This section provides a comprehensive overview of the duodenum, jejunum, and ileum, focusing on their anatomical characteristics, vascularization, innervation, and clinical relevance.
The duodenum, the initial segment of the small intestine, is divided into four parts: superior, descending, inferior, and ascending. The inner surface of the duodenum features numerous folds and villi that increase its surface area for nutrient absorption. Its wall structure comprises several layers, including the mucosa, submucosa, muscularis, and serosa. The arterial supply to the duodenum includes branches from the Right gastric artery, Supraduodenal artery, Right gastro-omental artery, superior pancreaticoduodenal artery, and inferior pancreaticoduodenal artery. Venous drainage from the duodenum occurs through the splenic (lienal), Superior mesenteric, and Hepatic portal veins. Lymphatic drainage follows a similar path, with lymph nodes along the arteries. Neural innervation of the duodenum involves the sympathetic and parasympathetic nervous systems, facilitating the regulation of digestive processes. Clinically, conditions such as duodenal ulcers and obstructions are common issues affecting the duodenum, necessitating a thorough understanding of its anatomy for effective diagnosis and treatment.
Moving to the jejunum and ileum, this section highlights the differences between these two parts of the small intestine. The jejunum, which follows the duodenum, is characterized by a thicker wall, larger diameter, and more prominent circular folds than the ileum. The ileum, the final part of the small intestine, has a thinner wall, smaller diameter, and fewer circular folds. It also features Peyer’s patches, lymphoid tissues crucial for immune function.
The mesentery, a fold of the peritoneum, supports the jejunum and ileum, providing a conduit for blood vessels, nerves, and lymphatics. A notable clinical condition associated with the ileum is the ileal diverticulum (Meckel’s diverticulum), a congenital anomaly that can lead to complications such as bleeding or inflammation.
The wall structure of the small intestine is similar to that of the duodenum, with adaptations that facilitate absorption. Circular folds, or plicae circulares, are prominent in the jejunum and gradually diminish towards the ileum, vital in increasing the surface area for nutrient absorption. In clinical practice, understanding the anatomical and functional distinctions between the jejunum and ileum and their common pathologies is essential for accurate diagnosis and effective management of gastrointestinal disorders.