This higher-magnification view of the boxed area in upper figure shows the interconnections of the bone spicules (BS) of the developing mandible. Within and around the spaces enclosed by the developing spicules is mesenchymal tissue. These mesenchymal cells will give rise to new osteoblasts as well as to the cells that will form the vascular components of the bone. The more dense connective tissue (CT) will differentiate into the periosteum on one side of the developing mandible. Other structures shown in the field include numerous blood vessels (BV) and the enamel organ of a developing tooth (DT).
(Ob2) that are actively secreting new osteoid appear as tall, columnar-like cells adjacent to osteoid. One of the spicules shows a cell completely surrounded by bone matrix; this is an osteoblast that has become trapped in its own secretions and is now an osteocyte (OC). At this magnification, the very loose connective tissue characteristics of the mesenchyme and the sparseness of the mesenchymal cells (MC) are well demonstrated. The highly cellular connective tissue (CT) on the right margin of the figure is the developing perichondrium. Some of its cells will also develop into osteoblasts to allow growth of the bone at its surface.
• KEY BS, bone spicules BV, blood vessels CT, connective tissue DT, developing tooth EO, enamel organ Ep, epithelium MC, Meckel’s cartilage (Fig. 1.) MC, mesenchymal cells (Fig. 3.) Ob1 , inactive osteoblast Ob2 , active osteoblast OC, oral cavity (upper figure) OC, osteocyte (lower right figure)
OVERVIEW OF ADIPOSE TISSUE / 254 WHITE ADIPOSE TISSUE / 254 Function of White Adipose Tissue / 254 Differentiation of Adipocytes / 255 Structure of Adipocytes and Adipose Tissue / 256 Regulation of Adipose Tissue / 257 BROWN ADIPOSE TISSUE / 259 Folder 9.1 Clinical Correlation: Obesity / 261 Folder 9.2 Clinical Correlation: Adipose Tissue Tumors / 262 Folder 9.3 Clinical Correlation: PET Scanning and Brown Adipose Tissue Interference / 264
Adipose tissue is a specialized connective tissue that plays an important role in energy homeostasis.
Individual fat cells, or adipocytes, and groups of adipocytes are found throughout loose connective tissue. Tissues in which adipocytes are the primary cell type are designated adipose tissue. Adipocytes play a key role in energy homeostasis.
For its survival, the body needs to ensure a continuous delivery of energy despite highly variable supplies of nutrients from the external environment. To meet the body’s energy demands when nutrient supplies are low, adipose tissue efficiently stores excess energy. The body has a limited capacity to store carbohydrate and protein, therefore energy reserves are stored within lipid droplets of adipocytes in the form of triglycerides. Triglycerides represent a dynamic form of energy storage that is added to when food intake is greater than energy expenditure and is tapped when energy expenditure is greater than food intake. The energy stored in adipocytes can be rapidly released for use at other sites in the body.