Structure of Pancreas

Introduction

The pancreas is a soft, elongated organ measuring approximately 12–15 cm, nestled behind the stomach. It is both an exocrine gland (secretes digestive enzymes) and an endocrine gland (releases hormones like insulin and glucagon). Understanding its structure helps appreciate how it efficiently performs these complex tasks.

Anatomical structure of Pancreas

2. Anatomical Position and Gross Anatomy 

Location: 

Retroperitoneal space of the upper abdomen, extending transversely from the duodenum (right) to the spleen (left). 

Parts of the Pancreas:

• 1. Head: Nestled in the curve of the duodenum.

  2. Uncinate process: A hook-like projection from the head.

  3. Neck: A narrow portion between head and body.

  4. Body: Central, elongated segment.

  5. Tail: Tapered end touching the spleen.

Blood Supply: 

Arterial: Mainly from the splenic artery, and branches of the celiac trunk and superior mesenteric artery. 

Venous drainage: Primarily through the splenic vein and superior mesenteric vein → hepatic portal vein.

3. Histological Structure

The pancreas is composed of two major types of tissue:

A. Exocrine Component (≈ 98%) 

Acinar Cells: 

Pyramid-shaped cells arranged in clusters (acini). They produce digestive enzymes (amylase, lipase, proteases). 

Duct System:

Intercalated ducts → Intralobular ducts → Interlobular ducts → Main pancreatic duct (of Wirsung). These ducts carry enzyme-rich secretions to the duodenum via the ampulla of Vater.

B. Endocrine Component (≈ 2%)

Found in Islets of Langerhans scattered throughout the pancreas. 

Each islet contains: 

α-cells → secrete glucagon, 

δ-cells → secrete somatostatin, 

F (PP) cells → secrete pancreatic polypeptide,

β-cells → secrete insulin

These cells are surrounded by a dense capillary network for hormone distribution.

4. Functional Zonation 

The head is mainly exocrine-heavy, helping in digestion. 

The tail contains the highest concentration of islets, vital for endocrine function. 

This functional and structural zonation ensures precise regulation of digestion and metabolism.

Frequently Asked Questions (FAQs)

Q1. Is the pancreas an endocrine or exocrine organ?
A: Both. Its acinar cells secrete digestive enzymes (exocrine), while islets of Langerhans release hormones like insulin and glucagon (endocrine).

Q2. Where are the islets of Langerhans located?
A: They are scattered throughout the pancreas but are most concentrated in the tail region.

Q3. What is the role of the pancreatic duct?
A: It transports digestive enzymes from the acini to the duodenum, helping in food breakdown.

Q4. Why is pancreatic structure clinically important?
A: Structural issues (e.g., tumors, inflammation, blockages) can affect both digestion and blood sugar regulation, leading to conditions like pancreatitis or diabetes.

Q5. How can we differentiate between acinar and islet tissue under the microscope?
A: Acini appear as dark, enzyme-rich clusters, while islets are lighter-stained, round or oval clusters interspersed between acini.

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References

1. Guyton and Hall – Textbook of Medical Physiology, 14th Edition (Elsevier, 2020)

2. Snell – Clinical Anatomy by Regions, 10th Edition (Lippincott, 2018)

3. Ross & Pawlina – Histology: A Text and Atlas, 8th Edition (Wolters Kluwer, 2020)