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Transcript
Chapter 5 Notes – Tissues Tissue: a group of similar cells sharing a common origin that are united to perform a particular function -includes extracellular fluid and intercellular materials (products that exist between cells) -4 major types • epithelial • connective • muscle • nerve Epithelial Tissue (epithelium): consists of cells that are very closely packed together w/ little or no intercellular materials -avascular – tissue w/o blood vessels -function is to cover body surfaces, line inside of body cavities/organs, form glands, secrete and absorb substances, protect Covering and Lining Epithelium -covers body surfaces and lines walls of body cavities/openings -cells are stationary – anchored to the surface by a thin layer of intercellular material called the basement membrane (connects epithelium to an underlying region of connective tissue) -free surface – open to body cavities/organs or external environment; (lumen – hollow area) 3 Shapes 1) squamous – flat 2) cuboidal – cube-shaped 3) columnar – cylindrical or elongated (rectangular) 2 Cell arrangements 1) simple – single cell layer 2) stratified – multiple cell layers ** Simple Squamous Epithelium – consists of a single layer of flattened cells - all cells touch a basement membrane and a free surface - cells have a centrally located nucleus - very tightly packed together - allows for efficient diffusion of materials -found inside walls of blood and lymphatic vessels -forms walls of capillaries, air sacs in lungs, linings of body cavities ** Simple Cuboidal Epithelium – consists of a single layer of cube-shaped cells -centrally located nucleus -often contain cilia or microvilli along free surface -forms walls of small tubes (ducts) that carry secretions from one place to another -found in kidneys, liver, ovaries, and many glands ** Simple Columnar Epithelium – single layer of cylindrical cells -nuclei found near basement membrane -cells frequently secrete a product (lots of rough endoplasmic reticula + golgi bodies) -many goblet cells (secrete mucus) -found in uterus, stomach, small intestines ** Stratified Squamous Epithelium – many layers, surface layer is squamous; deepest layers contain cuboidal/columnar cells -forms outer layer of skin and dips in all body openings (protection) -lines oral cavity, esophagus, vagina, and anal canal **Stratified Cuboidal Epithelium – two or three layers of cuboidal cells surrounding a lumen; -line ducts in mammary glands, sweat glands, salivary glands, and pancreas **Stratified Columnar Epithelium – several layers of cells (cuboidal cells near basement membrane, columnar cells near free surface) -found in male reproductive tract and parts of the pharynx ** Pseudostratified Columnar Epithelium – appears multilayered, but is NOT -different shaped cells and locations of nuclei -each cell touches the basement membrane, but not all touch free surface -lines part of the respiratory tract (trachea, bronchi) -some cells contain long cilia that create currents to move mucous (pseudostratified ciliated columnar epithelium) ** Transitional Epithelium – multilayered arrangement of cubelike/irregular shaped cells -elasticity – ability to stretch -extensibility – ability to return to original shape -lines urinary bladder and ureters, urethra Glandular Epithelium - consists of closely packed cells that are highly specialized to manufacture and secrete products **Exocrine gland – empties products into ducts -ducts transport product onto body surface or into a cavity -sweat/oil glands in skin, salivary glands, singlecelled mucous glands ** Endocrine glands – secrete products into extracellular space, where they move into the bloodstream -bloodstream transports products throughout body -pituitary gland, thyroid gland, adrenal gland, etc. (hormones) Connective Tissue – composed of widely scattered cells that lie w/in a large amount of nonliving intercellular material Function: supports/protects body parts; manufactures blood cells; holds tissues/organs in place -Cells are 2 types 1) Macrophages – wandering cells Function: protects tissue from infection 2) Fibroblasts – fixed (stationary) cells Function: produces and maintains intercellular fluid (mixture of ground substance (sugar-protein molecules and interstitial fluid) and several types of protein fibers); -3 types of fibers present in intercellular fluid 1) Collagenous fibers – most abundant, thick, wavelike strands made of collagen - flexible protein that is tensile (resists stretching) -found in tendons (connect muscle to bone), ligaments (connect bone to bone), and organs that remain stationary in body; forms scar tissue 2) Elastic fibers – composed of elastin (protein that has elasticity + extensibility) 3) Reticular fibers – composed of reticulin (thin, branching protein that resists physical stress); not abundant Connective tissue is vascular – blood vessels pass though intercellular material (allows tissue to grow and repair) -4 major types of connective tissue 1) connective tissue proper 2) cartilage 3) bone 4) blood-forming tissue Connective Tissue Proper -fibroblast – cells that produce intercellular material *3 general groups (differ in amounts + types of fibers present in the matrix) 1) Loose Connective Tissue (Areolar) – most widespread; forms many membranes in body -all 3 types of protein fibers are found in a loose, disorganized network surrounded by a fluid ground substance: small # of cells interspersed - mostly fibroblasts and macrophages (phagocytic white blood cells) -provides