Venous circulation and lymph flow Flashcards
Comparing the vessel wall of an artery and a vein
- Smaller lumen of arteries
- radius – wall thickness ratio is different
- difference in the composition of connective tissue (elastic and collagenous fibers)
- difference in smooth muscle cell (SMC) coverage
- distensibility of veins is larger
- compliance of veins are larger
- venous valves
What is distensibility?
The capability of being distended or stretched under pressure
Compare Compliance of the vena cava and the aorta
Is the venous system a low or high pressure system?
The venous system is a low pressure system
Comparing the compliance of a vein and an artery (draw the graph)
Increased vascular tone decreases the compliance
-> How can this occur?
alpha1-dependent sympathetic stimulations
-> vasoconstriction
-> rigidity will be increased
-> compliance is lowered
Distribution of total blood volume in the venous system
What are the 5 organs with high venous blood storage capacity
- liver
- abdominal veins
- heart
- plexuses of the skin
- spleen
Which factor we need to increase for mobilization of blood from the venous system?
Increased sympathetic activity
Increased sympathetic activity- mobilization of blood from the venous system
-> What are the 2 ways to achieve this?
- exercise – blood volume in the gastrointestinal tract decreases; blood flow of the coronaries and skeletal muscle increases
- excessive bleeding
Venous pressure changes depend on the arterial pressure change
-> T/F?
F (No pulsatility beyond the capillaries)
What are the 3 factors influencing venous pressure changes
- Cardiac cycle – retrograde effect of the heart function
- Respiration
- Muscle contractions
Factors influencing venous pressure changes - respiration dependent changes-
=> How can inspiration and expiration affect intrathoracic pressure?
Inspiration – decreases the intrathoracic pressure
Expiration – reverses the process
Factors influencing venous pressure changes - foot veins
-> How does Muscle pump work?
rhytmic contraction of the muscles of the leg
Factors influencing venous pressure changes - foot veins
-> What is the function of the venous valves?
Maintaining the forward flow
what are the 2 components of central venous pressure (CVP) (anatomically)
Vena cava, right atrium
What is Central venous pressure (CVP)? (number)
0-2 Hgmm
Central venous pressure (CVP) is influenced by __
- inflow from the arterial side
- myogenic and neurogenic tone of postcapillary
- resistance vessels function of the right ventricule
What happen if central venous pressure (CVP) is increased?
Heart failure, increased volume, Valsalva maneuver (max. 20-30 Hgmm)
Symptoms of Valsalva maneuver (max. 20-30 Hgmm) ( a breathing method that may slow your heart when it’s beating too fast)
closed glottis, increased intrathoracic pressure
What happen if Central venous pressure (CVP) is decreased?
volume loss (min. (-3) – (-5) Hgmm)
What is mean systemic filling pressure (MSFP)?
the mean pressure that exists in the circulatory system when there is no blood motion.
Q = 0 ml/min
Give the number of mean systemic filling pressure (MSFP)?
7 Hgmm
Make a schematic diagram for The heart is restarted after the cardiac arrest
The effect of gravity on venous pressures
-> Pressures in the foot veins in a standing person
-> How can compensation occur?
Compensation
- α1-dependent increase of the vascular tone
- Low compliance at the high pressures
What is the venous pressure Outside the chest?
4-6 Hgmm
What is the Abdominal venous pressure?
approx. 6 Hgmm
What is the venous pressure of pregnancy, obesity, abdominal tumors?
15-20 Hgmm
The function of the venous valves
- deals with extensive mechanical forces
- maintaining forward flow, preventing the back flow of blood
- lowering the venous pressure in the tissues
Characteristics of venous valves
- bicuspid valves
- endothelial cell coverage, collagen content
Function of Peripheral musculovenous pump
Lowering Venous Pressure in the Leg
How do Thoraco-abdominal pump work?
Inspiration – decreases intrathoracic pressure
Expiration – reverses the process
Further functions of the venous system
- Microcirculation - postcapillary resistance
- Biosynthetic activity and angiogenesis
- Inhibition of thromboembolic reactions
- Contribution to immunological processes, e.g. the cooperation between the immune cells and high endothelial venules (HEV)
- Special organ-specific functions - cerebral venous blood drainage: intra- and extracranial veins, portal veins, skin veins
what is chronic venous disease?
