Chapter 4.3. Histology of the Four Tissue Types

Transcription

1 Chapter 4.3 Histology of the Four Tissue Types

2 Overview of Tissue Epithelial (simple / stratified) Muscle (skeletal / smooth / cardiac) Connective tissue Fibrous loose (areolar / reticular) Fibrous dense (regular / irregular) Adipose Bone Blood Cartilage (hyaline / elastic / fibrous) Nervous (voluntary / involuntary) Note: Chapter 4 covers in detail the epithelial and connective tissues. We will cover the histology of muscle tissue in Chapter 10 and nervous tissue in Chapter 12. Blood is a type of connective tissue and this will be studied in Chapter 19.

3 Epithelial Tissue consists of a flat sheet of closely adhering cells one or more cells thick free surface / upper surface usually exposed to the environment or an internal space in the body covers body surface or 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 is avascular (no blood vessels) tissue allows no room for blood vessels lie on a layer of loose connective tissue that provide blood vessels for nourishment and waste removal

4 Basement Membrane of Epithelial Tissue 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 Basal lamina / secreted by epithelial cells Reticular lamina / secreted by fibroblast Note: in diabetes mellitus / basement membrane of capillaries thickens reduces diffusion / which causes cell death in capillary rich tissues like the eye (blindness) and kidneys (renal failure)

6 Epithelial Cells Shapes and Classes

7 Epithelial Cells Shapes and Classes 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

8 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

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10 Simple Squamous Epithelium Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Squamous epithelial cells Nuclei of smooth muscle Basement membrane (a) (b) single row of thin cells permits rapid diffusion or transport of substances secretes serous fluid alveoli, glomeruli, endothelium, and serosa

11 Simple Cuboidal Epithelium Lumen of kidney tubule Cuboidal epithelial cells Basement membrane (a) (b) single layer of square or round cells absorption and secretion, mucus production and movement liver, thyroid, mammary and salivary glands, bronchioles, and kidney tubules

12 Simple Columnar Epithelium Brush border (microvilli) Connective tissue Basement membrane Nuclei Goblet cell Columnar cells (a) (b) 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

13 Pseudostratified Epithelium Cilia Basement membrane Basal cells Goblet cell (a) (b) 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 and portions of male urethra

14 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

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16 Keratinized Stratified Squamous Dead squamous cells Living epithelial cells Dense irregular connective tissue Areolar tissue (a) (b) 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 penetration by pathogenic organisms Cutaneous membrane

17 Nonkeratinized Stratified Squamous Living epithelial cells Connective tissue (a) (b) same as keratinized epithelium without the surface layer of dead cells tongue, oral mucosa, esophagus and vagina resists abrasion and penetration of pathogens Adult vagina, oral cavity, esophagus

18 Stratified Cuboidal Epithelium Cuboidal cells Epithelium Connective tissue (a) (b) 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 tubules

19 Transitional Epithelium Basement membrane Connective tissue Binucleate epithelial cell (a) (b) multilayered epithelium surface cells that change from round to flat when stretched allows for filling of urinary tract ureter and bladder

20 Membranes Cover surfaces / line body surfaces, cavities and cover the viscera (organs) Four Type cutaneous membrane (covered Chapter 5) synovial membrane serous membrane (serosa) mucous membrane (mucosa)

21 Membranes cutaneous membrane the skin = largest membrane in the body stratified squamous epithelium (epidermis) over connective tissue (dermis) relatively dry layer serves protective function

22 Membranes synovial membrane - lines joint cavities connective tissue layer only, secretes synovial fluid Cells which form this membrane are not epithelial but connective tissue cells

23 Membranes 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)

24 Mucous coat Cilia Epithelium Mucin in goblet cell Ciliated cells of pseudostratified epithelium Mucous membrane (mucosa) Basement membrane Blood vessel Lamina propria Collagen fibers Fibroblast Elastic fibers Muscularis mucosae Mucous Membranes (Mucosa) 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 covered with mucus

