BMSP 2135 Anatomy Physiology Chapter 5
BMSP 2135 Anatomy Physiology Chapter 5 2135 BMSP
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This 20 page Class Notes was uploaded by Marlena Trone on Saturday September 10, 2016. The Class Notes belongs to 2135 BMSP at Virginia Polytechnic Institute and State University taught by in Fall 2016. Since its upload, it has received 14 views.
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Date Created: 09/10/16
CHAPTER FIVE: Histology HISTOLOGY: Study of Tissues and how they are arranged into organs TISSUE: a group of similar cells and cell products that arise from the same region of embryo and work together to perform a specific structural or physiological role in an organ. ORGAN: structure with discrete boundaries that is composed of two or more tissue types THE STUDY OF TISSUES • The body consists of 50 trillion cells of 200 different cell types • Four broad categories of tissues ‾ Epithelial tissue: composed of layers of closely spaced cells that cover organ surfaces, form glands, and serve for protection, secretion and absorption. • Inner lining of digestive tract • Liver • Glands ‾ Connective tissue: usually more matrix than cell volume, often specialized to support, bind and protect organs • Tendons • Ligaments • Cartilage • Bone • Blood ‾ Nervous tissue: Containing excitable cells specialized for rapid transmission of coded information to other cells. • Brain • Spinal cord • Nerves ‾ Muscular tissue: composed of elongated, excitable muscle cells specialized for contraction • Skeletal muscles • Heart (Cardiac Muscle) • Walls of viscera (Smooth Muscle) • the relative amount of space occupied by cells versus matrix varies in the tissue types PRIMARY TISSUE CLASSES • four primary tissues differ from one another in the: ‾ cells ‾ Matrix (Extracellular material) • Composed of: – Fibrous proteins – a clear gel known as ground substance , tissue fluid, extracellular fluid (ECF), interstitial fluid, or tissue gel • surrounds the cells EMBRYONIC TISSUES : • 3 primary germ layers ‾ ectoderm (outer) • gives rise to epidermis and nervous system ‾ endoderm (inner) • gives rise to mucous membrane lining digestive and respiratory tracts, digestive glands ‾ mesoderm (middle) becomes gelatinous tissue mesenchyme • wispy collagen fibers and fibroblasts in gel matrix • gives rise to muscle, bone, blood • Humans begin as a single cell (these tissues are the first to form) INTERPRETING TISSUE SECTIONS • preparation of histological specimens ‾ fixative prevents decay (formalin) ‾ histological sections: tissue is sliced into thin sections one or two cells thick ‾ stains: tissue is mounted on slides and artificially colored with histological stain • stains bind to different cellular components • sectioning reduces threedimensional structure to twodimensional slice SECTIONING SOLID OBJECTS • sectioning a cell with a centrally located nucleus • some slices miss the cell nucleus • in some the nucleus is smaller SECTIONING HOLLOW STRUCTURES • cross section of blood vessel, gut, or other tubular organ. • longitudinal section of a sweat gland. notice what a single slice could look like. TYPES OF TISSUE SECTIONS • longitudinal section (l.s.) ‾ tissue cut along long direction of organ • cross section (c.s. or x.s.) or transverse section (t.s.) ‾ tissue cut perpendicular to length of organ • oblique section ‾ tissue cut at angle between cross and longitudinal section NONSECTIONED PREPARATION • smear – tissue is rubbed or spread across the slide ‾ spinal cord or blood • spread – cobwebby tissue is laid out on a slide ‾ areolar tissue EPITHELIAL TISSUE • flat sheet of closely adhering cells, one or more cells thick ‾ epithelia allows no room for blood vessels • extracellular material is so thin it is not visible with a light microscope • covers body surface, lines body cavities, forms the external and internal linings of many organs, constitutes most glands BASEMENT MEMBRANE • All epithelial tissue is connected to a basement membrane, which anchors the epithelium to the connective tissue below it • basal surface: surface of an epithelial cell that faces the basement membrane ‾ Basement and Basal start with B • apical surface: surface of an epithelial cell that faces away