Which cell type is responsible for the characteristic appearance of the pancreatic islet of Langerhans, and what is the most abundant cell population?

Explanation

## Pancreatic Islets of Langerhans Histology ### Cellular Composition The islets of Langerhans are **endocrine clusters** embedded within the exocrine pancreatic tissue. They comprise several distinct cell types with different staining properties and hormone products. **Key Point:** **Beta cells** constitute **60–70%** of the islet population and are the **most abundant** cell type. They are located centrally and produce **insulin**. ### Cell Types and Distribution | Cell Type | Hormone | % of Islet | Location | Staining | | --- | --- | --- | --- | --- | | **Beta (B)** | Insulin | 60–70% | Central | Basophilic | | **Alpha (A)** | Glucagon | 20–25% | Peripheral | Acidophilic | | **Delta (D)** | Somatostatin | 5–10% | Scattered | Neutral | | **Gamma (F)** | Pancreatic polypeptide | <5% | Rare | Acidophilic | ### Histological Features **High-Yield:** - Islets appear as **pale, well-vascularized clusters** surrounded by a **thin capsule** of connective tissue. - Beta cells are centrally located and stain **basophilic** due to abundant rough ER (insulin synthesis). - Alpha cells are **peripherally located** and stain **acidophilic** (cytoplasmic granules). - The islet is separated from exocrine acini by a **reticulin capsule**. ### Clinical Pearl In **Type 1 diabetes**, autoimmune destruction targets beta cells selectively, leading to loss of the central pale core of the islet on histology. In **Type 2 diabetes**, islets may show **amyloid deposition** (amylin/IAPP) within and around beta cells. ### Mnemonic **ABDF** = **A**lpha (glucagon, peripheral), **B**eta (insulin, central, most abundant), **D**elta (somatostatin), **F** (pancreatic polypeptide, rare) [cite:Robbins 10e Ch 19]