Histology Notes Pre-Health PDF

HISTOLOGY 5-1  Chapter 5 Lecture Outline 5-2 Copyright (c) The McGraw-Hill Comp...

HISTOLOGY 5-1  Chapter 5 Lecture Outline 5-2 Copyright (c) The McGraw-Hill Companies, Inc. Permission required for reproduction or display.  Histology: Objectives Describe the composition of tissues. Name the three (3) embryonic germ layers and the adult tissues derived from them. Name and differentiate among the four (4) primary classes into which all tissues are classified. Describe the properties that distinguish Epithelium from other classes of tissue. List and classify eight (8) types of epithelia, distinguish them from each other and state where each type can be found. Explain how the structural differences between epithelia, relate to their functional differences. Visually identify each type of epithelium from photographs. Describe the types of glandular epithelium. Describe the properties that are common to most Connective Tissues. Describe the types of cells found in Connective Tissues. Explain what the Matrix of a Connective Tissue is and describe its components. Name the types of Connective Tissue, describe their cellular components and Matrix and explain what distinguishes them from each other. 5-3  The Study of Tissues 50 trillion cells of 200 different cell types four broad categories of tissues – epithelial tissue – connective tissue – nervous tissue – muscular tissue organ - structure with discrete boundaries that is composed of two or more tissue types histology (microscopic anatomy) – the study of tissues and how they are arranged into organs 5-4  The Primary Tissue Classes tissue – a group of similar cells and cell products that arise from the same region of the embryo and work together to perform a specific structural or physiological role in an organ. four primary tissues differ from one another in the: – types and functions of their cells – the characteristics of the matrix (extracellular material) – the relative amount of space occupied by cells versus matrix matrix – (extracellular material) is composed of : – fibrous proteins – a clear gel known as ground substance , tissue fluid, extracellular fluid (ECF), interstitial fluid, or tissue gel 5-5  Embryonic Tissues human development begins as single cell the fertilized egg – divides to produce scores of identical, smaller cells – first tissues appear when these cells start to organize themselves into layers first two, and then three strata 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, and among other things – mesoderm (middle) becomes gelatinous tissue - mesenchyme wispy collagen fibers and fibroblasts in gel matrix gives rise to muscle, bone, blood 5-6  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 three-dimensional structure to two-dimensional slice 5-7  Sectioning Solid Objects Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. sectioning a cell with a centrally located nucleus some slices miss the cell nucleus in some the nucleus is smaller (a 5-8 ) Figure 5.1a  Sectioning Hollow Structures Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. cross section of blood vessel, gut, or other tubular organ. longitudinal section of a sweat gland. notice what a (c ) single slice could look like. (b ) 5-9 Figure 5.1b,c  Types of Tissue Sections Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Longitudinal sections longitudinal section (l.s.) – tissue cut along long direction of organ cross section (c.s. or x.s.) or Cross sections transverse section (t.s.) – tissue cut perpendicular to length of organ oblique section Oblique sections – tissue cut at angle between cross and longitudinal section Figure 5.2 5-10  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 5-11  Epithelial Tissue consists of a flat sheet of closely adhering cells one or more cells thick upper surface usually exposed to the environment or an internal space in the body covers body surface lines body cavities forms the external and internal linings of many organs constitutes most glands extracellular material is so thin it is not visible with a light microscope epithelia allows no room for blood vessels lie on a layer of loose connective tissue and depend on its blood vessels for nourishment and waste removal 5-12  Basement Membrane basement membrane – layer between an epithelium and the underlying connective tissue basement membrane contains: – collagen – laminin and fibronectin adhesive glycoproteins – heparin sulfate - large protein-carbohydrate complex anchors the epithelium to the connective tissue below it basal surface – surface of an epithelial cell that faces the basement membrane apical surface – surface of an epithelial cell that faces away from the basement membrane 5-13  Simple vs. Stratified Epithelia Simple epithelium Stratified epithelium – contains one layer of cells – contains more than one layer – named by shape of cells – named by shape of apical cells – all cells touch the basement – some cells rest on top of others membrane and do not touch basement