Upper Anal Canal Vs Lower Anal Canal - USMLE Forums
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USMLE Step 1 Bits & Pieces High yield short focused points, monographs, charts, illustrations, tables, and other stuff related to the USMLE Step 1 Exam.


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  #1  
Old 11-19-2009
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GIT Upper Anal Canal Vs Lower Anal Canal

The USMLE classically asks question that requires the knowledge of the differences between the upper half (or two thirds) of the anal canal and the lower half (or one third) of the anal canal.
They have different embryonic origins, epithelial lining, nerve supply, venous drainage, arterial supply, and lymphatic drainage.
The line that marks the boundary between the two is called the Pectinate Line.
It's important not to confuse this line with the Hilton's White Line. The Hilton's White Line is an anatomical landmark that marks the change between unkeratinized stratified squamous epithelium (mucosa) above it and the keratinized stratified squamous epithelium (skin) below it. It also marks the border between the internal and external anal sphincters.

Here's a Table that lists the differences;
Upper Anal Canal Vs Lower Anal Canal-anal-canal.jpg
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  #2  
Old 12-20-2009
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what is the dentate line then?
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Old 04-08-2011
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i think dentate line is another name for pectinate line.
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Old 04-08-2011
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Correct Answer

Yes the Dentate Line and the Pectinate Line are synonymous
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Old 06-10-2011
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GIT Pectinate Line vs Dentate Line

wjat is the difference between pectinate line and dentate line?? which one marks the upper and lower anal canl?? stratified non-keratinized squamous epithelium is it with the upper or lower anal canl??
it is really confusing me
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Old 06-10-2011
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See the thread.
Upper anal canal vs lower anal canal
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Old 06-10-2011
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pectinate line = dentate line
this is from Netter
http://id.medicine.ucsf.edu/analcanc...diagram562.jpg

Now, histology...
this is a nice picture from Di Fiore's Atlas
Upper Anal Canal Vs Lower Anal Canal-di-fiore-s-atlas.jpg
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  #8  
Old 06-10-2011
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Check out FA 2011 page 313.
Pectinate line is the same as dentate line. Is the line dividing upper anal canal (endoderm) and lower anal canal (ectoderm, squamous epithelium).
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  #9  
Old 06-10-2011
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Embryologically speaking, the lower part of the anal canal comes from the ectoderm. Now this pectinate line is very important in that the blood supply, lymphatics, nerve supply and malignant cells arising from each part differ.
The area above the pectinate line is supplied by the superior rectal artery which is a branch of the inferior mesenteric artery and drains into the superior rectal vein which in turn drains into the inferior mesenteric vein and thus goes to the portal circulation, the malignancy is usually an adenocarcinoma.
The area below the pectinate line is supplied by the inferior rectal artery which is a branch of the internal pudendal artery and drains into inferior rectal vein --> internal pudendal vein --> internal iliac vein --> inferior vena cava and thus goes to the systemic circulation, and malignancy is usually a squamous cell carcinoma. It is supplied by the pudendal nerve which is a somatic nerve, whereas the upper part is supplied by the autonomic nervous system. This also explains why internal hemorrhoids are usually painless if secondary to lets say cirrhosis of the liver because of the portal hypertension, whereas external hemorrhoids are usually painful.
Good luck!

Last edited by add1; 06-10-2011 at 09:54 AM.
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Old 06-10-2011
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thanx all..but what is the difference between pectinate and hilton line??
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Anatomy-, Gastrointestinal-Tract-, Histology-, Tables-

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