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Classification of Tissues (Histology)Study Guide
Simple squamous epithelium
Photomicrograph: Simple squamous epitheliumforming part of the alveolar (air sac) walls (140).
Air sacsof lungtissue
Nuclei ofsquamous
epithelialcells
Location: Kidney glomeruli; airsacs of lungs; lining of heart,blood vessels, and lymphaticvessels; lining of ventral bodycavity (serosae).
Function: Allows passage ofmaterials by diffusion andfiltration in sites where protectionis not important; produceslubricating fluid in serosae.
Description: Single layer offlattened cells with disc-shapedcentral nuclei and sparsecytoplasm; the simplest of the epithelia.
Simple squamous epithelium
Simple cuboidal epithelium
Description: Single layer ofcubelike cells with large,spherical central nuclei.
Function: Secretion andabsorption.
Location: Kidney tubules;ducts and secretory portions ofsmall glands; ovary surface.
Photomicrograph: Simple cuboidal epitheliumin kidney tubules (430).
Simplecuboidalepithelialcells
Basementmembrane
Connectivetissue
Simple columnar epithelium
Description: Single layer of tallcells with round to oval nuclei;some cells bear cilia; layer maycontain mucus-secretingunicellular glands (goblet cells).
Photomicrograph: Simple columnar epitheliumof the small intestine (650).
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.
Microvilli
GobletcellSimplecolumnarepithelialcell
Basementmembrane
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.
Photomicrograph: Pseudostratified ciliatedcolumnar epithelium lining the human trachea(780).
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.
Trachea
Basementmembrane
Pseudo-stratifiedepitheliallayer
Gobletcell
Cilia
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.
Photomicrograph: Stratified squamousepithelium lining the esophagus (280).
Function: Protects underlyingtissues in areas subjected toabrasion.
Location: Nonkeratinized typeforms the moist linings of theesophagus, mouth, and vagina;keratinizedvarietyforms theepidermis ofthe skin, adry membrane.
Stratifiedsquamousepithelium
Nuclei
Basementmembrane
Connectivetissue
Stratified cuboidal epithelium
Photomicrograph: Stratified cuboidal epitheliumforming a salivary gland duct (290).
Description: Generally twolayers of cubelike cells.
Function: Protection.
Location: Largest ducts ofsweat glands, mammary glands,and salivary glands.
Basementmembrane
Cuboidalepithelialcells
Duct lumen
Stratified columnar epithelium
Photomicrograph: Stratified columnar epitheliumlining the male urethra (360).
Description: Several cell layers;basal cells usually cuboidal;superficial cells elongatedand columnar.
Function: Protection; secretion.
Location: Rare in the body;small amounts in male urethraand in large ducts of someglands.
Urethra
Stratifiedcolumnar
epithelium
Basementmembrane
Underlyingconnective
tissue
Transitional epithelium
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.
Description: Resembles bothstratified squamous and stratifiedcuboidal; basal cells cuboidal orcolumnar; surface cells domeshaped or squamous-like,depending ondegree oforganstretch.
Function: Stretches readily andpermits distension of urinaryorgan by contained urine.
Location: Lines the ureters,bladder, and part of the urethra.
Transitionalepithelium
BasementmembraneConnectivetissue
Mesenchymalcells
Groundsubstance
Fibers
Embryonic connective tissue: mesenchyme
Location: Primarily in embryo.
Function: Gives rise to allother connective tissue types.
Description: Embryonicconnective tissue; gel-likeground substance containingfibers; star-shapedmesenchymal cells.
Photomicrograph: Mesenchyme, an embryonicconnective tissue (385). The matrix is composedof the fluid ground substance (clear-appearing background)and fine, sparse fibers.
Connective tissue proper: loose connective tissue, areolar
Photomicrograph: Areolar connective tissue,a soft packaging tissue of the body (340).
Description: Gel-like matrix withall three fiber types; cells:fibroblasts, macrophages, mastcells, and some white blood cells.
Function: Wraps and cushionsorgans; its macrophagesphagocytize bacteria; playsimportant role in inflammation;holds and conveys tissue fluid.
Location: Widely distributedunder epithelia of body, e.g.,forms lamina propria of mucousmembranes; packages organs;surrounds capillaries.
Epithelium
Laminapropria
Collagenfibers
Fibroblastnuclei
Groundsubstance
Elasticfibers
Connective tissue proper: loose connective tissue, adipose
Photomicrograph: Adipose tissue from thesubcutaneous layer under the skin (350).
Description: Matrix as in areolarconnective tissue, but very sparse;closely packed adipocytes, or fatcells, have nucleus pushed to theside by large fat droplet.
Function: Provides reserve foodfuel; insulates against heat loss;supports and protects organs.
Location: Under skin in thehypodermis; around kidneys andeyeballs; within abdomen;in breasts.
Adiposetissue
Mammary glands
Nucleusof fat cell
Vacuolecontainingfat droplet
Connective tissue proper: loose connective tissue, reticular
Photomicrograph: Dark-staining network ofreticular connective tissue fibers forming theinternal skeleton of the spleen (350).
Description: Network ofreticular fibers in a typical looseground substance; reticularcells lie on the network.
Function: Fibers form a softinternal skeleton (stroma) thatsupports other cell typesincluding white blood cells,mast cells, and macrophages.
Location: Lymphoid organs(lymph nodes, bone marrow,and spleen).
Spleen
Reticularfibers
Whiteblood cell(lymphocyte)
Connective tissue proper: dense connective tissue, dense irregular
Photomicrograph: Dense irregular connectivetissue from the dermis of the skin (300).
