Connective Tissue 1 2013

8/10/2019 Connective Tissue 1 2013

1/78

CONNECTIVE TISSUE


2/78

Components of Connective Tissue

Cells

Fibers

Ground Substance

The proportion of these individual componentsvaries with each type of connective tissue.


3/78

Functions of Connective Tissue

Structural support (capsules, bone,cartilage)

Nutrition Defense (non-specific and immune)

Cell growth and differentiation Cell migration

Insulation


4/78

Connective Tissues: Special Characteristics

Common embryological origin (from mesoderm)

Innervated and Vascularized (direct blood supply)

Cartilage is the only exception with no capillarybeds

Extracellular Matrix ground substance (gelatinous glycoproteins)

structural fibers (fibrous proteins, e.g. collagen,elastin, reticulin)


5/78

Types of Connective Tissues

Connective Tissue Proper loose connective tissue

dense (fibrous) irregular connective tissue

dense (fibrous) regular connective tissue

Specialized connective tissue adipose tissue

reticular connective tissue

Elastic connective tissue

cartilage hyaline cartilage

elastic cartilage

fibrocartilage

bone

blood


6/78

Types of Connective Tissue

Classified by the

characteristics of the matrix

gelatinous mineralized liquid


7/78

Connective tissue

Elements:

Ground substance

Fibers

Cells

Extracellular matrix


8/78

Connective Tissue Structure


9/78


10/78

Connective Tissue Elements

Ground substance:

- Proteoglycans- large polysaccharide

molecules bound to a protein core (like abottle brush).

- Glycosaminoglycans (GAGs)are linearpolysaccharides composed of repetitivedisaccharide units, attached to proteoglycans


11/78

Glycosaminoglycans (GAGs)

They trap water,

hyaluronic acidgelatinous, separates cells, trapsextracellular fluid; lubricates joints; gives shape toeyeballs; fills body spaces

chondroitin sulfatecapable of being mineralized;cartilage, bones, skin, blood vessels

dermatan sulfateharder; skin, tendons, bloodvessels, heart valves

keratin sulfate - still harder; bone, cartilage,cornea of the eyes


12/78

Ground Substance: Proteoglycan StructureThe proteoglycan monomer is composed of a core protein to whichGAGs are covalently bound. The PG monomer consists of aprox. 100

GAG units joined to the core protein.


13/78

Edema is a condition of abnormally large fluid volume

in the circulatory system or in tissues between thecells (interstitial spaces).

Edema


14/78

Connective Tissue Elements Fibers

Proteins that are embedded in the ground substance Provide structural support, adhesion, connect cells

Collagen

Tough; provide high tensile strength

Also called white fibers

Highly polymerized, gigantic molecules

Tough, moderate flexibility

Bone, cartilage, tendons, ligaments


15/78

Elastic fibers = elastin

branched; smaller, thinner fibers than collagen

very flexible and elastic but also strong

can be stretched to 150% of its original length

Also called yellow fibers


16/78


Reticular fibers (collagen type III)

branched fibers that form delicate networks

thin, less polymerized collagen fibers

Elastic & reticular fibers require special stains to

be seen in the light microscope


17/78

Cellsfewer, rarely touching, surrounded by a

matrix immature forms (-blasts) secrete the matrix and can stilldivide

once the matrix is secreted, the cells mature intocyteswhich have decreased cell divisions and secrete less matrix

material fibroconnective, chondro- cartilage, osteo- bone etc.

Fibroblasts/fibrocytes connective tissue proper

Chondroblasts/chondrocytes cartilage

Osteoblasts/ osteocytesbone

Hematopoietic stem cells blood



18/78

Connective tissue

Fibers


19/78

Fibers

Long, rope-like protein extracellular polymers

Present in variable proportions in the different

types of connective tissues Three types: collagen, reticularand elastic

fibers. Collagen and reticular fibers arecomposed of various types of collagen, elastic

fibers are composed mainly of elastin


20/78

Collagen fibers

Are the most abundant type ofconnective tissue fibers.

There are many types of collagen thatdiffer in their origin, chemicalcomposition, functions, distribution and

pathology


21/78

Collagen biosynthesis


22/78



23/78



24/78

The characteristicfeature is a pattern of cross- banding with a periodicity ofapproximately 64 nm wich results from the polymerisation of tropocollagen molecules

such that each molecule overlaps the next by approx. one- quarter of its length.


