Upper and Lower Divisions
The anal canal is divided into two unequal sections, upper and lower.
- The upper 2/3 has longitudinal folds or elevations of tunica mucosa. Its mucosa is lined by simple columnar epithelium. Its lower ends are joined together by folds of mucus membrane called anal valves. The upper 2/3 of the anal canal is supplied by the superior rectal artery which is a branch of the inferior mesenteric artery.
- The lower 1/3 of the anal canal is lined by stratified squamous epithelium that blends with the skin. The lower third of the anal canal is supplied by the inferior rectal artery which is a branch of the internal pudendal artery.
A whitish line called Hilton's white line or pecten of Jon Stroud indicates the junction between keratinized stratified squamous epithelium and unkeratinized stratified squamous epithelium.
Read more about this topic: Anal Canal
Famous quotes containing the words upper and lower, upper and/or divisions:
“Upper and Lower Kingdom will declare
God’s in this wooden toy,
no less
than where
great Taurus ploughs his course.”
—Hilda Doolittle (1886–1961)
“You doubt we read the stars on high,
Nathless we read your fortunes true;
The stars may hide in the upper sky,
But without glass we fathom you.”
—Ralph Waldo Emerson (1803–1882)
“I find myself ... hoping a total end of all the unhappy divisions of mankind by party-spirit, which at best is but the madness of many for the gain of a few.”
—Alexander Pope (1688–1744)