7. Venous and Lymphatic systems Flashcards
Describe vein structure in relation to function
Thin walls
Smooth muscle + elastic tissue
Large radii
One way valves
Conduit vessels- act as a passage way back to the heart
Storage - capacitance vessels- store blood and mobilise when required
What is venous return?
The volume of blood returning to heart from systemic veins
What determines venous return?
The pressure gradient
Venous resistance
What is cardiac output?
The amount of blood that pumps through the circulatory system in a minute
What is stroke volume?
amount of blood pumped by the left ventricle in one contraction
What does an increase in venous return cause?
Increase in end-diastolic volume
Increase in stroke volume
Increase in cardiac volume
What are the factors that facilitate venous return?
Venous valves Cardiac suction Pressure of the blood due to cardiac contractions Blood volume Respiratory pump Skeletal muscle pump
What is venous tone?
property of the venous system which reflects the venous resistance and pressure. (TENSION)
What are the factors that increase venous tone and thus leading to venoconstriction?
Sympathetic stimulation
Activated venous stretch receptors
Hormones
What does the reduction of venous tone lead to?
Vascular smooth muscles relax
What is meant by venous compliance?
The rate of change in volume with changing pressure
What are the characteristics of veins?
Highly distensible: high vascular compliance
Accommodate changes in blood volume without much change in presssure
Large storage capacity , blood reservoir, capicatance vessels - low resistance and high volume
What are the two components of venous pressure?
Pressure generated by heart
Hydrostatic pressure
What is the central venous pressure?
Pressure in the thoracic vena cava near the right atrium
What does the central venous pressure depend on?
Venous return
Right ventricular function
What is a normal right atrial pressure?
0-5 mmHg
What would a right atrial pressure of 20-30 mmHg indicate?
Serious heart failure, large blood transfusion
What would a right atrial pressure of -3 to -5 mmHg indicate?
When the heart pumps vigorously, after haemorrhage
look at table on slide 14
Arteries and veins difference
Table slide 18
Lymphatic system
Where is the lymphatic system?
Runs in parallel to the circulatory system
What is the role of the lymphatic system?
Transport lymph
What is lymph?
Clear, yellowish fluid containing white blood cells, proteins and fats
What are the structures of the lymphatic system?
Lymphatic capillaries Lymphatic vessels Lymph nodes Lymphatic trunks Lymphatic ducts Lymph drains into central veins
What are the three primary functions of the lymphatic system?
- Fat absorption
- Defence against disease
- Fluid balance
