## **Core Concept**
Coccidioides immitis is a pathogenic fungus that causes coccidioidomycosis, also known as Valley fever. This fungus exists in two forms: a mold form in the soil and a yeast form in tissues. The tissue form of Coccidioides immitis is characterized by the production of specific structures.

## **Why the Correct Answer is Right**
In tissues, Coccidioides immitis produces **spherules**. Spherules are large, spherical structures that contain endospores. They are a key feature of the parasitic phase of Coccidioides immitis and are formed in the lungs and other tissues of infected individuals. The spherules rupture to release endospores, which then go on to infect other cells and tissues.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not accurately describe the tissue form of Coccidioides immitis.
- **Option B:** This option is incorrect because it does not accurately describe the tissue form of Coccidioides immitis.
- **Option D:** This option is incorrect because it does not accurately describe the tissue form of Coccidioides immitis.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that Coccidioides immitis is endemic to the southwestern United States, Mexico, and parts of Central and South America. Infection typically occurs through inhalation of arthrospores from the soil. Spherules are a diagnostic feature that can be seen in tissue samples from infected patients.

## **Correct Answer:** .