membrane Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. (a) Classes of epithelium Simple Pseudostratified Stratified columnar (b) Cell shapes Squamou Cuboida Columna s l r 5-14 Figure 5.3  Simple Epithelia four types of simple epithelia three named for their cell shapes – simple squamous (thin scaly cells) – simple cuboidal (square or round cells) – simple columnar (tall narrow cells) fourth type – – pseudostratified columnar not all cells reach the free surface shorter cells are covered over by taller ones looks stratified every cell reaches the basement membrane goblet cells – wineglass-shaped mucus secreting cells in simple columnar and pseudostratified epithelia 5-15  Simple Squamous Epithelium Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Squamous epithelial Nuclei of smooth cells muscle Basement membrane (a (b ) ) a: © The McGraw-Hill Companies, Inc./Dennis Strete, photographer Figure 5.4a Figure 5.4b,i single row of thin cells permits rapid diffusion or transport of substances secretes serous fluid alveoli, glomeruli, endothelium, and serosa 5-16  Simple Cuboidal Epithelium Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lumen of kidney tubule Cuboidal epithelial cells Basement membrane (a (b) ) a: © The McGraw-Hill Companies, Inc./Dennis Strete, photographer Figure 5.5a Figure 5.5b,i single layer of square or round cells absorption and secretion, mucus production and movement liver, thyroid, mammary and salivary glands, bronchioles, and kidney tubules 5-17  Simple Columnar Epithelium Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Brush border Connective Basement Goblet Columnar (microvilli) tissue membrane Nuclei cell cells (b ) Figure 5.6b,i 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, uterus, kidney and uterine tubes 5-18  Pseudostratified Epithelium Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cilia Basement membrane Basal cells Goblet cell (a (b ) a: © The McGraw-Hill Companies, )Inc./Dennis Strete, photographer Figure 5.7a Figure 5.7b,i looks multilayered; some not reaching free surface; all touch basement membrane – nuclei at several layers – with cilia and goblet cells secretes and propels mucus 5-19 respiratory tract and portions of male urethra  Stratified Epithelia range from 2 to 20 or more layers of cells some cells resting directly on others only the deepest layer attaches to the basement membrane three stratified epithelia are named for the shapes of their surface cells – stratified squamous – stratified cuboidal – stratified columnar (rare) fourth type – transitional epithelium most widespread epithelium in the body deepest layers 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 two kinds of stratified squamous epithelia – keratinized – found on skin surface, abrasion resistant – nonkeratinized – lacks surface layer of dead cells 5-20 Keratinized Stratified Squamous Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Dense irregular Dead squamous Living epithelial cells connective tissue cells Areolar tissue (a (b ) ) DeGrandis, photographer a: © The McGraw-Hill Companies, Inc./Joe Figure 5.8a Figure 5.8b,i multiple cell layers with cells becoming flat and scaly toward surface epidermis; palms and soles heavily keratinized resists abrasion; retards water loss through skin; resists 5-21 penetration by pathogenic organisms Nonkeratinized Stratified Squamous Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Living epithelial Connective cells tissue (a (b ) ) a: © Ed Reschke Figure 5.9a Figure 5.9b,i same as keratinized epithelium without the surface layer of dead cells tongue, oral mucosa, esophagus and vagina 5-22 resists abrasion and penetration of pathogens  Stratified Cuboidal Epithelium Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cuboidal Epitheliu Connective cells m tissue (a (b ) ) a: © The McGraw-Hill Companies, Inc./Dennis Strete, photographer Figure 5.10a Figure 5.10b,i two or more cell layers; surface cells square or round secretes sweat; sperm production and produces ovarian hormones sweat gland ducts; ovarian follicles and seminiferous 5-23 tubules  Transitional Epithelium Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Basement Connectiv Binucleate membran e epithelial e tissue cell (a (b ) a: Johnny R. )Howze Figure 5.11a Figure 5.11b,i multilayered epithelium surface cells that change from round to flat when stretched allows for filling of urinary tract 5-24 ureter and bladder  Connective Tissue connective tissue – a type of tissue in which cells usually occupy less space than the extracellular material binds organs to each other support and protect organs 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 5-25 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 5-26  Components of Fibrous Connective Tissue cells – fibroblasts produce fibers and ground substance – macrophages phagocytize foreign material and activate immune system when sense foreign matter (antigen) arise from white blood cell - monocytes – leukocytes or white blood cells neutrophils wander in search of and attacking