Short-bowel Syndrome
Digestion is not as simple as eating and wasting; most of all the nutrients our bodies survive on are absorbed throughout the digestive tract. Neuromuscular and natural immunological factors play an important role in maintaining homeostasis; destruction would impair the process to do so.
An adult small bowel is approximately 6m in length, divided into the duodenum, jejunum and the ileum. The immunological function of the small bowel is to absorb and transport water, electrolytes and macromolecules; ultimately made possible by a specialized inner lining of columnar epithelial tissue, called mucosa. This neuromuscular property is characterized by repetitive folds called plicae circulares, lined with long fingerlike projections called villi. Anterograde and retrograde peristalsis mixes food and promotes maximal contact of nutrients with the mucosa {1}. The greater absorptive surface available allows for maximum nutrient absorption.
Chemical digestion begins when the small bowel secrets a hormone called cholecystokinin, triggering the pancreas to secrete digestive enzymes which attack food waste; taking from the key nutrients which each enzyme is targeted to. Then by diffusion, the nutrients are absorbed back through the mucosa into the blood vessels of the small bowel. Peyers patches within the mucosa house macrophages, B-cells and T-cells which help defend against any unwanted pathogens possibly absorbed along with the necessary nutrients. Chemical digestion ends with the iliocecal valve, a sphincter that limits colonic contents entering back into the ileum; this being the site for vitamin B-12 and steroid acid absorption.
If the small bowel is impaired, homeostasis is set off balance by lack of nutrient absorption; resulting in malabsorption. Short-bowel syndrome, being one of the more severe forms of malabsorption, is an acquired dysfunction either congenital or pathological. Etiologic factors concerning a decreased size...