Stroma () is the part of a tissue or

organ Organ may refer to: Biology * Organ (biology), a part of an organism Musical instruments * Organ (music), a family of keyboard musical instruments characterized by sustained tone ** Electronic organ, an electronic keyboard instrument ** Hammond ...

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 Parenchyma () is the bulk of functional substance in an animal organ or structure such as a tumour. In zoology it is the name for the tissue that fills the interior of flatworms. Etymology The term ''parenchyma'' is New Latin from the word � ...

, 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 The Cells is a 3-piece American rock band based in Chicago, currently made up of singer/guitarist Cory Hance, bassist Johnny Furman and drummer Mark Doyle. The band was formed in 1998 by singer/guitarist Cory Hance and bassist Brede Hovland. Hovl ...

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 The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans it is in the neck and consists of two connected lobes. The lower two thirds of the lobes are connected by a thin band of tissue called the thyroid isthmus. The thy ...

* stroma of

thymus The thymus is a specialized primary lymphoid organ of the immune system. Within the thymus, thymus cell lymphocytes or '' T cells'' mature. T cells are critical to the adaptive immune system, where the body adapts to specific foreign invaders ...

stroma of bone marrow Bone marrow is a semi-solid tissue found within the spongy (also known as cancellous) portions of bones. In birds and mammals, bone marrow is the primary site of new blood cell production (or haematopoiesis). It is composed of hematopoietic c ...

* 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

l 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 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 ...

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 whic ...

aggregates - and connective tissue fibers. There are three types of fibers commonly found within the stroma:

collagen type I Type I collagen is the most abundant collagen of the human body. It forms large, eosinophilic fibers known as collagen fibers. It is present in scar tissue, the end product when tissue heals by repair, as well as tendons, ligaments, the end ...

elastic Elastic is a word often used to describe or identify certain types of elastomer, elastic used in garments or stretchable fabrics. Elastic may also refer to: Alternative name * Rubber band, ring-shaped band of rubber used to hold objects togethe ...

, and

reticular In chemistry and biology a cross-link is a bond or a short sequence of bonds that links one polymer chain to another. These links may take the form of covalent bonds or ionic bonds and the polymers can be either synthetic polymers or natural ...

(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 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 ...

- 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 Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellu ...

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)