Lecture 1: Design of Circulation and Haemodynamics
Friday, 3 July 2015 7:14 p.m.
Understand the basic function of the cardiovascular system.
Blood's Purpose
- The purpose of the blood is to deliver metabolites and oxygen to the cells in our
tissues and organs and to remove their waste products
- All blood flows through the systemic circuit and then the pulmonary circuit
Direction of Flow
- Blood flows from the left side of the heart, around the body then back to the right side
of the heart
- Blood also flows from the right side of the heart, to the lungs and then back to the left
side of the heart
Arteries and Veins
- Arteries go away from the heart, carrying oxygenated blood away to tissues
○ Pulmonary circulation: carries deoxygenated blood
- Veins go toward the heart, carrying deoxygenated blood back to the heart
○ Pulmonary circulation: carries oxygenated blood
The direction blood flows through the circulation is as follows:
Right heart → Lungs (pulmonary circulation) → left heart → body (systemic circulation)
Left Atrium: freshly oxygenated blood arrives here from the lungs, it flows through the
bicuspid/mitral valve reaching the…
Left Ventricle: oxygenated blood flows out of the left ventricle, through the aortic valve and
into the arterial system to supply the body via parallel circuits of blood vessels. It travels
back towards the heart through the venous system and flows into the…
Right Atrium: the receiving chamber for deoxygenated blood arriving from blood vessels
called the superior vena cava and the inferior vena cava and the coronary sinus. Once it is
full, the tricuspid valve opens and blood flows into the…
Right Ventricle: from here the deoxygenated blood is sent off through the pulmonary valve
to the lungs to be oxygenated
Left atrium (receives oxygenated blood from lungs)
Mitral valve (AV valve)
Left ventricle
Aortic valve (semilunar valve)
Body
Veins
Superior vena cava, inferior vena cava and coronary sinus
Right atrium
Tricuspid valve (AV valve)
Right ventricle
Pulmonary valve (semilunar valve)
Lungs
Left atrium…
Valves
CARDIOVASCULAR SYSTEM Page 1
,Valves
Valves are only found in veins, because the pressure generated by the heart in arteries is
high enough to accomplish uni-directional flow in these vessels.
1. Venous valves
- Have cusps that prevent the backflow of blood but allow blood to flow forward when
the pressure inside the veins increases due to muscle contraction
2. Atrioventricular valves3
- Tricuspid and mitral
- Separate the atria from the ventricles
- When blood has filled the ventricles they snap shut, preventing backflow of blood into
the atria
3. Semilunar valves
- Pulmonary and aortic
- Separate the ventricles from the pulmonary trunk and the aorta
- These prevent blood from flowing back into the ventricles after the heart has pumped
it into the pulmonary trunk or aorta
Systemic vs Pulmonary
- Systemic circuit: left ventricle to organs to right atrium
- Pulmonary circuit: right ventricle toward lungs (gets more oxygen) then to left atrium
Know the difference between blood flow in series and in parallel.
Series
Systemic and pulmonary circuits lie in series: Ensures that all blood flows through the lungs
then flows through the systemic circulation and to all organs.
Parallel
- Systemic circuits lie in parallel with eachother, meaning that each part of the body gets
a fresh blood supply
CARDIOVASCULAR SYSTEM Page 2
, a fresh blood supply
- Arterial blood continually divides as it flows away from the heart.
- All organs receive the oxygenrich blood that left the lungs.
- No organ receives the carbon dioxide-rich blood leaving another organ (except the
liver which has its own blood supply).
- The liver receives 'used' blood from the intestines and the stomach so that it can filter
it and process the sugars, toxins and fatty acids for metabolism
Why can blood only flow one direction?
1. Valves
- Tricuspid valve: stops deoxygenated blood from leaving the right ventricle into the
right atrium meaning it can only leave through the pulmonary valve and artery
- Bicuspid valve: stops oxygenated blood from leaving the left ventricle through the left
atrium, meaning it can only leave via the aortic valve into the aorta
2. Veins
- e.g. in our legs we have valves in our veins which allow blood to go towards the heart
- These valves are aided by muscles contracting and squeezing so blood cannot pass
Define the variables that determine blood flow.
1. Resistance of the vessel
2. The blood pressure/pressure difference across the ends of the valve
Size of Blood Vessel vs Resistance
- The smaller the blood vessel, the higher the resistance
- Total peripheral resistance is the sum of the arterial, capillary and venous resistances
in the systemic system
- Blood flows due to a difference in blood pressure
CARDIOVASCULAR SYSTEM Page 3
, Summary
- In the systemic circuit, oxygen-rich blood is pumped away from the heart in the
arteries, while oxygen-poor blood moves toward the heart in the veins.
- The systemic and pulmonary circuits move blood in series, while individual organs and
Cssues receive blood in parallel.
- Blood flow is influenced by pressure generated by the heart and by the total resistance
of the vessels.
