d. Mitochondria (Plural). Mitochondria are the "powerhouses" of the cell. The
mitochondria provide the energy wherever it is needed for carrying on the cellular
e. Endoplasmic Reticulum. The endoplasmic reticulum is a network of
membranes, cavities, and canals. The endoplasmic reticulum helps in the transfer of
materials from one part of the cell to the other.
f. Ribosomes. Ribosomes are "protein factories" in the cell. They are
composed mainly of nucleic acids which help make proteins according to instructions
provided by the genes.
g. Centrioles. Centrioles help in the process of cell division.
h. Lysosomes. Lysosomes are membrane bound spheres which contain
enzymes that can digest intracellular structures or bacteria.
Individual cells have fairly specific life spans. Some types of cells have longer
life spans than others. During the processes of growth and repair, new cells are being
formed. The usual process of cell multiplication is called mitosis. There are two
important factors to consider:
a. From one cell, we get two new cells.
b. The genes of the new cells are identical (for all practical purposes) to the
genes of the original cell.
Hypertrophy and hyperplasia are two ways by which the cell mass of the body
a. With HYPERTROPHY, there is an increase in the size of the individual cells.
No new cells are formed. An example is the enlargement of muscles due to exercise by
the increased diameter of the individual striated muscle fibers.
b. With HYPERPLASIA, there is an increase in the total number of cells. An
example of abnormal hyperplasia is cancer.
c. ATROPHY is seen when there is a loss of cellular mass.