Dermatophytes involve-
**Core Concept**
Dermatophytes are a group of fungi that infect the outermost layers of the skin, hair, and nails, causing conditions such as ringworm, athlete's foot, and onychomycosis. They obtain their nutrients by breaking down keratin, a protein found in these tissues.
**Why the Correct Answer is Right**
Dermatophytes infect the keratinized tissues by producing enzymes that break down keratin, such as keratinases and proteases. These enzymes degrade the keratin protein into smaller peptides and amino acids, which can be absorbed by the fungi. The infection occurs when the fungi penetrate the outermost layers of the skin, hair, or nails, and begin to produce these enzymes.
**Why Each Wrong Option is Incorrect**
**Option A:** Dermatophytes are not known to involve the mucous membranes, such as those found in the respiratory or gastrointestinal tracts.
**Option B:** While dermatophytes do infect keratinized tissues, they do not involve the deeper layers of the skin, such as the dermis or hypodermis.
**Option C:** Dermatophytes do not involve the underlying tissues, such as muscles or bones.
**Clinical Pearl / High-Yield Fact**
Dermatophytes are typically spread through direct contact with an infected person or contaminated surface, and can also be transmitted through contaminated clothing or footwear.
**Correct Answer: D. Dermatophytes are fungi that infect the keratinized tissues, obtaining their nutrients by breaking down keratin.**