tissues and histology

8/8/2019 Tissues and Histology

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4 Levels of Organization

1. Cellsbasic unit of life

2. Tissues- groups of cells with similar structureand functions

3. Organs- body structures composed ofseveral different tissues that for a structural

and functional unit4. Organ System- group of organs that

function together to carry out majoractivities of the body


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Study of themicrostructure of

tissues


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Four major types of tissues

Each composed of different types of

cells with characteristic shape, size andarrangement.

Aggregates of cells with similar structures

and functions Cells are bound together forming sheets or

layers except blood


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4 Principal Types of Tissues

Epithelial Tissues Connective Tissues

Muscle Tissues

Nerve Tissues


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Derived from all germ layers

Lines surfaces of the body as well as internal

body spaces

Have important role in homeostasis of thebody

Cells of the epithelial tissue are tightlybound together with little space betweenthem


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Attached firmly on the underlyingconnective tissue called the BASAL

LAMINA orBASEMENT MEMBRANE

Classified according toshape of the cells

and number of cell layer


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Squamous

Cuboidal

Columnar


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Irregularly flattenedcells with tapered

edges

Clear cytoplasm andeccentric oval nucleus

Found in linings oflungs, capillary wallsand blood vessels

Also in cheek cells(buccal mucosa)


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Cells roughly

hexagonal I shapewith nucleus at thecenter

Found in kidneytubules as well aslumen of small ductssuch as bile duct


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Resemblescuboidal cellswhen viewed

from the surface

Appear tallerthan broader

(rectangular)with nucleusnear the base

Found ingallbladder,urinary papilla,stomach andintestinal lining


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Simple

Stratified

Pseudo

stratified

Transitional


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Derived from embryonic mesoderm

Most abundant type of tissue in ananimal body

3 basic elements Cells

Intercellular substances (ground matrix)

Fibers


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Binds, anchors and supports body parts

Consistency ranges from gel-like softnessof areolar connective tissue to hardnessof bones


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Fixed cellspermanent residents of C.T.

Fibroblasts- principal cells of C.T.

- RESPONSIBLE FOR SECRETION OF ALL CELL

TYPES

Chondrocytes- matrix-secreting cells of cartilage

Osteocytes- matrix-secreting cells of bones

Macropahges- phagocytic cells derived frommonocytes

Adipocytes- specialized cells to store neutral fat

Mast cells- granules containing histamine,heparin, and anaphylactic factors


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Wandering cells- transient migrants whohave entered C.T. from blood in

response to specific stimuli Lymphocytes

Plasma cells

Neutrophils

Eosinophils

Basophils

Monocytes


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Ground matrix

Occupies space between cells and fibers ofC.T.

Has high water content

Amorphous in appearance


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Collagen fibers

Reticular fibers

Elastic fibers


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Most common type

Flexible with high tensile strength

Wavy lines of variable width and

indeterminate length

Made up of thread-like subunits called

collagen fibrils


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Made of type III collagen fibrils

Fibrils are of narrow diameter

Do not bundle to form thick fibers Given such name due to mesh-like

pattern

Provide support framework for cellularconstituents of various tissues and organs

Produced by fibroblasts


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Thinner than collagen

Arranged in branching pattern to form

3D network Gives tissue ability to cope with strength

and distension

Interwoven with collagen fibers Composed of elastin and microfibrils

Produced by fibroblasts


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Connective Tissue Proper

Loose or Areolar Connective Tissue

Dense Connective Tissue Dense Regular C.T.

Dense Irregular C.T.

Specialiazed Type of Connective Tissue

Adipose Tissue

Cartilage

Bone

Blood


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Collagen fibres packed in dense regular

arrays between lie rows of cells

Found in tendons, ligaments and

aponeuroses


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Collagenous fibres make up bulk of tissue

Fibroblasts the only cell type present

Bundles arranged in various directions

which enables the tissue to withstand

various stresses

Found on the outside of many organs, in

dermis of skin and in submucosa in various

or ans


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Adipocytesspecialized to store fats When dominant cells, called ADIPOSE TISSUE

Contains single, large lipid inclusion

Thin layer of cytoplasm

signet ring appearance

Stores nutrients, provide insulation and acts

as cushions as well as fill crevices in organs


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Soft and pliable

Specialized matrix secreted by

chondrocytes Housed inside spaces called lacunae

3 types

Hyaline Cartilage

Elastic Cartilage

Fibrocartilage


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Most common type

Clear homogenous

matrix

Covered with denseC.T. called

perichonrium

Chondrocytes arein clustersCartilage cells

housed in lacunae

Found in cartilageof trachea


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Similar to hyalinecartilage but with

abundant elasticfibres andlamellae

Found in externalear, epiglottis,eustachean tubeand larynx


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Resembles C.T.proper

Chondrocytes +

dense C.T.

Presence indicatesthat resistance tocompresion as well as

to shear forces

Found inintervertebral disks,symphysis pubis,

places wheretendons attach tobones


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Mineralized extracellular matrix

Osteocytes

Consists mainly of mineralized collagen

fibers arranged in lamellae

For support, protection, movement,

formation of blood cells and reservoir of

calcium


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Fluid C.T. that circulates the body

Several functions

Brings nutrients and oxygen throughout thebody

Removes waste products

Transports large number of products such as

hormones and immunogenic agents as wellas in maintaining homeostasis

RBCs (erythrocytes) and WBCs

(leukocytes)


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During

maturation, loses

their nucleus,

mitochondriaand endoplasmic

reticulum

With iron-containing

protein called

hemoglobin


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With nuclei andmitochondria butlacks red pigment

Differentiated intotwo types

Agranular WBC Granular WBC


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Granulated cytoplasm and multi-lobulated nucleus whose lobes areconnectd by chromatin material

EOSINOPHILS

BASOPHILS

NEUTROPHILS


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Without granules in their cytoplasm

LYMPHOCYTES

MONOCYTES

PLATELETS


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Motors of the body Unique due to presence of actin and

myosin filaments

Specialized for contraction Responsible for movement of the body

and changes in size and shape ofinternal organs

3 types

Skeletal

Smooth

Cardiac


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M l


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Muscleattached toskeleton

Controlsmovementand posture

Striation due toarrangementof myosin and

actin filaments Nuclei found at

the periphery


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Found in theheart at thebase of the

venae cavae Have one or

two nucleiwhich arecentrallylocated

Intrinsic muscle of


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Intrinsic muscle ofinternal organs,blood vessels, iris

and cilliary body ofthe eye

Each bundle is

fusiform in shapewhit thicker centralportion andtapered at bothends

Single nucleus atcentral part of fibre


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Consists of nerve cells and associatedsupporting cells

Cells are called NEURONS 3 PARTS:

CELL BODY

DENDRITES

AXON


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