Difference Between Astrocytes and Oligodendrocytes

The key difference between astrocytes and oligodendrocytes is that astrocytes are the most common type of glial cells in the central nervous system and they form the blood brain barrier and regulate chemicals around the neurons while oligodendrocytes are the glial cells that synthesize the myelin sheath around the axons of the central nervous system

Glial cells, also known as neuroglia, are a type of supportive cells in the central nervous system. They are non-neural cells involved in regulating homeostasis in CNS and PNS and provide support and protection to the functioning of the nervous system. They hold the neurons in place and provide adequate nutrients and oxygen to them. They also insulate neurons by forming insulating layers around the axons, destroy potential pathogens and remove dead neurons from the nervous system. There are different types of glial cells as oligodendrocytes, astrocytes, ependymal cells, Schwann cells, microglia, and satellite cells. Both oligodendrocytes and astrocytes originate from a common lineage of neural progenitor cells.

CONTENTS

1. Overview and Key Difference
2. What are Astrocytes 
3. What are Oligodendrocytes
4. Similarities Between Astrocytes and Oligodendrocytes
5. Side by Side Comparison – Astrocytes vs Oligodendrocytes in Tabular Form
6. Summary

What are Astrocytes?

Astrocytes are the most numerous types of glial cell in the brain. They are star-shaped cells. There are two types of astrocytes as fibrous astrocytes and protoplasmic astrocytes. Fibrous astrocytes have long and slender arms while protoplasmic astrocytes have thick projections with lots of branches.

Astrocytes carry out several major functions in the brain. They form the blood brain barrier and regulate chemicals around the neurons and blood flow to the brain. Furthermore, astrocytes regulate brain energy metabolism and homeostasis. Apart from that, astrocytes play a key role in supplying food, water and ions from the periphery to the brain and in synchronizing the activity of axons.

What are Oligodendrocytes?

Oligodendrocytes are glial cells that form myelin sheaths in order to insulate the neuron axons of the central nervous system of the higher vertebrates. These cells are found ubiquitously throughout the CNS, in both white and grey matter. Oligodendrocytes are the prime supportive cells of the CNS.  They have a small cytoplasm surrounding a round nucleus. Moreover, they have several cytoplasmic processes branching out from the cell body. They look like spikey balls.

The central nervous system houses oligodendrocytes in order to form myelin sheaths around the axons. Myelin sheaths insulate the axons to prevent the loss of signals and to increase the rate of signal transmission. A single oligodendrocyte is capable of creating myelin sheath segments in about 50 axons since cytoplasmic processes of a single oligodendrocyte can extend up to 50 adjacent axons and form myelin sheaths. In addition to forming myelin sheath, oligodendrocytes secrete some growth factors to help neuronal growth and development.

What are the Similarities Between Astrocytes and Oligodendrocytes?

• Both astrocytes and oligodendrocytes are microglia cells in the central nervous system.
• They are supportive cells of the neurons in the CNS.
• Astrocytes, oligodendrocytes, and other cells originate from a flat sheet of neuroepithelial cells which are the earliest precursors in the developing CNS.

What is the Difference Between Astrocytes and Oligodendrocytes?

Astrocytes are the star-shaped glial cells that form the blood brain barrier, regulate chemicals around the neurons and blood flow to the brain. Oligodendrocytes, on the other hand, are the glial cells that form the myelin sheath around the axons. So, this is the key difference between astrocytes and oligodendrocytes. Moreover, astrocytes are the most common glial cells in the CNS compared to oligodendrocytes.

Furthermore, astrocytes are star-shaped while oligodendrocytes look like spikey balls. Astrocytes are involved in the formation of the blood brain barrier, regulation of chemicals around the neurons, regulation of the blood flow to the brain and regulation of the metabolism in the brain. In contrast, oligodendrocytes participate in the formation of a protective layer called the myelin sheath around the axons. They also provide stability and carry energy from blood cells to the axons. Thus, this is the functional difference between astrocytes and oligodendrocytes.

Summary – Astrocytes vs Oligodendrocytes

Astrocytes and oligodendrocytes are two types of glial cells in the central nervous system. Astrocytes are the most abundant glial cells in the central nervous system. They are star-shaped, and they play essential functions in blood brain barrier maintenance, neuronal survival, and in synapse formation, strength, and turnover. Oligodendrocytes are the glial cells that synthesize myelin sheath.  Myelin sheaths wrap around the axons to allow fast saltatory conduction of action potentials. Moreover, oligodendrocytes provide axonal metabolic support and contribute to neuroplasticity. Thus, this summarizes the difference between astrocytes and oligodendrocytes.

Reference:

1. “Glia.” Wikipedia, Wikimedia Foundation, 27 July 2020, Available here.
2. “Types of Glia.” Queensland Brain Institute, 16 June 2017, Available here.

Image Courtesy:

1. “Astrocyte5” By GerryShaw – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Neuron with oligodendrocyte and myelin sheath” (Public Domain) via Commons Wikimedia