3.6 - Transport in humans (2) — heart and blood
circulation
Heart
● Made up of network of blood vessels
● Arteries (動脈)
○ Carry blood away from heart to various organs under high pressure &
velocity
○ Branch off as arterioles (小動脈)
● Capillaries (毛細血管)
○ Allow substances to enter and leave blood through diffusion (between
blood and fluid-surrounding cells)
○ Very small vessels linking arterioles and venules
○ ***Branch off many times, lie in tissues of body among cells
○ ***Very small diameter, thin walls
● Veins (靜脈)
○ Bring blood from organs back to heart under low pressure & velocity
○ Branch off as venules (小靜脈)
○ Contain regular pocket valves (瓣膜), ensuring that blood does not go
backwards
Structure of the heart
● ***Heart is made up of four chambers (室) - left and right atrium (心房) [upper],
left and right ventricle (心室) [lower]
● Heart is double pump: left side sends blood to lungs (pulmonary circuit), right side
sends blood to rest of body (systemic circuit)
● Double pump ensures blood is forced quickly through all parts of circulatory
system
1
, ● Vena cava fills relaxed right atrium, pulmonary vein fills relaxed left atrium
● Heartbeat cycle of contraction when both atria contract, right atrium forces blood
through tricuspid valve into right ventricle, left atrium forces blood through
bicuspid (mitral) valve into left ventricle
● Ventricles contract, right ventricle forces blood out of heart through pulmonary
valve into pulmonary artery, pulmonary artery carries deoxygenated blood to
lungs; left ventricle forces blood out of heart through aortic valve into aorta, aorta
carries oxygenated blood to rest of body
● Tricuspid and bicuspid valves prevent blood going backwards from ventricles to
atria; semilunar valves lie near entrances of pulmonary artery and aorta, prevent
blood going backwards from arteries to ventricles
Summary*** (→ force in one direction, ⇒ fill,
⭆ carry, ⇏ prevent direction to)
1.
● Vena cava (腔靜脈) ⇒ right atrium (右心房)
● Pulmonary vein (肺靜脈) ⇒ left atrium (左心房)
2.
● Right atrium (右心房) → (tricuspid valve [三尖瓣]) → right ventricle (右心室)
● Left atrium (左心房) → (bicuspid/mitral valve [二尖瓣]) → left ventricle (左心室)
3.
● Right ventricle (右心室) → (pulmonary valve [肺動脈瓣]) → pulmonary artery (肺動
脈) ⭆ (deoxygenated blood) ⭆ lungs
● Left ventricle (左心室) → (aortic valve [主動脈瓣]) → aorta (主動脈) ⭆ (oxygenated
blood) ⭆ rest of body
4.
2
circulation
Heart
● Made up of network of blood vessels
● Arteries (動脈)
○ Carry blood away from heart to various organs under high pressure &
velocity
○ Branch off as arterioles (小動脈)
● Capillaries (毛細血管)
○ Allow substances to enter and leave blood through diffusion (between
blood and fluid-surrounding cells)
○ Very small vessels linking arterioles and venules
○ ***Branch off many times, lie in tissues of body among cells
○ ***Very small diameter, thin walls
● Veins (靜脈)
○ Bring blood from organs back to heart under low pressure & velocity
○ Branch off as venules (小靜脈)
○ Contain regular pocket valves (瓣膜), ensuring that blood does not go
backwards
Structure of the heart
● ***Heart is made up of four chambers (室) - left and right atrium (心房) [upper],
left and right ventricle (心室) [lower]
● Heart is double pump: left side sends blood to lungs (pulmonary circuit), right side
sends blood to rest of body (systemic circuit)
● Double pump ensures blood is forced quickly through all parts of circulatory
system
1
, ● Vena cava fills relaxed right atrium, pulmonary vein fills relaxed left atrium
● Heartbeat cycle of contraction when both atria contract, right atrium forces blood
through tricuspid valve into right ventricle, left atrium forces blood through
bicuspid (mitral) valve into left ventricle
● Ventricles contract, right ventricle forces blood out of heart through pulmonary
valve into pulmonary artery, pulmonary artery carries deoxygenated blood to
lungs; left ventricle forces blood out of heart through aortic valve into aorta, aorta
carries oxygenated blood to rest of body
● Tricuspid and bicuspid valves prevent blood going backwards from ventricles to
atria; semilunar valves lie near entrances of pulmonary artery and aorta, prevent
blood going backwards from arteries to ventricles
Summary*** (→ force in one direction, ⇒ fill,
⭆ carry, ⇏ prevent direction to)
1.
● Vena cava (腔靜脈) ⇒ right atrium (右心房)
● Pulmonary vein (肺靜脈) ⇒ left atrium (左心房)
2.
● Right atrium (右心房) → (tricuspid valve [三尖瓣]) → right ventricle (右心室)
● Left atrium (左心房) → (bicuspid/mitral valve [二尖瓣]) → left ventricle (左心室)
3.
● Right ventricle (右心室) → (pulmonary valve [肺動脈瓣]) → pulmonary artery (肺動
脈) ⭆ (deoxygenated blood) ⭆ lungs
● Left ventricle (左心室) → (aortic valve [主動脈瓣]) → aorta (主動脈) ⭆ (oxygenated
blood) ⭆ rest of body
4.
2
