A 75-year-old man has a history of transient attacks of loss of vision. The only abnormalities on physical examination are bruits over the carotids in the neck. Two days later he suddenly becomes hemiplegic and loses consciousness. He is rushed to the emergency room and a CT scan shows evidence of cerebral infarction. He is put on life support but dies 5 days later. At autopsy, there is an area of necrosis and microscopically these lesions are noted to have increased numbers of cells distributed around the central zone of necrosis. Which of the following cell types is most likely to have a phagocytic function in these lesions?
A 75-year-old man has a history of transient attacks of loss of vision. The only abnormalities on physical examination are bruits over the carotids in the neck. Two days later he suddenly becomes hemiplegic and loses consciousness. He is rushed to the emergency room and a CT scan shows evidence of cerebral infarction. He is put on life support but dies 5 days later. At autopsy, there is an area of necrosis and microscopically these lesions are noted to have increased numbers of cells distributed around the central zone of necrosis. Which of the following cell types is most likely to have a phagocytic function in these lesions?
💡 Explanation
## **Core Concept**
The question revolves around the pathophysiology of cerebral infarction (stroke) and the cellular response to tissue necrosis in the brain. Specifically, it focuses on the types of cells involved in the phagocytosis of necrotic tissue.
## **Why the Correct Answer is Right**
In the context of cerebral infarction, after the initial necrotic damage, the body responds with an inflammatory reaction. Part of this response involves the infiltration of various types of cells, including those with phagocytic capabilities, to clean up the necrotic debris. Microglia are the resident macrophages of the brain and play a critical role in the immune surveillance and response within the central nervous system (CNS). Following cerebral infarction, microglia are activated, proliferate, and accumulate around the area of necrosis. They have a phagocytic function, helping to clear dead neurons and cellular debris.
## **Why Each Wrong Option is Incorrect**
- **Option A:** Astrocytes are a type of glial cell in the brain that provide nutrients to neurons, maintain the blood-brain barrier, and are involved in the repair and scarring process of the brain and spinal cord following traumatic injuries. While they do play a role in the response to brain injury, they are not primarily phagocytic cells.
- **Option B:** Oligodendrocytes are responsible for myelinating neuronal axons in the CNS. They are not known for phagocytic activity.
- **Option D:** Endothelial cells line the interior surface of blood vessels and lymphatic vessels, forming an interface between circulating blood or lymph in the lumen and the rest of the vessel wall. They play critical roles in the regulation of blood pressure, blood clotting, and the formation of new blood vessels. While they interact with immune cells, they are not primarily phagocytic.
## **Clinical Pearl / High-Yield Fact**
A key point to remember is that microglia act as the first and main form of active immune defense in the CNS. Their activation and proliferation are hallmark responses to CNS injury, including cerebral infarction. The presence of increased numbers of cells with phagocytic function around areas of necrosis is indicative of microglial activation.
## **Correct Answer:** .
✓ Correct Answer: D. Microglia
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