White adipose tissue

(hematoxylin and eosin)

is found in the omentum, mesentery, retroperitoneal space, and beneath the skin (hypodermis)

Hypodermis (subcutaneous tissue):

• is formed by clusters of large (50-150 μm) adipose cells, which have a spherical shape (they may be of irregular shape on slides)
• a mature adipose cell is marked by the cytoplasm that is almost entirely filled by a single lipid droplet; such cells are unilocular adipose cells (when processed with alcohol, lipids are removed from the adipose cells, and the cytoplasm becomes empty, except for a thin peripheral rim)
• small elliptical nuclei are eccentric
• takes part in lipid storage and mobilization, exerts such functions as mechanical support, thermal insulation, endocrine production (1synthesis of estrogens and of leptin hormone, which signals satiety)

There are stripes of loose connective tissue between the clusters of adipose cells

Brown adipose tissue

(hematoxylin and eosin)

is well-developed in newborns; in adult persons, it is found in the interscapular region, armpits, between great vessels of the neck, and in the perirenal adipose tissue

Brown adipose tissue:

• consists of smaller (up to 60 μm) adipose cells of irregular shape (compared to white adipose tissue)
• the cytoplasm of adipose cells is filled there by numerous rather fine lipid droplets. These cells are multilocular adipose cells (the cytoplasm becomes cellular after a removal of lipids)
• has rounded nuclei that are found centrally or are slightly eccentric
• contains a dense network of blood capillaries #1, #2, #3
• participates in heat generation

The perirenal adipose tissue also comprises some white adipose tissue.

The section shows a renal pelvis lined by transitional epithelium, as well as a part of renal pyramid with tubules lined by simple squamous and simple cuboidal epithelium.

For more details see Electron microscopy image of a brown adipose cell