The layers of the digestive tract Flashcards
The entire digestive tract is a tube, what are the 4 layers throughout its length?
Mucosa
Submucosa
Muscularis externa
Serosa
What are the three component layers of the mucosa?
Epithelium, lamina propria, muscularis mucosa.
What is the epithelium layer of the mucosa?
A thin layer which lines the lumen of the tube, it may be simple or stratified, squamous or columnar.
It forms a selective barrier that digested molecules must cross.
It may contain mucus secreting goblet cells and endocrine cells secreting digestive hormones.
What is the lamina proprietor layer of the mucosa?
A layer of loose connective tissue.
It has a good blood supply and often contains lymphatics and numerous white blood cells, it is the first immunological barrier to pathogens in the mucosal layer.
What is the muscularis mucosa layer of the mucosa?
A thin layer of smooth muscle cells, causing localised contractions in the mucosa.
What is the submucosa?
A layer of dense connective tissue that contains the submucosal plexus.
What does the submucosal plexus do?
It controls secretion and blood flow. It also relays information from the gut epithelium and stretch receptors in the wall.
It is part of the enteric nervous system.
What is the enteric nervous system?
A branch of the autonomic nervous system, which can operate independently of the CNS.
What does the enteric nervous system consist of?
Two major plexi within the GI wall, the myenteric and submucosal plexi.
What is the structure and function of the muscularis externa?
It consists of two layers of smooth muscle: an inner circular and outer longitudinal layer. Waves of contraction and relaxation along these layers force food along the digestive tract, an action known as peristalsis.
What lies between the two layers of muscularis externa?
The myenteric plexus, it is involved mainly in the control of GI motility.
What does the serosa form?
It forms parts of the peritoneum.
What is the peritoneum?
It lines the abdominal cavity and covers all of the abdominal organs, anchoring them to the body wall.
