Microcirculation and Fluid Balance

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Questions and Answers

What is the net filtration pressure at the arterial end of the capillaries?

Negative

Positive (correct)

Variable

Zero

What is the primary function of the lymphatic system?

To produce antibodies

To preserve fluid balance and transport fats and foreign materials (correct)

To regulate blood pressure

To remove waste products from the body

What allows for the one-way entry of fluid into lymphatic capillaries?

Semi-permeable membranes

Tissue compression

Intercellular clefts (correct)

One-way valves

What is responsible for pumping fluid forward in the lymphatic system?

Pacemaker cells Signup and view all the answers

What is the purpose of afferent lymphatic trunks?

To run alongside major blood vessels Signup and view all the answers

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

To reabsorb some lymph fluid Signup and view all the answers

What is the pressure required to prevent pumping in the lymphatic system?

40-50 mmHg Signup and view all the answers

What is the destination of efferent lymphatic trunks?

Left or right subclavian vein Signup and view all the answers

What is the primary function of the microcirculation in the vascular system?

To facilitate exchange of substances between blood and body tissues Signup and view all the answers

What is the main reason for increased capillary pressure in heart failure?

Increased venous pressure due to backflow Signup and view all the answers

What is the result of increased venular permeability due to inflammation?

Increased protein leakage into the interstitium Signup and view all the answers

What is the typical pressure gradient through the capillaries?

30 mmHg at the arterial end to 10 mmHg at the venous end Signup and view all the answers

What is a consequence of lymphatic obstruction?

Reduced lymphatic flow and increased oedema formation Signup and view all the answers

Which of the following is NOT a factor contributing to oedema formation?

Decreased capillary permeability Signup and view all the answers

What is the result of decreased plasma oncotic pressure?

Increased fluid leakage into the interstitium Signup and view all the answers

What is the term for the principle that describes fluid balance in the microcirculation?

Starling principle Signup and view all the answers

Study Notes

Learning Outcomes

Understanding how water and substances cross the capillary wall
Familiarity with the Starling principle concerning fluid balance in microcirculation
The lymphatic system's function in regulating interstitial fluid balance
Identification of four key factors contributing to oedema formation

Microcirculation

Composed of terminal arterioles, capillaries, and post-capillary venules
Key site for gas, water, nutrient, and waste exchange between blood and tissues
Forms a three-dimensional meshwork of blood vessels facilitating absorption and lymphatic flow
Oedema can arise from:
- Increased capillary hydrostatic pressure (e.g., heart failure, thromboembolism)
- Elevated capillary or venular permeability (e.g., inflammation)
- Decreased plasma oncotic pressure (e.g., malnutrition, burns, liver dysfunction)
- Lymphatic obstruction (e.g., lymph node removal, inflammation, parasitic invasion)

Capillary Pressures

Pressure gradient exists in capillaries: ~30 mmHg at the arterial end and ~10 mmHg at the venous end
Net Filtration Pressure (NFP) is positive at the arterial end and negative at the venous end
Approximately 90% of fluid lost at arterial end returns via venous capillaries; remaining fluid is cleared by lymphatics

The Lymphatic System

Essential for preserving fluid balance and transporting absorbed fats from the small intestine to the circulatory system
Transports foreign materials to lymph nodes for immune surveillance
Composed of lymphatic capillaries with intercellular clefts allowing one-way fluid entry
Fluid movement is driven by tissue compression and facilitated by lymphangions, which act as miniature hearts
Smooth muscle contractions in lymphatic trunks aid in fluid transport and require tissue compression between 40-50 mmHg to function effectively

Lymphatic Drainage

Afferent and efferent lymphatics connect to major blood vessels, delivering lymph to either the thoracic duct or the right subclavian duct
Lymph nodes play a crucial role in reabsorbing some lymph fluid and facilitating immune responses

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Description

Test your knowledge of microcirculation, fluid balance, and the lymphatic system's role in regulating interstitial fluid. Learn about the Starling principle and factors contributing to oedema formation.