The large intestine is the organ responsible for digestion and absorption, and plays an important role in the functioning of the human body. When food reaches the small intestine, about 90% is absorbed, and the remaining 10%, the water that is not absorbed by the small intestine, is absorbed in the large intestine. How much do you know about the large and small intestines?
Schematic／
The small intestine is a tube about 6 to 7 meters long. It starts near the stomach and is divided into the duodenum, jejunum, and ileum. About 90% of the substances digested in the small intestine are absorbed.
The "duodenum" is named because it is about 12 fingers long.
There are about 500,000 villi on the wall of the small intestine. There are lymphatic vessels and capillaries inside the villi. Among the absorbed substances, almost all lipids pass through the lymphatic vessels, while glucose and amino acids are transported through the capillaries. There are absorbing epithelial cells in the villi, and the surface of the absorbing epithelial cells is covered by microvilli about 1 micrometer (mm) long.
Although the length of one fluff is only 1mm, the combined surface area of all the fluff is 200m2, which is equivalent to the area of a tennis court.
The small intestine secretes alkaline intestinal juices that neutralize substances from the stomach. The small intestine (duodenum) secretes secretin and cholecystokinin, CCK) and other digestive tract hormones to promote the secretion of pancreatic juice and other effects.
In addition, there are digestive enzymes in the microchorion that absorbs epithelial cells, which play an important role in absorbing nutrients; the digestion performed by the microchorion is called "membrane digestion". There are digestive enzymes on the surface of the microvilli, which play an important role in the digestion and absorption of nutrients; this kind of digestion on the microvilli is called "endocytosis".
How long does it take for food to be ingested and excreted? The average Japanese spends 34 to 44 hours, the average American spends 70 hours, the British are about 104 hours, and the Indians and Africans are about 10 hours; the length of the intestines and the content of the diet will affect the digestion of the human body. absorb.
The large intestine is located at the last part of the digestive tract and is a tube about 1.6 to 2 meters long; from the point close to the small intestine, it is divided into the cecum, colon (ascending colon, transverse colon, descending colon, sigmoid colon), and rectum.
The wall of the large intestine is covered by goblet cells, which secrete a large amount of mucus to form easily excreted feces. There are more than 100 kinds of intestinal bacteria in the large intestine, and the fermentation of these bacteria will break down dietary fiber into short-chain fatty acids. Short-chain fatty acids are absorbed in the large intestine and become a source of heat for organs such as the intestines.
Dietary fiber is a food component that cannot be digested and decomposed by human digestive enzymes, but intestinal bacteria can be fermented tobreak down. In addition, the bacteria in the gut also produce vitamin K.
◎ This article is excerpted from / "Visible Nutrition" written by Yukiko Kawashima ◎ Image source / Dashi Culture·Dazhi Image / courtesy of shutterstock
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