25 Epithelial Glands Endocrine vs exocrine Unicellular vs multicellular Functional classification of exocrine glands

26 Endocrine and Exocrine Glands What is a gland? cell or organ that secrete substances for use elsewhere in the body // or releases substance for elimination from the body composed of epithelial tissue in a connective tissue framework and capsule some organs have both endocrine and exocrine function // e.g. = liver, gonads, pancreas

27 Endocrine and Exocrine Glands 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 produce hormones secretion of endocrine glands = messenger molecule secrete (hormones) directly into blood thyroid, adrenal and pituitary glands unicellular glands found in epithelium that is predominantly non-secretory tissue can be endocrine or exocrine mucus-secreting goblet or endocrine cells of stomach and small intestine

28 Endocrine Glands

29 Unicellular Gland

30 Exocrine Gland Structure capsule connective covering of most glands Lobules Lobes Parenchyma Stroma: Capsule Septum (a) Secretory acini Duct Secretory vesicles 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 (b) Duct Acinus supports and organizes glandular tissue parenchyma // the cells that perform the tasks of synthesis and secretion typically cuboidal or simple columnar epithelium

31 Structural Types of Exocrine Glands Simple coiled tubular Compound acinar Compound tubuloacinar Example: Sweat gland Key Duct Secretory portion Example: Mammary gland Example: Pancreas 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

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33 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

34 Methods of Secretion Merocrine glands Apocrine glands Holocrine glands

35 Method of Secretion // Merocrine Glands merocrine glands (eccrine glands) have vesicles that release their secretion by exocytosis tear glands, pancreas, gastric glands apocrine glands special type of merocirne gland / primarily a merocrine mode of secretion pinch off part of cytoplasm Merocrine gland Exocytosis Nucleus Secretory vesicle become active during adolescence Produce scent molecules Located in axillary, genital, beards of male

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38 Methods of Secretion The Holocrine Glands Holocrine gland 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

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40 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

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42 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

43 Components of Connective Tissue (Cells / Fibers / Matrix) Cell Types fibroblasts produce fibers and ground substance adipocytes store triglycerides (fat molecules) blood cells (RBC / macrophage / plasma cells / mast cells / leukocytes / platelets) Note: covered in Chapter 19

44 Components of Connective Tissue (Cells / Fibers / Matrix) Blood s formed elements able to emigrate into CT and travel throughout CT (i.e. the reticuloendothelial system) macrophages phagocytize foreign material and activate immune system when sense foreign matter (antigen) // arise from white blood cell monocytes leukocytes or white blood cells // five type // neutrophils wander in search of and attacking bacteria // lymphocytes react against bacteria, toxins, and other foreign material plasma cells (type of lymphocyte) synthesize disease fighting antibodies // arise from lymphocytes mast cells found along side of blood vessels // secrete heparin inhibits clotting // histamine that dilates blood vessels

45 Components of Connective Tissue (Cells / Fibers / Matrix) Fiber Type // collagenous fibers most abundant of the body s proteins 25% tough, flexible, and resist stretching // if stretched will not return to resting length like taffy! tendons, ligaments, and deep layer of the skin are mostly collagen less visible in matrix of cartilage and bone white fibers

46 Components of Connective Tissue (Cells / Fibers / Matrix) Fiber Type // reticular fibers thin collagen fibers coated with glycoprotein form framework of such organs as spleen and lymph nodes (the stroma) form walls of blood vessels

47 Components of Connective Tissue (Cells / Fibers / Matrix) Fiber Type // elastic fibers thinner than collagenous fibers branch and rejoin each other made of protein called elastin allows stretch and recoil // up to 150% and return to resting length yellow fibers fresh elastic fibers

48 Component of Connective Tissue (The Matrix) Ground Substance (Matrix) // 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 // trap water = hydrated proteins!!!! chondroitin sulfate most abundant GAG in blood vessels and bone responsible for stiffness of cartilage

49 Component of Connective Tissue (The Matrix) hyaluronic acid a type of GAG viscous, slippery substance forms an effective lubricant in joints constitutes much of the vitreous body of the eyeball WBC, sperm, and some bacteria produce hyaluronidase = enzyme that breaks down hyaluronic acid

