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4 PART 1

4 PART 1. Tissues Pages 64-73, 77-95. Tissues. Cells work together in functionally related groups called tissues Tissue A group of closely associated cells that perform related functions and are similar in structure. Four Basic Tissue Types and Basic Functions.

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4 PART 1

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  1. 4 PART 1 Tissues Pages 64-73, 77-95

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

  3. Four Basic Tissue Types and Basic Functions • Epithelial tissue—covering • Connective tissue—support • Muscle tissue—movement • Nervous tissue—control

  4. Epithelial Tissue • Covers a body surface or lines a body cavity • Forms parts of most glands • Functions of epithelia • Protection • Diffusion • Absorption, secretion, and ion transport • Filtration • Forms slippery surfaces

  5. Special Characteristics of Epithelia • Cellularity • Cells separated by minimal extracellular material • Specialized contacts • Cells joined by special junctions • Polarity • Cell regions of the apical surface differ from the basal surface

  6. Special Characteristics of Epithelia • Support by connective tissue • Avascular butinnervated • Epithelia receive nutrients from underlying connective tissue • Regeneration • Lost cells are quickly replaced by cell division

  7. Special Characteristics of Epithelia Narrow extracellular space Cilia Microvilli Apical region of an epithelial cell Cell junctions Tight junction Epithelium Adhesive belt Desmosome Gap junction Basal region Basal lamina Basement membrane Reticular fibers Nerve ending Connective tissue Capillary Figure 4.1

  8. Classifications of Epithelia • First name of tissue indicates number of cell layers • Simple—one layer of cells • Stratified—more than one layer of cells

  9. Classifications of Epithelia • 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

  10. Classifications of Epithelia Apical surface Squamous Basal surface Simple Apical surface Cuboidal Basal surface Stratified (a) Classification based on number of cell layers Columnar (b) Classification based on cell shape Figure 4.2

  11. Simple Squamous Epithelium • Description—single layer; flat cells with disc-shaped nuclei • Function • Passage of materials by passive diffusion and filtration • Secretes lubricating substances in serosae • Location • Alveoli of lungs • Lining of heart, blood, and lymphatic vessels • Lining of ventral body cavity (serosae)

  12. Simple Squamous Epithelium (a) Simple squamous epithelium Description: Single layer of flattened cells with disc-shaped central nuclei and sparse cytoplasm; the simplest of the epithelia. Air sacs of lung tissue Function: Allows passage of materials by diffusion and filtration in sites where protection is not important; secretes lubricating substances in serosae. Nuclei of squamous epithelial cells Location: Kidney glomeruli; air sacs of lungs; lining of heart, blood vessels, and lymphatic vessels; lining of ventral body cavity (serosae). Photomicrograph: Simple squamous epithelium forming part of the alveolar (air sac) walls (200). Figure 4.3a

  13. Simple Cuboidal Epithelium • Description • Single layer of cubelike cells with large, spherical central nuclei • Function • Secretion and absorption • Location • Kidney tubules, secretory portions of small glands, ovary surface

  14. Simple Cuboidal Epithelium (b) Simple cuboidal epithelium Description: Single layer of cubelike cells with large, spherical central nuclei. Simple cuboidal epithelial cells Function: Secretion and absorption. Basement membrane Location: Kidney tubules; ducts and secretory portions of small glands; ovary surface. Connective tissue Photomicrograph: Simple cuboidal epithelium in kidney tubules (430). Figure 4.3b

  15. Simple Columnar Epithelium • Description—single layer of column-shaped (rectangular) cells with oval nuclei • Some bear cilia at their apical surface • May contain goblet cells • Function • Absorption; secretion of mucus, enzymes, and other substances • Ciliated type propels mucus or reproductive cells by ciliary action

  16. Simple Columnar Epithelium • Location • Nonciliated form • Lines digestive tract, gallbladder, ducts of some glands • Ciliated form • Lines small bronchi, uterine tubes, and uterus

  17. Figure 4.3c Epithelial tissues. 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).

  18. Pseudostratified Columnar Epithelium • Description • All cells originate at basement membrane • Only tall cells reach the apical surface • Nuclei lie at varying heights within cells • Gives false impression of stratification

  19. Pseudostratified Columnar Epithelium • Function—secretion of mucus; propulsion of mucus by cilia • Locations • Nonciliated type • Ducts of male reproductive tubes • Ducts of large glands • Ciliated variety • Lines trachea and most of upper respiratory tract

  20. Figure 4.3d Epithelial tissues. 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

  21. Figure 4.4 Goblet cell (unicellular exocrine gland). Microvilli Secretoryvesiclescontainingmucin Golgiapparatus Rough ER Nucleus

