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== Basic Anatomy and Physiology ==
== Basic Anatomy and Physiology ==
=== Introduction ===
The intestines are a portion of the alimentary tract extending from the pylorus to the anus. In mammals, the intestines are divided into two main segments: the small intestine and the large intestine. The small intestine, which consists of the duodenum, jejunum and ileum is the main site of absorption for digestive products in the gastrointestinal tract. The large intestine, which consists of the caecum and colon, functions to extract water, electrolytes and nutrients as well as to concentrate and propulse faecal material to the rectum for defaecation. (Dyce et. al, 2002; Young & Heath, 2000).
The intestines are a portion of the alimentary tract extending from the pylorus to the anus. In mammals, the intestines are divided into two main segments: the small intestine and the large intestine. The small intestine, which consists of the duodenum, jejunum and ileum is the main site of absorption for digestive products in the gastrointestinal tract. The large intestine, which consists of the caecum and colon, functions to extract water, electrolytes and nutrients as well as to concentrate and propulse faecal material to the rectum for defaecation. (Dyce et. al, 2002; Young & Heath, 2000).
In contrast to the small intestine, the large intestinal mucosa has no villi and consists of 2 main cell types: absorptive cells and mucus secreting goblet cells. A distinguishing histologic and anatomic characteristic is the thick muscularis mucosa layer that aids in propulsion of faeces to the rectum. Another important feature of the large intestine is the presence of commensal bacteria which plays different digestive roles depending upon the type of animal.
In contrast to the small intestine, the large intestinal mucosa has no villi and consists of 2 main cell types: absorptive cells and mucus secreting goblet cells. A distinguishing histologic and anatomic characteristic is the thick muscularis mucosa layer that aids in propulsion of faeces to the rectum. Another important feature of the large intestine is the presence of commensal bacteria which plays different digestive roles depending upon the type of animal.
=== Defense Mechanisms ===
=== Defense Mechanisms ===