Blood brain barrier is formed by
(a) Astrocytes
(b) Oligodendrocytes
(c) Glial cells
(d) Microglial cells

Options

A. Astrocytes
B. Oligodendrocytes
C. Glial cells
D. Microglial cells

Answer

To answer the question "Blood brain barrier is formed by", let's analyze the options provided step by step:

1. **Understanding the Blood-Brain Barrier (BBB)**:
- The blood-brain barrier is a selective permeability barrier that separates the circulating blood from the brain and extracellular fluid in the central nervous system (CNS). It is crucial for maintaining the brain's environment.

**Hint**: Remember that the BBB protects the brain by controlling what substances can enter from the blood.

2. **Components of the Blood-Brain Barrier**:
- The BBB is primarily composed of specialized endothelial cells that line the brain's capillaries. These cells are tightly joined together, preventing most substances from passing through.
- In addition to endothelial cells, the BBB includes a basement membrane, neuroglial membrane, and glial podocytes.

**Hint**: Focus on the types of cells involved in forming the barrier.

3. **Role of Astrocytes**:
- Among the various cells involved in the formation of the BBB, astrocytes play a significant role. They have projections that extend to the blood vessels and help regulate the permeability of the barrier.
- Astrocytes are a type of glial cell, but they have a specific function in maintaining the integrity of the BBB.

**Hint**: Consider which type of glial cell has a direct role in forming and maintaining the BBB.

4. **Evaluating the Options**:
- (a) Astrocytes: Correct, as they are crucial for the formation of the BBB.
- (b) Oligodendrocytes: Incorrect, as they primarily provide support and insulation to axons in the CNS.
- (c) Glial cells: While astrocytes are a type of glial cell, this option is too broad and does not specifically identify the key player.
- (d) Microglial cells: Incorrect, as they are involved in immune defense within the CNS but do not form the BBB.

5. **Conclusion**:
- The correct answer is (a) Astrocytes, as they are the primary cells involved in the formation and maintenance of the blood-brain barrier.

**Final Answer**: (a) Astrocytes