SMALL INTESTINE Flashcards
Describe the gross and microscopic anatomy of the small intestine along with their secretions and functions
1
Q
Small intestine
A
coiled mass filling most of the abdominal cavity inferior to the stomach and the liver
2
Q
Duodenum
A
- begins at the pyloric valve
- receives major and minor pancreatic ducts respectively
- arches around the head of the pancreas
- ends at a sharp bend called the duodenojejunal flexure
3
Q
Jejunum
A
- 40% of small intestine
- roughly 1.0 to 1.7 m in a living person
- has large, tall, closely spaced circular folds
- wall is relatively thick and muscular
- especially rich blood supply which gives it a red color
- most digestion and nutrient absorption occurs here
4
Q
Ileum
A
- forms the last 60% of the small intestine
- about 1.6 to 2.7 meter long
- thinner, less muscular, less vascular, and paler pink color
- peyer patches—prominent lymphatic nodules in clusters on the side opposite the mesenteric attachment
- become progressively larger approaching the large intestine
5
Q
Ileocecal junction
A
end of the small intestine
where the ileum joins the cecum of the large intestine
6
Q
Ileocecal valve
A
a sphincter formed by the thickened muscularis of the ileum
protrudes into the cecum
regulates passage of food residue into the large intestine
7
Q
Circular folds (plicae circulares)
A
- largest folds of intestinal wall–Up to 10 mm high
- involve only mucosa and submucosa
- occur from the duodenum to the middle of the ileum
- cause chyme flow in spiral path causing more contact with mucosa
- promotes more thorough mixing and nutrient absorption
- relatively small and scarce in ileum and not found in distal half
- most nutrient absorption is completed by this point
8
Q
Villi
A
- fingerlike projections 0.5 to 1 mm tall
- make mucosa look fuzzy
- villus covered with two types of epithelial cells
- absorptive cells (enterocytes)
- goblet cells—secrete mucus
- embedded in the lamina propria are an arteriole, a capillary network, a venule, and a lymphatic capillary called a lacteal
9
Q
Microvilli
A
fuzzy border on apical surface of each absorptive cell
about 1 μm high
brush border increases absorptive surface area
10
Q
Brush border enzymes
A
- contained in the plasma membrane of microvilli
- carry out some of the final stages of enzymatic digestion
- not released into the lumen
- contact digestion: chyme must contact the brush border for digestion to occur