a structural anchor to body parts b/c of many fibers -found between skin and muscle, on surfaces of organs, filling in spaces between organs 2) Adipose Tissue – composed mostly of fibroblasts called adipocytes – large spherical cells containing a deposit of fat - little intercellular material surrounding adipose cells w/ many reticular fibers - stores energy as fat; insulates organs/ provides a shock-absorbing cushion - fat stored in adipose cells – triglycerides 3) Dense Connective Tissue – tightly packed protein fibers w/ little space for other substances including cells -abundant collagen fibers 2 types *Dense irregular connective tissue - non-parallel protein fibers that branch - randomly distributed fibroblasts -forms dermis (deep skin layers); wraps around bones and cartilage *Dense regular connective tissue - parallel protein fibers -linear fibroblasts -forms tendons and ligaments Cartilage – contains a very dense and firm intercellular material (matrix) that is composed of many protein fibers w/in a thickened, gel-like ground substance -harder/more solid than connective tissue proper -provides support, frameworks, and attachments; forms models for developing bones • chondrocyte – cartilage cells that maintain the matrix • lacunae – spaces where chondrocytes are found • perichondrium – vascular layer of dense connective tissue surrounding cartilage; nourishes chondrocytes * 3 types of cartilage 1) Hyaline – most abundant - bluish-white (must be dyed to see it) - composed of collagen - located in the upper portion of the respiratory tract; at the ends of bones where it forms movable joints; at the ends of ribs - forms skeleton of fetus 2) Elastic -yellowish -composed of elastic fibers -firm, but flexible -located in ears, ends of nose, small lid over opening to larynx (epiglottis) 3) Fibrocartilage – consists of a solid, but flexible matrix w/ collagen fibers -found in joints like knees and pelvis, intervertebral discs Bone – intercellular material is filled w/ mineral salts and collagenous fibers, making it the hardest/most durable tissue •matrix – intercellular material of bone •osteocytes – bone cells (contained in lacunae) which maintain the matrix of bone •lamellae – layers of bone that form around Haversian canals (where blood vessels are found) •periosteum – membrane surrounding bone where blood vessels penetrate and nourish osteocytes •canaliculi – tiny channels that extend outward from bone cells (connect cells) * compact bone – matrix is densely packed w/ deposits of mineral salts and collagen * spongy bone – matrix is not as dense; filled w/ blood-forming tissue called red marrow Blood-Forming Tissue and Blood Blood-forming tissue – manufactures cellular components of blood 3 components 1) stem cells that produce blood cells 2) newly formed maturing blood cells 3) small amount of protein -softest connective tissue b/c it lacks collagen and mineral salts 2 types of blood-forming tissue * red marrow – found in cavities w/in spongy bone (hematopoietic tissue – initiates production of all blood cells) * lymphoid tissue – found throughout body in lymph nodes, tonsils, spleen, thymus (white blood cells mature) Blood • formed elements – red blood cells, white blood cells, platelets -surrounded by a fluid matrix known as plasma; transports gases, nutrients, and waste Muscle Tissue -consists of specialized cells that contain protein filaments (parallel bundles) that cause cells to contract (shorten and thicken) -during contraction, actin filaments slide over myosin filaments 3 types of muscle tissue 1) Skeletal Muscle – attached to bones by tendons (bands of dense regular connective tissue) -located deep under skin -voluntary (under conscious control) -have striations – alternating dark/light bands that show protein filaments -multinucleated 2) Smooth (visceral) Muscle – forms part of blood vessel walls and visceral organs -contractions make substances move through -involuntary (NOT under conscious control) -no striations -cells are spindle shaped -single, centrally located nucleus 3) Cardiac Muscle – found in heart walls (myocardium) -contractions make heart pump blood -involuntary -striated -intercalated disks – junctions between cardiac cells Nervous Tissue -sends and carries electrochemical signals throughout body -2 types of cells (found in brain, spinal cord, and nerves) 1) neurons – conduct message 2) neuroglia – support neurons (structural) Membranes -combinations of tissue (usually connective and epithelium) forming a thin sheet -divide areas of organs, line inside surfaces of organs, anchor organs to other structures 3 types of epithelial membranes 1) Cutaneous membrane – skin 2) Serous membranes – line internal surfaces of thoracic and abdominopelvic cavities, cover organs in these cavities, bind organs to each other and to body walls -includes pericardium, pleural cavities, peritoneum (lines abdominal cavities) -secretes a clear, watery fluid (serous fluid) that provides lubrication 3) Mucous membranes – line internal walls of digestive tract from mouth to anus, respiratory tract from nasal cavity to air sacs in lungs, urinary tract, and reproductive tract -secrete mucous – sticky, thick liquid composed of water and carbohydrates -trap/remove foreign particles, maintain moist internal environment, protect cells from harmful liquids (stomach acid) Synovial Membranes -line inside walls of cavities that surround certain joints (knee, elbow, shoulder); no epithelium, has loose connective tissue w/ fat -secretes synovial fluid – lubricates bones and nourishes cartilage