Each cilium requires a basal body. The generation of centrioles, which occurs during the process of ciliogenesis, is responsible for the production of basal bodies. The newly formed centrioles migrate to the apical surface of the cell and serve as  organizing centers for the assembly of the microtubules of the cilium. The core structure (axoneme) of a motile cilium is composed of a complex set of microtubules consisting of two central microtubules surrounded by nine microtubule doublets (9 2 configuration). The organizing role of the basal body differs from that of the MTOC. The axonemal microtubule doublets are continuous with the A and B microtubules of the basal body from which they develop by addition of and -tubulin dimers at the growing plus end. A detail description of the structure of cilia, basal bodies, and the process of ciliogenesis can be found in Chapter 5, Epithelial Tissue.
Inclusions contain products of metabolic activity of the cell and consist largely of pigment granules, lipid droplets, and glycogen.
Inclusions are cytoplasmic or nuclear structures with characteristic staining properties that are formed from the metabolic products of cell. They are considered nonmoving and nonliving components of the cell. Some of them, such as pigment granules, are surrounded by a plasma membrane; others (e.g., lipid droplets or glycogen) instead reside within the cytoplasmic or nuclear matrix.  Lipofuscin is a brownish-gold pigment visible in routine
H&E preparation. It is easily seen in nondividing cells such as neurons and skeletal and cardiac muscle cells. Lipofuscin accumulates during the years in most eukaryotic cells as a result of cellular senescence (aging); thus, it is often called the “wear-and-tear” pigment. Lipofuscin is a conglom erate of oxidized lipids, phospholipids, metals, and organic molecules that accumulate within the cells as a result of oxidative degradation of mitochondria and lysosomal digestion. Phagocytotic cells such as macrophages may also
One of the critical components of normal cell division is the precise redistribution of chromosomes and other cell or-ganelles during mitosis. Following replication of chromoso-mal DNA in the S phase of the cell cycle, centrioles undergo a single round of duplication that is closely coor-dinated with cell-cycle progression. During mitosis, centri-oles are responsible for forming the bipolar mitotic spindle, which is essential for equal segregation of chromosomes between daughter cells. Alterations of mechanisms regu-lating centriole duplication may lead to multiplication and abnormalities of centrioles and surrounding centrosomes (MTOCs). Such changes may distort the mitotic spindle (i.e., the presence of multipolar or misoriented spindles) (Fig. F.2.3.1), leading to abnormal sorting of chromosomes during cell divisions. The resulting changes in chromoso-mal number (aneuploidy) may increase the activity of onco-genes or decrease protection from tumor-suppressor genes. These changes are known to promote malignant cell transformation. Increased numbers of centrioles are frequently observed in tumor cells. 