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