25/78

Collagen fibrils, TEM


26/78

Collagen fibrils, TEM


27/78

Collagen fibers, SEM


28/78

Collagen fibers, SEM


29/78


30/78

Collagen types

Fibril-forming collagen: types I, II,III, V and XI

Fibril-associated collagen: types IXand XII

Network-forming collagen: type IV

Anchoring collagen: type VII


31/78

Collagen types

Collagen I Forms fibrils, the most resistant to mechanical

tension In: connective tissue of skin, bone, tendon,

dentin and organ capsules

Collagen II Forms fibrils In hyaline and elastic cartilage

Collagen III

In reticular lamina and reticular connectivetissue First collagen secreted in wound healing

Collagen IV Forms a network in the basal laminae of

epithelia


32/78

Elastic fibers

Isolated, thin fibers or arranged in networks

Localized in lung, urinary bladder, skin, aorta

and elastic cartilage

Special staining : orcein

Are composed of 2 structural components: a

central core of elastin and surrounding fibrillin

microfibrils.


33/78

Elastic fibers, ORCEIN x40


34/78

Elastic fibers

Elastin molecules are joined by covalent bondsto generate an extensive cross-linked network.

Because each elastin molecule in the networkcan expand and contract like a random coil, the

entire network can stretch and recoil like arubber band.


35/78

Elastic fibers


36/78

Marfans syndrome

A defective gene forelastin -inherited

Affects skin, mitralvalve and arteries(ruptured descendingaorta common)


37/78

RETICULAR FIBERS

Provide a supporting framework for the cellular

constituents of various tissues and organs.

Thin fibers, forming networks

Distribution : liver, spleen, lymph nodes,

haematopoietic organs, endocrine glands.

Special staining : silver impregnation


38/78

Reticular fibers, Silver Impregnation x40


39/78

Connective

TissueCells


40/78

Connective tissue cells


41/78

Connective tissue cellsclassification

Cells that produce/degrade the extracellularmatrix

fibroblasts, osteoblasts, condroblasts, macrophages

Metabolic cells adipocytes

Defense (specific/non-specific) Lymphocytes, macrophages, neutrophils, mast cells,

plasma cells


42/78

Fibroblast

The most frequent cell

LM- Elongated cells, 20 mm, branched

processes, basophilic cytoplasm, oval ,euchromatic nucleus, 1 or 2 nucleoli

TEM-abundant RER and a prominent

Golgi apparatus.


43/78

Fibroblasts


44/78

Fibroblasts

Produce:

Elements of the extracellular matrix:procollagen, proelastin, fibrillin, GAG, PGand GP;

Enzymes: matrix metalloproteinases -collagenase (degrades collagen at neutral

pH), elastase; Growth factors


45/78

Fibroblast

Properties:

Ability to switch its fenotype

fibroblast

fibrocyte Can change shape

Mobile

Induces differentiation of surroundingcells


46/78

Myofibroblasts

Are fibroblasts that contain actinfilaments associated with dense bodies -

fibronexus

Have a contractile function as well as a

role in secretion of extracellular matrix.


47/78

Fibrocyte

Less active than fibroblasts LM - smaller, elongated/spindle shaped,

lesser cytoplasm, a few short unbranched

processes Eosinophilic cytoplasm Elongated and heterochromatic nucleus TEM-sparse RER and a small Golgi

apparatus.

Fibroblasts fibrocytes


48/78

Fibroblasts, fibrocytes


49/78

Fibroblasts, fibrocytes, HE 400x


50/78

Unilocular (white) adipocyte

LM- round (when isolated) orpolygonal in groups One large lipid droplet (inclusion)A thin rim of cytoplasm at the periphery that

contains a flattened, heterochromatic nucleus(signet ring)

TEM-small Golgi complex, RER,mitochondria and microfilaments.


51/78

White adipocytes, col. HE, 400x


52/78

White adipocytes, col. SUDAN III , 400x


53/78

Multilocular (brown) adipocyte

Smaller cells than the white adipocytes

Many small lipid droplets in the cytoplasmfoamy look

Round, central nucleus

Mostly found before birth and in neonates

Role in thermogenesis

TEM- many mitochondria (the high concentration ofcytochromes in the mithocondria is responsible for the

brown color of aggregates of multilocular adipocytes; thebrown color is also due to high vascularization-3capillaries for each brown adipocyte).


54/78

Brown adipocytes, col. AZAN, 600x


55/78

Brown adipocyte


56/78

Brown adipocytes (3-4 capillaries/1 brown adipocytes)

R ti l ll


57/78

Reticular cells

Produce reticular fibers, which form the fine structuralnetwork of organs such as the lymph nodes, spleenand bone marrow.

