Week 3 GI workbook Flashcards
The entire GI Tract from oesophagus to anus shares certain common histological features. They all show 4 distinct functional layers throughout what are they?
mucosa
(epithelium, lamina propria, and muscular mucosae)
submucosa
muscularis propria
(inner circular muscle layer, outer longitudinal muscle layer)
serosa / adventitia
what is the role of the mucosa?
layer which lines the gut tube – it is exposed to the contents of the gut tube. Therefore, it needs to serve different purposes depending on location in the gut tube
what are the four basic mucosal types found in the GI tract?
protective
secretory
absorptive
absorptive / protective
where would you find protective mucosa?
Oral cavity, pharynx, oesophagus & anal canal
where would you find secretory mucosa?
Seen only in the stomach
where would you find absorptive mucosa?
Typical of entire small intestine
where would you find absorptive / protective mucosa?
Lines the whole of the large intestine
what are the four junctions GI Tract mucosa undergoes abrupt transition?
Gastro -oesophageal junction
gastro-duodenal junction
ileo-cecal junction
Recto - anal junction
what kind of epithelium would you find in the oesophagous?
Stratified squamous non-keratinised epithelium
what type of muscle makes up the upper 1/3 of the muscularis mucosae in the oesophagous?
Muscular layer – upper 1/3 skeletal, middle 1/3 – smooth+ skeletal, lower 1/3 - smooth
what are the three layers of the oesophagous?
surface epithelium
lamina propria
muscularis mucosae
What two orientations do the muscular layers sit in?
inner circular
outer longitudinal
What do you notice about the thickness of the muscularis externa of the oesophagous?
notably thicker than in the stomach and intestine
Muscularis externa of the esophagus consists of the standard inner circular and outer longitudinal layers of smooth muscle, with Auerbach’s plexus in between
What is the epithelial lining of the stomach?
Epithelium – simple columnar [looks very pale staining]
What are the large folds present in the wall of the stomach?
When the stomach is empty, and not distended, the lining is thrown up into folds called rugae. After eating, these folds flatten, and the stomach is able to distend greatly. [gastric pits]
What secretory cells are present in the gastric glands of the stomach?
(Mucous secreting) Epithelial cells (simple columnar)
what are four distinctive features of the small intestine?
Villi (finger like projection of the mucosa)
Columnar epithelium with striated borders
Goblet cells (like bowl shaped drinking cups with no handles)
Short tubular intestinal glands (Crypts of Leiberkuhn)
what is the type of surface epithelium in the small intestine?
Simple columnar epithelium
Muscularis mucosae (interna). What type of muscle is this in the small intestine?
smooth muscle
It consists of an outer longitudinal and inner circular layer of smooth muscle cells. It is a fairly thin layer, being only 3 to 10 cells thick, extending into the circular folds (plicae circularis).
What are the cells found in the small intestine called and what do they secrete?
Parietal cells (stain pink) – secrete HCl
What type of cells are present in the surface epithelium of the small intestine?
Enterocytes are the major cell type in intestinal epithelium. They are simple columnar epithelial cells and play important roles in nutrient absorption (e.g., ions, water, sugar, peptides, and lipids) and in secreting immunoglobulins.
Where, along the gut tube, do glands extend down beyond the muscularis mucosae (interna) into the submucosa?
occasionally, some acini) penetrate the muscularis mucosae and open into a crypt of Lieberkühn in the small intestine
What is the distinguishing structure shown that tells you an image is the duodenum?
Brunner’s glands in submucosa
What is the function of brunners glands?
located in the submucosa of the duodenum. They secrete an alkaline fluid containing mucin, which protects the mucosa from the acidic stomach contents entering the duodenum
what is found in the ileum?
peyers patches
what are peyers patches?
Peyer’s patches are small clusters of lymphatic tissue found in the wall of the small intestine. Specifically, they reside within the lamina propria and extend into the submucosa of the ileum. Peyer’s patches act as the immune system’s first line of defense against microbial and dietary antigens
summarise the histological findings of the small intestine?
villi
lymphocyte aggregation in lamina propria
mucous glands in submucosa
summarise the histological findings of the duodenum?
short leaf shaped abundant and closely packed of varying heights
no lymphocyte aggregation
brunners glands
summarise the histological findings of the jejunum?
tongue shapes with swoolen ends, less abundant and of different heights
lymphocyte aggregation absent or rare
no mucous glands
summarise the histological findings of the ileum?
thin finger shaped less abundant with upper level variable
prominent lymphoid aggregations known as peyers patches
mucous glands absent
What is the predominant cell present in the surface epithelium of colon?
enterocytes
What do you notice about the muscularis externa of the colon?
Muscularis externa of the colon has the standard layers of inner circular and outer longitudinal smooth muscle, with ganglia of Auerbach’s plexus scattered in between. The longitudinal muscle is gathered into three distinct bands, the taenia coli. The outer layer of the colon is a serosa attached to mesentery
appendix histological features
the mucosa has no villi and fewer goblet cells compared to the colon. It has a ring of lymph follicles in the lamina propria.
what type of epithelium is present before and after the ano-rectal junction?
Before = simple columnar
After = stratified squamous
what are the main histological features of the liver?
Cells are arranged in sheets and converging towards the central vein
At the corner of the lobule connective tissue encloses portal areas which contain blood vessels and ducts (portal tracts or portal triad)
what are the main histological features of the pancreas?
Islets of Langerhans composed of clumps of small poorly stained cells
Pure serous acini composed of large strongly stained cells
Small lobules surrounded by connective tissue septa
describe the histological features of the spleen?
The spleen is covered by a dense fibromuscular capsule formed of collagen and elastic fibres with scattered smooth muscle. Branching trabeculae radiate inside the spleen. The parenchyma of spleen is called pulp.
what is white pulp?
white pulp is lymphoid tissue that usually surrounds splenic blood vessels as part of the immune system, the white pulp produces white blood cells
what is red pulp?
The red pulp is a network of splenic cords (cords of Billroth) and sinusoids (wide vessels) filled with blood, and it is in the red pulp that most of the filtration occurs
