8WB00 Heart and Blood
Jaar 2, kwartiel 4
College 1+2: Cardiovascular System and Hemodynamics (p.410-
418+423-426)
An organ system: a collection of organs that forms one functional unit. (Why are multiple organs
needed in the cardiovascular system?)
Circulation: an evolutionary consequence of body size and complexity, aids transport in large
organisms. (Why/when are 2 pumps needed? -> the system is far more efficient, using one circuit for
exchainge of gases with the external
milieu and another circuit for exchange
of nutrients and nongaseous wastes. )
Functions of the cardiovascular system
- Primary function: distribution/transport of dissolved gases and other molecules for nutrition,
growth, and repair
- Secondary functions:
o Fast chemical signaling to cells: hormones, neurotransmitters
o Dissipation of heat: delivery of heat from core to body surface
o Mediation of inflammatory and host defense responses against invading
microorganisms
The heart consist of two pumps, the left heart, or main pump, and the right heart, or boost pump.
These operate in series and require a delicate equalization of their outputs. The circulating fluid is an
organ itself, kept in a liquid state by mechanisms that actively prevent cell-cell adhesion and
coagulation. With each heartbeat, the ventricles impart the energy necessary to circulate the blood
by generating the pressure head that drives the flow of blood through the vascular system.
Systemic circulation: big circulation, pulmonary circulation: lungs.
High-pressure part: extending from the contracting left ventricle to the systemic capillaries
Low-pressure part: extending from the systemic capillaries, through the right heart, across the
pulmonary circulation and left atrium, and into the left ventricle in its relaxed state.
1
,Transport in the cardiovascular system
Component of the cardiovascular system
- 3 basic functional parts:
o A pump: heart
o A liquid: blood
o A pipe/container: vessels
- How does the cardiovascular system work to
transport blood through the vessels? Hemodynamics
2
, Hemodynamics
To understand the steady flow of blood,
driven by a constant pressure head, we can
apply slissical hydrodynamic laws:
ΔP=F * R
- ΔP: pressure difference
o Fairly constant over time
o Heart behaves more like a
generator of a constant pressure head than of a constant flow
- F: Flow (volume/time)
o Proportional to pressure difference
o Variable in time; depends greatly on physiological circumstances
- R: Resistance
o Opposes blood flow
o Variable in time
o Varies with location within the body
o Overall resistance Rtot across a circulatory bed results from parallel and serial
arrangements of branches.
Series: Rtot = R1 + R2 + R3
Parallel: 1/Rtot = 1/R1 + 1/R2 + 1/R3
How to measure blood pressure?
- Physiologically, by the height it can drive a column of liquid
P=ρ*g*h
o ρ: density of liquid in the column (usually mercury)
o g: gravitational constant (9,81 m/s²)
o h: height of the column
1 mmHG = 133.32 Pa
Hydrostatic pressure
- pressure exerted on the walls of the container by the fluid within the container
- proportional to the height of the water column
Blood flows down a pressure gradient
The mean blood pressure of the systematic circulation ranges from 93 mmHG in the aorta to a few
mmHg in the vanae cavae.
Fluid flow through a tube depends on the pressure gradient
- Flow depends on the pressure gradient (ΔP), not on
the absolute pressure (P)
- ΔP is equal in these tubes so the flow is the same
3
Jaar 2, kwartiel 4
College 1+2: Cardiovascular System and Hemodynamics (p.410-
418+423-426)
An organ system: a collection of organs that forms one functional unit. (Why are multiple organs
needed in the cardiovascular system?)
Circulation: an evolutionary consequence of body size and complexity, aids transport in large
organisms. (Why/when are 2 pumps needed? -> the system is far more efficient, using one circuit for
exchainge of gases with the external
milieu and another circuit for exchange
of nutrients and nongaseous wastes. )
Functions of the cardiovascular system
- Primary function: distribution/transport of dissolved gases and other molecules for nutrition,
growth, and repair
- Secondary functions:
o Fast chemical signaling to cells: hormones, neurotransmitters
o Dissipation of heat: delivery of heat from core to body surface
o Mediation of inflammatory and host defense responses against invading
microorganisms
The heart consist of two pumps, the left heart, or main pump, and the right heart, or boost pump.
These operate in series and require a delicate equalization of their outputs. The circulating fluid is an
organ itself, kept in a liquid state by mechanisms that actively prevent cell-cell adhesion and
coagulation. With each heartbeat, the ventricles impart the energy necessary to circulate the blood
by generating the pressure head that drives the flow of blood through the vascular system.
Systemic circulation: big circulation, pulmonary circulation: lungs.
High-pressure part: extending from the contracting left ventricle to the systemic capillaries
Low-pressure part: extending from the systemic capillaries, through the right heart, across the
pulmonary circulation and left atrium, and into the left ventricle in its relaxed state.
1
,Transport in the cardiovascular system
Component of the cardiovascular system
- 3 basic functional parts:
o A pump: heart
o A liquid: blood
o A pipe/container: vessels
- How does the cardiovascular system work to
transport blood through the vessels? Hemodynamics
2
, Hemodynamics
To understand the steady flow of blood,
driven by a constant pressure head, we can
apply slissical hydrodynamic laws:
ΔP=F * R
- ΔP: pressure difference
o Fairly constant over time
o Heart behaves more like a
generator of a constant pressure head than of a constant flow
- F: Flow (volume/time)
o Proportional to pressure difference
o Variable in time; depends greatly on physiological circumstances
- R: Resistance
o Opposes blood flow
o Variable in time
o Varies with location within the body
o Overall resistance Rtot across a circulatory bed results from parallel and serial
arrangements of branches.
Series: Rtot = R1 + R2 + R3
Parallel: 1/Rtot = 1/R1 + 1/R2 + 1/R3
How to measure blood pressure?
- Physiologically, by the height it can drive a column of liquid
P=ρ*g*h
o ρ: density of liquid in the column (usually mercury)
o g: gravitational constant (9,81 m/s²)
o h: height of the column
1 mmHG = 133.32 Pa
Hydrostatic pressure
- pressure exerted on the walls of the container by the fluid within the container
- proportional to the height of the water column
Blood flows down a pressure gradient
The mean blood pressure of the systematic circulation ranges from 93 mmHG in the aorta to a few
mmHg in the vanae cavae.
Fluid flow through a tube depends on the pressure gradient
- Flow depends on the pressure gradient (ΔP), not on
the absolute pressure (P)
- ΔP is equal in these tubes so the flow is the same
3