  22. Stratified Epithelia • Properties • Contain two or more layers of cells • Regenerate from below (basal layer) • Major role is protection • Named according to shape of cells at apical layer

  23. Stratified Squamous Epithelium • Description • Many layers of cells are squamous in shape • Deeper layers of cells appear cuboidal or columnar • Thickest epithelial tissue • Adapted for protection from abrasion

  24. Stratified Squamous Epithelium • Two types—keratinized and non-keratinized • Keratinized • Location—epidermis • Contains the protective protein keratin • Waterproof • Surface cells are dead and full of keratin • Non-keratinized • Forms moist lining of body openings

  25. Stratified Squamous Epithelium (e) Stratified squamous epithelium Description: Thick membrane composed of several cell layers; basal cells are cuboidal or columnar and metabolically active; surface cells are flattened (squamous); in the keratinized type, the surface cells are full of keratin and dead; basal cells are active in mitosis and produce the cells of the more superficial layers. Stratified squamous epithelium Nuclei Function: Protects underlying tissues in areas subjected to abrasion. Basement membrane Location: Nonkeratinized type forms the moist linings of the esophagus, mouth, and vagina; keratinized variety forms the epidermis of the skin, a dry membrane. Connective tissue Photomicrograph: Stratified squamous epithelium lining the esophagus (430). Figure 4.3e

  26. Stratified Cuboidal Epithelium • Description—generally two layers of cube-shaped cells • Function—protection • Location • Forms ducts of • Mammary glands • Salivary glands • Largest sweat glands

  27. Stratified Cuboidal Epithelium (f) Stratified cuboidal epithelium Description: Generally two layers of cubelike cells. Basement membrane Cuboidal epithelial cells Function: Protection Location: Largest ducts of sweat glands, mammary glands, and salivary glands. Duct lumen Photomicrograph: Stratified cuboidal epithelium forming a salivary gland duct (285). Figure 4.3f

  28. Stratified Columnar Epithelium • Description—several layers; basal cells usually cuboidal; superficial cells elongated • Function—protection and secretion • Location • Rare tissue type • Found in male urethra and large ducts of some glands

  29. Figure 4.3g Epithelial tissues. 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

  30. Transitional Epithelium (h) Transitional epithelium Description: Resembles both stratified squamous and stratified cuboidal; basal cells cuboidal or columnar; surface cells dome shaped or squamous-like, depending on degree of organ stretch. Transitional epithelium Function: Stretches readily and permits distension of urinary organ by contained urine. Basement membrane Location: Lines the ureters, bladder, and part of the urethra. Connective tissue Photomicrograph: Transitional epithelium lining the bladder, relaxed state (390); note the bulbous, or rounded, appearance of the cells at the surface; these cells flatten and become elongated when the bladder is filled with urine. Figure 4.3h

  31. Classes of Connective Tissue • Most diverse and abundant tissue • Main classes • Connective tissue proper • Cartilage • Bone tissue • Blood • Cells separated by a large amount of extracellular matrix • Extracellular matrix is composed of ground substance and fibers

  32. Structural Elements of Connective Tissue • Connective tissues differ in structural properties • Differences in types of cells • Differences in composition of extracellular matrix • However, connective tissues all share structural elements

  33. Structural Elements of Connective Tissue • Cells—primary cell type of connective tissue produces matrix • Fibroblasts • Make protein subunits • Secrete molecules that form the ground substance • Chondroblasts—secrete matrix in cartilage • Osteoblasts—secrete matrix in bone

  34. Structural Elements of Connective Tissue • Cells (continued) • Blood cells—an exception • Do not produce matrix • Areolar connective tissue contains • Fat cells • White blood cells • Mast cells

  35. Structural Elements of Connective Tissue Cell types Extracellular matrix Ground substance Macrophage Fibers Collagen fiber Elastic fiber Fibroblast Reticular fiber Lymphocyte Fat cell Capillary Mast cell Neutrophil Figure 4.9

  36. Structural Elements of Connective Tissue • Fibers—function in support • Collagen fibers—strongest; resist tension • Reticular fibers—bundles of special type of collagen • Cover and support structures • Elastic fibers—contain elastin • Recoil after stretching

  37. Structural Elements of Connective Tissue • Ground substance • Is produced by primary cell type of the tissue • Is usually gel-like • Cushions and protects body structures • Holds tissue fluid • Blood is an exception • Plasma is not produced by blood cells

