Lymph, lymph nodes, & lymphatic system | Life processes | Biology | Khan Academy

Summary

This video explains the vital role of the lymphatic system, including its components: lymph, lymph vessels, and lymph nodes. Lymph is a colorless fluid that leaks from blood capillaries due to pressure and fills the spaces between cells. Lymph vessels collect this fluid and return it to the bloodstream through veins. Lymph nodes act as filters, removing pathogens to protect the body. Additionally, the lymphatic system helps transport fats from the digestive system into the blood. The video highlights the importance of lymph in maintaining bodily functions, immunity, and nutrient absorption.

Takeaways

• 😀 The lymphatic system is responsible for draining excess lymph fluid from tissues to prevent swelling.
• 😀 Lymph is the plasma that leaks from blood capillaries, which helps exchange gases and nutrients between the blood and cells.
• 😀 Lymph does not contain red blood cells and is colorless, hence the term 'lymph' derived from the Latin word meaning 'water-like'.
• 😀 The capillaries have small holes that allow plasma to leak out, but red blood cells remain inside due to their size.
• 😀 Lymph vessels, including lymph capillaries, help clear out the lymph from tissues and return it to the circulatory system.
• 😀 Lymph capillaries have overlapping cells that function like one-way doors to allow lymph fluid to enter but prevent it from flowing back out.
• 😀 The lymphatic system prevents the blood from becoming too thick by returning plasma to the circulatory system.
• 😀 The lymphatic system helps with immunity by filtering out pathogens through lymph nodes, which contain white blood cells.
• 😀 Swollen lymph nodes near the neck or ears are a sign of infection, and doctors check for them during physical exams.
• 😀 Lymph vessels also transport digested fats from the small intestine into the bloodstream, as fat molecules are too large for capillaries.

Q & A

What is lymph and how is it formed?

Lymph is a fluid that forms when plasma leaks out of capillaries due to blood pressure. It is colorless and lacks red blood cells (RBCs), and it contains a small amount of proteins.

Why do doctors check the neck and behind the ears during a routine checkup?

Doctors check these areas because they contain lymph nodes. Swollen lymph nodes can indicate an infection or other health issues.

What causes the swelling in elephantiasis?

Elephantiasis occurs when lymph accumulates in tissues, causing swelling in the limbs, typically due to blocked lymphatic vessels.

What is the difference between blood and lymph?

The primary difference is that lymph does not contain red blood cells and is colorless. It is essentially the plasma that leaks from capillaries into tissues.

What role do capillaries play in the formation of lymph?

Capillaries allow blood plasma to leak through their walls, forming lymph. The plasma leaks due to the pressure from blood flow, and this fluid accumulates in the surrounding tissues.

Why are there holes in the walls of capillaries?

The holes in capillary walls are necessary for the exchange of gases, nutrients like glucose, and waste products between blood and cells. This exchange wouldn't be possible without the small openings.

How does the lymphatic system prevent lymph from flowing back out of lymph capillaries?

Lymph capillaries have overlapping cells that act like one-way doors. When lymph enters due to pressure, these overlapping cells close, preventing the fluid from flowing back out.

Why do lymph vessels connect to veins instead of arteries?

Lymph vessels connect to veins because veins have lower pressure compared to arteries. This low pressure allows lymph to enter the circulatory system without being forced back out.

What is the role of lymph nodes in the lymphatic system?

Lymph nodes act as filters in the lymphatic system. They contain white blood cells (WBCs) that detect and destroy pathogens, such as bacteria, that may enter the lymph from infected tissues.

How does the lymphatic system help transport fats into the bloodstream?

The lymphatic system collects digested fats from the small intestine, as they are too large to enter blood capillaries directly. These fats are then transported through the lymphatic vessels to the bloodstream.