Y9 Biology: Heart and Blood

Why does the human body have a double circulatory system?

To maintain high blood pressure and completely separate oxygenated and deoxygenated blood for efficiency.

How does deoxygenated blood enter the heart?

It enters the right atrium via the vena cava from the body tissues.

Why does the left ventricle have a much thicker wall than the right ventricle?

To generate enough pressure to pump blood around the entire systemic circulation.

How do heart valves function to maintain unidirectional flow?

They open as blood passes through and snap shut to prevent any backward flow.

Why are the pulmonary artery and vein named unusually?

Arteries always carry blood away from the heart and veins toward it, regardless of oxygen content.

How does the septum contribute to heart efficiency?

It physically divides the left and right sides, stopping oxygenated and deoxygenated blood from mixing.

Why do coronary arteries branch directly off the aorta?

To supply the heart muscle cells with the oxygen and glucose needed for respiration.

How does a heart attack occur?

When coronary arteries become blocked by fatty plaques, starving heart muscle of oxygen.

Why do arteries have thick, elastic walls?

To withstand and smooth out the high-pressure pulses of blood pumped by the heart.

How do capillaries facilitate efficient exchange?

Their walls are only one cell thick, providing a very short diffusion distance.

Why do veins contain valves while arteries do not?

Blood pressure in veins is very low, so valves prevent backflow against gravity.

How are veins structurally adapted to return blood?

They have thin walls with large lumens to reduce resistance and contain pocket valves.

Why is plasma important for transport?

It is a liquid medium that dissolves and carries carbon dioxide, digested food, urea, and hormones.

How are red blood cells adapted to carry oxygen?

They lack a nucleus, contain hemoglobin, and have a biconcave disc shape.

Why do red blood cells have a biconcave disc shape?

To maximize their surface-area-to-volume ratio for rapid oxygen diffusion.

How do white blood cells protect the body?

By engulfing pathogens via phagocytosis or producing specific antibodies and antitoxins.

Why are platelets essential for injury recovery?

They release chemical factors that trigger blood clotting to seal wounds.

How does the process of blood clotting work?

Platelets convert soluble fibrinogen into insoluble fibrin threads to trap cells and form a scab.

Why does heart rate increase during exercise?

To supply working muscles with more oxygen and glucose and remove carbon dioxide faster.

How does the pacemaker control resting heart rate?

By sending regular electrical impulses through the heart muscle to stimulate contraction.

Why might a person need an artificial pacemaker?

If their natural pacemaker fails to maintain a steady or normal heart rhythm.

How does adrenaline prepare the body for action?

It increases heart rate and blood flow to muscles while reducing blood to digestion.

Why is the circulatory system described as closed?

Because blood is entirely contained within a continuous network of blood vessels.

How do substances move out of capillaries into tissues?

Through tissue fluid via diffusion, driven by concentration gradients and hydrostatic pressure.

Why do mammals need a circulatory system instead of simple diffusion?

Because they have a small surface-area-to-volume ratio, making simple diffusion too slow.

How do lymphocytes provide long-term immunity?

By creating memory cells that recognize specific pathogens upon future infection.

Why is oxygen carried as oxyhemoglobin?

It allows large amounts of oxygen to be reversibly bound and transported efficiently.

How does carbon dioxide travel back to the lungs?

Mostly dissolved in plasma as hydrogen carbonate ions or bound loosely to hemoglobin.

Why do active tissues have a denser capillary network?

To ensure a short diffusion distance and adequate supply of nutrients and oxygen.

How do doctors measure a patient's pulse?

By feeling the rhythmic expansion and recoil of an artery as the heart beats.

Why does high blood pressure damage vessels over time?

It places excessive mechanical stress on vessel walls, causing micro-tears and plaque buildup.

How do lifestyle factors affect the circulatory system?

Poor diet and smoking increase cholesterol, damage vessel linings, and raise blood pressure.

Why does the left atrium receive blood from the pulmonary veins?

Because this blood has just been oxygenated in the lungs and returns to the heart.

How does blood flow past atrioventricular valves?

Blood passes from atria into ventricles when atrial contraction pushes the valves open.

Why do multicellular organisms require specialized transport systems?

To overcome long diffusion distances and supply every cell with vital resources.