White adipocyte : easy and brief description

White adipocyte :

These types of adipocytes are predominantly found in adult. White adipocytes are spherical, but they may appear polyhedral or oval when crowded together. It contains unilocular fat which store triglyceride, flatten nucleus, rim of cytoplasm. Adipocyte looks like signet ring so it also known as signet ring cell.  Early lipoblasts look like fibroblasts but develop small lipid inclusions and a thin external lamina.

Unilocular adipocytes are large cells, sometimes 100 µm or more in diameter. The lipid mass in the adipocyte is not membrane bounded. It thin cytoplasmic rim contain a Golgi complex, few poorly developed mitochondria, poorly developed cisternae of the rough endoplasmic reticulum, and free polyribosomes,  the lipid droplet contains cisternae of smooth endoplasmic reticulum and numerous pinocytotic vesicles. Each adipose cell is surrounded by a basal lamina.

Innervation: Few sympathetic nerve fibers

Secretions:  White adipose tissue produces a variety of hormones, growth factors, and cytokines.

ASP(Acylation-stimulating protein ) Influences the rate of triglyceride synthesis in adipose tissue

Insulinlike growth factor I (IGF-I) : Stimulates proliferation of a wide variety of cells and mediates many of the effects of growth hormone

Leptin Regulates appetite and body energy expenditure

Plasminogen activator inhibitor-1 (PAI-1):  Inhibits the fibrinolytic system

Elevated levels are associated with increased formation of blood clots

Prostaglandins I2 F2_, (PGI2 and PGF2_) Helps regulate inflammation, blood clotting, ovulation, menstruation,and acid secretion

Resistin:  Increases insulin resistance ,Linked to obesity and to type 2 diabetes

Distribution: subcutaneous tissue, breast, greater omentum, mesenteries, visceral pericardium, orbital cavity, retroperitoneal space, bone marrow

Metabolism:

It hydrolyzes the stored lipids into fatty acids and glycerol, which are released from the cell.

 Functions of white adipose tissue include

1.      metabolic energy storage,

2.      insulation,

3.      cushioning of vital organs, and

4.      secretion of hormones,

5.       Source of metabolic water.  

6.       Subcutaneous layers of adipose tissue help to shape the surface of the body, whereas deposits in the form of pads act as shock absorbers, chiefly in the soles and palms.