bacteria lymphocytes react against bacteria, toxins, and other foreign material – plasma cells synthesize disease fighting antibodies arise from lymphocytes – mast cells – found along side of blood vessels secrete heparin inhibits clotting histamine that dilates blood vessels – adipocytes store triglycerides (fat molecules) 5-27  Components of Fibrous fibers Connective Tissue – 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 branch and rejoin each other made of protein called elastin allows stretch and recoil yellow fibers – fresh elastic fibers 5-28  Components of Fibrous Connective Tissue ground substance – usually a gelatinous to rubbery consistency resulting from three classes of large molecules – glycosaminoglycans (GAG) long polysaccharide composed of unusual disaccharides called amino sugars and uronic acid play important role of regulating water and electrolyte balance in the tissues chondroitin sulfate – most abundant GAG – in blood vessels and bone – responsible for stiffness of cartilage hyaluronic acid – viscous, slippery substance that forms an effective lubricant in joints and constitutes much of the vitreous body of the eyeball – proteoglycan gigantic molecule shaped like a test-tube brush forms thick colloids that creates strong structural bond between cells and extracellular macromolecules – holds tissues together – adhesive glycoproteins – bind components of tissues together 5-29 Types of Fibrous Connective Tissue Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. loose connective tissue – much gel-like ground substance between cells Tendons – types areolar reticular dense connective tissue – fibers fill spaces between cells – types vary in fiber orientation © The McGraw-Hill Companies, Inc./Rebecca Gray, photographer/Don Kincaid, dissections dense regular connective tissue Figure 5.13 dense irregular connective tissue 5-30  Areolar Tissue loosely organized fibers, abundant blood vessels, and a lot of seemingly empty space possess all six cell types 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 5-31  Areolar Tissue Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Ground Elasti Collagenous substance c fibers Fibroblasts fibers (a (b) ) a: © The McGraw-Hill Companies, Inc./Dennis Strete, photographer Figure 5.14a Figure 5.14b,i 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 5-32  Reticular Tissue Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Reticula Leukocyte r s fibers (a (b ) ) a: The McGraw-Hill Companies, Inc./Al Telser, photographer Figure 5.15a Figure 5.15b,i mesh of reticular fibers and fibroblasts forms supportive stroma (framework) for lymphatic organs found in lymph nodes, spleen, thymus and bone 5-33 marrow Dense Regular Connective Tissue Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Collagen Ground Fibroblast fibers substance nuclei (a) (b) a: © The McGraw-Hill Companies, Inc./Dennis Strete, photographer Figure 5.16a Figure 5.16b,i densely, packed, parallel collagen fibers – compressed fibroblast nuclei tendons attach muscles to bones and ligaments hold bones together 5-34 Dense Irregular Connective Tissue Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Bundles of Glan Fibroblas Ground collagen d t substanc fibers ducts nuclei e (a (b) ) a: © The McGraw-Hill Companies, Inc./Dennis Strete, photographer Figure 5.17a Figure 5.17b,i densely packed, randomly arranged, collagen fibers and few visible cells – withstands unpredictable stresses – deeper layer of skin; capsules around organs 5-35  Adipose Tissue adipose tissue (fat) – tissue in which adipocytes are the dominant cell type space between adipocytes is occupied by areolar tissue, reticular tissue, and blood capillaries fat is the body’s primary energy reservoir 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 provides thermal insulation anchors and cushions organs such as eyeball, kidneys contributes to body contours – female breast and hips on average, women have more fat than men too little fat can reduce female fertility most adult fat is called white fat brown fat – in fetuses, infants, children – a heat generating tissue 5-36  Adipose Tissue Copyright © The McGraw-Hill Companies, Inc. 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Blood Adipocyt Lipid in vesse e adipocyt l nucleus e (a (b) ) a: © The McGraw-Hill Companies, Inc./Dennis Strete, photographer Figure 5.18a Figure 5.18b,i empty-looking cells with thin margins; nucleus pressed against cell membrane energy storage, insulation, cushioning – subcutaneous fat and organ packing – brown fat (hibernating animals) produces heat 5-37  Cartilage supportive connective tissue with flexible, rubbery matrix gives shape to ear, tip of nose, and larynx chondroblasts produce matrix and surround them selves 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 5-38 – hyaline cartilage, fibrocartilage and elastic cartilage  Hyaline Cartilage Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cell Matri nes Perichondriu Lacuna Chondrocyte x t m e s (a (b) ) a: © Ed Reschke Figure 