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CONNECTIVE TISSUE
Common characteristics of CT:
1. Common origin : all types of connective tissues arise from the mesenchyme ( mesoderm ). 2. Variable degrees of vascularity : some types of connective tissue have a rich supply of blood vessels, other is poorly-vascularized e.g. dense CT and cartilage is avascular. 3. Several types of cells : they are widely- separated and immersed in an abundant intercellular substance (extracellular matrix) formed by these cells. 4. Extracellular matrix: where as all other tissues are composed mainly of cells, connective tissue is formed of abundant non-living extracellular matrix , which separates the living cells of the tissue.
CONNECTIVE TISSUE
- The connective tissue (CT) is found everywhere in the body. It is the most abundant and widely-distributed tissue by its several types.
- Structural elements of connective tissue: it is made up of
cells
extracellular matrix which in turn has 2 elements the
- ground substance
- CT fibers.
- Functions:
- Architectural framework of the body
- Bind together and provide mechanical support for other tissue (metabolic, defense, transport, storage)
- Nutrition
- Wound repair
- Protection: inflammatory response
Extracellular Matrix (ECM)
Ground Substance
1. Glycosaminoglycans (GAG) - linear (unbranched) polysaccharides, e.g. heparan sulfate, condroitin sulfate, keratan sulfate, hyaluronic acid - attract sodium & hold water - very hydrophilic due to abundant negative charges. - except for hyaluronic acid, are usually bound covalently to protein core as part of **a proteoglycan
- Proteoglycans:** Forms thick gel that slows the spread of pathogens - core protein + GAG side chains (like a bottle brush) - bind cells, other proteins, and/or ECM components 3. Multiadhesive glycoproteins
- small glycosylated proteins containing NUMEROUS binding sites to cells, signaling molecules, and other ECM components
- e.g. fibronectin and laminin : important for adhesion of epithelial cells to the basal lamina via transmembrane integrin receptors. Tissue fluid: Similar to blood plasma
Lamina :structure in cell laminin :glycoprotein in ground substance
^Ground substance: filling spaces between connective tissue. Interstitial fluid role is nutrition
Glycoprotein: adhesion cell with ground substance. OR: adhesion fibers with ground substance.
Core of protein
The connective tissue ground substance:
- It is the material that fills the spaces between the cells and contains the fibers. It is composed of:
Interstitial tissue fluid , formed of plasma proteins of low molecular weight that escape through the capillary wall as a result of the hydrostatic pressure.
Edema: is an increase in the quantity of the tissue fluid due to loss of the equilibrium between the tissue fluids entering and leaving the matrix of CT.
Adhesive glycoproteins e.g. fibronectin and laminin. They serve mainly as connective tissue glue that allows connective tissue cells to bind themselves to matrix elements.
- Proteoglycans , consist of a protein core to which glycosaminoglycans (GAGs) are attached. The strand-like GAGs are large, negatively-charged polysaccharides that extend from the core protein like the fibers of a bottle brush. GAGs are like chondroitin sulfate and keratan sulfate.
- The proteoglycans tend to form huge proteoglycan aggregates with hyaluronic acid that trap water, forming a substance that varies from a fluid to a viscous gel
- Hyaluronic acid that trap water, forming a substance that varies from a fluid to a viscous = Jelly like
،ال السائل الداخل فين انه الزم يكون فيه توازن بين )* intracellular space and the fluid )طالع (in the lymphatic.
Jelly like: هاي الخاصية بتخليها تمنع انتشار العدوى Prevent Spread of infection
Connective tissue fibers
- The fibers of connective tissue provide support. They are embedded in connective tissue matrix. There are three types of CT fibers;
collagen fibers,
elastic fibers
reticular fibers. (^) Type 3 collagen fiber
في الحقيقة نوعين فقط
^Collagen: 20 type Just 3 found in basement membrane Type 3,4,
Collagen fibers
Elastic fibers Reticular fibers
Collagen fibers= (white fibers)
Characters:
Collagen fibers are the most abundant CT fibers.
They are the strongest (also flexible) and provide high tensile strength (that is the ability to resist longitudinal stress). Stress test shows that collagen fibers are stronger than steel fibers of the same size.
In fresh state, collagen fibers have a glistening white appearance; they are therefore also called white fibers.
In longitudinal section, collagen fibers appear as cylindrical structures that run in wavy bundles
The individual fibers do not branch while the bundles of fibers often do.
They stain pink with H&E (eosinophilic), blue with Mallory’s stain and green with Masson’s trichrome stain.
Type 1 ,, site : in the eye , tendons , ligaments of muscles.
Most common in the body (عموما)
Hematoxylin = violet //Eosin = pink
Collagen protein take acidic dye = pink
ALDOL CONDENSATION
DISULFIDE BONDS
Collagen Synthesis
واالشياء الزيادة بصيرلهم منهم وبتلزقهم وبتعمل 3 الفا هيلكس بتاخد... تبدا الخلية تصنع وبعمل بصيرله وبطلعCleavage
Triple-helix collagen فيها جزء فاتح no overlap Collagen fiber Overlap Collagen fibril
جزء غامقover lap
Collagen Fibers
H & E (^) fibrils
fibers
Irregular type (بوجود) capsule of Organs. Regular (white color) collagen type >> which is regularly arranged.
Major Collagen Fiber Types (out of at least 20) According to the chemical composition of collagen molecules
Collagen Type Tissues Function
Fibril-forming collagens (these are visible)
I (most abundant)
Skin, tendon, bone, dentin Resistance to tension II Cartilage, vitreous of eye Resistance to pressure III (reticulin)
Skin, muscle, blood vessels, liver, etc.
Structural framework and stability
Network-forming collagens
IV All basement membranes Support and filtration
Fibril-associated collagens with interrupted triple helices (FACIT)
VI, IX Assoc. w/ type I and II fibrils^ Fibril-fibril / fibril-ECM binding
Anchoring filament collagens
VII Epithelia Epidermis to basal lamina
Elastic fibers
Characters:
- These fibers contain protein, elastin that allows them to stretch and recoil like rubber bands. Because the fresh elastic fibers appear yellow, they are called the yellow fibers.
- Histological features:
- Elastic fibers may exist in two different forms:
- Individual long and thin fibers that branch in the extracellular matrix.
- In the wall of large blood vessels they form fenestrated parallel sheets
- They stain weakly with H&E.
- Special staining with orcein stain gives a brick-red color to elastic fibers, while staining with V.VG stain gives them a dark violet color.
As aorta
Network of elastin molecules can stretch
and recoil like a rubber band
Fibers
The most numerous White if in great number (white fibers) Strong and flexible Fibers do not branch but bundles can do Formed of collagen protein Stain pink with eosin Types of Collagen Fibres
Thin branching Not stained by H&E Stained dark brown with silver stain Consist of type III collagen Supportive function
Yellow if in great number (Yellow fibers)
Elastic and stretchable Fibers can branch and unit Formed of elastin protein Stained weakly by H&E Stain brick red by orcein Stain dark violet with V.V.G stain.
Highly cellular Organ = support Sites : liver , bone marrow , lymphatic organ (spleen)
