A Level Biology Revision "Tissue Fluid and Lymph Fluid"

Summary

This educational video explains the formation and function of tissue and lymph fluid in the body. It describes how blood flows through capillaries, where fluid is forced out into the tissues via hydrostatic pressure and returns through osmosis due to oncotic pressure. It also explains the formation of tissue fluid, its role in nutrient and waste exchange, and the reabsorption process at the venous end of the capillaries. Additionally, the video covers how the remaining fluid enters the lymphatic system, contributing to immune function and returning to the bloodstream.

Takeaways

• 😀 Blood consists of blood cells (red blood cells, white blood cells, platelets) and blood plasma, which contains dissolved substances like glucose, amino acids, and plasma proteins.
• 😀 The capillaries, narrow blood vessels with thin walls, allow for the exchange of fluids between the blood and surrounding tissues.
• 😀 Tissue fluid forms when fluid is pushed out of blood capillaries at the arterial end, providing nutrients (like oxygen and glucose) to tissue cells.
• 😀 Waste products, such as carbon dioxide, are removed from tissue cells into the tissue fluid, which helps in waste disposal.
• 😀 The movement of fluid into and out of the capillaries is governed by two opposing pressures: hydrostatic pressure and oncotic pressure.
• 😀 Hydrostatic pressure, caused by the heart's pumping, forces fluid out of the capillaries into the surrounding tissues.
• 😀 Oncotic pressure, created by plasma proteins like albumin, tends to draw water back into the capillaries through osmosis.
• 😀 At the arterial end of the capillary, hydrostatic pressure is greater than oncotic pressure, leading to the formation of tissue fluid through ultrafiltration.
• 😀 At the venous end of the capillary, hydrostatic pressure is lower, and oncotic pressure is higher, causing water to return to the blood via osmosis.
• 😀 Around 90% of tissue fluid is reabsorbed back into the blood, while the remaining 10% enters lymph capillaries, forming lymph fluid.
• 😀 The lymphatic system transports lymph fluid back to the bloodstream, assisted by skeletal muscle contractions and one-way valves in lymph vessels.

Q & A

What is the primary function of tissue fluid?

The primary function of tissue fluid is to bathe tissue cells and facilitate the exchange of molecules, such as oxygen and glucose, with the cells, while also carrying away waste products like carbon dioxide.

How is tissue fluid formed in the capillaries?

Tissue fluid is formed when blood passes through capillaries, where hydrostatic pressure forces fluid out of the blood, which then bathes the tissue cells.

What role do plasma proteins, like albumin, play in the formation of tissue fluid?

Plasma proteins, such as albumin, lower the water potential of blood plasma, which creates oncotic pressure that draws water back into the blood at the venous end of the capillary.

What is hydrostatic pressure and how does it affect tissue fluid formation?

Hydrostatic pressure is the pressure exerted by the blood against the walls of the capillaries. It tends to force fluid out of the blood vessels into the surrounding tissue, contributing to tissue fluid formation.

What is oncotic pressure and how does it contribute to the movement of tissue fluid?

Oncotic pressure is the osmotic pressure exerted by plasma proteins, particularly albumin, which draws water back into the capillaries at the venous end. It counteracts the hydrostatic pressure to regulate fluid balance.

What is the process of ultrafiltration?

Ultrafiltration is the process by which tissue fluid is forced out of the blood at the arterial end of the capillary due to the higher hydrostatic pressure, while blood cells and plasma proteins remain in the blood due to their size.

How do hydrostatic and oncotic pressures interact at the arterial and venous ends of the capillary?

At the arterial end of the capillary, hydrostatic pressure is higher than oncotic pressure, causing fluid to leave the capillary. At the venous end, hydrostatic pressure is lower, and oncotic pressure remains high, which causes water to return to the capillary by osmosis.

What happens to the tissue fluid that is not reabsorbed into the blood?

The tissue fluid that is not reabsorbed into the blood enters the lymphatic system via lymph capillaries. This fluid, now called lymph, eventually returns to the bloodstream.

What role does the lymphatic system play in the circulatory process?

The lymphatic system drains excess tissue fluid that is not reabsorbed into the blood and returns it to the bloodstream. It also plays a role in immunity by filtering pathogens and waste from the lymph fluid.

How does lymph fluid move through the lymphatic system?

Lymph fluid moves through the lymphatic system when nearby skeletal muscles squeeze the lymph vessels. Valves in the vessels help to prevent backflow and ensure the fluid moves forward towards the bloodstream.