Duodenum – Function, Anatomy & Diseases
The duodenum is the first and shortest segment of the small intestine, playing a central role in the digestion and absorption of nutrients.
Things worth knowing about "Duodenum"
The duodenum is the first and shortest segment of the small intestine, playing a central role in the digestion and absorption of nutrients.
What is the Duodenum?
The duodenum is the first and shortest section of the small intestine, connecting directly to the stomach. It is approximately 25 to 30 centimetres long – roughly the width of twelve fingers, which is reflected in its name (from the Latin duodeni, meaning twelve). The duodenum has a characteristic C-shaped curve that wraps around the head of the pancreas.
Anatomy and Structure
The duodenum is divided into four parts:
- Superior part (Pars superior): The first segment, connecting to the stomach outlet (pylorus).
- Descending part (Pars descendens): This section receives the openings of the common bile duct and the pancreatic duct via the Ampulla of Vater.
- Horizontal part (Pars horizontalis): Runs transversely across the abdomen.
- Ascending part (Pars ascendens): Transitions into the jejunum (the second part of the small intestine).
Functions of the Duodenum
The duodenum serves several vital functions in digestion:
- Neutralisation of gastric acid: Acidic chyme from the stomach is neutralised by bicarbonate secreted by the pancreas, protecting the intestinal lining.
- Initiation of digestion: Bile salts from the liver and digestive enzymes from the pancreas are released here, beginning the breakdown of fats, proteins, and carbohydrates.
- Nutrient absorption: Key micronutrients such as iron, calcium, and fat-soluble vitamins are preferentially absorbed in the duodenum.
- Hormone production: Specialised enteroendocrine cells produce hormones like secretin and cholecystokinin (CCK), which regulate digestive gland activity.
Common Diseases of the Duodenum
Duodenal Ulcer
A duodenal ulcer is one of the most common conditions affecting the duodenum. It is an open sore in the lining of the duodenum, most often caused by infection with Helicobacter pylori bacteria or the long-term use of non-steroidal anti-inflammatory drugs (NSAIDs). Typical symptoms include upper abdominal pain, often occurring at night or on an empty stomach.
Duodenitis
Duodenitis refers to inflammation of the duodenal lining. It shares similar causes with duodenal ulcers and can lead to symptoms such as nausea, abdominal discomfort, and digestive disturbances.
Coeliac Disease
Coeliac disease is an autoimmune condition in which the ingestion of gluten triggers an immune response that damages the villi (tiny finger-like projections) of the duodenum and small intestine. This significantly impairs nutrient absorption. Diagnosis often involves a biopsy (tissue sample) taken from the duodenum during endoscopy.
Duodenal Cancer
Malignant tumours of the duodenum are rare but can occur. They are often detected late and typically require surgical intervention, sometimes combined with chemotherapy or radiotherapy.
Diagnosis of Duodenal Conditions
The primary diagnostic method for evaluating the duodenum is gastroduodenoscopy (upper endoscopy), in which a flexible endoscope is passed through the mouth to visualise the stomach and duodenum. Tissue samples (biopsies) can be collected during this procedure. Complementary imaging techniques such as ultrasound, CT scan, or MRI may also be used.
Treatment Options
Treatment of duodenal conditions depends on the underlying cause:
- For ulcers caused by Helicobacter pylori, eradication therapy combining antibiotics with acid-suppressing medications is used.
- For coeliac disease, a strict lifelong gluten-free diet is the only effective treatment.
- For inflammation, proton pump inhibitors (PPIs) reduce acid production and support healing of the duodenal lining.
- Duodenal tumours are typically treated surgically, often in combination with chemotherapy or radiation therapy.
References
- Standring, S. (Ed.) (2020). Gray's Anatomy: The Anatomical Basis of Clinical Practice, 42nd Edition. Elsevier.
- Kasper, D. L. et al. (2018). Harrison's Principles of Internal Medicine, 20th Edition. McGraw-Hill Education.
- World Gastroenterology Organisation (WGO). Practice Guidelines: Peptic Ulcer Disease. Available at: https://www.worldgastroenterology.org
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