Stroma () is the part of a
tissue or
organ with a structural or connective role. It is made up of all the parts without specific functions of the organ - for example, connective tissue, blood vessels, ducts, etc. The other part, the
parenchyma, consists of the cells that perform the function of the tissue or organ.
There are multiple ways of classifying tissues: one classification scheme is based on tissue functions and another analyzes their cellular components. Stromal tissue falls into the "functional" class that contributes to the body's support and movement.
The cells which make up stroma tissues serve as a matrix in which the other cells are embedded.
Stroma is made of various types of
stromal cells.
Examples of stroma include:
*
stroma of iris
*
stroma of cornea
*
stroma of ovary
* stroma of
thyroid gland
* stroma of
thymus
The thymus (: thymuses or thymi) is a specialized primary lymphoid organ of the immune system. Within the thymus, T cells mature. T cells are critical to the adaptive immune system, where the body adapts to specific foreign invaders. The thymus ...
*
stroma of bone marrow
*
lymph node stromal cell
*
multipotent stromal cell (mesenchymal stem cell)
Structure
Stromal connective tissues are found in the stroma; this tissue belongs to the group connective tissue proper. The function of connective tissue proper is to secure the
parenchymal tissue, including blood vessels and nerves of the stroma, and to construct organs and spread mechanical
tension to reduce localised stress. Stromal tissue is primarily made of
extracellular matrix containing connective tissue cells. Extracellular matrix is primarily composed of
ground substance - a porous, hydrated gel, made mainly from
proteoglycan
Proteoglycans are proteins that are heavily glycosylated. The basic proteoglycan unit consists of a "core protein" with one or more covalently attached glycosaminoglycan (GAG) chain(s). The point of attachment is a serine (Ser) residue to w ...
aggregates - and connective tissue fibers. There are three types of fibers commonly found within the stroma:
collagen type I,
elastic
Elastic is a word often used to describe or identify certain types of elastomer, Elastic (notion), elastic used in garments or stretch fabric, stretchable fabrics.
Elastic may also refer to:
Alternative name
* Rubber band, ring-shaped band of rub ...
, and
reticular (collagen type III) fibres.
Cells
*
Wandering cells - cells that migrate into the tissue from blood stream in response to a variety of stimuli; for example, immune system blood cells causing inflammatory response.
* Fixed cells - cells that are permanent inhabitants of the tissue.
*
Fibroblast - produce and secrete the organic parts of the ground substance and extracellular fibers of the matrix.
Types
# Loose connective tissue - This type is mainly located under the
epithelial membranes and glandular epithelium, attaching the epithelia to other tissues. It supports the blood vessels and nerves supplied to the epithelia. Additionally, it serves as the main site of
inflammatory response within the body.
# Dense irregular connective tissue - the function of this type is binding at a
high tensile strength between tissues to convert tension from one point.
References
External links
{{Authority control
Tissues (biology)