a. Ground substance (GS)
The component of CT between cells and fibres. The ground substance may be fluid, semifluid, gelatinous, or calcified. The GS supports cells, binds them together, stores water, and provides a medium through which substances exchange between blood and cells. It also plays an active role in how tissues migrate, proliferate and change shape. The GS contains water and an assortment of large organic molecules (complex combinations of polysaccharides and proteins). Collectively they are called Glycosaminoglycans (GAG). The polysaccharides include: 1) Hyaluronic Acid, which is a viscous, slippery substance that binds cells together, lubricates joints and helps maintain the shape of the eyeballs. 2) Chondroitin Sulfate which provides support and adhesiveness in cartilage, bone, skin, and blood vessels. 3) Adhesion Proteins are responsible for linking the components of the GS to one another and to the surface of cells.
b. Fibres
Fibres are embedded in the in the extracellular matrix between cells. There are 3 types of fibres found in the matrix:
i. Collagen :
Are very strong and resist pulling forces but are not stiff allowing for greater tissue flexibility. Chemically, they consist of a protein collagen which is the most abundant protein in your body (25%). These fibres are found in most CT especially bone, cartilage, tendons and ligaments.
ii. Elastic Fibres :
Smaller in diameter than collagen and branch and join together to form a network within the tissue. These fibres contain the protein elastin surrounded by a glycoprotein named fibrillin which adds strength and stability. As the name implies, elastic fibres can be are strong but can be stretched up to 150% of their resting state and can return to their original state (property called Elasticity). These fibres are found in the skin, blood vessel walls, and lung tissue.
iii. Reticular fibres:
These fibres consist of collagen arranged in fine bundles with a glycoprotein coating to provide support in the walls of blood vessels and form a network around the cells in some tissue such as areolar CT, adipose tissue and smooth muscle tissue. Like collagen fibres, reticular fibres provide support and strength. They are plentiful in CT that forms a stroma of supporting framework of soft organs such as the spleen and lymph nodes.
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