Cardiovascular System Flashcards
Why is the heart important?
The heart is the pumping muscle that keeps the blood in motion
Ultimately all of the functions of the body depend on the heart keeping the blood moving
Rapid transport
oxygen, glucose, amino acids, fatty acids, vitamins, drugs and water to the tissues
Carbon dioxide, urea and creatinine away from the tissues
Control system
Distributing hormones to the tissues and secreting a hormone (atrial natriuretic peptide)
how does body temperature regulation work?
Transporting heat from deep organs to the skin surface for dissipation
Functions of the CVS
Rapid transport
Control system
Body temperature regulation
Important points
Both circuits begin and end at the heart
Blood must travel through them in sequence
Blood is constantly moving in both circuits
Both ventricles eject equal amounts of blood at the same time
One way valves ensure that the blood follows this pattern
The pulmonary circulation is unique in that the arteries carry oxygen poor blood and the veins carry oxygen rich blood
Normal values
Stroke volume in a normal adult is typically 70-80ml
Cardiac Output
Cardiac output (CO) is the volume of blood ejected by one ventricle in one minute
heart rate
The number of times the heart contracts in a minute
stroke volume
Each time a ventricle contracts the amount of blood ejected
Blood flow
the volume of blood flowing through a vessel in a given period (ml/min)
Blood pressure
the force per unit area exerted on a vessel wall by the contained blood, expressed as mmHg. The pressure gradient provides the driving force to keep blood moving
Resistance
the opposition to flow and is the amount of resistance blood encounters as it passes through the vessels
Darcy’s law of flow
Flow, Q (written with a dot over it) is the volume transferred per unit time (ml/min)
Flow is proportional to the pressure difference between the inlet pressure and outlet pressure in a steady state, along a rigid tube – P1-P2 (mmHg)
Resistance (mmHg/ml/min), R is inversely proportional to conductance the ease of flow
Hence: Q = (P1-P2)/R
Resistances in series
Resistances in wide vessels is low, in narrow vessels is high
When vessels are connected in series their resistances are added
the resistance of the large aorta is low as it is connected in series to narrow arterioles and capillaries the overall resistance of the systemic circulation is high
Systemic circulation resistance is 0.02mmHg per ml/min
Pulmonary circulation resistance is much lower at 0.003mmHg per ml/min
Changes in local blood flow
The law of flow allows us to understand how flow to an organ is regulated
Locally changes in blood flow are regulated by changes in vascular resistance
Changes are brought about by contraction and relaxation of the narrow terminal branches of the arterial system
Two ways to increase flow
Increase the driving pressure
Reduce the vascular resistance
Right and Left Timing
Both atria contract at roughly the same time
Both ventricles contract at roughly the same time
The ventricles eject equal volumes of blood into the pulmonary and systemic circuits in a normal heart
Ventricular contraction is called systole
Ventricular relaxation is called diastole
Tricuspid valve
sits between the right atrium and right ventricle (3 leaflets)
These valves are called ‘atrioventricular’
Their leaflets are attached to papillary muscles in each ventricle by chordae tendinae
These help support the leaflets and ensure the valves remain closed when the ventricles contract
Mitral valve
sits between the left atrium and left ventricle (2 leaflets)
These valves are called ‘atrioventricular’
Their leaflets are attached to papillary muscles in each ventricle by chordae tendinae
These help support the leaflets and ensure the valves remain closed when the ventricles contract
Aortic valve
sits between the left ventricle and the aorta (3 cusps)
These are called semilunar valves – their cusps are crescent shaped and are attached to the walls of the artery like pockets
Pulmonary valve
sits between the right ventricle and the pulmonary artery (3 cusps)
These are called semilunar valves – their cusps are crescent shaped and are attached to the walls of the artery like pockets
Valves Opening
Valves open passively when the pressure of the blood behind them exceeds the pressure in the chamber in front of them
E.g. the mitral valve opens when the pressure in the left atrium exceeds the pressure in the left ventricle
Vales Closing
The valves close when the pressure of blood in the chamber behind them falls below that of the chamber in front of them
E.g. The aortic valve closes when the pressure in the left ventricle drops below the pressure in the aorta
The mitral and tricuspid valves are also helped to close by the contraction of the ventricles/papillary muscles
Location
- located in the chest between the two lungs
- size of a clenched fist and is angled towards the left-hand-side.
How many chambers does the heart have?
4
The artia (left and right) are the filling chambers of the heart, where blood is delivered to.
Where does the heart sit?
behind the sternum. The sternum connects the ribs and forms the front of the rib-cage.
The rib-cage offers protection to the heart, lungs and major blood vessels.
Arteries
vessels that always carry blood away from the heart.
They deliver oxygen rich blood to the tissues and organs of the body.
As blood leaves the left ventricle, the first artery blood travels through is the aorta.
aorta
The largest artery in the body, this is where blood it at the highest pressure.
The aorta branches into a network of smaller arteries that extend throughout the body.
The arteries’ smallest branches are called arterioles.
Veins
carry blood towards the heart - they deliver oxygen poor blood from the tissues and organs back to the heart.
When oxygen and nutrients have been delivered to the tissues, blood then travels into venules, these are the smallest veins.
These connect to other venules to form veins, these get progressively larger as they get closer to the heart. The largest veins are the superior and inferior vena cava (SVC and IVC).
These veins deliver blood to the right atrium
blood vessels
dynamic, elastic and constantly changing.
capillaries
the smallest blood vessels
these are permeable, solutes can flow out of the capillary and waste products can flow into the capillary.