5.19a Figure 5.19b,i clear, glassy microscopic appearance because of unusual fineness of the collagen fibers usually covered by perichondrium articular cartilage, costal cartilage, trachea, larynx, fetal skeleton eases joint movement, holds airway open, moves vocal cords during 5-39 speech  Elastic Cartilage Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Elasti Perichondriu c Lacuna Chondrocyte m fibers e s (a (b) ) a: © Ed Reschke Figure 5.20a Figure 5.20b,i cartilage containing elastic fibers covered with perichondrium provides flexible, elastic support – external ear and epiglottis 5-40  Fibrocartilage Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Collage n Chondrocyte fibers s (a) (b) a: Dr. Alvin Telser Figure 5.21a Figure 5.21b,i cartilage containing large, coarse bundles of collagen fibers never has perichondrium resists compression and absorbs shock – pubic symphysis, menisci, and intervertebral discs 5-41  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 - trabeculae 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 more complex arrangement cells and matrix surround vertically oriented blood vessels in long bones 5-42  Bone Tissue (compact bone) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Concentric lamellae Central Lacunae Canalicul of osteon canal Osteo i n (a (b) ) a: © The McGraw-Hill Companies, Inc./Dennis Strete, photographer Figure 5.22a Figure 5.22b,i most compact bone is arranged in cylinders that surround central (haversian or osteonic) canals that run longitudinally through shafts of long bones – blood vessels and nerves travel through central canal bone matrix deposited in concentric lamella – onionlike layers around each central canal osteon – central canal and its surrounding lamellae osteocytes – mature bone cells that occupy the lacunae canaliculi – delicate canals that radiate from each lacuna to its neighbors, and allows osteocytes to contact each other periosteum – tough fibrous connective tissue covering of the bone as a whole 5-43  Blood Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. fluid connective tissue Platelets Neutrophils Lymphocyte Erythrocytes Monocyte 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 (b cells – defense against ) infection and other diseases Figure 5.23b,i – platelets – cell fragments involved in clotting and other mechanisms 5-44  Excitable Tissues Muscular & 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 5-45  Nervous Tissue Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. nervous tissue – specialized for Nuclei of glial cells Axon Neurosoma Dendrites 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 neuron parts – neurosoma (cell body) (b) houses nucleus and other organelles cell’s center of genetic control and protein synthesis – dendrites multiple short, branched processes Figure 5.24b,i receive signals from other cells transmit messages to neurosoma – axon (nerve fiber) sends outgoing signals to other cells can be more than a meter long 5-46  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, cardiac, and smooth 5-47  Skeletal Muscle long, threadlike cells – muscle fibers most attach to bone exceptions – in tongue, upper esophagus, facial muscles, some sphincter muscles – (ringlike or cufflike muscles that open and close body passages) contains multiple nuclei adjacent to plasma membrane striations – alternating dark and light bands voluntary – conscious control over skeletal muscles Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Nucle Striation Muscle i s fiber (a (b ) ) a: © Ed Reschke Figure 5.25a Figure 5.25b,i 5-48  Cardiac Muscle limited to the heart myocytes or cardiocytes are much shorter, branched, and notched at ends contain one centrally located nucleus surrounded by light staining glycogen intercalated discs join cardiocytes end to end – provide electrical and mechanical connection striated, and involuntary (not under conscious control) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Intercalated discs Striations Glycoge n (a) (b) © Ed Reschke 5-49 Figure 5.26a Figure 5.26b,i  Smooth Muscle Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Nucle Muscle i cells (a (b) ) a: © The McGraw-Hill Companies, Inc./Dennis Strete, photographer Figure 5.27a Figure 5.27b,i lacks striations and is involuntary relatively short, fusiform cells (thick in middle, tapered at ends) 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, regulates diameter of blood vessels 5-50  Intercellular Junctions Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Tight junction Plasma membrane Membrane protein Intercellular space Membrane Desmosom protein e Intermediate filaments Cell nucleus Glycoprotein Protein plaque Intercellular space Plasma membrane Gap junction Por Basement e Connexo n Por e membrane Hemidesmosom Figure 5.28 P e roteins 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 5-51  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 near its apical pole – seals off intercellular space – makes it impossible for something to pass