- Type of Connective Tissue.
- Comprises adipocytes (fat cells).
- Located throughout the body.
White Adipose Tissue
- Most common in the body
- "Bubble-like" matrix of large adipocytes that contain a fat droplet when mature.
– White adipocytes are called "unolocular" because of single fat droplet.
– Fat is usually removed in slide preparation by the alcohol, leaving empty vacuole.
– Nucleus is pushed to periphery.
– Other cellular organelles (Golgi, ER, etc.) are also present (not shown in our example).
- Rich vascularization.
- Located throughout the body:
– Subcutaneous deposits with noticeable accumulations in certain areas (breasts, thighs, hips, abdomen).
– Visceral deposits (esp. kidneys, eyeballs; excessive depositions may occur around heart and abdominal viscera, for example).
Functions
–
Triglycerides
– Fatty acids from diet, adipocytes can also synthesize fatty acids from glucose.
– Mitochondria, smooth ER required for lipid uptake and storage.
- Responds nervous and endocrine system cues.
– Releases fatty acids/glycerol into blood.
Adipocytes release leptin*
– "Satiety factor" regulates appetite.
– Poor heat conduction
- Cushions and maintains organ placement
– Absorbs shock
Brown Adipose Tissue
- Numerous fat droplets in adipocytes = "Multilocular"
- Brown adipocytes are smaller than white adipocytes.
- Abundant mitochondria in each cell.
- Central nuclei
- Sympathetic innervation
- Scarce in adults (around collarbones, mediastinum, and kidneys/adrenal glands).
- More prevalent (and more important) in newborns (and hibernating animals).
Functions:
- Nonshivering thermogenesis:
– Mitochondria have thermogenin (aka, uncoupling protein) in inner membranes, which promotes heat production.
– Close association with capillaries allows for heat dissipation via the bloodstream.
- Brown adipose can increase as part of cold adaptation.
