Ch. 4: Tissue: The Living Fabric

MicroscopyEpithelial TissueConnective TissueNervous TissueMuscle TissueCovering and Lining MembranesWound repair; development

Microscopy

Microscopic AnatomyFix (Preserve)Section (Slice)Stain (Add Contrast)

Light Microscopy Add colorDifferent stains for different tissues

H&E the defaultDifferent aspects of different tissues

Electron MicroscopyAdd heavy metal to deflect electron beam

Artifacts of fixation, sectioning, staining

Skeletal muscle, H&E stainwww.anatomy.uiowa.edu/genhisto/GHWIN/unit1/image/i-08.jpg

Light microscopy: organ of Corti, earKeele University, UK, www.keele.ac.uk/depts/bi/emunit/galleries/gallery1/index.htm

Scanning electron microscopy: organ of Corti, earKeele University, UK, www.keele.ac.uk/depts/co/em96/em96.htm

Outer hair cells, earScanning and transmission electron micrographs

Keele University, UK, www.keele.ac.uk/depts/co/em96/em96.htm

Epithelial Tissue

Special CharacteristicsPolarity, sidedness: apical (microvilli), basalSpecialized contacts on the sides: tight junctions,

desmosomesSupported by connective tissue: basal lamina

(noncellular) and reticular connective tissue belowAvascular, innervatedHigh regeneration rate

ClassificationGlandular

Epithelial Tissue

Special CharacteristicsClassification

Two-part namesPart 1: cell layers

Simple (1), stratified (>1)Part 2: shape (of apical layer in stratified)

Squamous, cuboidal, columnarGlandular

Figure 4.1

Figure 4.2a

Figure 4.2b

Figure 4.2c

Figure 4.2d

Figure 4.2e

Figure 4.2f

Epithelial Tissue

Special CharacteristicsClassificationGlandular

Endocrine glandsMake & release hormones into blood; ductless;

most are small organs; ch. 16Exocrine glands

Make & secrete product to “outside”Unicellualr: goblet cell make mucin, forms mucus;

resp & GI tractsMulticellular: duct & secretory unit (acinus); sweat,

various in GI tract, mammary, salivary

Figure 4.3

Goblet cellUnicellular exocrine gland

Figure 4.4

Types of multicellular exocrine glandsClassified by structure

Connective Tissue

Common CharacteristicsOrigin: embryonic mesenchymeLarge amount of extracellular matrix

Structural ElementsGround substance – between the cellsFibers

CollagenElasticReticular

CellsSee Fig 4.6. -blasts vs. -cytes

Types

Figure 4.6

Connective TissueTypes

Connective Tissue ProperLoose

Areolar: support, hold fluid, defense v. infectionAdipose: cushion, store energy, insulate; often subQReticular: like areolar but only retic fibers; many

lymphocytes; lymph nodes, spleen, bone marrowDense (Fibrous: fibers are main component)

Regular: unidirectional collagen fibers; ligaments, tendons

Irregular: multidirectional collagen fibers; makes sheets; dermis, joint capsules, etc.

Elastic: elastic (large) arteriesCartilageBoneBlood

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Areolar connective tissue as general connective tissue example

Macrophage

Fibroblast

Lymphocyte

Fat cell

Mast cell

Neutrophil

Capillary

Cell typesExtracellular matrix

• Collagen fiber• Elastic fiber• Reticular fiber

Ground substance

Figure 4.7

Figure 4.8a

Figure 4.8b

Figure 4.8c

Figure 4.8d

Figure 4.8e

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(f) Connective tissue proper: dense connective tissue, elastic

Description: Dense regularconnective tissue containing a highproportion of elastic fibers.

Function: Allows recoil of tissuefollowing stretching; maintainspulsatile flow of blood througharteries; aids passive recoil of lungsfollowing inspiration.

Location: Walls of large arteries;within certain ligaments associatedwith the vertebral column; within thewalls of the bronchial tubes.

