Changes

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).

Functional differences between the small and large intestine are reflected in their anatomic and histologic organisation (Figure 1).  The small intestinal mucosa in many species is highly folded and made up of numerous villi that greatly increase the absorptive surface area.  Enterocytes, the main absorptive cells, are the most numerous and characteristic cells of the small intestinal epithelium. Other cells include goblet cells, paneth cells, neuroendocrine cells, stem cells, and intraepithelial lymphocytes. Another important feature of the small intestine is the presence of Peyer's patches within the lamina propria.  They are important in immune function and generation of immune response within the mucosa.   

Functional differences between the small and large intestine are reflected in their anatomic and histologic organisation (Figure 1).  The small intestinal mucosa in many species is highly folded and made up of numerous villi that greatly increase the absorptive surface area.  Enterocytes, the main absorptive cells, are the most numerous and characteristic cells of the small intestinal epithelium. Other cells include goblet cells, paneth cells, neuroendocrine cells, stem cells, and intraepithelial lymphocytes. Another important feature of the small intestine is the presence of Peyer's patches within the lamina propria.  They are important in immune function and generation of immune responses within the mucosa.   

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 histological and anatomical feature is the thick muscularis mucosa layer which acts to create powerful peristalsis 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 histological and anatomical feature is the thick muscularis mucosa layer which acts to create powerful peristalsis 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.