1. Lifestyle, health and risk
1.a The Circulatory System
Mass transport
Definition
● The bulk movement of gases or liquids through a system of vessels
Features
● Transport medium
● Network of vessels
● Controlled direction (valves)
● Maintenance of speed
Benefits
● Transportation of substances
● Maintains concentration gradient
● Ensures cell activity
Water
● Water is a polar molecule, due to an uneven distribution of charge within the
molecule - the hydrogen atoms are positive and the oxygen charges are negative,
causing one end of the molecule to be more positive than the other
● Due to its polarity, water acts as a solvent so can be used to transport many
biological molecules
● Hydrogen bonding between water molecules creates cohesion and adhesion - this
creates effective transport of water and dissolved substances through xylem vessels
● Hydrogen bonding is strong, causing water to have a high specific heat capacity
meaning that a lot of energy is required to break these bonds giving water a stable
temperature
Blood vessels
1. Arteries
● Most carry oxygenated blood to body tissues and deoxygenated blood to
lungs
● Narrow lumen to maintain high blood
pressure
● Smooth inner endothelial lining
● Thick layer of smooth muscle to dilate and
constrict vessels
● Elastin fibres to stretch and recoil vessel
● Collagen fibres to support vessel
, 1. Lifestyle, health and risk
2. Veins
● Most carry deoxygenated blood to lungs and oxygenated blood to heart
● Large lumen to reduce resistance of blood
flow
● Thinner layer of smooth muscle and elastin
fibres
● Less collagen fibres
● Valves to control direction of blood flow
3. Capillaries
● Smallest blood vessel
● Branch between cells and tissues
● Narrow lumen
● Thin endothelial wall (one cell
thick) to maintain short diffusion
distance
● No smooth muscle, collagen fibres or elastin fibres
Structure of the heart
The cardiac cycle
1. Atrial systole
● Ventricles are relaxed
● The atria contract, decreasing volume of chambers and increasing pressure
● This pushes blood into ventricles
● Causes slight increase in ventricular pressure and chamber volume
1.a The Circulatory System
Mass transport
Definition
● The bulk movement of gases or liquids through a system of vessels
Features
● Transport medium
● Network of vessels
● Controlled direction (valves)
● Maintenance of speed
Benefits
● Transportation of substances
● Maintains concentration gradient
● Ensures cell activity
Water
● Water is a polar molecule, due to an uneven distribution of charge within the
molecule - the hydrogen atoms are positive and the oxygen charges are negative,
causing one end of the molecule to be more positive than the other
● Due to its polarity, water acts as a solvent so can be used to transport many
biological molecules
● Hydrogen bonding between water molecules creates cohesion and adhesion - this
creates effective transport of water and dissolved substances through xylem vessels
● Hydrogen bonding is strong, causing water to have a high specific heat capacity
meaning that a lot of energy is required to break these bonds giving water a stable
temperature
Blood vessels
1. Arteries
● Most carry oxygenated blood to body tissues and deoxygenated blood to
lungs
● Narrow lumen to maintain high blood
pressure
● Smooth inner endothelial lining
● Thick layer of smooth muscle to dilate and
constrict vessels
● Elastin fibres to stretch and recoil vessel
● Collagen fibres to support vessel
, 1. Lifestyle, health and risk
2. Veins
● Most carry deoxygenated blood to lungs and oxygenated blood to heart
● Large lumen to reduce resistance of blood
flow
● Thinner layer of smooth muscle and elastin
fibres
● Less collagen fibres
● Valves to control direction of blood flow
3. Capillaries
● Smallest blood vessel
● Branch between cells and tissues
● Narrow lumen
● Thin endothelial wall (one cell
thick) to maintain short diffusion
distance
● No smooth muscle, collagen fibres or elastin fibres
Structure of the heart
The cardiac cycle
1. Atrial systole
● Ventricles are relaxed
● The atria contract, decreasing volume of chambers and increasing pressure
● This pushes blood into ventricles
● Causes slight increase in ventricular pressure and chamber volume