from the basement membrane ‾ typically faces the external environment or an organ surface ‾ Apical Away SIMPLE VS. STRATIFIED EPITHELIA • Simple epithelium ‾ contains one layer of cells ‾ named by shape of cells ‾ all cells touch the basement membrane • Stratified epithelium ‾ Contains more than one layer ‾ Named by shape of apical cells ‾ Some cells rest on top of others and do not touch basement membrane • Pseudostratified epithelium ‾ Not all cells reach the surface but all touch the basement membrane ‾ Considered simple SIMPLE EPITHELIA • four types of simple epithelia • three named for their cell shapes ‾ simple squamous (thin scaly cells) • Single row of thin cells • Permits rapid diffusion or transport of substances • Alveoli, glomeruli, endothelium ‾ simple cuboidal (square or round cells) • single layer of square or round cells • absorption and secretion, mucus production and movement • mammary and salivary glands, and kidney tubules ‾ simple columnar (tall narrow cells) • single row tall, narrow cells – oval nuclei in basal half of cell – brush border of microvilli, ciliated in some organs, may possess goblet cells • absorption and secretion; mucus secretion • lining of GI tract, uterine tubes • fourth type – ‾ pseudostratified columnar • not all cells reach the free surface (so it may appear to be stratified) but every cell contacts the basement membrane (therefore it is a simple epithelium) • goblet cells – wineglassshaped mucus secreting cells in simple columnar and pseudostratified epithelia • looks multilayered; some not reaching free surface; all touch basement membrane – nuclei at several layers – with cilia and goblet cells • secretes and propels mucus • respiratory tract STRATIFIED EPITHELIA • range from 2 to 20 or more layers of cells • only the deepest layer attaches to the basement membrane • three stratified epithelia are named for the shapes of their surface cells ‾ stratified squamous • most widespread epithelium in the body – resists abrasion • two kinds of stratified squamous epithelia – keratinized – found on skin surface, packed with keratin • multiple cell layers with cells becoming flat and scaly toward surface • resists abrasion; retards water loss through skin; resists penetration by pathogenic organisms • epidermis; palms and soles heavily keratinized – nonkeratinized – moist and slippery • same as keratinized epithelium without the surface layer of dead cells • resists abrasion and penetration of pathogens • tongue, oral mucosa, esophagus and vagina • deepest layers are cuboidal or columnar and undergo continuous mitosis – their daughter cells push toward the surface and become flatter as they migrate farther upward – finally die and flake off – exfoliation or desquamation ‾ stratified cuboidal • two or more cell layers; surface cells square or round • secretes sweat, sperm production, and produces ovarian hormones • sweat gland ducts ‾ stratified columnar (rare) • fourth type ‾ transitional epithelium • multilayered epithelium surface cells that change from round to flat when stretched • allows for filling of urinary tract • ureter and bladder CONNECTIVE TISSUE • connective tissue: cells usually occupy less space than the extracellular material ‾ most cells of connective tissue are not in direct contact with each other • separated by extracellular material • highly vascular – richly supplied with blood vessels • most abundant, widely distributed, and histologically variable of the primary tissues FUNCTIONS OF CONNECTIVE TISSUE • binding of organs – tendons and ligaments • support – bones and cartilage • physical protection – cranium, ribs, sternum • immune protection – white blood cells attack foreign invaders • movement – bones provide lever system • storage – fat, calcium, phosphorus • heat production – metabolism of brown fat in infants • transport blood COMPONENTS OF FIBROUS CONNECTIVE TISSUE • Ground substance ‾ usually a gelatinous to rubbery consistency • Cells ‾ fibroblasts produce fibers and ground substance ‾ macrophages phagocytize foreign material and activate immune system ‾ leukocytes or white blood cells react against bacteria, toxins, and other foreign material ‾ mast cells • secrete heparin inhibits clotting • histamine that dilates blood vessels ‾ adipocytes store triglycerides • Fibers ‾ collagenous fibers • most abundant of the body’s proteins – 25% • tough, flexible, and resist stretching • tendons, ligaments, and deep layer of the skin are mostly collagen • less visible in matrix of cartilage and bone ‾ reticular fibers • thin collagen fibers coated with glycoprotein • form framework of such organs as spleen and lymph nodes ‾ elastic fibers • thinner than collagenous fibers • made of protein called elastin • allows stretch and recoil TYPES OF FIBROUS CONNECTIVE TISSUE • loose connective tissue ‾ much gellike ground substance between cells ‾ Types: • Areolar – loosely organized fibers, abundant blood vessels, and a lot of seemingly empty space – fibers run in random directions • mostly collagenous, but elastic and reticular also present • found in tissue sections from almost every part of the body • surrounds blood vessels and nerves – nearly every epithelium rests on a layer of areolar tissue • blood vessels provide nutrition to epithelium and waste removal • ready supply of infection fighting leukocytes that move about freely in areolar tissue – loosely organized fibers, abundant blood vessels, and a lot of seemingly empty space – underlies all epithelia, in serous membranes, between muscles, passageways for nerves and blood vessels • Reticular – mesh of reticular fibers and fibroblasts – forms supportive stroma (framework) for lymphatic organs – found in lymph nodes, spleen, thymus • dense connective tissue ‾ fibers fill spaces between cells ‾ Types: • dense regular connective tissue – densely, packed, parallel collagen fibers • compressed fibroblast nuclei – tendons attach muscles to bones and ligaments hold bones together • dense irregular connective tissue – densely packed, randomly arranged, collagen fibers and few visible cells • withstands unpredictable stresses • deeper layer of skin; capsules around organs ADIPOSE TISSUE • adipose tissue (fat) – tissue in which adipocytes are the dominant cell type • the quantity of stored triglyceride and the number of adipocytes are quite stable in a person ‾ fat is recycled continuously to prevent stagnation ‾ new triglycerides are constantly synthesized and stored ‾ old triglycerides are hydrolyzed and released into circulation • on average, women have more fat than men ‾ too little fat can reduce female fertility • fat is the body’s primary energy reservoir • provides thermal insulation • anchors and cushions organs such as eyeball, kidneys • contributes to body contours – female breast and hips • Two types: ‾ White Fat ‾ Brown Fat • emptylooking cells with thin margins; nucleus pressed against cell membrane • energy storage, insulation, cushioning ‾ subcutaneous fat and organ packing ‾ brown fat produces heat CARTILAGE • supportive connective tissue with flexible, rubbery matrix • gives shape to ear, tip of nose, and larynx • chondroblasts produce matrix and surround themselves until they become trapped in little cavities (lacunae) • chondrocytes – cartilage cells in lacunae • perichondrium – sheath of dense irregular connective tissue that surrounds elastic and most hyaline cartilage (not articular cartilage) ‾ contains a reserve population of chondroblasts that contribute to cartilage growth throughout life • no blood vessels ‾ diffusion brings nutrients and removes wastes ‾ heals slowly • matrix rich in chondroitin sulfate and contain collagen fibers • types of cartilage vary with fiber types ‾ hyaline cartilage, fibrocartilage and elastic cartilage HYALINE CARTILAGE • clear, glassy microscopic appearance because of unusual fineness of the collagen fibers • usually covered by perichondrium • articular cartilage, costal cartilage, trachea, larynx • eases joint movement, holds airway open, moves vocal cords during speech ELASTIC CARTILAGE • cartilage containing elastic fibers • covered with perichondrium • provides flexible, elastic support ‾ external ear and epiglottis FIBROCARTILAGE • cartilage containing large, coarse bundles of collagen fibers • never has perichondrium • resists compression and absorbs shock ‾ pubic symphysis, menisci, and intervertebral discs BONE • ‘bone’ has two meanings: ‾ an organ of the body; femur, mandible; composed of multiple tissue types ‾ bone