What are villi and microvilli and why are they important to digestion?

Role of Villi in the Small Intestine

The duodenum, ileum, and jejunum, which make up the three sections of the small intestine’s 20-foot length, Circular mucosal folds, villi, and microvilli work together to allow the small intestine to properly digest and absorb nutrients.

The surface of the small intestine is folded. These are referred to as circular mucosal folds. A sheet of flat paper should be placed inside a box. Next, fold a second flat sheet of paper as small a square as you can by repeating the process. More of the folded paper can fit into the box. More paper can be present in the same space when the paper is folded. The folds in the small intestine also increase surface area in this manner. Despite being 20 feet long, the small intestine’s absorptive area is only about 2,700 square feet.

Crypts of Lieberkuhn are located in between the villi. Younger epithelial cells typically make up crypts, which also secrete digestive juices.

Lining the small intestine are villi. Villi increase the small intestine’s surface area, allowing the circulatory system to absorb more nutrients from the lumen. Imagine a piece of paper placed over a water spill. Take a piece of paper and line it with a sponge that is extremely thin. Place the paper over the water spill after tightly folding it. More water will be able to be absorbed by the sponge-coated, folded paper. This comparison can be used to better understand villi. Villi make nutrient absorption in the small intestine more effective. Villi face the lumen, the intestine’s internal open space.

Villi are covered with even smaller hairlike structures called microvilli. Microvilli projections are smaller than villi. Additionally, it is their responsibility to increase the surface area so that each villus can absorb the most nutrients possible. Under a microscope, the border of the microvilli cells resembles a brush, and is known as the brush border.

The primary purpose of villi in the small intestine is to absorb nutrients from the lumen. The nutrients can quickly pass from the villi into the blood because the villi’s walls are only one cell thick. They do this using a process called diffusion. Below are the structures of a villus and their function.

Blood vessels transport proteins and carbohydrates.

Lymphatic capillaries remove emulsified fats called chyle.

The lacteal transports excess fluids, fatty acids, and glycerol away from the small intestine into the blood.

Brush border enzymes vary along segments of the small intestine and within animals. These enzymes generally include maltase-glucoamylase and sucrase-isomaltase, which breaks down dietary starch, lactase (breaks down lactose), peptidases (breaks down proteins), and lipases (breaks down fat).

Villi in the placenta are known as chorionic villi. Chorionic villi increase surface area, similar to villi in the small intestine, enabling the fetus to absorb more nutrients from the mother.

Enterocytesare the columnar cells making up villi. These cells’ primary job is to absorb nutrients following the stomach’s enzymatic digestion of the food. These cells secrete enzymes that break down peptides and disaccharides.

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The walls of the villi are one cell thick. This allows substances to be absorbed by diffusion quicker and easier.

Each villus is made of a network of blood capillaries that are responsible for transporting glucose and amino acids into the blood.

The internal structure of the villus is called a lacteal. Each villus moves nutrients from the intestine to a network of capillaries and fine lymphatic vessels. These lymphatic vessels are called lacteals. The lacteals transports excess fluid, fatty acids, and glycerol away from the small intestine into the blood. Glycerol is a compound found during carbohydrate and lipid metabolism.

A mucous-membrane layer makes up the villi’s epithelium (outer layer). The layer has different types of cells.

The tall, narrow columnar cells of villi called enterocytes are covered in microvilli. The microvilli lining the villi cells are about 1 micrometer. This is about 1,000 times shorter than a villus. There are estimated to be about 600 microvilli on each columnar cell. These columnar cells are responsible for absorbing substances passed into the blood.

The second type of cells covering each villus are called goblet cells. Goblet cells are rounded at the end and secrete mucus into the intestinal cavity. The purpose of mucus is to protect and lubricate the surface of the intestine.

Chorionic villi are also small finger-like projections. They are very tiny, similar to villi, but chorionic villi’s size and density vary. The size of chorionic villi varies with placenta age and environmental changes. Similar to villi in the intestine, chorionic villi have a network of capillaries that are linked to the fetus’s circulatory system. The chorionic villi can range in size from small, numerous, and highly vascularized to large and poorly vascularized. The chorionic villi become more vascularized as the fetus develops.

Digestive System:

Food enters the human digestive system through the mouth, where it passes through the esophagus and into the stomach. After leaving the stomach, food travels through the small and large intestines to be expelled from the body. This significant phenomenon makes it possible for nutrients and other substances to be absorbed.

The Intestinal Villi Explained || Absorption