Stroma (animal tissue)

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Stroma (animal tissue)
Prostate under a microscope This image shows the microscopic glands of the prostate
Code TH H2.
Anatomical terminology

In animal tissue, stroma (from Greek στρῶμα, meaning “layer, bed, bed covering”) is the part of a tissue or organ that has a connective and structural role. It consists of all the parts which do not conduct the specific functions of the organ, for example, connective tissue, blood vessels, nerves, ducts, etc. The other part is the parenchyma, which is the cells that perform the function of the tissue or organ.[1] There are multiple ways of classifying tissues: one way of classifying tissues is based on their functions and another is based on their cellular components. Stromal tissue falls into the class that functions in contributing to the body’s support and movement. The cells that stroma tissues are composed of serve as a matrix in which the other cells are embedded.[2] Stroma is made of various types of stromal cells.

Examples of stroma include:

The connective tissue of the stroma[edit]

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 aggregates - and connective tissue fibers. There are three types of fibers commonly found within the stroma: collagen type I, elastic, and reticular (collagen type III) fibres.[3]

Cells of the stromal tissue[edit]

  • 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.

There are two types of stromal tissue[edit]

  1. 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.
  2. Dense irregular connective tissue - the function of this type is binding at a high tensile strength between tissues to convert tension from one organ to another.[4]


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