Biology

Villus

A villus is a tiny, thin, fingerlike structure with a blood supply that sticks out from the surface. More than one villus is known as villi. Villi are located in different areas of the body. Most commonly, the term is used to describe the many tiny, fingerlike structures that stick out and are located in groups over the entire mucous surface (a type of thin sheet of tissue) of the small intestine. The intestine is a tube shaped structure that is part of the digestive tract. The small intestine is a part of the intestine that takes in all of the nutrients (healthy substances) that the body needs.

The villi help to increase the total area on the outside of the small intestine. Villi help absorb, move, and distribute some of the fluids and nutrients into the blood and lymphatic system. The lymphatic system is a system of vessels that drain lymph from all over the body back into the blood. Lymph is a milky fluid that contains proteins, fats, and white blood cells (which help the body fight off diseases). Food particles that are broken down in the digestive system reach the blood through the capillaries (very tiny blood vessels) in the villi.

A villus is covered by types of cells known as epithelium. Cells are the smallest, most basic units of life, which are capable of existing by themselves. It is the epithelial cells that actually help absorb, move, and distribute some of the fluids and nutrients in the body. You can also see that the villus has a network of capillaries, which are very tiny blood vessels. The villus also has another type of tiny vessel known as a lacteal, which fills with milky white fluid known as chyle after a fatty meal.

Capillaries

Capillaries are very thin and fragile they are actually only one epithelial cell thick. They are so thin that blood cells can only pass through them in single file. The exchange of oxygen and carbon dioxide takes place through the thin capillary wall. The red blood cells inside the capillary release their oxygen which passes through the wall and into the surrounding tissue. The tissue releases its waste products, like carbon dioxide, which passes through the wall and into the red blood cells.

Arteries and veins run parallel throughout the body with a web-like network of capillaries, embedded in tissue, connecting them. The arteries pass their oxygen-rich blood to the capillaries which allow the exchange of gases within the tissue. The capillaries then pass their waste-rich blood to the veins for transport back to the heart. Capillaries are also involved in the body's release of excess heat. During exercise, for example, your body and blood temperature rises. To help release this excess heat, the blood delivers the heat to the capillaries which then rapidly release it to the tissue. The result is that your skin takes on a flushed, red appearance. If