GENERAL STRUCTURE I 9 



bundles and elsewhere loosely joining structures together. 

 Reticular tissue forms binding tissue of many glands. These 

 recognized by their cells are fat or adipose tissue, pigmented 

 tissue, and lymphatic or adenoid tissue. 



Skeletal connective tissues form the more rigid supporting 

 tissues of the body. They are of two kinds: cartilage and hone. 

 There are three kinds of cartilage, distinguished by the char- 

 acter of the intercellular substance or matrix. 



Hyaline cartilage is characterized by its homogeneous matrix 

 in which the cells are imbedded singly or in groups of two or 

 more. It is the most abundant and is commonly known as 

 gristle. It forms the articular cartilage of long bones, the costal 

 cartilage of ribs, and the cartilages of the respiratory system. 

 The entire embryonic skeleton with exception of a few bones of 

 the skull was at first hyaline cartilage. White fihro cartilage 

 and yelloiv elastic cartilage are recognized by the presence of 

 white or yellow fibers as the name indicates and have a much 

 more limited distribution. 



Bone is a much more compact firm tissue than cartilage and is 

 limited to the skeleton. The superficial layers of flat bones and 

 of the epiphysis and the main portion of the diaphysis or shaft 

 of long bones are composed of compact bone while the middle 

 layer of long flat bones and the larger portion of the epiphysis 

 of long bones is spongy or cancellous bone (Fig. 14). In the 

 epiphysis the plates of cancellous bone are arranged in curved 

 lines such as to give the greatest strength to the bone (Fig. 14). 



Muscular tissues are of three types: striated, unstriated or 

 smooth and cardiac. The voluntary striated are the skeletal 

 muscles of the body. They are composed of long cylindrical 

 fibers or cells having a number of nuclei located peripherally just 

 beneath the cell membrane, or sarcolemma. The unit of struc- 

 ture is the myofibril or sarcostyle which is cross-striated and 

 gives the characteristic appearance to this type of muscle. The 

 number of myofibrillae in each cell or muscle fiber may be 

 very great. The involuntary or smooth muscle cell has no 



