Histology presentation

1. The white adipose tissue
Unilocular adipose tissue

2. Unilocular adipose tissue
 Made up of unilocular adipose cells
 Unilocular adipose cells have one
large fat droplet in cell
 Predominantly in adult humans

3. Unilocular adipose tissue

4. Anatomy of Unilocular
Adipocytes
 Generally large cells 50-150μm
 Spherical when isolated,
polyhedral/oval in situ
 Large owing to lipid accumulation in
cell
 Flattened nucleus displaced to one
end of lipid mass
 Thin rim cytoplasm around lipid mass
 External lamina made of type IV
collagen

5. Anatomy of white adipose
tissue
 Grossly viewed as white/ yellowish
mass.
 Tissue has a rich blood supply
 Capillaries found where adjacent
adipocytes meet
 Numerous mast cells present
 Unmyelinated nerve cells present

6. FUNCTIONS OF WHITE
ADIPOSE TISSUE
SYNTHESIS, STORAGE AND
MOBILISATION OF LIPIDS
INSULATION
CUSHIONING OF VITALS
SECRETION OF HORMONES

7. 1. SYNTHESIS, STORAGE &
MOBILISATION OF LIPIDS
 Triglycerides are synthesised from
dietary fats.
 Dietary fats ~ VLDL, chlyomicrons,
free fatty acids, glycerol
 Chlyomicrons intestinal epithelial cells
product of digestion
 VLDL complexes of lipids and proteins
 Adipocytes secrete lipoprotein lipase
to hydrolyse VLDL & chlyomicrons

8. SYNTHESIS, STORAGE &
MOBILISATION OF LIPIDS
(contd) Free fatty acids absorbed into adipocytes
 Resynthesis into triglycerides
 Fusion with glycerol phosphate
triglyceride
 Triglyceride deposition into growing lipid
droplet
o Role of insulin;
 Stimulates uptake of glucose
 Increased synthesis of lipoprotein lipase
 Inhibits hormone sensitive lipase

9. MOBILISATION OF FATTY
ACIDS
 Hormonal or nervous stimulation e.g.
Glucagon; Growth hormone;
Norepinephine
 Activation of hormone sensitive lipase
 Breakdown of triglycerides at surface
of lipid droplet
 Triglyceride FFA glycerol
albumen bound liver bound

10. 2. Insulation
 Panniculus adiposus layer under skin
 Adipose tissue high concentration of
fat thus poor heat conduction
 Helps thermally insulate the body
 Concentration under skin of abdomen,
buttocks and thighs, breasts
 Distribution influenced by age and
gender
sex hormones and adrenocorticoid

11. Insulation image
#distribution of fat

12. 3. Cushion
 Internally cushions vital organs like the
liver, heart, kidneys etc
 The fat acts as a space filler bringing
stability to the organs
 Shield from ever mobile external
environment
 Preferential locations; greater omentum,
mesentry, retroperitoneal space
 Retains this structural function even
under stress
 Fat in these locations undepleted

13. 4. HORMONAL SECRETION
 Endocrine organ qualities
 Synthesis and secretion of growth
factors and cytokines
Leptin
 16 kDa peptide hormone
 Synthesised in unilocular cells
 Functions in regulation of energy
homeostasis
 Satiety factor that inhibits food intake

14. HORMONAL SECRETION
(Leptin contd)
 Communication of energy state of
adipose tissue to regulators
 Appetite killer
 Regulates the formation of new white
adipose tissue
 Stimulates the metabolic rate i.e.
Triglyceride catabolism

15. HORMONAL SECRETION
(contd)
OTHER HORMONES PRODUCED
 Angiotensinogen (AGE)
 Adiponectin
 Resisten
 Steroid hormones e.g. Testosterone,
oestrogen, glucocorticoids

16. HISTOGENESIS OF
UNILOCULAR ADIPOSE

17. HISTOGENESIS OF UNILOCULAR
ADIPOSE
MESENCHYMAL
STEM CELL
• PLURIPOTENT CONNECTIVE TISSUE CELL
(MESNCHYMAL)
• PEROXISOME PROLIFERATOR ACTIVATOR ACCEPTOR
(PPAR)
EARLY LIPOBLAST,
MIDSTAGE
LIPOBLAST
• EARLY LIPOBLAST RESEMBLES FIBROBLAST
• MIDSTAGE ASSUMES OVAL SHAPE
• BOTH ARE MULTILOCULAR
LATE LIPOBLAST
MATURE
LIPOBLAST
• THE LATE LIPOBLAST ASSUMES A POLYHEDRAL SHAPE
• COALESCENCE OF THE TRIGLYCERIDES UNILOCULAR

18. MEDICAL IMPLICATIONS