Dysfunction of the venous system with infections
What is pulmonary embolism?
What is Secondary lymphedema?
Secondary lymphedema may happen if your lymphatic system is damaged from surgery, trauma or radiation therapy.
(breast cancer patient after axillary lymph node removal)
What is - Lymphatic system?
A blind-ended open capillary network
What are the 4 Components of the lymphatic system?
- Lymphatic capillaries
- Collecting lymphatics
- Lymph nodes
- Central lymphatics(thoracic duct)
Characteristics of Lymphatic capillaries
- blind-ended vessels
- lymphatic endothelial cells (LECs)
- trans- and paracellular transports
- uptake of fluid, large molecules (e.g. proteins) and immune cells
Type and function of junctions in Lymphatic capillaries
Lymphatic capillaries: button-like junctions
(functioning as primary lymphatic valves)
Characteristics of Collecting lymphatics
- Lymphatic valves
- Smooth muscle cell (SMC) coverage
What are the 2 phases of collecting lymphatics?
- Expansion phase
- Compression phase
What happen during the expansion phase of of collecting lymphatics?
What happen during the compression phase of of collecting lymphatics?
How can collecting lymphatics maintain the forward flow of lymph?
- SMC coverage of collecting lymphatics
- lymphatic valves
- Intermittent external compression of lymphatic vessels skeletal muscle contraction thorax, abdomen
Type and function of valve of Central lymphatics (thoracic duct)
lymphovenous valve
– separating the blood and lymphatic compartments
Development of the lymphatics
Primary lymph sac sprout into the developing organs
Development of the lymphatics on molecular level
VEGFC is a key lymphangiogenic factor inducing lymphatic growth
-> The VEGFR3 - VEGFC lymphangiogenic pathway
Functions of the lymphatic system
3.1 Regulating fluid balance and the clearance of macromolecules
3.2 Regulating the migration and trafficking of immune cells
3.3 Absorption of lipids in the small intestine
3.4 Novel and unexpected functions of lymphatics
Functions of lymphatic system
-> Regulating fluid balance and the clearance of macromolecules
-> Give the number for Filtration and Reabsorption
- Filtration: 20 l/day
- Reabsorption: 16-18 l/day
Functions of lymphatic system
-> Regulating fluid balance and the clearance of macromolecules
-> Give the number for lymph flow and protein uptake
- 2-4 l/day
- 200 g/day protein taken up by the lymphatics
Functions of lymphatic system
-> Regulating fluid balance and the clearance of macromolecules
-> Describe Gel phase
99 % of interstitial H2O is in gel phase: H2O molecules constitute the - interconnected - hydrate coat
of matrix proteins (and proteoglycans, glucoseaminoglicans, hialuronic acid, etc.)
Functions of lymphatic system
-> Regulating fluid balance and the clearance of macromolecules
-> Describe Soluble phase
1 % of the total H2O is free fluid in the compartment
greatly increased in interstitial edema
The function of lymphatic capillaries – fluid and macromolecule uptake
-> Make a graph relative lymph flow and mean Pif
Increasing interstitial pressure will increase ___
lymph flow
4 factors leading to increasing Pint
What is Edema
Edema is defined as a palpable swelling produced by expansion of the interstitial fluid volume.
How is Edema formed?
Increased permeability or filtration of capillaries (b Starling forces)
Example of Primary lymphedema
Milroy disease – mutation of VEGFR3
What are the components that involve in Regulating the migration and trafficking of immune cells?
Secondary lymphoid organs (e.g. lymph nodes) and lymph vessels
How can lymphatic system participate in Absorption of lipids in the small intestine?
Some Novel and unexpected functions of lymphatic system
- Skin lymphatics in systemic blood pressure regulation
- Meningeal lymphatics in the clearance of macromolecules and trafficking of immune cells
- Cardiac regeneration - etc.
How can lymphatic system participate in Regulation of systemic blood pressure?
by modulating the sodium pool in the skin interstitium
Meningeal lymphatics impairment affect CNS
-> How
Meningeal lymphatics impairment might be involved in the pathophysiology of diseases affecting the CNS
* Alzheimer’s Disease
* Multiple Sclerosis
Lymphatics and lymphangiogenic signaling in cardiac regeneration
-> How?
VEGFC promotes functional improvement post myocardial infarct
