The lymphatic system's role in immunity | Lymphatic system physiology | NCLEX-RN | Khan Academy

Summary

The lymphatic system plays a critical role in collecting excess fluid from tissues and returning it to the bloodstream, while also supporting the immune system by filtering harmful bacteria and viruses. Infections typically occur in tissues rather than in the blood, and the lymphatic vessels transport these pathogens to nearby lymph nodes. There, B and T cells tailor immune responses to fight off specific invaders. The lymph nodes act as filters, ensuring that any harmful agents are removed before lymph fluid reenters the blood. This system protects the body from widespread infection and keeps the bloodstream clean.

Takeaways

• 💧 The lymphatic system collects fluid squeezed out of blood vessels and returns it to the blood, preventing fluid loss.
• 🦠 Infections usually occur in tissues, not directly in the blood, and are often localized in specific areas like a finger, lung, or urinary tract.
• 👮 The lymphatic system plays a critical role in immune response by transporting bacteria and macrophages to lymph nodes where they meet B and T cells.
• 🔬 B and T cells are part of the adaptive immune system, specialized to target specific invaders, unlike macrophages, which target a variety of threats.
• 🚦 Lymph nodes act as filtration points where bacteria and debris are captured and dealt with before the lymph fluid returns to the blood.
• 🦷 In the lymph nodes, macrophages help gobble up bacteria, and B and T cells multiply and specialize to fight infections.
• 🗺️ There are around 600 lymph nodes in the body, located along lymphatic vessels, with some close enough to the skin to be felt during medical examinations.
• 🧠 Lymph nodes are small, measuring between 1 and 25 millimeters, and are distributed throughout the body, especially in areas like the neck, groin, and armpits.
• 🧪 Lymph fluid from any tissue in the body passes through at least one lymph node before being returned to the bloodstream, ensuring that it is filtered.
• 🔄 Lymph nodes prevent bacteria from entering the bloodstream, reducing the risk of serious blood infections.

Q & A

What is the primary purpose of the lymphatic system?

The primary purpose of the lymphatic system is to collect fluid that is squeezed out of blood vessels and return it to the blood, preventing the loss of too much fluid.

Why do infections usually occur in tissues rather than in the blood?

Infections typically occur in tissues because infections are usually localized. If an infection were in the blood, it would spread throughout the entire body, which is much more dangerous. Most infections remain confined to specific areas like the skin, urinary tract, or lungs.

What is the role of B cells and T cells in the immune response?

B cells and T cells are part of the adaptive immune system. They respond to specific invaders, such as bacteria, by specializing and multiplying to fight the infection more effectively. Unlike macrophages, which attack a broad range of bacteria, B and T cells are highly targeted in their response.

How does the lymphatic system help in fighting infections?

The lymphatic system helps fight infections by sweeping bacteria and macrophages (which may have ingested bacteria) into lymphatic vessels. These are carried to the nearest lymph node, where B and T cells can encounter and react to the invaders, initiating an immune response.

What are lymph nodes, and what is their function?

Lymph nodes are small, circular structures located throughout the body along lymphatic vessels. They filter lymph fluid, removing bacteria and debris, and house B and T cells that specialize and multiply to fight infections.

How does the lymphatic system prevent bacteria from entering the bloodstream?

Lymph nodes act as filters for lymph fluid, preventing bacteria from being directly reintroduced into the bloodstream. This prevents the spread of infection, which could be much more dangerous if it reached the blood.

What is the size range of lymph nodes, and how many are there in the body?

Lymph nodes are small, ranging from 1 to 25 millimeters in size. There are approximately 600 lymph nodes in the human body.

Where are lymph nodes located in the body?

Lymph nodes are located throughout the body, particularly in areas like the inguinal region (where the thigh meets the abdomen), along the clavicles, neck, face, and under the jaw. They are found along major lymphatic vessels.

What happens to the fluid after it passes through a lymph node?

After passing through a lymph node, the fluid continues through the lymphatic vessels and eventually reenters the bloodstream, free of bacteria and debris.

Why is it important for lymph fluid to pass through at least one lymph node before returning to the blood?

It is important for lymph fluid to pass through a lymph node to ensure that it is filtered and free from bacteria and other harmful substances before being reintroduced into the blood. This prevents the risk of a more serious blood infection.