Tissues

1. 4 Tissues

2. I. Tissues A. Cells work together in functionally related groups called tissues B. Tissue - A group of closely associated cells that perform related functions and are similar in structure

3. II. Four Basic Tissue Types and Basic Functions ► Epithelial tissues - covering ► Connective tissues - support ► Muscle tissues - movement ► Nervous tissue - control

4. III. Epithelial Tissue A. Covers all body surfaces and lines all body cavities B. Functions of epithelia 1. protection 2. secretion 3. absorption 4. diffusion 5. filtration 6. sensory reception

5. C. Special Characteristics of Epithelia 1. cellularity - cells separated by minimal extracellular material 2. specialized contacts - cells joined by special junctions 3. polarity - cell regions of the apical surface differ from the basal surface 4. avascular (no blood vessels) - epithelia receive nutrients from underlying connective tissue 5. regeneration - lost cells are quickly replaced by cell division

6. Cilia Narrowextracellularspace Microvilli Apical region ofan epithelial cell Cell junctions Tight junction Epithelium Adhesive belt Desmosome Gap junction Basal region Basallamina Basementmembrane Reticularfibers Nerve ending Connectivetissue Capillary

7. ► First name of tissue indicates number of cell layers Simple epithelia - single layer of cells attached to basement membrane Stratified epithelia - multiple layers of cells (basal cells attached to basement membrane) ► Last name of tissue describes shape of cells Squamous—cells are wider than tall (plate-like) Cuboidal—cells are as wide as tall, like cubes Columnar—cells are taller than they are wide, like columns

8. Apical surface Basal surface Simple Apical surface Basal surface Stratified Classification based on numberof cell layers

9. Squamous Cuboidal Columnar Classification based on cell shape

10. Simple Squamous Epithelium • Description • A. single layer; flat cells with disc-shaped nuclei • Functions • A. passage of materials by passive diffusion and filtration • B. secretes lubricating substances in serosae • Location • A. alveoli of lungs • B. renal corpuscles • C. lining of heart, blood, and lymphatic vessels • D. lining of ventral body cavity (serosae)

11. Simple squamous epithelium Description: Single layer offlattened cells with disc-shapedcentral nuclei and sparsecytoplasm; the simplest of the epithelia. Air sacsof lungtissue Nuclei ofsquamousepithelialcells Function: Allows passage ofmaterials by diffusion andfiltration in sites where protectionis not important; produceslubricating fluid in serosae. Location: Kidney glomeruli; airsacs of lungs; lining of heart,blood vessels, and lymphaticvessels; lining of ventral bodycavity (serosae). Photomicrograph: Simple squamous epitheliumforming part of the alveolar (air sac) walls (140).

12. Simple squamous epithelium

13. Simple Cuboidal Epithelium • Description • A. single layer of cube-like cells; large, spherical central nuclei • Function • A. secretion and absorption • Location • A. kidney tubules, small glands, ovary surface

14. Simple cuboidal epithelium Description: Single layer ofcubelike cells with large,spherical central nuclei. Simplecuboidalepithelialcells Function: Secretion andabsorption. Basementmembrane Location: Kidney tubules;ducts and secretory portions ofsmall glands; ovary surface. Connectivetissue Photomicrograph: Simple cuboidal epitheliumin kidney tubules (430).

16. Simple Columnar Epithelium • Description—single layer of column-shaped (rectangular) cells • A. some bear cilia at their apical surface • B. may contain goblet cells • Function • A. absorption; secretion of mucus, enzymes, and other substances • B. ciliated type propels mucus or reproductive cells by ciliary action • Location • A. nonciliated- stomach, intestines, gall bladder • B. ciliated – bronchi, uterine tubes, uterus

17. Simple columnar epithelium Description: Single layer of tallcells with round to oval nuclei;some cells bear cilia; layer maycontain mucus-secretingunicellular glands (goblet cells). Microvilli Gobletcell Simplecolumnarepithelialcell Function: Absorption; secretionof mucus, enzymes, and othersubstances; ciliated type propelsmucus (or reproductive cells) byciliary action. Location: Nonciliated type linesmost of the digestive tract(stomach to anal canal),gallbladder, and excretory ductsof some glands; ciliated varietylines small bronchi,uterine tubes,and someregions ofthe uterus. Basementmembrane Photomicrograph: Simple columnar epitheliumof the small intestine (650).

