This chapter should help the student to:
- Relate the functions of adipose tissue to its structural characteristics.
- Describe adipose tissue as a connective tissue in terms of its cells, fibers, and ground substance.
- Know the differences and similarities between the two types of adipose tissue.
- Recognize the type of adipose tissue present in a micrograph of a tissue or organ.
1. Explain why the body must store fuel (I.A).
2. List the functions of unilocular (white, yellow) adipose tissue (II.A–C).
3. Describe collagen and reticular fiber distribution in adipose tissue (I.B).
4. Compare unilocular and multilocular adipose tissue in terms of:
Cell size (II.A; III.A)
Cytoplasmic lipid distribution (II.A; III.A)
Nuclear shape and location (II.A; III.A)
Number of mitochondria (II.A; III.A)
Organelle distribution (II.A; III.A)
Precursor cell (II.D; III.D)
Function (II.C; III.C)
Vascular supply (II.A)
Autonomic nerve distribution (II.C.2.c; III.C)
Abundance (II.A; III.A)
Location (II.B; III.B)
5. Name the chief biochemical constituent of the lipid droplets in adipocytes (II.C).
6. List the factors that lead to:
Increased lipid storage and synthesis by adipocytes (lipogenic factors; II.C.1)
Increased lipid mobilization by adipocytes (lipolytic factors; II.C.2)
7. During starvation, which lipid deposits are mobilized first and which are mobilized last (II.C.2)?
8. Describe the source, target, and activity of the hormone, leptin. Explain leptin resistance and its consequences (II.D).
9. What accounts for the color of brown adipose tissue (III.A) and of yellow adipose tissue (II.A)?
I. General Features of Adipose Tissue
Adipose tissue, or fat, is a connective tissue that is specialized to store fuel. If we were unable to store fuel, all of our time would be spent obtaining food. The cytoplasm of fat cells, or adipocytes, contains large triglyceride deposits in the form of one or more lipid droplets with no limiting membranes. Together, adipocyte clusters throughout the body constitute an important metabolic organ that varies widely in size and distribution, depending on such factors as age, sex, and nutritional status.
Adipocyte clusters are divided into lobes and lobules by connective tissue septa of variable density. Individual cells are surrounded by a reticular fiber network. Ground substance is sparse.
There are two basic types of adipose tissue: white adipose tissue (white fat) and brown adipose tissue (brown fat).
A. Distinguishing Features
White adipose tissue, the more abundant of the two types, is also termed unilocular adipose tissue—a reference to the single fat droplet in each cell. In mature adipocytes, the droplet is so large that it displaces ...