Final answer:
The divisions of the small intestine in order are the duodenum, jejunum, and ileum.
Step-by-step explanation:
The divisions of the small intestine in order beginning at the pyloric sphincter are:
- Duodenum: The shortest region of the small intestine that is approximately 25.4 cm (10 inches) long. It starts at the pyloric sphincter, bends posteriorly behind the peritoneum, becomes retroperitoneal, and then makes a C-shaped curve around the head of the pancreas before ascending anteriorly again to return to the peritoneal cavity.
- Jejunum: The second region of the small intestine. It follows the duodenum and is the site of most chemical digestion and nutrient absorption. It's longer than the duodenum and has a larger diameter.
- Ileum: The longest and final region of the small intestine. It connects to the jejunum and extends until it reaches the large intestine. It is responsible for further nutrient absorption, particularly vitamin B12 and bile salts.