Histology of GI Flashcards
What are the 4 main layers of the GI tract?
- Mucosa (innermost) 2. Submucosa 3. Muscular propria 4. Adventitia/serosa (outermost)
Where does the oesophagus sit?
Behind the trachea
What is the epithelium in the oesophagus?
Squamous –> protective mechanism (due to abrasion from food)
Labelled cross-section of oesophagus
What do oesophageal submucosal glands secrete? Where are they?
In the submucosa
Secrete mucous to lubricate the oesophageal wall
What does the muscosa layer of the oesophagus consist of?
Consists of the epithelium, the lamia propria and the muscularis mucosa
What is the muscularis mucosa?
A thin layer of smooth muscle. This layer becomes more pronounced in the distal aspects of the oesophagus.
Describe the submucosa in the oesophagus
The submucosa lies external to the muscularis mucosa and is highly vascular. This layer is formed from loose connective tissue and also contains oesophageal submucosal glands
Describe the muscularis propria in the oesophagus
This is a more substantial quantity of muscle than the muscularis mucosa. At the proximal end of the oesophagus, this layer is formed from skeletal muscle which gradually transitions to smooth muscle in the distal third.
Describe the adventitia of the oesophagus?
The adventitia of the oesophagus is formed from mesothelium and connective tissue
the pale area between the epithelium and the submucosa.
What does the lamina propria contain?
Lymphatic vessels and tissue, capillaries, oesophageal cardiac glands and loose connective tissue
What do the oesophageal cardiac glands secrete?
pH neutral mucous to protect from stomach acid
Where are oesophageal cardiac glands found?
Found within the mucosa of the oesophageal wall. These glands are predominantly found in the distal part of the oesophagus
What do longitudinal mucosal folds in the oesophagus allow?
Expansion to accommodate fod
What is the stomach lined by?
Simple columnar epithelium
What do the cells of the stomach epithelium act as?
Surface mucous cells –> their secretion protects the stomach lining from the harshness of the acidic stomach contents
Describe the musculature in the oesophagus compared to the stomach
Stomach thinner musculature than oesophagus
Describe the difference in mucosa from the oesophagus to the stomach
Oesophagus –> squamous mucosa
Stomach –> glandular mucosa
What effect can excess acid have on oesophagus?
Reflux can cause glandular metaplasia at base of oesophgus (where you wouldn’t normally see glandular epithelium) –> Barrett’s metaplasia/oesophagus
Can cause cancer