permanent folds are called plicae circulares temporary folds are called rugae.
They are called "plicae circulares"
rugae It's not rugae - for stomach. Small intestine wall is plicae circulares.
No, the length increases. When you are alive, the muscles are contracted in folds, and when you die, these folds relax, expanding the small intestine.
the lining of the small intestine has folds, and are covered with finger-like projections called villi, which are covered with thousands of micro-villi
The villi are the tiny finger-like projections that cover the folds of the small intestine. The singular of villi is villus.
The tiny folds inside the small intestine are called villi. They increase the surface area of the intestine, allowing for better absorption of nutrients into the bloodstream. Each villus contains blood vessels and lacteals to facilitate the absorption process.
circular folds
It's impossible to count. The entire structure of the small intestine is folded and coiled so it's impossible to identify individual folds. Also the small intestine can move around within the abdomen, so changes in shape are normal.
folds and villi
The circular folds or plicae circularis are the permanent folds or ridges of the mucosa.
Peritoneum
It increases the surface area available for absorption of digestion nutrients.