78 HUMAN TISSUES 



I. Describe the material covering the enlarged head of the bone. 



A. Is this material (cartilage or gristle) shiny or dull; moist or dry; 

 smooth or rough ; tough or soft ? 



II. How does the texture of the bone under the cartilage differ from the 

 bone of the shank ? 



III. Describe the material filling the space in the center of the bone. This 

 is bone marrow and consists largely of fat cells. Compare the marrow in the 

 head of the bone with that in the other parts. 



IV. The outer membranous covering of bone is the periosteum (peri — 

 around; osteon — bone). 



Problem. Siudy of microscopic structure of bone. 



I. Mount a prepared slide of bone cells under the microscope. Note the 

 spiderlike, irregular cells arranged around a central space. In living bone, this 

 space is filled with blood vessels and nerves. Food passes through the blood 

 vessels to the cells, and wastes from the cells are diffused into the blood 

 vessels. The bone cells take calcium salts from the blood and deposit these 

 minerals around their irregular projections. 



A. Explain why bone cells with irregular projections of cytoplasm 

 deposit greater amounts of intercellular mineral matter than they would 

 if these cells were perfectly round. 



B. Suggest a material that probably fills the spaces among the bone 

 cells. 



C. Draw a single bone cell five times larger than it appears under the 

 microscope. 



D. Draw a group of bone cells showing how they fit together and 

 how they are arranged around the space through which the blood vessels 

 run. Label cell, intercellular material, and canal. 



U. Mount a prepared slide of hyaline cartilage under the microscope. 



A. Describe the shape of the cells. 



B. Describe the formation of the cells. 



C. Wliat evidence of intercellular material is there ? The intercellular 

 material of hyaline cartilage appears homogeneous throughout. 



D. Draw a group of cartilage cells. Label cell, intercellular material, 

 or matrix. 



Cartilage and bone are closely related in their development, 

 location, and function. In the embryo, the bones are first pre- 



