extracellular matrix

Examples of extracellular matrix in the following topics:

• Hemidesmosomes

  • Hemidesmosomes are asymmetrical and connect the basal face of the expressing cell to the extracellular matrix or to other cells.
  • While desmosomes link two cells together, hemidesmosomes attach one cell to the extracellular matrix.
  • The integrin might then attach to one of many multi-adhesive proteins such as laminin, resident within the extracellular matrix, thereby forming one of many potential adhesions between cell and matrix.
  • Thin, extracellular, electron-dense lines, parallel to the plasma membrane, subjacent to the outer plaque are visible in one third of HDs and are termed sub-basal dense plates (SBDPs).

• Characteristics of Connective Tissue

  • Together the ground substance and fibers make up the extracellular matrix.
  • It is composed of proteoglycans and cell adhesion proteins that allow the connective tissue to act as glue for the cells to attach to the matrix.
  • Collagen fibers are fibrous proteins and are secreted into the extracellular space and they provide high tensile strength to the matrix.
  • Elastic fibers are long, thin fibers that form branching network in the extracellular matrix.
  • Connective tissues consist of three parts: cells suspended in a ground substance or matrix; and most have fibers running through it.

• Development of Joints

  • Chondrification (also known as chondrogenesis) is the process by which cartilage is formed from condensed mesenchyme tissue, which differentiates into chondroblasts and begins secreting the molecules that form the extracellular matrix.
  • Articular cartilage function is dependent on the molecular composition of its extracellular matrix (ECM), which consists mainly of proteoglycans and collagens.
  • Articular cartilage is maintained by embedded chondrocytes that comprise only 1% of the cartilage volume, and remodeling of cartilage is predominantly affected by changes and rearrangements of the collagen matrix, which responds to tensile and compressive forces experienced by the cartilage.
  • Cartilage growth generally refers to matrix deposition, but can include both growth and remodeling of the extracellular matrix.

• Cartilage Growth

  • Mesenchyme tissue differentiates into chondroblasts and begins secreting the molecules that form the extracellular matrix (ECM).
  • The extracellular matrix consists of ground substance (proteoglycans and glycosaminoglycans) and associated fibers, such as collagen.
  • The chondroblasts then trap themselves in lacunae, small spaces that are no longer in contact with the newly created matrix and contain extracellular fluid.
  • Cartilage growth thus mainly refers to matrix deposition, but can include both growth and remodeling of the ECM.
  • Also, because cartilage does not have a blood supply, the deposition of new matrix is slow.

• Deep Wound Healing

  • Therefore, proper reconstitution of the epidermis is often only seen at the edge of the wound, with fibrous scar tissue—formed from the extracellular matrix (ECM) deposited during the proliferative phase—covering the rest of the wound site.

• Marfan Syndrome

  • Fibrillin-1 protein is essential for the proper formation of the extracellular matrix, including the biogenesis and maintenance of elastic fibers.
  • The extracellular matrix is critical for both the structural integrity of connective tissue, but also serves as a reservoir for growth factors.

• Fluid Compartments

  • For example, the mitochondrial matrix separates the mitochondrion into compartments.
  • Extracellular fluid (ECF) or extracellular fluid volume (ECFV) usually denotes all body fluid outside of cells.
  • The extracellular fluid also includes the transcellular fluid; making up only about 2.5% of the ECF.
  • The pH of extracellular fluid is tightly regulated by buffers and maintained around 7.4.
  • It is the intravascular fluid part of extracellular fluid (all body fluid outside of cells).

• Structural Elements of Connective Tissue

  • The tropocollagen subunits spontaneously self-assemble, with regularly-staggered ends, into even larger arrays in the extracellular spaces of tissues.
  • Elastic fibers (or yellow fibers) are bundles of proteins (elastin) found in extracellular matrix of connective tissue and produced by fibroblasts and smooth muscle cells in arteries.

• Structure, Type, and Location of Cartilage

  • Chondrocytes are first chondroblast cells that produce the collagen extracellular matrix (ECM) and then get caught in the matrix.
  • The remodeling of cartilage is predominantly affected by changes and rearrangements of the collagen matrix, which responds to tensile and compressive forces experienced by the cartilage.
  • If a thin slice of cartilage is examined under the microscope, it will be found to consist of cells of a rounded or bluntly angular form, lying in groups of two or more in a granular or almost homogeneous matrix.
  • Elastic cartilage is histologically similar to hyaline cartilage but contains many yellow elastic fibers lying in a solid matrix.

• Bone Remodeling

  • Evidence suggests that bone cells produce growth factors for extracellular storage in the bone matrix.
  • The release of these growth factors from the bone matrix could cause the proliferation of osteoblast precursors.