4- Gallbladder and pancreas

2- The Endocrine Portion of the Pancreas (Islets of Langerhans)

• The Islets of Langerhans are highly vascularized clusters of secretory cells.

• These islets are separated from the exocrine portion by a thin connective tissue (C.T.) capsule.

• The pale endocrine cells are organized in cords and clumps, interspersed with fine C.T. containing capillaries.

• Islet size and number vary across different regions of the pancreas, with a higher concentration found in the tail region.

Cell Types in the Islet

• The islets contain four main types of cells:

1. A (Alpha) Cells

• These are glucagon-secreting cells and generally located peripherally within the islet.

• Characterized by large size and acidophilic granules in their cytoplasm.

• Constitute approximately 20% of the islet's mass.

• Function: Secrete glucagon, which increases blood sugar levels.

2. B (Beta) Cells

• More numerous than alpha cells and mainly located in the center of the islets.

• Contain basophilic granules and make up approximately 70% of islet mass.

• Function: Secrete insulin, which decreases blood sugar levels.

3. D (Delta) Cells

• These somatostatin-secreting cells are rare in humans, accounting for less than 5% of islet cells.

• Their position within the islets is variable.

• Function: Secrete somatostatin, which inhibits the release of hormones from other islet cells.

4. F (Gamma) Cells

• Rare and with a variable position within the islets.

• Function: Secrete pancreatic polypeptide, which regulates gastric secretion.