Description: Primarilyirregularly arranged collagenfibers; some elastic fibers;major cell type is the fibroblast;defense cells and fat cells arealso present.
Function: Able to withstandtension exerted in manydirections; provides structuralstrength.
Location: Fibrous capsules oforgans and of joints; dermis ofthe skin; submucosa ofdigestive tract.
Fibrous layer ofjointcapsule
Collagenfibers
Nuclei offibroblasts
Connective tissue proper: dense connective tissue, dense regular
Photomicrograph: Dense regular connectivetissue from a tendon (425).
Description: Primarily parallelcollagen fibers; a few elasticfibers; major cell type is thefibroblast.
Function: Attaches muscles tobones or to muscles; attachesbones to bones; withstands greattensile stress when pulling forceis applied in one direction.
Location: Tendons, mostligaments, aponeuroses.
Shoulderjoint
Ligament
Tendon
Collagenfibers
Nuclei offibroblasts
Connective tissue proper: dense connective tissue, elastic
Photomicrograph: Elastic connective tissue inthe wall of the aorta (250).
Description: Dense regularconnective tissue containing ahigh proportion of elastic fibers.
Function: Allows recoil of tissuefollowing stretching; maintainspulsatile flow of blood througharteries; aids passive recoil oflungs following inspiration.
Location: Walls of large arteries;within certain ligaments associatedwith the vertebral column; withinthe walls of the bronchial tubes.
Aorta
Heart
Elasticfibers
Photomicrograph: Elastic connective tissue inthe wall of the aorta (250).
Cartilage: hyaline
Photomicrograph: Hyaline cartilage from acostal cartilage of a rib (470).
Description: Amorphous butfirm matrix; collagen fibers forman imperceptible network;chondroblasts produce thematrix and, when mature(chondrocytes), lie in lacunae.
Function: Supports andreinforces; serves as resilientcushion; resists compressivestress.
Location: Forms most of theembryonic skeleton; covers theends of long bones in jointcavities; forms costal cartilagesof the ribs; cartilages of the nose,trachea, andlarynx.
Costalcartilages
Matrix
Chondrocytein lacuna
Cartilage: elastic
Photomicrograph: Elastic cartilage from thehuman ear pinna; forms the flexible skeleton ofthe ear (510).
Description: Similar to hyalinecartilage, but more elasticfibers in matrix.
Function: Maintains the shapeof a structure while allowinggreat flexibility.
Location: Supports theexternal ear (pinna); epiglottis.
Chondrocytein lacuna
Matrix
Cartilage: fibrocartilage
Photomicrograph: Fibrocartilage from anintervertebral disc (175).
Description: Matrix similar to but less firm than that inhyaline cartilage; thickcollagen fibers predominate.
Function: Tensile strengthwith the ability to absorbcompressive shock.
Location: Intervertebraldiscs; pubic symphysis;discs of knee joint.
Intervertebraldiscs
Collagen fibers
Chondrocytesin lacunae
Others: bone (osseous tissue)
Photomicrograph: Cross-sectional view of bone(175).
Description: Hard, calcifiedmatrix containing many collagenfibers; osteocytes lie inlacunae. Very well vascularized.
Function: Supports andprotects (by enclosing); provideslevers for the muscles to act on;stores calcium and otherminerals and fat; marrow insidebones is the site for blood cellformation (hematopoiesis).
Location: Bones.
Centralcanal
Lacunae
Lamella
Connective tissue: blood
Photomicrograph: Smear of human blood (1650);shows two white blood cells surrounded by redblood cells.
Description: Red andwhite blood cells in a fluidmatrix (plasma).
Function: Transportrespiratory gases, nutrients,wastes, and othersubstances.
Location: Contained withinblood vessels.
Red blood cells(erythrocytes)
White blood cells:
Plasma
• Lymphocyte• Neutrophil
Skeletal muscle
Striations
Nuclei
Part ofmusclefiber (cell)
Description: Long,cylindrical, multinucleate cells;obvious striations.
Function: Voluntarymovement; locomotion;manipulation of theenvironment; facial expression.
Location: In skeletal musclesattached to bones oroccasionally to skin.
Photomicrograph: Skeletal muscle (450).Notice the obvious banding pattern and thefact that these large cells are multinucleate.
Cardiac muscle
Photomicrograph: Cardiac muscle (355);notice the striations, branching of cells, andthe intercalated discs.
Description: Branching,striated, generally uninucleatecells that interdigitate atspecialized junctions(intercalated discs).
Function: As it contracts,it propels blood into thecirculation; involuntarycontrol.
Location: The walls of the heart. Nucleus
Striations
Intercalateddiscs
Cardiac muscle
Smooth muscle
Photomicrograph: Sheet of smooth muscle fromthe digestive tract (465).
Description: Spindle-shaped cellswith central nuclei; no striations;cells arranged closely to formsheets.
Function: Propels substances orobjects (foodstuffs, urine, a baby)along internal passageways;involuntary control.
Location: Mostly in the walls ofhollow organs.
Smoothmuscle
cell
Nuclei
Nervous tissue
Photomicrograph: Neurons (125).
Description: Neurons arebranching cells; cell processesthat may be quite long extend fromthe nucleus-containing cell body;also contributing to nervous tissueare nonconducting supportingcells, neuroglia (not illustrated).
Function: Transmit electricalsignals from sensory receptorsand to effectors (muscles andglands) that control the activityof the effector organs.
Location: Brain, spinalcord, and nerves.
Cell body of a neuron
Neuronprocesses
Nuclei ofneuroglia
Neuron processes Cell body
Dendrites
Axon