19. Pseudostratified Columnar Epithelium • Description • A.like simple columnar, but uneven surface • B. may contain goblet cells and bear cilia • C. nuclei lie at varying heights within cells • D. gives false impression of stratification • Function—secretion of mucus; propulsion of mucus by cilia • Locations • A. non-ciliated type • i. ducts of male reproductive tubes • ii. ducts of large glands • B. ciliated type • i. lines trachea and most of upper respiratory tract

20. Pseudostratified columnar epithelium Description: Single layer ofcells of different heights, somenot reaching the free surface;nuclei seen at different levels;may contain mucus-secretinggoblet cells and bear cilia. Cilia Gobletcell Pseudo-stratifiedepitheliallayer Function: Secretion, particularlyof mucus; propulsion of mucusby ciliary action. Location: Nonciliated type inmale’s sperm-carrying ducts andducts of large glands; ciliatedvariety lines the trachea,most of the upper respiratorytract. Basementmembrane Photomicrograph: Pseudostratified ciliatedcolumnar epithelium lining the human trachea(780). Trachea

22. Stratified Squamous Epithelium • Description • A. many layers of cells are squamous in shape • B. deeper layers of cells appear cuboidal or columnar • C. thickest epithelial tissue • D. adapted for protection from abrasion • 1. Keratinized • a. Location - epidermis of the skin • b. contains the protective protein keratin • c. waterproof • d. surface cells are dead and full of keratin • 2. Non-keratinized • a. Forms moist lining of body openings

23. Stratified squamous epithelium Description: Thick membranecomposed of several cell layers;basal cells are cuboidal orcolumnar and metabolicallyactive; surface cells are flattened(squamous); in the keratinizedtype, the surface cells are full ofkeratin and dead; basal cells areactive in mitosis and produce thecells of the more superficiallayers. Stratifiedsquamousepithelium Nuclei Function: Protects underlyingtissues in areas subjected toabrasion. Basementmembrane Connectivetissue Location: Nonkeratinized typeforms the moist linings of theesophagus, mouth, and vagina;keratinizedvarietyforms theepidermis ofthe skin, adry membrane. Photomicrograph: Stratified squamousepithelium lining the esophagus (280).

25. Stratified Cuboidal Epithelium(rare) • Description - generally two layers of cube-shaped cells • Function - protection • Location • Forms ducts of: • 1. mammary glands • 2. salivary glands • 3. largest sweat glands

26. Stratified cuboidal epithelium Description: Generally twolayers of cubelike cells. Basementmembrane Cuboidalepithelialcells Function: Protection. Location: Largest ducts ofsweat glands, mammary glands,and salivary glands. Duct lumen Photomicrograph: Stratified cuboidal epitheliumforming a salivary gland duct (290).

28. Stratified Columnar Epithelium (rare) • Description • A. several layers • B. basal cells usually cuboidal superficial cells elongated • Function - protection and secretion • Location • A. rare tissue type • B. found in male urethra and large ducts of some glands

29. Stratified columnar epithelium Description: Several cell layers;basal cells usually cuboidal;superficial cells elongatedand columnar. Stratifiedcolumnarepithelium Basementmembrane Function: Protection; secretion. Underlyingconnectivetissue Location: Rare in the body;small amounts in male urethraand in large ducts of someglands. Photomicrograph: Stratified columnar epitheliumlining the male urethra (360). Urethra

31. Transitional Epithelium • Description • A. characteristics of stratified cuboidal and stratified squamous • B. superficial cells dome-shaped when bladder is relaxed • C. squamous when full • Function • A. permits distension of urinary organs when filled with urine • Location-urinary bladder and ureters

32. Transitional epithelium Description: Resembles bothstratified squamous and stratifiedcuboidal; basal cells cuboidal orcolumnar; surface cells domeshaped or squamous-like,depending ondegree oforganstretch. Transitionalepithelium Function: Stretches readily andpermits distension of urinaryorgan by contained urine. Basementmembrane Location: Lines the ureters,bladder, and part of the urethra. Connectivetissue Photomicrograph: Transitional epitheliumlining the bladder, relaxed state (365); note thebulbous, or rounded, appearance of the cells atthe surface; these cells flatten and becomeelongated when the bladder is filled with urine.

