Large Intestine Research Paper
Structure of the large intestine
The large intestine (also known as large bowel or colon) is the last part of the gastrointestinal (GI) tract. It extends from the cecum to the anus, with the ascending colon, the transverse colon, the descending colon, the sigmoid colon and the rectum in between.
The large intestine consists of four layers of tissue: the mucosa, submucosa, muscle and serosa (figure 1). The mucosa is made out of an epithelial layer, with a layer of connective tissue, called the lamina propria, underneath it. The lamina propria contains immune cells, capillaries, a spare layer of smooth muscle, also known as the lamina muscularis mucosae, and enteric neurons. Intestinal stem cells are localized at the bottom of epithelial crypts. (1) They give rise to progenitor cells, which can differentiate into different subtypes of cells that comprise the …show more content…
The abnormality is based on the absence of ganglion cells from submucosal (Meissner) and myenteric (Auerbach) nerve plexus. There is an absence of these nerve cells in the distal rectum and a variable length of contiguous bowel. These nerve cells are part of the enteric nervous system and are responsible for the peristalsis of the bowel.
The aganglionary segment stretches in 70-80% of the cases no further than the rectum and the distal part of the sigmoid. In 20% of the cases, the aganglionary segment involves the more proximal bowel, with the total colon being aganglionic in 8-10% of the patients.
The absence of the ganglia in a certain part of the colon results in the inability to relax in response to proximal distention, this causes a convulsive contraction. Eventually this will lead to expansion of the area in front of the aganglionary segment, because faeces and gas build up. (bron 25 van