What Is The Main Function Of Connective Tissue – Different types of connective tissue maintain the shape of organs throughout the body. Connective tissue provides the matrix that supports and physically connects other tissues and cells together in organs. The interstitial fluid of the connective tissue provides metabolic support to the cells as a distribution medium for nutrients and waste products.

Unlike other types of tissue (epithelium, muscle, and nerves), which consist mainly of cells, the main component of connective tissue is the extracellular matrix (ECM). Extracellular matrices contain different combinations of protein fibers (such as collagens and elastic fibers) and ground substance. Ground substance is a complex of anionic, hydrophilic proteoglycans, glycosaminoglycans (GAGs), and many adhesive glycoproteins (laminin, fibronectin, and others). As briefly described in Chapter 4 on the basal lamina, such glycoproteins help stabilize the ECM by binding to other matrix components and integrins in the cell membrane. The watery nature of the connective tissue of the soil provides a means for the exchange of nutrients and metabolic waste between the cells and the blood supply.

What Is The Main Function Of Connective Tissue

The various types of connective tissue in the body exhibit differences in the composition and number of cells, fibers, and substrates that are responsible for the marked structural, functional, and pathologic diversity of connective tissue.

Describe Structure And Various Functions Of Connective Tissues

Connective tissue originates from the embryonic mesenchyme, a tissue that develops mainly from the middle layer of the embryo, the mesoderm (Figure 5-1). Mesenchyme consists mainly of a viscous matrix with few collagen fibers. Mesenchymal cells are undifferentiated and have large nuclei, prominent nucleoli and fine chromatin. They are often said to be “spindle-shaped,” and their thin cytoplasm is extended as two or more thin cytoplasmic processes. Mesodermal cells leave their place of birth in the embryo, surround and invade the developing organs. In addition to producing all types of connective tissue and specialized connective tissue for bone and cartilage, the embryonic mesenchyme includes stem cells for other tissues such as blood, vascular endothelium, and muscle. This chapter focuses on proper tissue connections.

Fibroblasts and other specific cells are often present in connective tissue (Figure 5-2 and Table 5-1). Fibroblasts originate from mesenchymal cells and are permanent residents of connective tissue; other cells found here, such as macrophages, plasma cells, and mast cells, originate from hematopoietic stem cells in the bone marrow, circulate in the blood, and then proceed to the connective tissue where they function. White blood cells (leukocytes) are transient cells of many connective tissues; they also start in the bone marrow and move to the connective tissue where they are active for a few days, then die by apoptosis.

Fibroblasts (Figure 5-3), the most common cells in connective tissue, produce and maintain many extracellular tissue components. Fibroblasts synthesize and secrete collagen (the body’s most abundant protein) and elastin, which form large fibers, as well as GAGs, proteoglycans, and many adhesive glycoproteins that compose the substrate. As described later, many of the secreted ECM components are further remodeled outside the cell before they are assembled as a matrix.

Two levels of fibroblast activity can be seen histologically (Figure 5-3b). Cells with intense synthetic activity differ from quiescent fibroblasts scattered within the already integrated matrix. Some histologists reserve the term “fibroblast” to describe an active cell and “fibrocyte” to indicate a quiescent cell. A functional fibroblast has abundant and irregularly branched cytoplasm. Its nucleus is large, ovoid, euchromatic, and has a prominent nucleolus. The cytoplasm has a very dense endoplasmic reticulum (RER) and a well-developed Golgi apparatus. A quiescent cell is smaller than an active fibroblast, usually spindle-shaped with few processes and a very small RER, and contains a dark, heterochromatic nucleus.

What Is Tissue? Which Are The Functions Of Tissue?

Fibroblasts are targets of several families of proteins called growth factors that influence cell growth and differentiation. In adults, connective tissue fibroblasts rarely divide. However, stimulated by locally released growth factors, cycling and mitotic activity resumes when tissues need more fibroblasts, for example, to repair an injured organ. Fibroblasts involved in wound healing, sometimes called myo-fibroblasts, have a well-developed contractile function and are enriched with the type of actin found in smooth muscle cells.

, cell), or fat cells, are found in the connective tissues of many organs. These large, mesenchymal-derived cells are specialized in keeping cytoplasmic lipid as neutral fat, or slowly to produce heat. The excess fat in adipose tissue cells also serves to strengthen and cushion the skin and other organs. Adipocytes have great metabolic and medical importance and are described and discussed in Chapter 6.

