarcomere = unit of skeletal muscle contraction Cardiac Muscle Located in walls of heart Striated (has sarcomeres) HIGHLY vascular Differs from skeletal: Short, branched, MONOnucleated cells Intercalated discs Smooth Muscle NOT striated Has ability to regenerate Has actin and myosin, but not regularly arranged (no sarcomeres) Cells are mononucleated Not as vascular as other 2 types Found in bladder, uterus, stomach, tube circumference, etc. ("involuntary" control) Nervous Tissue Function: nerve impulse transmission (communication) Composed of nerve cells and support tissue Location: brain, spinal cord, nerves Cells = neurons (aka nerve fibers) 3 components: axon, body, dendrites long fiber (axon)- can be as long as muscle fibers, but only one nucleus- signal transmission body (aka perikaryon) dendrites- sense signal (receive impulses) Support tissue for neurons nourishment More abundant than neurons Insulate and protect neurons Neuroglia Tissue Injury and Repair Injury Inflammation Non-specific, local, acute Heat, redness, swelling, pain Immune response Highly specific, takes a while to develop Repair Regeneration Replacement of tissue by same kind Fibrosis Creation of fibrous CT (scar tissue) Tissue Throughout Life Stem cells Undifferentiated cells that continuously renew and produce new cells when necessary Found mostly in rapidly replacing tissues (e.g., epidermis), but are in other tissues too (e.g., brain) 3 types: embryonic, embryonic germ, adult Embryonic: human embryo, 5 days Embryonic germ: 5-9 weeks less research on these, but appear more limited Adult: found in bone marrow, skin, blood, brain Umbilical cord and placenta are also being explored Treatment of neurological disorders Ethical issues Stem cell line: mass of cells descending from original cell ...
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This note was uploaded on 03/19/2008 for the course KIN 216 taught by Professor Pfeifer during the Spring '08 term at Michigan State University.

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