All of the following are characteristic histological features of the pancreas EXCEPT:

Explanation

## Histology of the Pancreas ### Pancreatic Structure Overview The pancreas is a mixed gland with both exocrine (acinar) and endocrine (islet) components. Understanding the distinguishing features of each is essential for histological identification. ### Exocrine Pancreas (Acini) **Key Point:** Pancreatic acini are composed of serous cells that produce and secrete digestive enzymes (amylase, lipase, proteases) into the acinar lumen. **High-Yield:** Acinar cells exhibit the classic ultrastructure of protein-secreting cells: - Abundant rough endoplasmic reticulum (RER) for enzyme synthesis - Numerous mitochondria for ATP production - Zymogen granules (secretory vesicles) concentrated at the apical surface - Basophilic cytoplasm due to high RER content ### Ductal System **Clinical Pearl:** The pancreatic duct system progresses from intercalary ducts → intralobular ducts → interlobular ducts → main pancreatic duct (duct of Wirsung). The main duct is lined by **simple columnar epithelium** (not cuboidal), which transitions to stratified columnar near the ampulla. **Warning:** The stem states "simple cuboidal epithelium" for the main pancreatic duct — this is **incorrect**. The main duct is lined by simple **columnar** epithelium. ### Endocrine Pancreas (Islets of Langerhans) **Key Point:** Islets are clusters of endocrine cells (α, β, δ, PP cells) that: - Lack a duct system (hormones are secreted directly into the bloodstream) - Are surrounded by a rich capillary plexus for hormone distribution - Are separated from acini by a thin connective tissue capsule - Comprise only 1–2% of pancreatic mass but receive ~10% of pancreatic blood flow ### Summary Table | Feature | Exocrine Acini | Endocrine Islets | | --- | --- | --- | | Cell type | Serous cells | α, β, δ, PP cells | | Product | Digestive enzymes | Hormones (insulin, glucagon, somatostatin) | | Secretion route | Via ducts to intestine | Direct into blood | | Vascularity | Moderate | Very rich (fenestrated capillaries) | | Ultrastructure | RER, mitochondria, zymogen granules | Secretory granules, fewer organelles | | Duct system | Present (intercalary → main) | Absent | ### Why Option 2 Is Wrong The main pancreatic duct is lined by **simple columnar epithelium**, not simple cuboidal. This is a critical histological distinction that must be memorized for exam success. [cite:Junqueira's Histology 14e Ch 17]