48 TISSUES 



organs respectively. The connective tissues are derived 

 from the mesoderm. 



They are classified as follows: (1) fibrous; (a) loose, 

 (b) dense; (2) yellow elastic; (3) mucous; (4) retiform; 

 (5) mixed or areolar; (6) adipose or fatty; (7) 

 lymphoid; (8) cartilage; (9) bone; (10) dentin (teeth); 

 (11) blood. 



1. Fibrous Tissue. (a) The loose variety consists of 

 fine thread-like fibers held in bundles by a small 

 quantity of cement substance, and scattered through- 

 out those groups of fibrils are seen a few cells. This 

 variety is mostly for the support of capillary blood- 

 vessels, the capsules of organs, and as a suppurative 

 element in the tunica propria and submucosa in the 

 mucous membrane of the respiratory and alimentary 

 tracts. 



(6) The dense variety differs from the former in 

 the fibrils being thicker and the bundles larger. The 

 dense is best seen in tendons of muscles, when it occurs 

 as parallel bundles. Seen under the microscope on 

 a cross-section the whole structure is seen surrounded 

 by a loose sheath of fibers, the epitendineum, from which 

 septa are seen passing into and dividing it into dis- 

 tinct or separate bundles of fibers, the peritendineum. 

 The tendon cells are seen arranged in rows lying 

 between the individual bundles of fibers. 



White fibrous tissue is very strong, inelastic, is 

 pearly white in color, as seen when the skin is removed 

 and dissections made of ligaments and tendons. It 

 serves as a stocking-like covering to muscles, where 

 it is termed fascia; and is seen as a bluish-white mem- 

 brane reinforcing muscles and strengthening their 

 insertions to bones, particularly in the region of joints, 

 called an aponeurosis. 



2. Yellow Elastic Tissue. This, as the name implies, 

 possesses elasticity; the fibrils are coarser than the 

 white variety. It is found in the ligamentum nuchse, 

 which extends from the occipital bone to the spinous 



