Gastrointestinal Histology Flashcards
What are the common structural features of the GIT?
mucosa, submucosa, muscularis externa, serosa/adventitia, neurons and immune cells
Which is the best structural feature to look at to determine which part of the GIT you’re in?
The mucosa
What is the mucosa?
The innermost layer of the GIT
What are the 3 layers of the mucosa?
epithelium, lamina propria, muscularis mucosae
What type of epithelium is in the mucosa?
simple columnar or stratified squamous
What is the lamina propria of the mucosa?
Loose connective tissue with nerves, blood vessels and immune cells
What type of muscle is in the muscularis mucosae?
a thin layer of smooth muscle - for mixing
At which part of the gut is there stratified squamous epithelium in the mucosa?
The oesophagus and the anus
At which part of the gut does the mucosa have a secretory structure?
The stomach and the large intestine - there are big pits of glands for secretion
At which part of the gut does the mucosa have an absorptive structure?
The small intestine - the mucosa has lots of folds
What is the submucosa?
A layer of dense, irregular connective tissue adjacent to the mucosa
What is the function of the submucosa?
Elasticity and structural support
What does the submucosa contain?
Nerves, small ganglia, blood vessels and sometimes glands and immune cells
What is the muscularis externa?
2 layers of muscle adjacent to the submucosa
What are the 2 layers of muscle?
The inner is circumferential and the outer is longitudinal
Where in the GIT is there 3 layers of muscle in the muscularis externa?
In the stomach
What ganglia are between the 2 layers of muscle?
The myenteric ganglia
What is the serosa/adventitia?
The outer surface of the gut
What is serosa?
A fluid secreting simple squamous epithelium to allow organ movement plus a thin layer of connective tissue
What is adventitia?
connective tissue joining GIT with surrounding structures e.g. at the oesophagus and rectum
What is the enteric nervous system?
The nervous system of the gut
What is the role of the myenteric ganglia?
To control smooth muscle activity
What is the role of the sub mucous ganglia?
To regulate absorptive and secretory processes
What type of epithelium is present in the oesophagus?
non-keratinised squamous epithelium
What are the two types of muscle in the oesophagus?
Striated at the top where contraction is voluntary and smooth at the bottom where contraction is involuntary
What is the z line?
The transition from oesophagus to stomach
How many layers of muscle are there in the stomach?
3
In what direction is the 3rd layer of muscle?
Oblique
What do mucous cells secrete?
mucous
What do parietal cells secrete?
hydrochloric acid
What do chief cells secrete?
pepsinogen
What do enteroendocrine cells secrete?
gastrin
Where in the gland are mucous cells?
At the surface and the neck of the gland
Where in the gland are parietal cells?
Scattered throughout the gland (except not at the top)
Where in the gland are chief cells?
at the base
Where in the gland are enteroendocrine cells?
very few throughout the base and neck
Can the different secretory cells be differentiated on a H&E stain?
No
How are the 3 regions of small intestine distinguished on H&E stain?
Their mucosa
What is plica circulares?
The macroscopically visible folded surface
What is a villus?
The folding on the plica circulares
What is a microvilli?
The folded surface on the enterocyte
What are the crypts of leiberkuhn?
The lumen between the villi where the glands empty into
What type of epithelium is there in the small intestine?
simple columnar
What cels are present in the epithelium of the small intestine?
enterocytes, goblet cells, enteroendocrine cells, paneth cells, stem cells
What are paneth cells?
cells which secrete antimicrobial peptides
What is in the lamina propria of the small intestine?
connective tissue, blood vessels, lymph and immune cells as well as extensions of the muscularis mucosae to move the villi
What is the distinctive feature of the duodenum?
Brunner’s glands
What are Brunner’s glands?
coiled glands in the submucosa that release alkaline mucus to negative acid from the stomach
What is the distinctive feature of the ileum?
Peyer’s patches
What are Peyer’s patches?
aggregates of lymph tissue in the submucosa
What is the taeniae coli?
3 bands of longitudinal muscle in the large intestine
Can the regions of the large intestine be distinguished histologically?
No
What does the mucosa of the large intestine look like?
There are no villi, long pits of glands and a layer of simple columnar epithelium
What cells are present in the epithelium of the large intestine?
enterocytes, goblet cells, enteroendocrine cells, stem cells
Are there more goblet cells in the small intestine or large intestine?
Large intestine
