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Fibrous connective tissue
Last reviewed: 23.04.2024
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Fibrous connective tissues include loose and dense fibrous connective tissues. Dense fibrous connective tissue, in turn, has two varieties - unformed and decorated dense connective tissue.
Loose fibrous connective tissue is located mainly along the course of the blood and lymphatic vessels, nerves, forms the stroma of many internal organs, as well as its own plate of the mucous membrane, submucosal and subserous bases, and the adventitia shell. It contains numerous cells: fibroblasts, fibrocytes, macrophages, mast cells (tissue basophils), adipocytes, pigment cells, lymphocytes, plasmocytes, leukocytes. In the intercellular substance of loose fibrous connective tissue, an amorphous substance predominates, and the fibers are usually thin. Fibers are small, they are located in different directions, so this fabric is called loose.
Dense fibrous connective tissue, due to well-developed fibrous structures, performs mainly supporting and protective functions. The intercellular substance is dominated by fibers, the amorphous substance is small, the number of cells is less significant. Connective tissue fibers or intertwined in different directions (unformed dense fibrous tissue), or located parallel to each other (formed dense fibrous tissue).
Unformed dense fibrous connective tissue forms cases for muscles, nerves, capsules of organs and trabeculae leaving from them inside the organs. This tissue forms a sclera of the eye, periosteum and perichondrium, fibrous layer of articular capsules, reticular layer of the dermis, valvular valves, pericardium, dura mater.
The dense fibrous connective tissue forms tendons, ligaments, fasciae, interosseous membranes. Parallelally arranged collagen fibers are thin beams of the 1st order. Between them are the so-called tendon cells with characteristic dark nuclei of elongated shape. Bunches of collagen fibers of the 1st order are combined into thicker bundles of the second order, which are separated by interlayers of fibrous connective tissue. These bundles are formed tightly packed into the layers by collagen fibers, which in the adjacent layers cross almost at right angles. Between the layers there are flattened multigrade fibroblasts.
Elastic connective tissue forms an elastic cone of the larynx and its vocal cords, yellow ligaments, participates in the formation of the walls of the arteries of the elastic type (aorta, pulmonary trunk). The main elements of this tissue are closely adjacent elastic fibers, between which lie a small number of fibroblasts. Thin-fibrillar network, formed by collagen and reticular microfibrils, envelops the elastic fibers.
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