CARDIOVASCULAR SYSTEM Page 4
Friday, 3 July 2015 7:14 p.m.
Understand the basic function of the cardiovascular system.
Blood's Purpose
- The purpose of the blood is to deliver metabolites and oxygen to the cells in our
tissues and organs and to remove their waste products
- All blood flows through the systemic circuit and then the pulmonary circuit
Direction of Flow
- Blood flows from the left side of the heart, around the body then back to the right side
of the heart
- Blood also flows from the right side of the heart, to the lungs and then back to the left
side of the heart
Arteries and Veins
- Arteries go away from the heart, carrying oxygenated blood away to tissues
○ Pulmonary circulation: carries deoxygenated blood
- Veins go toward the heart, carrying deoxygenated blood back to the heart
○ Pulmonary circulation: carries oxygenated blood
The direction blood flows through the circulation is as follows:
Right heart → Lungs (pulmonary circulation) → left heart → body (systemic circulation)
Left Atrium: freshly oxygenated blood arrives here from the lungs, it flows through the
bicuspid/mitral valve reaching the…
Left Ventricle: oxygenated blood flows out of the left ventricle, through the aortic valve and
into the arterial system to supply the body via parallel circuits of blood vessels. It travels
back towards the heart through the venous system and flows into the…
Right Atrium: the receiving chamber for deoxygenated blood arriving from blood vessels
called the superior vena cava and the inferior vena cava and the coronary sinus. Once it is
full, the tricuspid valve opens and blood flows into the…
Right Ventricle: from here the deoxygenated blood is sent off through the pulmonary valve
to the lungs to be oxygenated
Left atrium (receives oxygenated blood from lungs)
Mitral valve (AV valve)
Left ventricle
Aortic valve (semilunar valve)
Body
Veins
Superior vena cava, inferior vena cava and coronary sinus
Right atrium
Tricuspid valve (AV valve)
Right ventricle
Pulmonary valve (semilunar valve)
Lungs
Left atrium…
Valves
CARDIOVASCULAR SYSTEM Page 1
,Valves
Valves are only found in veins, because the pressure generated by the heart in arteries is
high enough to accomplish uni-directional flow in these vessels.
1. Venous valves
- Have cusps that prevent the backflow of blood but allow blood to flow forward when
the pressure inside the veins increases due to muscle contraction
2. Atrioventricular valves3
- Tricuspid and mitral
- Separate the atria from the ventricles
- When blood has filled the ventricles they snap shut, preventing backflow of blood into
the atria
3. Semilunar valves
- Pulmonary and aortic
- Separate the ventricles from the pulmonary trunk and the aorta
- These prevent blood from flowing back into the ventricles after the heart has pumped
it into the pulmonary trunk or aorta
Systemic vs Pulmonary
- Systemic circuit: left ventricle to organs to right atrium
- Pulmonary circuit: right ventricle toward lungs (gets more oxygen) then to left atrium
Know the difference between blood flow in series and in parallel.
Series
Systemic and pulmonary circuits lie in series: Ensures that all blood flows through the lungs
then flows through the systemic circulation and to all organs.
Parallel
- Systemic circuits lie in parallel with eachother, meaning that each part of the body gets
a fresh blood supply
CARDIOVASCULAR SYSTEM Page 2
, a fresh blood supply
- Arterial blood continually divides as it flows away from the heart.
- All organs receive the oxygenrich blood that left the lungs.
- No organ receives the carbon dioxide-rich blood leaving another organ (except the
liver which has its own blood supply).
- The liver receives 'used' blood from the intestines and the stomach so that it can filter
it and process the sugars, toxins and fatty acids for metabolism
Why can blood only flow one direction?
1. Valves
- Tricuspid valve: stops deoxygenated blood from leaving the right ventricle into the
right atrium meaning it can only leave through the pulmonary valve and artery
- Bicuspid valve: stops oxygenated blood from leaving the left ventricle through the left
atrium, meaning it can only leave via the aortic valve into the aorta
2. Veins
- e.g. in our legs we have valves in our veins which allow blood to go towards the heart
- These valves are aided by muscles contracting and squeezing so blood cannot pass
Define the variables that determine blood flow.
1. Resistance of the vessel
2. The blood pressure/pressure difference across the ends of the valve
Size of Blood Vessel vs Resistance
- The smaller the blood vessel, the higher the resistance
- Total peripheral resistance is the sum of the arterial, capillary and venous resistances
in the systemic system
- Blood flows due to a difference in blood pressure
CARDIOVASCULAR SYSTEM Page 3
, Summary
- In the systemic circuit, oxygen-rich blood is pumped away from the heart in the
arteries, while oxygen-poor blood moves toward the heart in the veins.
- The systemic and pulmonary circuits move blood in series, while individual organs and
Cssues receive blood in parallel.
- Blood flow is influenced by pressure generated by the heart and by the total resistance
of the vessels.
CARDIOVASCULAR SYSTEM Page 4