Macrophages are characterized by their well-developed phagocytic ability and specialize in converting protein fibers and removing dead cells, tissue debris, or other particulate matter. They have many morphologic characteristics related to their functional state and the tissues they inhabit. A typical macrophage measures between 10 and 30 μm in diameter and has an oval or kidney-shaped nucleus. Macrophages are present in the connective tissues of many organs and are often referred to by pathologists as “histiocytes.”

In TEM, macrophages are shown to have an unusual feature with requests, protrusions, and indentations, a morphologic manifestation of their active pinocytotic and phagocytic activities (Figure 5-4). They usually have a well-developed Golgi apparatus and many lysosomes.

Nonenzymatic Protein Function For The Mcat: Everything You Need To Know — Shemmassian Academic Consulting

Macrophages are found in the precursor cells of the bone marrow that divide, producing monocytes that circulate in the blood. These cells cross the epithelial wall of the venules to enter the connective tissue, where they further differentiate, mature, and acquire the morphologic characteristics of phagocytic cells. Therefore, monocytes and macrophages are the same cell at different stages of maturation. Macrophages play an important role in the initial stages of repair after tissue damage, and under such inflammatory conditions these cells accumulate in the connective tissue through the spread of macrophages in addition to the recruitment of monocytes in the blood. Macrophages are distributed throughout the body and are present in many organs. Along with other cells found in monocytes, they comprise a family of cells called the mononuclear phagocyte system (Table 5-2). Macrophage-like cells are given different names in different organs, for example Kupffer cells in the liver, microglial cells in the central nervous system, Langerhans cells in the skin, and osteoclasts in bone tissue. However, they are all found in monocytes. All cells are long-lived and may live for months in tissues. In addition to the removal of waste, these cells are very important in the uptake, processing, and presentation of antigens for lymphocyte activation, a function discussed later with the immune system. The transition from monocytes to macrophages in connective tissue involves an increase in cell size, increased protein synthesis, and an increase in the number of Golgi complexes and lysosomes.

Mast cells are oval or irregularly shaped connective tissue cells, between 7 and 20 μm in diameter, whose cytoplasm is filled with basophilic secretory granules. The nucleus is centrally located and is often hidden by numerous secretory granules (Figure 5-5). These granules are electron dense and heterogeneous (ranging from 0.3 to 2.0 μm in diameter.) Due to their high content of acidic radicals in their sulfated GAGs, mast cell granules exhibit metachromasia, meaning it can change the color of certain basic dyes. (eg, toluidine blue) from blue to purple or red. Granules are not well preserved in conventional preparations, so mast cells are often difficult to see.

Mast cells function in the local release of many bioactive substances that contribute to local inflammatory responses, innate immunity, and tissue repair. A partial list of important molecules released from these secretory granules includes the following:

Occurring in the connective tissues of many organs, mast cells are especially abundant near small blood vessels in the skin and mesenteries.

Connective Tissue Supports Tissues And Organs

Mast cells); the granule content of the two individuals differs slightly. These large areas suggest that mast cells position themselves systematically to act as sentinels to detect microbial invasion.

Mast cells arise from progenitor cells in the bone marrow. Progenitor cells circulate in the blood, cross the wall of venules and capillaries, and enter the connective tissues, where they divide. Although in many ways similar to basophilic leukocytes, they appear to have a different lineage at least in humans.

The release of certain chemical mediators stored in mast cells also promotes an allergic reaction, also known as an immediate hypersensitivity reaction because it occurs a few minutes after exposure to an antigen in a person who has been sensitized to the same or a very similar antigen. There are many examples of immediate hypersensitivity reactions; Notable is anaphylactic shock, a potentially fatal condition. The process of anaphylaxis consists of the following sequential events. The first exposure to an antigen (allergen), such as bee venom, causes the production of the immunoglobulin E (IgE) class of immunoglobulins (antibodies) by plasma cells. IgE is bound to the surface of mast cells. A second exposure to the antigen results in binding of the antigen to IgE on the mast cells. This event causes the release of mast cell granules, releasing histamine, leukotrienes, chemokines, and heparin (Figure 5-6). Mast cell degeneration also occurs

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