Ground substance is an amorphous gel-like substance in the extracellular space that contains all components of the
extracellular matrix
In biology, the extracellular matrix (ECM), also called intercellular matrix, is a three-dimensional network consisting of extracellular macromolecules and minerals, such as collagen, enzymes, glycoproteins and hydroxyapatite that provide s ...
(ECM) except for fibrous materials such as
collagen
Collagen () is the main structural protein in the extracellular matrix found in the body's various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whol ...
and
elastin
Elastin is a protein that in humans is encoded by the ''ELN'' gene. Elastin is a key component of the extracellular matrix in gnathostomes (jawed vertebrates). It is highly elastic and present in connective tissue allowing many tissues in the bo ...
. Ground substance is active in the development, movement, and proliferation of tissues, as well as their metabolism. Additionally, cells use it for support, water storage, binding, and a medium for intercellular exchange (especially between blood cells and other types of cells). Ground substance provides lubrication for collagen fibers.
The components of the ground substance vary depending on the tissue. Ground substance is primarily composed of water and large organic molecules, such as
glycosaminoglycans
Glycosaminoglycans (GAGs) or mucopolysaccharides are long, linear polysaccharides consisting of repeating disaccharide units (i.e. two-sugar units). The repeating two-sugar unit consists of a uronic sugar and an amino sugar, except in the case ...
(GAGs),
proteoglycans, and
glycoproteins. GAGs are polysaccharides that trap water, giving the ground substance a gel-like texture. Important GAGs found in ground substance include
hyaluronic acid
Hyaluronic acid (; abbreviated HA; conjugate base hyaluronate), also called hyaluronan, is an anionic, nonsulfated glycosaminoglycan distributed widely throughout connective, epithelial, and neural tissues. It is unique among glycosaminoglyca ...
,
heparan sulfate
Heparan sulfate (HS) is a linear polysaccharide found in all animal tissues. It occurs as a proteoglycan (HSPG, i.e. Heparan Sulfate ProteoGlycan) in which two or three HS chains are attached in close proximity to cell surface or extracellular ma ...
,
dermatan sulfate
Dermatan sulfate is a glycosaminoglycan (formerly called a mucopolysaccharide) found mostly in skin, but also in blood vessels, heart valves, tendons, and lungs.
It is also referred to as chondroitin sulfate B, although it is no longer class ...
, and
chondroitin sulfate
Chondroitin sulfate is a sulfated glycosaminoglycan (GAG) composed of a chain of alternating sugars ( N-acetylgalactosamine and glucuronic acid). It is usually found attached to proteins as part of a proteoglycan. A chondroitin chain can have ove ...
. With the exception of hyaluronic acid, GAGs are bound to proteins called proteoglycans. Glycoproteins are proteins that attach components of the ground substance to one another and to the surfaces of cells.
Components of the ground substance are secreted by
fibroblasts
A fibroblast is a type of biological cell that synthesizes the extracellular matrix and collagen, produces the structural framework ( stroma) for animal tissues, and plays a critical role in wound healing. Fibroblasts are the most common cells ...
. Usually it is not visible on slides, because it is lost during staining in the preparation process.
Link proteins such as
vinculin,
spectrin and
actomyosin stabilize the proteoglycans and organize elastic fibers in the ECM.
[ Changes in the density of ground substance can allow collagen fibers to form aberrant cross-links.][ ]Loose connective tissue
Loose connective tissue, sometimes called areolar tissue, is a cellular connective tissue with thin and relatively sparse collagen fibers. Its ground substance occupies more volume than the fibers do. It has a viscous to gel-like consisten ...
is characterized by few fibers and cells, and a relatively large amount of ground substance. Dense connective tissue has a smaller amount of ground substance compared to the fibrous material.[
The meaning of the term has evolved over time.]
See also
* Milieu intérieur
References
External links
*
Biochemistry
Histology
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