2 histology

8/8/2019 2 Histology

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Histology:The Study of Tissues

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Tissues

A group of closelyassociated cells thatperform related functionsand are similar in

structure Four types-

epithelium (covering)

connective (support)

muscle (movement)

nervous (control)


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Extracellular Matrix Extracellular Protein

Fibers

Ground substance-syrup like fluid

ECF

Interstitial fluid

Tissue fluid

So lets summarize:

Tissues- cells and extracellular matrix (fibersand ground substance).

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Interpreting tissue sections

Histological sections areprepared by a microtome(thin slices of the tissue);smears; spreads

fixative Dehydrated (might occur

with fixation stage)

stained

Review your planes and

be sure you can seehow to put a tissue backtogether!


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Epithelia and Glands Epithelium is a sheet of cells

that covers a body surface orlines a body cavity

Inner lining of stomach andviscera, respiratory tubes,peritoneal cavity, innerlining of blood vessels,most of bodys glands

Occur at interfaces between

two different environments,provide a boundary

Protect and provide sensoryinformation, secrete,absorption, ion transport, formslippery surfaces

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Special Characteristics of Epithelia

1. Cellularity- composed of cells with minimal extracellular material

2. Attachment- anchored to a basement membrane

3. Polarity- free edge (apical) and lower (basal) surface.

4. Avascular but innervated- lack blood vessels but do receivenerve endings

5. Regeneration: Friction resistance! Constantly being rubbed offand replaced.

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Classification of Epithelia

Number of layersShapeALWAYS LOOK AT APICAL LAYER

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Simple Epithelia Single layer of cells Important for passive

diffusion (squamous) orabsorption/secretion(cuboidal or columnar)

Special cases:

endothelium (found in

heart and bloodvessels)

mesothelium (linesserosal cavities)

Pseudostratifiedcolumnar- all cellstouch basementmembrane!


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Simple Squamous

Epithelium

Common sites ofdiffusion andfiltration

Alveoli

Endothelium of

blood capillaries

Glomerulus

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Simple Cuboidal Epithelium

Functions in secretionand absorption

Kidney tubules

Ducts of salivaryglands, thyroid gland,pancreas

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Simple Columnar Epithelium Specialized for

absorption

Presence of gobletcells ( secrete mucus)

Gastrointestinal tract

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Pseudostratified ColumnarEpithelium

Protection, secretion,ciliary movement

often ciliated

Many goblet cells

Lines passages ofrespiratory system-trachea, bronchi

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Stratified Epithelia- 2 or morelayers

More durable andmajor role isprotection

Regenerate frombelow

Keratinized

(waterproofed bydead layer of cells-skin) vs. non-keratinized(esophagus, vagina-)

Stratified Squamous Epithelium

Protection ( wear andtear areas)

Outer layers flattened

Blocks variouschemicals andmicroorganisms fromentering

Found in mouth,esophagus, nasalcavity, anus, vagina,skin 14


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Transitional Epithelium Lines the inside of

hollow urinaryorgans (bladder)and umbilical cord

Allows fordistention(stretching)

Thus, it goesthroughtransitions inshape. 15

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Connective Tissue

Most abundant

Connective tissue proper

Supportive (cartilage and bone) Fluid (blood and lymph)

Function- connect cells, form skeleton (lever system),

store and carry nutrients, surround all the blood vesselsand nerves of the body, fight against infection, heatproduction, physical protection.

Cells always separated by a large amount of nonlivingextracellular material (extracellular matrix)

Originate from mesoderm (mesenchyme).


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Types of Connective tissue

Connective tissues

Connective tissue proper (fibrous) Fluid Supporting

Loose Dense Blood lymph cartilage bone

Solid, rubber

matrixSolid,crystallinematrix

Contained in

Cardiovascularsystem

Contained in

lymphaticsystem

Fibers create

loose, openframework

Fibers densely

packed

AreolarAdiposereticular

RegularIrregular

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Cells you would find in ConnectiveTissue Proper

Fibroblasts- produce fibers andground substance that formsthe matrix

Macrophages (derived frommonocytes- a type of WBC)

Mesenchymal cells

Leukocytes (WBC)

Mast cells-

Histamine- increases bloodflow by dilating bloodvessels

Heparin- inhibits bloodclotting

Adipocytes (fat cells)


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Fibers you would find in

Fibrous Connective Tissue

Collagenous fibers- whitefibers, tough and flexible(resist stretching)

Reticular fibers- thincollagen fibers--Formsponge-like framework(spleen and lymph nodes)

Elastic- Allows stretching

and recoiling (rubber band) Lungs, skin, arteries

Elasticity- NOT theability to stretch, ratherthe ability to recoil whenreleased)

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Areolar connective tissue (model type)

Support and bindingof tissues

Holding body fluids

Defending the bodyagainst infection

Storing nutrients asfat

Waste removal


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Other loose connective tissues Adipose tissue - function

is to store nutrients.Highly vascularized.Mostly found in

hypodermis (telasubcutanea)

Reticular Connectivetissue resembles

areolar tissue, but onlyhas reticular fibers inextracellular matrix.

spleen, lymph nodes,thymus and bone marrow

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Dense Connective Tissue

Dense irregularconnective tissue- similarto areolar tissue, butcollagen fibers muchthicker. Two layers

running perpendicular toeach other.

Dense regular connectivetissue- fibers run in thesame direction- parallel tothe direction of pull(ligaments, tendons,aponeuroses, elastictissue)


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Cartilage Resist compression

and tension

no blood vessels ornerves.

Hyaline-mostabundant

Elastic

fibrocartilage

Cartilage

Hyaline cartilage (glass) most abundant cartilage,many delicate collagen fibrils Provides support through flexibility

Epiphyseal plates, fetal skeleton, trachea, larynx

Elastic cartilage contains many elastic fibers andcollagen fibrils Able to tolerate repeated bending

Ear, external auditory canal, epiglottis

Fibrocartilage resists strong compression and strongtension An intermediate between hyaline and elastic cartilage, many

thick collagen fibers

Intervertebral discs, menisci, pubic symphysis.

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Bone matrix contains inorganic

calcium salts andcollagen fibers.

Spongy- heads of longbones

Compact

Haversian system(osteon) Central canal (Haversian

canal)

Lacunae

Lamellae

Canaliculi

Osteocytes

Periosteum

Osteoblasts

osteoclasts

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Blood Fluid ground substance Transports nutrients,

wastes, gases

Erythrocytes (RBCs)

Leukocytes (WBCs)-neutrophils,eosinophils, basophils,monocytes,lymphocytes (T and Bcells)

Platelets(thrombocytes)


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Muscle Movement

Posture/jointstability

Heat Production

Communication

(facial muscles)

Control of bodyopenings

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3 Classes of Muscle

Based on histological

appearance and function

Skeletal

Striated, voluntary,

myofibers

Cardiac

Striated, involuntary,

branched, cardiocytes

Smooth

Non-striated, involuntary,

fusiform in shape (spindle)


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Skeletal Muscle Striated

Voluntary

Multi-nucleated

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Cardiac Muscle

Striated

Involuntary

Branched

Cardiocytes


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Smooth Muscle Smooth (non-striated)

Involuntary

Fusiform (spindleshaped)

Nervous Tissue

Conductive cell = neuron

Receives/transmitselectrochemical

impulses Dendrites, body (soma),

axon

Glial cells (supportive)

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Homework: Pages 23- 24, due nextmeeting

2 histology

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