  38. Connective Tissue Proper • Has two subclasses • Loose connective tissue • Areolar, adipose, and reticular • Dense connective tissue • Dense irregular, dense regular, and elastic

  39. Classes of Connective Tissue Table 4.2 (1 of 2)

  40. Areolar Connective Tissue—A Model Connective Tissue • Areolar connective tissue • Underlies epithelial tissue • Surrounds small nerves and blood vessels • Has structures and functions shared by other CT • Borders all other tissues in the body

  41. Areolar Connective Tissue (b) Connective tissue proper: loose connective tissue, areolar Description: Gel-like matrix with all three fiber types; cells: fibroblasts, macrophages, mast cells, and some white blood cells. Elastic fibers Function: Wraps and cushions organs; its macrophages phagocytize bacteria; plays important role in inflammation; holds and conveys tissue fluid. Collagen fibers Location: Widely distributed under epithelia of body, e.g., forms lamina propria of mucous membranes; packages organs; surrounds capillaries. Fibroblast nuclei Epithelium Photomicrograph: Areolar connective tissue, a soft packaging tissue of the body (360). Lamina propria Figure 4.10b

  42. Areolar Connective Tissue • Tissue fluid (interstitial fluid) • Watery fluid occupying extracellular matrix • Tissue fluid derives from blood • Ground substance • Viscous, spongy part of extracellular matrix • Consists of sugar and protein molecules • Made and secreted by fibroblasts

  43. Areolar Connective Tissue • Main battlefield in fight against infection • Defenders gather at infection sites • Macrophages • Mast cells • White blood cells • Neutrophils, lymphocytes, and eosinophils

  44. Adipose Tissue (c) Connective tissue proper: loose connective tissue, adipose Description: Matrix as in areolar, but very sparse; closely packed adipocytes, or fat cells, have nucleus pushed to the side by large fat droplet. Function: Provides reserve food fuel; insulates against heat loss; supports and protects organs. Nucleus of fat cell Location: Under skin in the hypodermis; around kidneys and eyeballs; within abdomen; in breasts. Vacuole containing fat droplet Adipose tissue Photomicrograph: Adipose tissue from the subcutaneous layer under the skin (500). Mammary glands Figure 4.10c

  45. Reticular Connective Tissue (d) Connective tissue proper: loose connective tissue, reticular Description: Network of reticular fibers in a typical loose ground substance; reticular cells lie on the network. Function: Fibers form a soft internal skeleton (stroma) that supports other cell types including white blood cells, mast cells, and macrophages. White blood cell (lymphocyte) Location: Lymphoid organs (lymph nodes, bone marrow, and spleen). Reticular fibers Spleen Photomicrograph: Dark-staining network of reticular connective tissue fibers forming the internal skeleton of the spleen (555). Figure 4.10d

  46. Figure 4.10e Connective tissues. Connective tissue proper: dense connective tissue, dense irregular Description: Primarilyirregularly arranged collagenfibers; some elastic fibers;major cell type is the fibroblast;defense cells and fat cells arealso present. Nuclei offibroblasts Function: Able to withstandtension exerted in manydirections; provides structuralstrength. Collagenfibers Location: Fibrous capsules oforgans and of joints; dermis ofthe skin; submucosa ofdigestive tract. Photomicrograph: Dense irregular connectivetissue from the dermis of the skin (300). Fibrous layer ofjointcapsule

  47. Figure 4.10f Connective tissues. Connective tissue proper: dense connective tissue, dense regular Description: Primarily parallelcollagen fibers; a few elasticfibers; major cell type is thefibroblast. Collagenfibers Nuclei offibroblasts Function: Attaches muscles tobones or to muscles; attachesbones to bones; withstands greattensile stress when pulling forceis applied in one direction. Location: Tendons, mostligaments, aponeuroses. Photomicrograph: Dense regular connectivetissue from a tendon (425). Shoulderjoint Ligament Tendon

  48. Elastic Connective Tissue (g) Connective tissue proper: dense connective tissue, elastic Description: Dense regular connective tissue containing a high proportion of elastic fibers. Function: Allows recoil of tissue following stretching; maintains pulsatile flow of blood through arteries; aids passive recoil of lungs following inspiration. Elastic fibers Location: Walls of large arteries; within certain ligaments associated with the vertebral column; within the walls of the bronchial tubes. Photomicrograph: Elastic connective tissue in the wall of the aorta (85). Aorta Heart Figure 4.10g

  49. Cartilage • Firm, flexible tissue • Contains no blood vessels or nerves • Matrix contains up to 80% water • Cell type—chondrocyte • Hyaline cartilage • Elastic cartilage • Fibrocartilage

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