Elastic fibers

Aorta

HeartElastic connective tissue in the wall of the aorta (250x)

Figure 4.8f

Connective Tissue

Common CharacteristicsStructural ElementsTypes

Connective Tissue ProperCartilage

Hyaline c.Elastic c.Fibrocartilage

BoneBlood

Collagen• Most abundant protein in the body• Type I (most common): In bone, scar tissue, tendons,

ligaments.

• Type II: Hyaline cartilage.

• Type III: Found in extracellular matrix of early granulation (wound healing) tissue; replaced by type I collagen in mature scar tissue.

• Type IV: Lens of eye; basal lamina beneath epithelium (esp. in skin, beneath epidermis); capillaries, including glomeruli.

• Type V: Interstitial tissue (loose connective tissue); placenta.

• List goes up to XXVIII=28…

Collagen StructureHas 3 subunits (strands) which wrap around each other with a right-handed (RH) twist – i.e. a triple helix.

Each subunit (strand) is a LH helix (not an -helix which is RH).

Combination of RH and LH helices makes collagen hard to stretch.

How to tell the handedness of a helix: fingers show sense of rotation when travelling in direction that thumb points.

http://en.wikipedia.org/wiki/Image:Collagentriplehelix.png

Julian Voss-Andreae"Unraveling Collagen:

a metaphor for aging and growth”

Figure 4.8g

Figure 4.8h

Figure 4.8i

Connective Tissue

Common CharacteristicsStructural ElementsTypes

Connective Tissue ProperCartilageBoneBlood

Figure 4.8j

Connective Tissue

Common CharacteristicsStructural ElementsTypes

Connective Tissue ProperCartilageBoneBlood

Develops from mesenchymeHas a noncellular matrix - plasma

Figure 4.8k

Nervous Tissue

NeuronsExcitable (electro-chemically)Brain, spinal cord, nerves, some organsCell body = somaDendrites receive inputAxon carries output

Neuroglia = glial cellsSupport, insulate (electrically), protectNot excitable

Figure 4.9

Muscle TissueTypes of MuscleBy Looks: striated vs smooth

StriatedSkeletalCardiac

SmoothBy control: voluntary vs involuntary

Voluntary: skeletalInvoluntary: cardiac, smooth

Figure 4.10a

Figure 4.10b

Figure 4.10c

Covering and Lining Membranes

Cutaneous membrane (Skin)“largest organ”; epidermis over dermis; dry; ch. 5

Mucous membranes (mucosae)Line body cavities that connect to outside; wetSimple columnar or stratified squamous epithelium over

lamina propria (loose areolar conn. tiss.)Often adapted for absorption & secretionSome but not all secrete mucus

Serous membranes (serosae)In ventral body cavities: thorax, abdominopelvicHave inner (visceral) & outer (parietal) layers

Figure 4.11

Figure 4.11

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Minor skin wound repair: regeneration and fibrosis

1 Inflammation sets the stage:• Severed blood vessels bleed and inflammatory chemicals are released.• Local blood vessels become more permeable, allowing white blood cells, fluid, clotting proteins and other plasma proteins to seep into the injured area.• Clotting occurs; surface dries and forms a scab.

2 Organization restores the bloodsupply:• The clot is replaced by granulation tissue, which restores the vascular supply.• Fibroblasts produce collagen fibers that bridge the gap.• Macrophages phagocytize cell debris.• Surface epithelial cells multiply and migrate over the granulation tissue.

Scab Blood clot in incised wound

Epidermis

Vein

Inflammatory chemicals

Migrating whiteblood cell

Artery

Regenerating epithelium

Area ofgranulationtissue ingrowth

Fibroblast

Macrophage

3 Regeneration and fibrosiseffect permanent repair:• The fibrosed area matures and contracts; the epithelium thickens.• A fully regenerated epithelium with an underlying area of scar tissue results.

Regenerated epithelium

Fibrosed area Fig. 4.12

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Where it comes from: embryonic germ layersectoderm, mesoderm, endoderm

(outer, middle, inner)

MesodermEndoderm

16-day-old embryo(dorsal surface view, cephalic end up, length 1 mm)

EpitheliumNervous tissue(from ectoderm)

Muscle and connectivetissue (mostly frommesoderm)Ectoderm

Figure 4.13See also Medical Embryology, 4th ed, Langman, 1981.