CIRCULATORY SYSTEM
,Lesson 1 – Circulatory System
Function of Circulatory System
Transport system
- In relation to respiratory system, it transports O2 + CO2
- In relation to excretory system, it transports waste products
- In relation to digestive system, it transports nutrients + metabolites
- In relation to endocrine system, it transports hormones
- In relation to immune system, it transports defence mechanisms (white blood cells)
- Transports heat in form of energy (vasodilate + vasoconstrict)
3 components of circulatory system
Blood
- Primary transport medium
- About 5 L
- Red blood cells (erythrocytes) + White blood cells (leukocytes) + Platelets + Plasma = Blood
RBCs = have haemoglobin which carries Oxygen
WBCs = immune response, fight against infection
Platelets = blood clotting
Plasma = fluid portion to help transport ions, nutrients etc.
Blood vessels
- Help connect different systems
- Arteries – carry blood to tissues
- Capillary bed – main sight of gaseous exchange
- Veins – carry blood towards heart
Heart
- Muscular pump to propel blood through blood vessels
Open Circulatory System Closed Circulatory System
- Common in insects - Humans
- Has a pump with blood vessels that aren’t - Blood stays in the blood vessels
closed therefore the haemolymph (blood - Pressure helps nutrients, oxygen to bathe
equivalent) bathes the cells/tissues and then cells via interstitial fluid
gets sucked back into the pump by negative
pressure so that cycle can continue again.
, In closed circulatory system:
1. Single loop circulatory system/Single Circulation
- One ventricle/one atrium
2. Double loop circulatory system/Double Circulation
- Blood is returned to the heart before going to the other tissues
- Advantage: Allows for extra pumping of blood, ensuring blood is pumped at high speed to tissues
with high metabolic rates and so the blood is pumped at high pressure
- In Amphibians and reptiles, ventricle is not separated so there is mixing of blood which accounts for
the different way in which they breathe
Blood flow in human circulatory system
1. Pulmonary circuit
Deoxygenated blood that returned to the heart is pumped to the lungs via the pulmonary artery (only
artery that carries deoxygenated blood). This pulmonary artery transports the blood to the lungs where
it picks up the oxygen and then oxygenated blood is transported back to the heart via the pulmonary
vein (only vein that carries oxygenated blood).
2. Systemic circuit
Allows blood to flow to head, arms, digestive system, lower limbs. Oxygenated blood exits the heart
via the major artery, aorta. Aorta splits into multiple arteries and further arterioles and then into arteries
where gaseous exchange in the tissues occurs. These capillaries then join to form venules with
deoxygenated blood and then into veins to return deoxygenated blood back to heart.
,Lesson 1 – Circulatory System
Function of Circulatory System
Transport system
- In relation to respiratory system, it transports O2 + CO2
- In relation to excretory system, it transports waste products
- In relation to digestive system, it transports nutrients + metabolites
- In relation to endocrine system, it transports hormones
- In relation to immune system, it transports defence mechanisms (white blood cells)
- Transports heat in form of energy (vasodilate + vasoconstrict)
3 components of circulatory system
Blood
- Primary transport medium
- About 5 L
- Red blood cells (erythrocytes) + White blood cells (leukocytes) + Platelets + Plasma = Blood
RBCs = have haemoglobin which carries Oxygen
WBCs = immune response, fight against infection
Platelets = blood clotting
Plasma = fluid portion to help transport ions, nutrients etc.
Blood vessels
- Help connect different systems
- Arteries – carry blood to tissues
- Capillary bed – main sight of gaseous exchange
- Veins – carry blood towards heart
Heart
- Muscular pump to propel blood through blood vessels
Open Circulatory System Closed Circulatory System
- Common in insects - Humans
- Has a pump with blood vessels that aren’t - Blood stays in the blood vessels
closed therefore the haemolymph (blood - Pressure helps nutrients, oxygen to bathe
equivalent) bathes the cells/tissues and then cells via interstitial fluid
gets sucked back into the pump by negative
pressure so that cycle can continue again.
, In closed circulatory system:
1. Single loop circulatory system/Single Circulation
- One ventricle/one atrium
2. Double loop circulatory system/Double Circulation
- Blood is returned to the heart before going to the other tissues
- Advantage: Allows for extra pumping of blood, ensuring blood is pumped at high speed to tissues
with high metabolic rates and so the blood is pumped at high pressure
- In Amphibians and reptiles, ventricle is not separated so there is mixing of blood which accounts for
the different way in which they breathe
Blood flow in human circulatory system
1. Pulmonary circuit
Deoxygenated blood that returned to the heart is pumped to the lungs via the pulmonary artery (only
artery that carries deoxygenated blood). This pulmonary artery transports the blood to the lungs where
it picks up the oxygen and then oxygenated blood is transported back to the heart via the pulmonary
vein (only vein that carries oxygenated blood).
2. Systemic circuit
Allows blood to flow to head, arms, digestive system, lower limbs. Oxygenated blood exits the heart
via the major artery, aorta. Aorta splits into multiple arteries and further arterioles and then into arteries
where gaseous exchange in the tissues occurs. These capillaries then join to form venules with
deoxygenated blood and then into veins to return deoxygenated blood back to heart.
