Flashcards in Highi Deck (85)
Are you excited to study Histology right now?
I hope so! B/c here it comes....
How long is the SI? What are its 3 regions? What is its main function?
21-25 feet long
duodenum, jéjunum, ileum
digestion & absorption
Which portions of the duodenum are considered retroperitoneal?
2nd, 3rd, 4th portions
What structure separates the duodenum from the jejunum?
ligament of trietz
this part Highi thinks is peritoneal
The majority of the SI is suspended by what?
When something has mesentery it is considered____.
Describe the circular plicae in the SI.
They go around the circumference of the SI. Their height drops as we become more distal in the intestine. Once we're at the distal ileum-->no more circular plicae.
Vasa recta are the arteries that come off of the ____ & go into the ____ & form _______.
Come off of marginal arteries
go into the SI
form vascular planes
When you are proximal in the SI...what do the vascular planes look like? How about when you're distal?
Proximal: they are large & organized
Distal: they look like a mosaic & are smaller...
What are the histological layers of the SI...starting w/ mucosa?
Adventitia or Serosa
What 2 histological layers is the plicae circularis made up of?
mucosa & submucosa
What are the 2 layers of the muscularis externa in the SI?
B/c of surface modifications to the SI...its surface area is increased by what factor?
What 3 things increase the surface area of the SI & by what factor?
Plicae circularis: 2-3X
Intestinal Villi: 10X
Simple Columnar epithelium w/ microvilli: 20X
What type of epithelium is on the mucosa of the SI? & What 6 cell types accompany it?
Simple Columnar Epithelium
What's the deal with the enterocytes of the mucosal epithelium of the SI?
They are surface absorptive cells.
They transport substances from the lumen to the circulatory system. Intercellular junctions seal off the space in b/w the cells.
Also, microvilli increase the apical surface area.
What is the function of the goblet cells in the mucosal epithelium of the SI?
They secrete mucinogen. This is converted to mucous for protection.
What's the deal with the M Cells in the mucosa of the SI?
aka Microfold Cells
These are antigen presenting cells.
They are modified enterocytes.
They cover the lymphatic nodules of the LP.
Are the goblet cells in the SI the same as those in the respiratory system?
What's the deal with the enteroendocrine cells?
They produce peptide hormones...the same ones as in the stomach.
Where are paneth cells mainly found? What do they do? What do they regulate?
Mainly found in the distal ileum...they are found in the crypts...They secrete lysozyme that is antibacterial.
They regulate the intestinal flora.
They protect the SI from the bacteria of the LI.
The stem cells found in the SI mucosa are regenerative cells. How often do they regenerate the epithelial cells? The paneth cells?
Epithelial cells: every 5-6 days
Paneth cells: every 4 weeks
Where are the stem cells located w/i the mucosa?
at the neck of the crypts...they can restore bidirectionally...up the villi & down the crypt.
The fast rate of cell renewal by stem cells means that there is a _______. This allows us to use what type of drugs?
high mitotic index
What does the LP in the SI contain?
CT & lymphatic nodules
Where is the lacteal located w/i the SI? What is its function?
It is located w/i the villus of the SI.
It absorbs compounds that can't be absorbed by the circulatory system b/c they are too big. This includes chylomicrons.
What is the purpose of chylomicrons?
They make wonderful lipoproteins that help to build our nervous system.
Where do the lymphatic nodules become really large in the SI? What are they called then?
in the distal ileum & appendix
technically only considered Peyer's in the ileum, not the appendix.
What is the muscularis mucosae of the SI made up of?