50 Component of Connective Tissue (The Matrix) Proteoglycan gigantic molecule shaped like a testtube brush // proteoglycan form the core and the GAG project off of the proteoglycan forms thick colloids that creates strong structural bond between cells and extracellular macromolecules holds tissues together

51 Types of Fibrous Connective Tissue loose connective tissue // much gel-like ground substance between cells Types // areolar and reticular dense connective tissue // fibers fill spaces between cells Tendons types vary in fiber orientation dense regular connective tissue dense irregular connective tissue

52 Fibrous Loose Connective Tissue (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

53 Fibrous Loose CT / Areolar Tissue Ground substance Elastic fibers Collagenous fibers Fibroblasts (a) (b) 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

54 Fibrous Loose CT / Reticular Tissue Leukocytes Reticular fibers (a) (b) mesh of reticular fibers and fibroblasts forms supportive stroma (framework) for lymphatic organs found in lymph nodes, spleen, thymus and bone marrow

55 Fibrous Dense Regular Connective Tissue Collagen fibers Ground substance Fibroblast nuclei (a) (b) densely, packed, parallel collagen fibers compressed fibroblast nuclei tendons attach muscles to bones and ligaments hold bones together

56 Fibrous Dense Irregular Connective Tissue Bundles of Gland collagen fibers ducts Fibroblast nuclei Ground substance (a) (b) densely packed, randomly arranged, collagen fibers and few visible cells withstands unpredictable stresses deeper layer of skin; capsules around organs

57 Adipose Tissue = Another Form of CT 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

58 Adipose Tissue Blood vessel Adipocyte nucleus Lipid in adipocyte (a) (b) 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

59 Cartilage / Three Types types of cartilage vary with fiber types hyaline cartilage fibrocartilage elastic cartilage supportive connective tissue with flexible, rubbery matrix Cartilage gives shape to ear, tip of nose, and larynx No blood vessels // diffusion brings nutrients and removes wastes // heals slowly

60 Cells of Cartilage 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 matrix rich in chondroitin sulfate and contain collagen fibers

61 Hyaline Cartilage Matrix Cell nest Perichondrium Lacunae Chondrocytes (a) (b) 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 speech

62 Elastic Cartilage Perichondrium Elastic fibers Lacunae Chondrocytes (a) Blood vessel Adipocyte nucleus Lipid in adipocyte (a) (b) (b) cartilage containing elastic fibers covered with perichondrium provides flexible, elastic support external ear and epiglottis

63 Fibrocartilage Collagen fibers Chondrocytes (a) (a) Blood Adipocyte Lipid in Blood Adipocyte Lipid in vessel nucleus adipocyte vessel nucleus adipocyte (a) (b) (b) (b) cartilage containing large, coarse bundles of collagen fibers never has perichondrium resists compression and absorbs shock pubic symphysis, menisci, and intervertebral discs

64 Blood fluid connective tissue (Covered in Detail C19) transports cells and dissolved matter from place to place Platelets Neutrophils Lymphocyte Erythrocytes Monocyte 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

65 Bone (Covered in Detail C6) 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

66 Bone Tissue (compact bone) Concentric Lacunae Canaliculi lamellae of osteon Central canal Osteon (a) Blood vessel Adipocyte nucleus Lipid in adipocyte (a) (b) (b) 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

67 Excitable Tissues Muscular (C10) & Nervous Tissue (C12) Excitability a characteristic of 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

68 specialized for communication by electrical and chemical signals Nervous Tissue consists of neurons (nerve cells) detect stimuli respond quickly transmit coded information rapidly to other cells Nuclei of glial cells Axon Neurosoma Dendrites neuroglia (glial) protect and assist neurons housekeepers of nervous system neuron parts neurosoma (cell body) houses nucleus and other organelles cell s center of genetic control and protein synthesis dendrites multiple short, branched processes 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

69 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

70 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 Nuclei Striations Muscle fiber (a) (b)

71 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) Intercalated discs Striations Glycogen (a) (b)

72 Smooth Muscle Nuclei Muscle cells (a) (b) 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