Adipose Tissue
I. Introduction
§ Fat cells or adipocytes found in aggregate of varying sizes constitute adipose tissue
§ Accounts of 20-25% of weight in women and 15-20% of weight in men
§ Mesenchymal cell –> lipoblast –> multilocular or unilocular adipocytes
II. White adipose tissue
§ Unilocular fat
§ Most common
§ Single large lipid inclusion
§ May occur singly or in groups (tissue has empty appearance)
§ Ubiquitously distributed
III. Brown adipose tissue
§ Uncommon in adult humans
§ Heat generation (hibernation, survival after birth , during cold stress ((main site of non shivering heat production)
§ Widely distributed in first decade of life in humans, later confined to kidney
§ Lipid accumulates in fact cells as individual droplets ie multilocular pattern
§ Lipolysis- fatty acid enter mitochondria where oxid phos increases and energy liberated.
§ Dark color: Mitochondria and rich vascularity
IV. Brown is not white
§ Unilocular fat from fibroblst like precursor into cell with multiple lipid droplets (sim to brown); droplets coalesce into single lipid droplet
§ Extreme fasting can reverse this pattern, transforming cell to unilocular to multilocular to fibroblast like cell
§ Thus brown and white can resemble each other
§ But diff in mitochondria, vascularity, and function
|
|
White Fat |
Brown Fat |
|
Location in humans |
Ubiquitous at all ages |
Imp on in new born |
|
Composition |
82% fat, 15% water, 3% protein |
30% fat, 55% water, 15% protein |
|
Blood supply |
Rich capillary supply |
Much denser than white |
|
Innervation |
Sympathetic |
Sympathetic |
|
Function |
Food storage, padding |
Thermogenesis |
|
Derivation |
White-specific mesenchymal cell |
Brown specific cell |
|
Morphology |
Unilocular 80-150 mm |
Multilocular, 8-60 mm, prom mitoch. |
Tags: adipocytes, Adipose Tissue, Brown adipose tissue, fibroblst, lipid accumulation, lipid inclusion, lipoblast, Lipolysis, mesenchymal cell, mitochondria, Unilocular fat, White adipose tissue
