Ground substance is an amorphous gel-like substance in the extracellular space of
animals
Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia (). With few exceptions, animals consume organic material, breathe oxygen, have myocytes and are able to move, can reproduce sexually, and grow from a ...
that contains all components of the
extracellular matrix (ECM) except for fibrous materials such as
collagen
Collagen () is the main structural protein in the extracellular matrix of the connective tissues of many animals. It is the most abundant protein in mammals, making up 25% to 35% of protein content. Amino acids are bound together to form a trip ...
and
elastin
Elastin is a protein encoded by the ''ELN'' gene in humans and several other animals. Elastin is a key component in the extracellular matrix of gnathostomes (jawed vertebrates). It is highly Elasticity (physics), elastic and present in connective ...
. 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 acid, uronic sugar and an amino sugar, except i ...
(GAGs),
proteoglycans
Proteoglycans are proteins that are heavily glycosylation, glycosylated. The basic proteoglycan unit consists of a "core protein" with one or more covalent bond, covalently attached glycosaminoglycan (GAG) chain(s). The point of attachment is a ...
, and
glycoproteins
Glycoproteins are proteins which contain oligosaccharide (sugar) chains covalently attached to amino acid side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known a ...
. 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 glycosaminog ...
,
heparan sulfate
Heparan sulfate (HS) is a linear polysaccharide found in all animal tissues. It occurs in 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, and
chondroitin sulfate
Chondroitin sulfate is a sulfated glycosaminoglycan (GAG) composed of a chain of alternating sugars (N-Acetylgalactosamine, N-acetylgalactosamine and glucuronic acid). It is usually found attached to proteins as part of a proteoglycan. A chondroit ...
. 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. 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, also known as areolar tissue, is a cellular connective tissue with thin and relatively sparse collagen fibers. They have a semi-fluid matrix with lesser proportions of fibers. Its ground substance occupies more vol ...
is characterized by few fibers and cells, and a relatively large amount of ground substance. Dense connective tissue
Dense connective tissue, also called dense fibrous tissue, is a type of connective tissue with fibers as its main extracellular matrix, matrix element. The fibers are mainly composed of type I collagen. Crowded between the collagen fibers are rows ...
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
The internal environment (or ''milieu intérieur'' in French; ) was a concept developed by Claude Bernard, a French physiologist in the 19th century, to describe the interstitial fluid and its physiological capacity to ensure protective stabi ...
References
External links
*
{{Connective tissue
Biochemistry
Histology