34. V. Glands • A. Endocrine glands (INTO the blood) • ductless glands • secrete directly into surrounding tissue fluid • produce messenger molecules called hormones • B. Exocrine glands (ONTO a surface) • 1. ducts carry substances to epithelial surface • a. mucus-secreting glands • b. sweat and oil glands • c. salivary glands • d. liver and pancreas

35. C. Unicellular Exocrine Glands (The Goblet Cell) • 1. goblet cells produce mucin • 2. mucin water  mucus • 3. protects and lubricates many internal body surfaces • 4. goblet cells are a unicellular exocrine gland (e.g. intestine)

36. D. Multicellular Exocrine Glands • 1. have two basic parts • 2. epithelium-walled duct • 3. classified by structure of duct • a. simple • b. compound • c. tubular • d. alveolar • e. tubuloalveolar

37. Simple duct structure Compound duct structure (duct does not branch) (duct branches) Tubularsecretorystructure Simple branchedtubular Simpletubular Compound tubular ExampleStomach (gastric)glands ExampleIntestinal glands ExampleDuodenal glands of small intestine Alveolarsecretorystructure Simple branchedalveolar Simplealveolar Compound alveolar Compoundtubuloalveolar ExampleNo importantexample inhumans ExampleSebaceous (oil)glands ExampleMammary glands ExampleSalivary glands Surface epithelium Secretory epithelium Duct

38. E. Cell Junctions • 1. factors binding epithelial cells together • 2. adhesion proteins link plasma membranes of adjacent cells • F. Special cell junctions • 1. tight junctions - close off intercellular space • a. found at apical region of most epithelial tissues types • b. some proteins in plasma membrane of adjacent cells are fused • c. prevent molecules from passing between cells • 2. adhesive belt junctions - anchoring junction • 3. transmembrane linker proteins • a. attach to cytoskeleton and bind adjacent cells

39. 4. desmosomes—main junctions for binding cells together • a. scattered along abutting sides of adjacent cells • b. intermediate filaments extend across the cytoplasm • c. and anchor at desmosomes on opposite side of the cell • d. are common in cardiac muscle and epithelial tissue • 5. gap junctions - passageway between two adjacent cells • a. let small molecules move directly between cells • b. cells are connected by hollow protein channel • c. passage of small atoms (e.g. ions) or molecules • d. function in intercellular communication

40. Plasma membranesof adjacent cells Microvilli Intercellularspace Basement membrane Intercellularspace Intercellularspace Plaque Channelbetween cells(connexon) Interlockingjunctionalproteins Intercellularspace Linkerglycoproteins(cadherins) Intermediatefilament(keratin) Tight junctions: Impermeablejunctions prevent molecules frompassing through the intercellularspace. Desmosomes: Anchoring junctionsbind adjacent cells together and helpform an internal tension-reducingnetwork of fibers. Gap junctions: Communicatingjunctions allow ions and smallmolecules to pass from one cell to thenext for intercellular communication.

41. G. The Basal Lamina • 1. at boundary between the epithelium and connective tissue • 2. non-cellular supporting sheet between the epithelial tissue • 3. connective tissue deep to it • 4. consists of proteins secreted by epithelial cells • 5. Functions • a. determining which molecules from capillaries enter the epithelium • b. scaffolding along which regenerating epithelial tissue cells can migrate • c. underlying connective tissue deep to it form • the basement membrane

42. VI. Epithelial Surface Features • A. Microvilli—fingerlike extensions of plasma membrane • 1. have a core of actin filaments that stiffen the microvillus • 2. abundant in kidney tubules and small intestine • 3. surface across which small molecules enter or leave cells

43. Microvilli Microvillus Actinfilaments

44. B. Cilia – whiplike extensions of apical surface membranes • 1. microtubules held together by cross-linking proteins • 2. microtubules arranged in pairs called doublets • 3. movement is generated when adjacent doublets grip each • other with the motor protein dynein • 4. cilia originate as microtubules assemble around centrioles

45. Cilia Layer of mucus Cell surface

46. VII. Connective Tissue • A. Most diverse and abundant tissue • B. Main classes of connective tissue • 1. connective tissue proper • 2. cartilage • 3. bone tissue • 4. blood

47. C. Important functions of connective tissue type • 1. form basis of the skeleton • 2. store and carry nutrients • 3.surround blood vessels and nerves • 4. support and binding of other tissues • 5. holding body fluids (interstitial fluid  lymph) • 6. defending body against infection • 7. storing nutrients as fat and protection

48. D. Special Characteristics of Connective Tissue • 1. few cells, abundant extracellular matrix • 2. extracellular matrix is composed of ground substance • 3. extracellular fibers • 4. extracellular matrix produced by cells called fibroblasts • 5. common embryonic origin is mesenchyme

49. E. Structural Elements of Connective Tissue • 1. connective tissues differ in structural properties • 2. differences in types of cells • 3. differences in composition of extracellular matrix • 4. however, connective tissues all share structural elements

50. F. Cells • 1. fibroblasts - primary cell type of connective tissues produces the extracellular matrix • 2. chondroblasts secrete matrix in cartilage (chondro) • 3. osteoblasts secrete matrix in bone (osteo)