Stroma (tissue)


Stroma () is the part of a
tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North America * ''Triphosa dubitata'', a species of geometer mot ...
organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's tissues can be broadly cate ...
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 Zoology ()The pronunciation of zoology as is typically regarded as nonstandard, though it is not uncommon. is the branch of biolo ...
, 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 cell Stromal cells, or mesenchymal stromal cells, are differentiating cells found in abundance within bone marrow but can also be seen all around the body. Stromal cells can become connective tissue cells of any Organ (biology), organ, for example in the ...
s. Examples of stroma include: *
stroma of iris The stroma of the iris is a fibrovascular layer of tissue. It is the upper layer of two in the iris. Structure The stroma is a delicate interlacement of fibres. Some circle the circumference of the iris and the majority radiate toward the pupil ...
stroma of cornea The stroma of the cornea (or substantia propria) is a fibrous, tough, unyielding, perfectly transparent and the thickest layer of the cornea of the eye. It is between Bowman's membrane anteriorly, and Descemet's membrane Descemet's membrane (eponym ...
stroma of ovary Stroma may refer to: Biology * Stroma (tissue) Stroma () is the part of a Tissue (biology), tissue or organ (anatomy), organ with a structural or connective role. It is made up of all the parts without specific functions of the organ - for e ...
* stroma of thyroid gland * stroma of thymus * stroma of bone marrow * lymph node stromal cell *Mesenchymal stem cell, multipotent stromal cell (mesenchymal stem cell)


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 (physics), 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 aggregates - and connective tissue fibers. There are three types of fibers commonly found within the stroma: type I collagen, collagen type I, Elastic fiber, elastic, and reticular fiber, reticular (collagen type III) fibres.


* 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.


# Loose connective tissue - This type is mainly located under the epithelium, 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 inflammation, inflammatory response within the body. # Dense irregular connective tissue - the function of this type is binding at a Ultimate tensile strength, high tensile strength between tissues to convert tension from one point.


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