Chapter 3 Histology: The Study of Tissues - PowerPoint Presentation

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Chapter 3

Histology: The Study of Tissues

Dr.Duran Kala

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2Tissues and Histology

What is a Tissue?

A collection of similar cells and noncellular substances (extracellular matrix) secreted by the cells

Tissue Level of Organization

Epithelial

ConnectiveMuscleNervousHistology: Microscopic Study of Tissues

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3Main characteristics of the four basic types of tissues.

Tissues

Cells

Extra cellular matrix

Main functions

Epithelial

A

ccumulate

d

polyhedral cells

Small amount

Lining of surface or body cavities, glandular secretion

Connective

Several types of fixed and wandering cells

Abundant amount

Support and protection

Muscle

Elongated contractile cells

Moderate amount

Movement

Nervous

elongated

None

Transmission of nervous impulses

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41. EPITHELIAL TISSUE

Epithelial tissues form boundaries between environments.Epithelia are thus made of sheets of tightly connected cells.Types:

Covering & lining epithelium.

Outer layers of skin.

Linings of cavities.

Glandular epithelium.Glands

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5Epithelium Characteristics

Consists almost entirely of cells

Covers

body

surfaces and forms glands

Has free and basal surfaceAvascularUndergoes mitosis6. Regenerative.

7. Limited – layer or layers

Fig. 4.1

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6ROLE OF EPITHELIA

Protection.SkinAbsorption.

GI

Filtration.

Kidney

Secretion.GlandsSensory Perception.Skin, GI

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7Classification of Epithelium:

How to Make Sense of It All?

There are 2 basic features (or criteria) for classification of epithelium:

Number of cell layers

Simple

Single layerStratifiedMore than 1 layerExceptions?

Pseudostratified

Single layer; only some cells reach free surface

Transitional

Number of cell layers decreases as it is stretched

Fig. 4.2

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8Classification of Epithelium

Shape of cells

Squamous (=scaly)

Cells flattened

Cuboidal

Cells cube-shapedColumnarCells are taller than wide

Fig. 4.2

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9Types of Epithelial Tissues

Simple squamous: Lining of vessels (endothelium). Serous lining of cavities; pericardium, pleura, peritoneum (mesothelium).

Functions:

Facilitates the movement of the viscera (mesothelium), active transport by pinocytosis (mesothelium and endothelium), secretion of biologically active molecules (mesothelium)

Cell shapes are polygonal.

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10Types of Epithelial Tissues

Simple cuboidal: Covering the ovary, thyroid.Functions:

Covering, secretion.

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11Types of Epithelial Tissues

Simple columnar: Lining of intestine, gallbladder

Functions:

Protection, lubrication, absorption, secretion.

In the small intestine the apical surface of these cells have microvilli present on their surface and specialized gland cells called goblet cells which produce and secrete mucus.

microvilli on apical surface

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12Types of Epithelial Tissues

Pseudostratified columnar ciliated:layers of cells with nuclei at different levels; not all cells reach surface but all adhere to basal lamina

.

Lining of trachea, bronchi, nasal cavity

, and lining of the Fallopian tubes (oviducts) of female.Functions:Protection, secretion; cilia-mediated transport of particles trapped in mucus out of the air passages.

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13Types of Epithelial Tissues

Stratified squamous epithelial non-keratinized (moist)

lining of

Mouth, esophagus, larynx, vagina, anal canal.

Funtions:

Protection, secretion; prevents water loss.Cells can be cuboidal or columnar over the basal lamina but they are flattened near the surfaces.

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14Types of Epithelial Tissues

Stratified squamous epthithelium keratinized(dry)

:

Location:

Epidermis.Function:Protection; prevents water loss.Keratin is a layer a waterproof protein on the apical surface of stratified squamous keratinized epithelium (skin).

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16Stratified Cuboidal Epithelium

Sweat glands, developing ovarian follicles.Protection,

Secretes sweat; ovarian hormones & produces sperm

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17Stratified columnar epithelium

Multiple layers of cells in which the surface layer is cuboidal or columnar.

Function:

Protection or secretion.

Location

: Conjunctiva (mucus membrane on the eyeball and eyelids) ,Male Urethra, Sweat Glands

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18Types of Epithelial Tissues

Stratified Transitional: This epithelium is unique to the urinary bladder, ureters

and

renal calces.

Functions:

Protection, expandability. It has the unique property of expansion and contraction. This allows the tissue to adjust to the urinary bladder’s expansion and contraction when it is full or empty.

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19Glands

Secretory organs made mostly of epithelium

Form as invaginations (ingrowths) of outer layer of epithelium in embryo

Two basic types:

Exocrine

:Have ducts lined with epithelium

Salivary glands, sweat glands, mucus gland

Endocrine:

Have no ducts

Examples include pituitary gland, pancreas, thyroid gland

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20

Epithelial Cell Junctions

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Junctional Complexes

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Tight Junctions by TEM

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Tight Junctions by Freeze Fracture

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Tight Junction diagram

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Gap Junction by TEM

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Gap Junction

Connexin molecules

Open pores for ions, molecules, etc

2 nM gap between membranes

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TEM of Zonula Adherens (red arrows)

TEM of a Desmosome (blue arrow)

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TEM (colorized) of Adherens Junctions

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TEM of a Desmosome with tonofibrils

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Desmosome Structure

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31The macromolecular components of basal laminae

 Laminin ( large glycoprotein molecules),

Type IV collagen

(

m

onomers of type IV collagen contain three polypeptide chains ) Entactin, (a glycoprotein) Perlecan, a proteoglycan (mucopolysaccharide that containing polysaccharide and amino acid) with heparan sulfate side chains.These glycosylated proteins and others serve to link together the laminin and type IV collagen sheets.

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32Specializations of Cell Surface

MicrovilliFound mainly on absorptive cellsBrush border, 1

m

high

Cilia / flagella

Cylindrical, motile structures, 5-10m highContain microtubulesBasal bodiesSterocilia:arelong apical processes of cells in other absorptive epithelia such as that lining the epididymis and ductus deferens. These structures are much longer and less motile than microvilli

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33Microvilli

Apical region of an intestinal epithelial cell seen with TEM. Filaments that constitute the core of the microvilli are clearly seen. An extracellular cell coat (glycocalyx) is bound to the plasmalemma of the microvilli. x45,000.

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34

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35Stereocilia

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36Cilia

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37MEDICAL APPLICATION

Both benign and malignant tumors can arise from most types of epithelial cells.

C

arcinoma

(Gr.

karkinos, cancer, + oma, tumor) is a malignant tumor of epithelial cell origin Malignant tumors derived from glandular epithelial tissue are usually called adenocarcinomas (Gr. adenos, gland, + karkinos); these are by far the most common tumors in adults. Under certain abnormal conditions, one type of epithelial tissue may undergo transformation into another type in another reversible process called metaplasia.Examples are

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In heavy cigarette smokers, the ciliated pseudo-stratified epithelium lining the bronchi can be transformed into stratified squamous epithelium.

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In individuals with chronic vitamin A deficiency, epithelial tissues of the type found in the bronchi and urinary bladder are gradually replaced by stratified squamous epithelium

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