tissue – osseous tissue – makes up most of the mass of bone ‾ two forms of osseous tissue • spongy bone spongy in appearance – delicate struts of bone – covered by compact bone – found in heads of long bones and in middle of flat bones such as the sternum • compact bone – denser calcified tissue with no visible spaces – cells and matrix surround vertically oriented blood vessels in long bones COMPACT BONE • most compact bone is arranged in cylinders that surround central canals • osteon – central canal and its surrounding lamellae • osteocytes – mature bone cells that occupy the lacunae BLOOD • fluid connective tissue • transports cells and dissolved matter from place to place • plasma: blood’s liquid ground substance • formed elements: cells and cell fragments ‾ erythrocytes – red blood cells – transport O2 and CO2 ‾ leukocytes – white blood cells – defense against infection and other diseases ‾ platelets – cell fragments involved in clotting and other mechanisms EXCITABLE TISSUES: MUSCULAR and NERVOUS TISSUE • excitability – a characteristic of all living cells ‾ developed to highest degree in nervous and muscular tissues • membrane potential – electrical charge difference (voltage) that occurs across the plasma membranes is the basis for their excitation ‾ respond quickly to outside stimulus by means of changes in membrane potential ‾ nerves – changes result in rapid transmission of signals to other cells ‾ muscles – changes result in contraction, shortening of the cell NERVOUS TISSUE • nervous tissue – specialized for communication by electrical and chemical signals • consists of neurons (nerve cells) – ‾ detect stimuli ‾ respond quickly ‾ transmit coded information rapidly to other cells • and neuroglia (glial) ‾ protect and assist neurons ‾ ‘housekeepers’ of nervous system MUSCULAR TISSUE • muscular tissue – elongated cells that are specialized to contract in response to stimulation • primary job is to exert physical force on other tissues and organs • creates movements involved in body and limb movement, digestion, waste elimination, breathing, speech, and blood circulation • important source of body heat • three types of muscle: ‾ Skeletal • long, threadlike cells known as muscle fibers • most attach to bone • cells contain multiple nuclei • striations – alternating dark and light bands • voluntary – conscious control over skeletal muscles ‾ Cardiac • Only one location the heart • myocytes or cardiocytes are much shorter & branched • contain one centrally located nucleus • intercalated discs join cardiocytes end to end – provide electrical and mechanical connection • striated, and involuntary (not under conscious control) ‾ Smooth • Lacks striations and is involuntary • Relatively short, fusiform cells • One centrally located nucleus • Visceral muscle: forms layers of digestive, respiratory, and urinary tract: blood vessels, uterus and other viscera • Propels contents through an organ, regulated diameter of blood vessels INTERCELLULAR JUNCTIONS • intercellular junctions: connections between one cell and another • all cells (except blood and metastatic cancer cells) are anchored to each other or their matrix by intercellular junctions • resist stress and communicate with each other TIGHT JUNCTIONS • Tight junction: a region in which adjacent cells are bound together by fusion of the outer phospholipid layer of their plasma membranes. ‾ in epithelia, forms a zone that complete encircles each cell ‾ seals off intercellular space & makes it impossible for something to pass between cells DEMOSOMES • desmosomes: patch that holds cells together (like a clothing snap) • serves to keep cells from pulling apart – resists mechanical stress • hemidesmosomes – anchor the basal cells of epithelium to the underlying basement membrane ‾ epithelium can not easily peel away from underlying tissues GAP JUNCTIONS • gap (communicating) junction – formed by a ringlike connexon ‾ consists of six transmembrane proteins arranged like segments of an orange ‾ surrounding a waterfilled pores ‾ ions, glucose, amino acids and other solutes pass from one cell to the next GLANDS • Gland—cell or organ that secretes substances for use elsewhere in the body or releases them for elimination from the body ‾ Usually composed