**Question:** Keratohyaline granules are more evident in

A. basal cells of the epidermis
B. squamous cells of the epidermis
C. granular cells of the gastrointestinal tract
D. stratum corneum cells

**Correct Answer:** D. stratum corneum cells

**Core Concept:**
Keratohyaline granules are specialized structures found in certain cells of the human body. These granules play a crucial role in the structural and protective functions of the skin and other epithelia. There are four main types of keratohyaline granules: filaggrin, filaggrin-2, loricrin, and involucrin. These granules are essential components of the cornified envelope, which is a key part of the skin barrier function and defense against pathogens and environmental agents.

**Why the Correct Answer is Right:**
Keratohyaline granules are primarily found in cells of the stratum corneum, which is the outermost layer of the epidermis. Specifically, these granules are located in the granular cells of the epidermis (corneocytes) and are crucial for the formation of the cornified envelope, which is essential for the skin's barrier function and protection.

**Why Each Wrong Option is Incorrect:**

A. Basal cells of the epidermis: Keratohyaline granules are not present in these cells. Basal cells are the proliferative cells at the bottom of the epidermis, while keratohyaline granules are located in the granular layer, which is the layer above the basal layer.

B. Squamous cells of the epidermis: Keratohyaline granules are not present in these cells. Squamous cells are the cells in the spinous layer, which is the layer above the granular layer, and not the granular layer where keratohyaline granules are located.

C. Granular cells of the gastrointestinal tract: While granules are present in the granular cells of the gastrointestinal tract, the question is specifically asking about their presence in the epidermis. Keratohyaline granules are not found in granular cells of the gastrointestinal tract.

**Clinical Pearls:**

1. Keratohyaline granules contribute to the structural integrity and protection of the skin and other epithelia.
2. A deficiency or dysfunction of keratohyaline granules can result in diseases like ichthyoses, which are a group of genetic disorders characterized by dry, scaly skin and impaired barrier function. This emphasizes the importance of keratohyaline granules in maintaining the skin's barrier function and protection.