The gut wall

The wall of the GI tract – often referred to as the gut – has the same basic structure, from the oesophagus all the way to the anus. There are four layers:

• The mucosa is the innermost layer, and itself has three layers: the epithelium at the top (in contact with gut contents), connective tissue (rich in blood vessels, lymph nodes and glands), and smooth muscle fibres.
• The submucosa is comprised of connective tissue, supplied by blood vessels and nerve fibres, and also contains glands in some regions.
• The muscularis is formed of a layer of circular muscle and a layer of longitudinal muscle, which work together to push gut contents along the tract (peristalsis). At certain points, the circular muscles are thickened to form sphincter muscles which act as gates for food to move from one section of the gut to the next.
• The outermost layer is mainly connective tissue.

Did you know?

The appendix has long been considered a vestigial organ – a throwback to a different era when it had some purpose for humans, but now regarded as functionless. This belief arose due to there being seemingly no difference in someone’s health or wellbeing if the appendix is removed, for example due to appendicitis. However, more recently, a theory has developed that the appendix serves as a reservoir for beneficial bacteria, and hence keeps the gut flora in some kind of balance. This may mean that it has a role in maintaining a healthy immune system.