between cells Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Tight junction Desmosome Gap junction Figure 5.28 5-52  Desmosomes desmosomes - patch that holds cells together (like a clothing snap) serves to keep cells from pulling apart – resists mechanical stress hooklike J-shaped proteins arise from cytoskeleton – approach cells surface – penetrate into thick protein plaques linked to transmembrane proteins hemidesmosomes – anchor the basal cells of epithelium to the underlying basement membrane – epithelium can not easily peel away from underlying tissues Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Tight junction Desmosome Gap junction Figure 5.28 5-53  Gap Junctions gap (communicating) junction – formed by a ringlike connexon – consists of six transmembrane proteins arranged like segments of an orange – surrounding a water-filled pores – ions, glucose, amino acids and other solutes pass from one cell to the next Copyright © The McGraw-Hill Companies, Inc. 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Tight junction Desmosome Gap junction Figure 5.28 5-54 Endocrine and Exocrine Glands gland – cell or organ that secrete substances for use elsewhere in the body or releases them for elimination from the body – composed of epithelial tissue in a connective tissue framework and capsule exocrine glands - maintain their contact with the body surface by way of a duct (epithelial tube that conveys secretion to surface) – sweat, mammary and tear glands endocrine glands - lose their contact with the surface and have no ducts – hormones – secretion of endocrine glands – secrete (hormones) directly into blood – thyroid, adrenal and pituitary glands some organs have both endocrine and exocrine function – liver, gonads, pancreas unicellular glands – found in epithelium that is predominantly nonsecretory – can be endocrine or exocrine – mucus-secreting goblet or endocrine cells of stomach and small intestine5-55  Exocrine Gland Structure Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lobule s Lobe Secretor s y acini Duc t Parenchym a Secretor Stroma: y vesicles Capsul e Septu m (a) Figure 5.29 Duc Acinu (b) t s capsule – connective covering of most glands – septa or trabeculae – extensions of capsule that divide the interior of the gland into compartments (lobes) – further divided into smaller lobules stroma – connective tissue framework of the gland – supports and organizes glandular tissue parenchyma – the cells that perform the tasks of synthesis and secretion – typically cuboidal or simple columnar epithelium 5-56  Types of Exocrine Glands Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Simple coiled Compound acinar Compound tubuloacinar tubular Example: Sweat gland Example: Pancreas Ke y Duct Example: Mammary gland Secretory portion Figure 5.30 simple - unbranched duct compound - branched duct shape of gland – tubular – duct and secretory portion have uniform diameter – acinar - secretory cells form dilated sac (acinus or alveolus) – tubuloacinar - both tubular and acinar portions 5-57  Types of Secretions serous glands – produce thin, watery secretions perspiration, milk, tears and digestive juices mucous glands – produce glycoprotein, mucin, that absorbs water to form a sticky secretion called 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 5-58  Methods of Secretion Merocrine Gland Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. merocrine glands (eccrine glands) – have vesicles that release their secretion by exocytosis – tear glands, pancreas, gastric glands, and others apocrine glands – primarily Exocytosis merocrine mode of secretion Nucleus – axillary sweat glands, mammary Secretory vesicle glands (a) Merocrine gland Figure 5.31a 5-59  Methods of Secretion Holocrine Gland Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 5.31b (b) Holocrine gland holocrine glands – cells accumulate a product and then the entire cell disintegrates – secretion a mixture of cell fragments and synthesized substance – oil glands of scalp, glands of eyelids 5-60  Membranes membranes – line body cavities and cover their viscera cutaneous membrane - the skin – largest membrane in the body – stratified squamous epithelium (epidermis) over connective tissue (dermis) – relatively dry layer serves protective function mucous membrane (mucosa) – lines passageways open to the external environment serous membrane (serosa) - internal membrane – simple squamous epithelium over areolar tissue – produces serous fluid that arises from blood – 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 – connective tissue layer only, secretes synovial fluid 5-61 Mucous Membranes (Mucosa) Copyright © The McGraw-Hill Companies, Inc. 