Venous Return and Lymphatics Flashcards
What is the structure of veins in relation to their function?
Thin walls with smooth muscle and some elastic tissue, large radii, one-way valves.
What is the pressure gradient in the cardiovascular tree?
Blood pressure gradient from left ventricle to right atrium.
What factors affect venous return?
- Pressure gradient
- Venous resistance
What is venous compliance?
Rate of change in volume (ΔV) with changing pressure (ΔP).
What function do veins serve as capacitance vessels?
Storage of blood and mobilization when required.
Describe the normal distribution of blood volume at rest.
The venous system acts as a blood reservoir.
What regulates venous tone?
Factors that increase venous pressure and pressure gradient.
How do veins differ from arteries?
- Transport blood towards the heart
- Smooth flow
- Carry de-oxygenated blood
- Large lumen
- Less muscle/elastic tissue
- Transfer blood under low pressure
- Have valves
What is venous return?
The volume of blood returning to the heart from systemic veins.
What is the normal venous pressure in the venous system?
~ 18 mmHg.
What is the right atrial pressure?
~ 0 mmHg.
What promotes venous return?
- Increased cardiac output
- Increased stroke volume
- Increased end-diastolic volume
- Venous valves
- Cardiac suction effect
- Increased venous tone
- Skeletal muscle pump
- Respiratory pump
- Increased blood volume
What factors lead to venoconstriction?
- Sympathetic stimulation
- Activated venous stretch receptors
- Hormones like adrenaline and noradrenaline
What are the characteristics of veins?
- Highly distensible
- High vascular compliance
- Large storage capacity
What are specific blood reservoirs in the venous system?
- Spleen (<100ml)
- Liver (<400-600ml)
- Large abdominal veins (<300ml)
- Venous plexus (<400-600ml)
What are the components of venous pressure?
- Pressure generated by the heart
- Hydrostatic pressure
What is central venous pressure?
Pressure in the thoracic vena cava near the right atrium.
What is the normal range for right atrial pressure?
0-5 mmHg.
What can cause abnormal right atrial pressure?
- Serious heart failure
- Large blood transfusion
What are common pathological conditions affecting the venous system?
- Valve incompetence
- Venous obstruction
- Varicose veins
What are the primary functions of the lymphatic system?
- Fat absorption
- Defense against disease
- Fluid balance
What does the lymphatic system transport?
Lymph, a clear yellowish fluid containing white blood cells, proteins, and fats.
Fill in the blank: The lymphatic system runs in parallel to the _______.
[circulatory system]