Star-shaped cells with long and thin processes thatestablish anchoring junctions with neighboring cells;round, central, pale nucleus.

!!!!! Should not be confused with the reticulocyte,

an immature erythrocyte.


58/78


59/78

Cytoreticule

Double reticule

=Reticular cells

+Reticular fibers


60/78

Reticularcells &reticular fibers, HE&Silver

Impregnation, 400x

M l t


61/78

Melanocytes

Cells of ectodermal origin Consequently migrates to dermis,

epidermis, iris, hair root

Star-shaped cell, with many branchedprocesses; 30 mm

Melanin granules in the cytoplasm, dark-brown;

Round, central, small nucleus

M l


62/78

Melanocytes Melanosomesvisible in EM:

Primary melanosomes are Golgi vesiclesthat accumulate thyrosin (the melaninprecursor) and thyrosinase, located at thebase of cell processes

Secondary melanosomes are heterogenousvesicles (EM) that accumulate melanin

Tertiary melanosomes are found at the tips

of the cell processes; they are releasedfrom melanocytes and engulfed bysurrounding cells (keratinocytes)


63/78


64/78

Melanocyte, 600x


65/78

Macrophages

Derived from peripheral blood monocytes, Involvedin phagocytosis and inflammatory response

A family of cells with various shapes, localizationsand names:

Histiocytes: connective tissueKupffer cells: liver

Langerhans cells: intra-epidermal

Alveolary macrophages/Dust Cells : lung

Osteoclasts: boneMicroglia: central nervous system


66/78

Macrophages

They are part of themononuclear phagocytesystem(MPS/ RES).

Macrophages of the connective tissue: LM - about 30 mm,ruffledmembrane (irregular

shapes), acidophilic lysosomes in the cytoplasm, canhave various heterogenousinclusionsingestedmaterial

Round, oval or kidney-shaped, eccentric nucleus;can have nucleoli

TEM-numerous lysosomes, phagosomes andpseudopodia, abundant RER, SER, mitochondria andGolgi complex.


67/78

Macrophage

Main function: phagocytosis Triggered by a specific interaction between

membrane receptors and ligands. Consequences:

Cell movement towards target particle Pseudopodia formationengulfment Respiratory burst Secretion: cytokines, interferon, complement

& coagulation factors Production of matrix metalloproteinases

Alveolar macrophages vital staining and HE 600x


68/78

Alveolar macrophages, vital staining and HE, 600x


69/78

Macrophage, TEM

M t ll


70/78

Mast cells Localized in most of the loose connective tissue

areas, along blood vessels LM - Large, Oval cell, 20-30 mm

Cytoplasm has numerous basophilic, metachromaticgranules (elements of a cell stain in a different color from that of thedye solution- toluidine blue)

Round, small and central nucleus

TEM-granules, an extensive Golgi complex,

cisternae of RER, free ribosomes, mitochondriaand numerous microvilli and folds.


71/78

Mast cells

Granules contain heparin or chondroitin sulfate,histamine, Eosinophil Chemotactic Factor, etc.

The content can be released -degranulation.The process is triggered by chemical, physicalstimuli, or through binding of antigen-IgEcomplexes by specialized receptors

Degranulation is mediated by cAMP and leadsalso to leukotriene synthesis

Mast cells, Toluidine blue stain


72/78

Mast cell, TEM


73/78

,

Plasma cells


74/78

Plasma cells

Found in lymphoid organs (lymph nodes,spleen, bone marrow) and connective tissuesassociated to the respiratory and digestivemucosae

Originate in B lymphocytes, that are terminallydifferentiated as a response to antigenchallenge

Secrete immunoglobulins (antibodies): IgM,IgG, IgA, IgE

Plasma cells


75/78

Plasma cells LM

Ovoid/ pear shaped cells

Basophilic cytoplasm (due to abundant RER), with aperinuclear pale area (Golgi apparatus); can containacidophilic Russel bodies (secretory granules)

Eccentric nucleus, with hetero- and euchromatin in acharacteristic pattern:cart wheelorclockface(theheterochromatin resembling the spokes of the wheel or the numbers on

a clock), visible nucleolus.

TEM- extensive Golgi complex, abundant RER,secretory granules (Russel bodies), free ribosomesand mitochondria.

Plasma cells TB stain


76/78

Plasma cells, TB stain

Pl ll l MGG 400


77/78

Plasma cell, col. MGG, 400x

Plasma cell, TEM


78/78

Connective Tissue 1 2013

Documents

Transcript of Connective Tissue 1 2013