Small Intestine Flashcards
What is the diameter of the small intestine? Large intestine?
1 inch
2.5 inches
What are the three parts of the small intestine?
Duodenum
Jejunum
Ileum
How long is the duodenum? And where is it located?
About 10 inches
Retroperitoneal
The duodenum begins at the ________ _______ and wraps around the ______ of the _________.
Pyloric sphincter
Head of the pancreas
Which section of the small intestine is most active in digestion?
Duodenum
Ducts from the ________ and _______ enter in the duodenum.
Liver and pancreas
How long is the jejunum? How do blood and nerved reach it?
~8 feet
via mesentery
What occurs in the jejunum? What color is it?
Mostly absorption
Red, du to good blood supply
___% of the post-duodenal intestinal length is the jejunum, while ___% is ileum
40%
60%
What happens in the ileum?
Some absorption
Compare the ileum to jejunum
No clear boundary
Ileum is thinner and less vascular. Walls are thinner, more Peyer’s patches present.
How long is the small intestine in a cadaver? In an human? Why the difference?
20 feet long in cadaver, 7-13 in humans due to muscle tone
What 3 structural modifications increase the surface area of the small intestine? By what percentage over a smooth tube?
Plicae circulares/ Circular folds
VIlli
Microvilli
600x
In what tunics are plicae circularis found? How deep can they be?
Mucosa and submucosa
Up to an inch
Plicae circularis run in a _______ pattern along the inside of intestinal wall, and aren’t in the distal 1/2 of the _______.
transverse
Ileum
What is the function of the plicae circularis?
Causes the chyme to spiral down the tube, effectively slowing the chyme down
This leads to better mixing of the chyme, and therefore better absorption/digestion
Where are the plicae circularis tallest?
Jejunum
Villi are ____-like projections in duodenum, changing to ______-like further along intestine
leaf-like
finger-like
What 4 things are in each villus?
Core of lamina propria
Lacteal
Capillaries
Longitudinal strand of smooth muscle
What does the smooth muscle in the villus do?
Milks the lymph along lacteal, and ↑ contact of chyme with surfaces
What kind of epithelium covers the villi? What other cell is present?
Simple columnar
Goblet cell
Microvilli are finger-like projections of _______ membrane on the ______ surface of simple columnar cells.
plasma
apical
What is the brush border?
Exceptionally long microvilli
What does the brush border contain? In general, what does it do?
Brush border enzymes
“Contact digestion” chyme contacts brush border, enzymes digest upon contact
What do pores on the floor of the small intestine open to?
Crypts of Lieberkühn
What do crypts of Lieberkühn contain?
Contain absorptive cells, goblet cells, enteroendocrine cells, and Paneth cells
Intestinal crypts are similar to the ______ glands of the stomach. They extend through the ______ ______ to the ______ ________.
gastric
lamina propria
muscularis mucosa
Where are Paneth cells?
Clustered at the base of each intestinal crypt
What do Paneth cells secrete?
Secretes lysozyme and other digestive proteins
Describe intestinal juice
Make 1-2L/day pH 7.4-7.8, has water and mucus, little enzyme
Where are Brunner’s glands found?
Only in submucosa of duodenum
What do Brunner’s glands produce?
What does this do?
Secrete bicarb-rich mucus- ↑pH for protection from acid
Peyer’s patches are ______ ______ that increase in number approaching the _____.
Lymph nodules
Ileum
