Centre of tubercular granuloma is formed by –
**Core Concept**
The centre of a tubercular granuloma is formed by a collection of necrotic tissue and caseous material, which is a hallmark of tuberculosis infection. This process is mediated by the body's immune response to the Mycobacterium tuberculosis bacteria.
**Why the Correct Answer is Right**
The centre of a tubercular granuloma is formed by the necrosis of infected macrophages, which accumulate in the area and eventually die due to the overwhelming infection. This leads to the formation of a caseous centre, which is a mixture of dead cells, bacteria, and cellular debris. The caseous centre is surrounded by a rim of epithelioid cells, which are activated macrophages that have engulfed the bacteria. The presence of a caseous centre is a key feature of tuberculosis and is used as a diagnostic criterion.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the centre of a tubercular granuloma is not formed by lymphocytes. While lymphocytes play a crucial role in the immune response to tuberculosis, they are not the primary cells that form the centre of a granuloma.
**Option B:** This option is incorrect because the centre of a tubercular granuloma is not formed by neutrophils. Neutrophils are a type of white blood cell that plays a key role in acute inflammation, but they are not typically involved in the formation of granulomas.
**Option C:** This option is incorrect because the centre of a tubercular granuloma is not formed by plasma cells. Plasma cells are a type of white blood cell that produces antibodies, but they are not typically involved in the formation of granulomas.
**Clinical Pearl / High-Yield Fact**
The presence of a caseous centre in a granuloma is a key feature of tuberculosis and is used as a diagnostic criterion. However, it's worth noting that not all granulomas with a caseous centre are due to tuberculosis - other conditions such as sarcoidosis can also present with caseous granulomas.
**Correct Answer: C. Langhans giant cells and necrotic debris.**