Fattest Organ and Brain Histology

Fat and the Brain

• Common claim: The brain is the fattiest organ
• Question: How can the brain, with billions of neurons, be considered fat?
• Objective: Answer this by comparing a brain to fatty tissue (adipose tissue)

Histology: Study of Tissues

• Determines what something is made of
• Examples: Epidermis - epithelial tissue, Achilles tendon

Examining Adipose Tissue

• Cadaver dissection reveals layers:
  • Epidermis: Thin outer layer
  • Dermis: Thicker than epidermis
  • Hypodermis/Subcutaneous layer: Yellow tissue, adipose tissue
• Adipose tissue functions:
  • Energy storage
  • Insulation
  • Padding/protection
• Microscopic view: Adipose cells store lipids; tissue thickens as cells accumulate more lipids

Functions of Adipose (Fat) Tissue

• Energy storage for survival
• Insulator for body temperature (e.g., in animals like polar bears)
• Provides padding and protection

The Brain's Cellular Composition

• Main cell types: Neurons and Neuroglia cells
• Neurons: Over 100 billion
  • Central cell body, dendrites (signal intake), axon (signal output)
  • Axons can be very long, e.g., from lumbar spinal cord to toe
• Neuroglia cells: 10-50 trillion
  • Functions beyond support: Engulf pathogens, contribute to blood-brain barrier, form myelin sheath

Myelin Sheath and White Matter

• Myelin Sheath: Formed by oligodendrocytes
  • Insulates axons, speeding up electrical signal transmission
• White Matter: Contains myelinated axons; visible glistening in brain dissection

Lipids in Nervous Tissue

• Cell membranes made of phospholipids (a type of lipid)
  • Oligodendrocytes wrap axons with multilayered phospholipid membranes
  • Insulation enhances electrical signal speed (up to 50 times faster)
  • Not the same as adipose tissue but significant in brain function

Conclusion

• Misleading to call the brain fatty tissue or adipose-rich
• Brain's lipid composition relates to myelin sheaths in white matter
• Essential for rapid signal transmission in the nervous system