These include both long-term tissue residents, such as fibroblasts and adipose cells, and transient migratory residents, such as plasma cells and lymphocytes, which move back and forth between tissue space and blood or lymph. They store, synthesize, and secrete lipid under hormonal and neuronal regulation. Unilocular adipocytes have a single, central lipid droplet . They are common in well vascularized loose connective tissue. These cells function in heat generation , and are highly developed in hibernating animals.
Humans have few, primarily in infants.
They enlarge after entering connective tissue and can reside there for months. They can also migrate in tissue in response to various inflammatory stimuli. They are most easily resolved histologically after phagocytizing substances such as ink particles or ferritin. They have abundant lysosomes , reflecting their active role in digesting scavenged material. When stimulated they can also be active in secretion and then have well developed RER and Golgi.