Lymphatic Capillaries: Function & Explanation

Lymphatic Capillaries: Function & Explanation
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  • 0:00 Overview of Blood Flow
  • 1:15 What are Lymphatic…
  • 2:50 The Lymphatic System
  • 4:23 Lesson Summary
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Lesson Transcript
Instructor: Stephen Christensen
In this lesson you will learn what lymphatic capillaries are. You will also learn why they are important for removing excess fluid from your tissues and how they fit into your lymphatic system.

Overview of Blood Flow

Lymphatic capillaries are among a number of structures belonging to your lymphatic system. Your lymphatic system works in close concert with your circulatory system, which transports blood throughout your body. A working knowledge of your circulatory system will help you understand how your lymphatic system functions.

Your circulatory system consists of a pump, your heart, and a network of tubes that conduct blood throughout your body, your blood vessels. With each beat of your heart, blood is forced into your arteries, which carry blood away from your heart and toward all of your tissues and organs. As your arteries travel farther from your heart, they divide into progressively smaller vessels called arterioles, which themselves divide into tiny, thin-walled, leaky vessels called capillaries.

As blood travels through your capillaries, oxygen, nutrients, and fluid are pushed into the surrounding tissues, and carbon dioxide and other cellular wastes are retrieved. The blood then proceeds on its way, coursing into progressively larger vessels called venules and then into even larger veins, which finally return the blood to your heart.

What Are Lymphatic Capillaries?

If your body didn't have a mechanism for recovering the fluid leaking from your blood capillaries, your tissues would soon resemble waterlogged sponges, and the cells within your tissues would quickly drown. This is where your lymphatic system goes to work.

Mingled among the millions of blood capillaries throughout your body is another network of tiny, thin-walled vessels called lymphatic capillaries. The structure of a lymphatic capillary is similar to that of a blood capillary, but its function is distinctly different. Like a system of storm drains channeling rainwater from a city's streets, your lymphatic capillaries pick up the fluid that leaks into your tissues and help return it to your circulatory system.

The key to your lymphatic capillaries' efficiency is a simple physical property: fluids flow from areas of higher pressure toward areas where pressures are lower. Unlike your circulatory system, your lymphatic system doesn't have a pump to push fluid through its network of vessels. The main driving force that pushes fluid into your lymphatic system is derived from the circulatory system itself.

The blood entering your blood capillaries is still being forced along by the pressure generated by your heartbeat. This pressure is, in fact, what forces fluid into your tissues. Fortunately, the pressure within your lymphatic capillaries is slightly lower than that in your blood capillaries - or even within your tissues. This creates a pressure gradient that moves fluid from your blood capillaries into your tissues and finally into your lymphatic capillaries, much like water in a stream flows downhill.

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