Lecture Notes: Fluid Dynamics in Capillaries

Introduction

Explanation of hydrostatic and osmotic pressure.
Importance: Understanding cases of edema (tissue swelling).

Capillary Function

Capillaries are designed for exchange of nutrients, gases, wastes, and fluid.
Fluid movement:
- Filtered out at the arteriole end.
- Reabsorbed at the venous end to prevent swelling (edema).

Hydrostatic Pressure

Drives fluid out of blood vessels.
Example:
- Demonstrated using a straw filled with water.
- Gravity pulls water down, applying pressure (hydrostatic pressure) to force fluid out.
In capillaries:
- Hydrostatic pressure at arteriole end forces fluid out through pores and channels.

Osmotic Pressure

Drives fluid back into blood vessels.
Key Concept:
- Water flows towards regions with higher osmolarity (higher solute concentration).
Example:
- High concentration of large particles (proteins) inside a vessel.
- Water reabsorbed into vessel towards higher concentration.
Colloid Osmotic Pressure (Oncotic Pressure):
- Caused by large proteins (e.g., albumin) in blood.
- Drives reabsorption of fluid into blood.
Na+ and Cl- do not contribute to osmotic pressure for fluid reabsorption.

Fluid Dynamics in Capillaries

Arteriole End:
- Higher hydrostatic pressure than osmotic pressure.
- Fluid forced out into interstitial space.
Venous End:
- Hydrostatic pressure decreases.
- Osmotic pressure becomes greater, reabsorbing fluid back into capillary.

Lymphatic System

Reabsorbs remaining fluid not reabsorbed by osmotic pressure.
Prevents swelling or edema.

Conclusion

Overview of how hydrostatic and osmotic pressures regulate fluid in capillaries.
Preview of future topics: Cases of edema caused by abnormal pressure changes (e.g., standing too long).

These notes cover the main ideas discussed in the video on fluid dynamics in capillaries, including the roles of hydrostatic and osmotic pressures and the lymphatic system in regulating fluid movement and preventing edema.

Understanding Fluid Dynamics in Capillaries