of epithelial tissue in a connective tissue framework and capsule ‾ Secretion: product useful to the body ‾ Excretion: waste product Endocrine and Exocrine Glands ‾ Endocrine glands secrete hormones into the blood • have no ducts; secrete hormones directly into blood • Hormones: chemical messengers that stimulate cells elsewhere in the body • Examples: thyroid, adrenal, and pituitary glands ‾ Exocrine glands secrete products into a duct • maintain their contact with surface of epithelium by way of a duct – Surfaces can be external (examples: sweat, tear glands) or internal (examples: pancreas, salivary glands) ‾ Some organs have both endocrine and exocrine functions • Examples: liver, gonads, pancreas ‾ Unicellular glands—found in an epithelium that is predominantly nonsecretory • Can be exocrine or endocrine • Examples: mucussecreting goblet cells in trachea or endocrine cells of stomach EXOCRINE GLAND STRUCTURE • Capsule: connective covering of most glands • Stroma: connective tissue framework of the gland • Parenchyma: the cells that perform the tasks of synthesis and secretion TYPES OF SECRETIONS • serous glands ‾ produce thin, watery secretions • perspiration, milk, tears and digestive juices • mucous glands ‾ produce mucin that absorbs water to form mucus ‾ goblet cells – unicellular mucous glands • mixed glands ‾ contain both cell types and produce a mixture of the two types of secretions • cytogenic glands ‾ release whole cells, sperm and egg cells MODELS OF SECRETION • Secretion modes: ‾ Merocrine • Merocrine secretion (used by eccrine glands) uses vesicles that release their secretion by exocytosis – Examples: tear glands, pancreas, gastric glands, and others ‾ Apocrine • lipid droplet covered by membrane and cytoplasm buds from cell surface • Mode of milk fat secretion by mammary gland cells • Also “apocrine” is used to describe axillary sweat glands even though they use merocrine secretion mode ‾ Holocrine • Cells accumulate a product until they disintegrate – Secrete a mixture of cell fragments and synthesized substances – Examples: oil glands of scalp and skin, and glands of eyelids MEMBRANES • Line body cavities and cover their viscera • cutaneous membrane skin – largest membrane in the body • mucous membrane (mucosa) – produces mucus ‾ consists of two to three layers: • epithelium • lamina propria – areolar connective tissue • muscularis mucosae – smooth muscle layer ‾ absorptive, secretory, and protective functions • serous membrane (serosa) – produces serous fluid ‾ covers organs and lines walls of body cavities • endothelium lines blood vessels and heart • mesothelium line body cavities (pericardium, peritoneum and pleura) • synovial membrane lines joint cavities ‾ secretes synovial fluid TISSUE GROWTH • hyperplasia tissue growth through cell multiplication • hypertrophy enlargement of preexisting cells ‾ muscles grow through exercise ‾ accumulation of body fat • neoplasia: development of a tumor (neoplasm) ‾ benign or malignant ‾ composed of abnormal, nonfunctional tissue TISSUE DEVELOPMENT • Tissues can change types within certain limits • Differentiation—development of more specialized form and function by unspecialized tissue ‾ Example: embryonic mesenchyme becoming muscle • Metaplasia ‾ Changing from one type of mature tissue to another • Simple cuboidal tissue of vagina before puberty changes to stratified squamous after puberty • Pseudostratified columnar epithelium of bronchi of smokers to stratified squamous epithelium TISSUE REPAIR • regeneration replacement of dead or damaged cells by the same type of cell as before ‾ restores normal function ‾ skin injuries and liver regenerate • fibrosis replacement of damaged cells with scar tissue ‾ holds organs together ‾ does not restore normal function • severe cuts and burns, healing of muscle injuries, scarring of lungs in tuberculosis TISSUE SHRINKAGE AND DEATH • atrophy: shrinkage of a tissue through a loss in cell size or number • necrosis: premature, pathological death of tissue due to trauma, toxins, or infections • apoptosis: programmed cell death ‾ normal death of cells that have completed their function and best serve the body by dying and getting out of the way
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