. Essentials of biology presented in problems. Biology. THE METAZOA —DIVISION OF LABOR 205 complex animals the cells are more and more unlike as their work becomes more and more different. Let us sec what these cells may be, what their structure is, and, in a general way, what func- tion each has in the human body. Muscle Cells. — A large part of our body is made up of muscle. Muscle cells are elongated in shape, and have great con- tractile power. Their work is that of causing movement, and this is usually done by means of attachment to a skeleton inside the body. In man the>' may be of tw
. Essentials of biology presented in problems. Biology. THE METAZOA —DIVISION OF LABOR 205 complex animals the cells are more and more unlike as their work becomes more and more different. Let us sec what these cells may be, what their structure is, and, in a general way, what func- tion each has in the human body. Muscle Cells. — A large part of our body is made up of muscle. Muscle cells are elongated in shape, and have great con- tractile power. Their work is that of causing movement, and this is usually done by means of attachment to a skeleton inside the body. In man the>' may be of two kinds, voluntary (under con- trol of the will) and r)iae»^ms of sections of cells, greatlj- magnified, e, flat cell (epithelium) from mouth ; c, columnar epithelium from food tube ; b, bone-forming cell ; I, liver cell; m, muscle cell; /, fat cell; n, nervo cell. Epithelial Cells. — Such cells cover the outside of a body or hne the inside of the cavities in the body. The shape of such cells varies from flat plates to little cubes or columns depending upon their position inside or outside the body. Some bear ciha, an adaptation. Can you think of their purpose ? Connective Tissue Cells. — Such cells form the connection between tissues in the body. They are characterized by possess- ing nmnerous long processes. They also secrete, as do many other ceUs, a substance like jelly, called intercellular substance. This stands in the same relation to the cells as does mortar to the bricks in a wall. Several other types of cells might be mentioned, as blood cells, cartilage cells, bone cells, and nerve colls. A glance at the Figure shows their great variety of shapes and Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Hunter, George William, 1873-1948. New York, Cincinnati [etc. ] Americ
Size: 2378px × 1051px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectbiology, bookyear1911