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Mucous coat Cilia Mucin in Epithelium goblet cell Ciliated cells of pseudostratified epithelium Basement Mucous membran membrane e (mucosa) Blood vessel Lamina Collagen fibers propria Fibroblast Elastic fibers Muscularis mucosae Figure 5.32 lines passages that open to the external environment – digestive, respiratory, urinary, and reproductive tracts consists of two to three layers: – epithelium – lamina propria – areolar connective tissue – muscularis mucosae – smooth muscle layer absorptive, secretory, and protective functions 5-62 covered with mucus  Tissue Growth tissue growth – increasing the number of cells or the existing cells grow larger hyperplasia - tissue growth through cell multiplication hypertrophy - enlargement of preexisting cells – muscle grow through exercise – accumulation of body fat neoplasia – development of a tumor (neoplasm) – benign or malignant – composed of abnormal, nonfunctional tissue 5-63  Changes in Tissue Types Tissues can change types Differentiation – unspecialized tissues of embryo become specialized mature types mesenchyme to 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 5-64  Stem Cells stem cells - undifferentiated cells that are not yet performing any specialized function – have potential to differentiate into one or more types of mature functional cells developmental plasticity – diversity of mature cell types to which stem cells can give rise embryonic stem cells – totipotent - have potential to develop into any type of fully differentiated human cell source - cells of very early embryo – pluripotent – can develop into any type of cell in the embryo source - cells of inner cell mass of embryo adult stem cells - undifferentiated cells in tissues of adults – multipotent - bone marrow producing several blood cell types – unipotent – most limited plasticity - only epidermal cells produced5-65  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 5-66  Wound Healing Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. severed blood vessels bleed into cut mast cells and damaged cells release histamine – dilates blood vessels – increases blood flow to area – makes capillaries more permeable 1 Bleeding into the wound blood plasma seeps into the wound carrying: – antibodies – clotting proteins Figure 5.33 (1) – blood cells 5-67  Wound Healing Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. blood clot forms in the tissue – loosely knitting edges of cut together – inhibits spread of pathogens Scab from injury site to healthy tissue Blood clot Macrophages forms scab that temporarily Fibroblasts Leukocytes seals wound and blocks infection 2 Scab formation and macrophages phagocytize macrophage activity and digest tissue debris Figure 5.33 (2) 5-68  Wound Healing Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. new capillaries sprout from nearby vessels and grow Scab into wound deeper portions become infiltrated by capillaries and Macrophages fibroblasts Fibroblasts – transform into soft mass – Blood capillar granulation tissue y Granulation – macrophages remove the tissue blood clot – fibroblasts deposit new 3 Formation of granulation tissue (fibroblastic phase of repair) collagen – begins 3-4 days after injury and lasts up to 2 weeks Figure 5.33 (3) 5-69  Wound Healing surface epithelial cells Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. around wound multiply and migrate into wound area beneath scab epithelium regenerates connective tissue undergoes fibrosis Epidermal regrowth scar tissue may or may not Scar tissue (fibrosis) show through epithelium 4 Epithelial regeneration and connective tissue fibrosis (remodeling phase of remodeling (maturation) repair) phase begins several weeks after injury and may Figure 5.33 (4) last up to two years 5-70  Tissue Shrinkage and Death atrophy – shrinkage of a tissue through a loss in cell size or number – senile atrophy through normal aging – disuse atrophy from lack of use (astronauts) necrosis – premature, pathological death of tissue due to trauma, toxins, or infections – infarction – sudden death of tissue when blood supply is cut off – gangrene – tissue necrosis due to insufficient blood supply – decubitus ulcer – bed sore or pressure sore pressure reduces blood flow to an area a form of dry gangrene – gas gangrene - anaerobic bacterial infection 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 5-71  Tissue Engineering tissue engineering – artificial production of tissues and organs in the lab for implantation in the human body – framework of collagen or biodegradable polyester fibers – seeded with human cells – grown in “bioreactor” (inside of mouse) supplies nutrients and oxygen to growing tissue skin grafts already available – research in progress on heart valves, coronary arteries, bone, liver, tendons – human outer ear grown on back of mouse and recent replacement of urinary bladder wall sections 5-72 Tissue Engineering Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 5.34 5-73  Stem Cell Controversy possible treatment for diseases caused by loss of functional cell types by embryonic stem cells – cardiac muscle cells, injured spinal cord, insulin-secreting cells skin and bone marrow stem cells have been used in therapy for years adult stem cells have limited developmental potential – difficult to harvest and culture 5-74 5-75 5-76