IGCSE Biology Circulation

Summary:

The circulatory system comprises red blood cells, white blood cells, plasma, and platelets. Red blood cells transport oxygen from the lungs to cells using their biconcave shape and hemoglobin. White blood cells, including phagocytes and lymphocytes, play a role in defending the body against pathogens. Memory cells help establish immunity to diseases after initial infection or vaccination. Plasma carries substances throughout the blood, including carbon dioxide, glucose, amino acids, urea, and hormones. Platelets are involved in blood clotting when a blood vessel is damaged.

Adrenaline is a hormone that increases heart rate and prepares the body for action in response to a threat. Coronary heart disease occurs when fatty deposits block the coronary arteries, reducing the oxygen supply to the heart. Risk factors include smoking, lack of exercise, and a high-fat diet. Treatment may involve using stents to open up the narrowed arteries.

Some babies are born with a hole in the heart, which allows oxygenated and deoxygenated blood to mix, leading to reduced oxygen transportation and potential cell damage.

Excerpt:

IGCSE Biology Circulation

Circulation:
Red blood cells: transport oxygen from the lungs to cells. Adaptations → Biconcave shape (Large SA for absorbing and releasing oxygen.) No nucleus, which means more space. Contain hemoglobin which binds to oxygen to form oxyhaemoglobin.

White blood cells:
– Phagocytes detect foreign things in the body, such as pathogens. These then engulf the pathogens and digest them. They are non-specific – will destroy anything foreign.
– Lymphocytes destroy specific pathogens, by recognising antigens on the surface of a pathogen. They then produce antibodies specific to the pathogen’s antigens, which attach to the pathogen so other white blood cells can detect and destroy them.

There are also memory cells, which remain in the body and remember a specific antigen, meaning they
can produce antibodies faster, and in greater numbers if reinfected by the same pathogen. This is how
you become immune to disease if you already have it.