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Connective Tissue

fibres, cells, white, substance, ground and found

CONNECTIVE TISSUE, the most im portant supporting tissue of the body, derived like bone and cartilage from the mesenchyme of the embryo. It is made up of cells, which are relatively scanty, fibres and an intercellular ground substance secreted by the cells. The cells may be amceboid (in embryonic tissue), or may be the vacuolated so-called plasma-cells, or may assume a spindle-like or plate-like shape; and may contain pigment, granules of substance showing a peculiar affinity for certain dyes or fat. Besides these cells formed in situ, leucocytes often invade connective tissue. The white fibres of connective tissue are formed in bundles, are easily stained by acid fuchsin, yield gelatin on boiling, and are digested by artificial gastric juice, though not by pan creatin. The yellow fibres or elastic fibres, un like the white branch and anastamose, are highly refractive, and during life, owing to the tension under which they are, are straight They are only slowly digested by the gastric juice, but rapidly by the pancreatic pice. Orcein acts as a specific stain for elastic tissue. The so-called reticulutn is made up of fibres much like the white fibres, but not so easily attacked by artificial gastric juice.

Embryonic connective tissue is made up of spindle-shaped and amceboid, stellate cells, with few fibres and, in the less mature tissues, all of these white. The ground substance is fluid. Embryonic connective tissue is found not only in fceti and infants, but also in tumors and during the regeneration of injured connective tissue.

Gelatinous connective tissue occurs only in the umbilical cord and in the vitreous humor of the eye. It contains plate-like cells and rcticulum, sparse in thc vitreous humor and relatively dense in the umbilical cord. The ground substance is gelatinous.

Areolar connective tissue occupies all other wise unfilled regions. The white fibres form interlacing bundles. The elastic fibres are isolated and comparatively few in number.

The cells are of all varieties. The ground sub stance is a fluid which can be coagulated by silver nitrate.

Dense white fibrous tissue consists mainly of parallel bundles of white fibres with plate like cells in their interstices. Yellow fibres are scarce and there is little ground substance. This tissue forms most tendons, ligaments, fascial and muscular sheaths, and envelopes many of the viscera. The valves of the heart, the chordm tendinw and the tendinous rings about the mouths of the great vessels are all formed from white fibrous tissue.

Elastic tissue is made up of bundles of elastic fibres with sheaths of white fibres. It contains but little ground substance. It is found in the ligasnenta subflava dorsal to the spinal column and in the ligamentum nuchm supporting the head in the lower mammals.

Adipose tissue is composed of cells dis tended until they have become mere sacs of fat and of fibrous bands supporting these cells. It is found beneath the skin of many parts c,f the body, about the lymphatic nodes, adrenals and kidneys, in thc mediastinum and the grooves of the heart wall, and in the mesentery and omentum.

Reticular tissue is found as the stroma of many glands and in hone marrow. Its tissue juice is lymph. It consists of a reticulum of fibres closely joined in anastomosing bundles, with cells of a plate-like nature at the points of bifurcation.

Lymphoid tissue is reticular tissue per meated by the close-packed spheroidal lym phatic corpuscles. Lymphoid tissue is found in the tonsils, spleen, thymus, lymphatic glands, and in Peyers patches and the solitary follicles of the intestine. More diffuse lymphoid tissue is found elsewhere in the respiratory and di gestive tract.

Connective tissues are richly supplied with blood vessels and nerves. They are nourished by the lymph exuding from the blood capil laries. The waste products of metabolism are taken up by the lymph capillaries.