Blood Vessels & Blood (AQA GCSE Biology): Revision Note

Blood vessels

• The body contains three different types of blood vessels:

  • arteries: transport blood away from the heart

  • veins: transport blood to the heart

  • capillaries: links arteries to veins and are the site of substance exchange with the body cells

Rate calculations: Blood flow

• The rate of blood flow can be calculated if the volume of blood flow and the time is known

Structure & function: Blood

• The role of blood is to transport useful substances to every cell of the body, and to remove harmful waste substances

  • It also plays a role in temperature regulation

• Blood is a tissue that contains:

  • plasma

  • red blood cells

  • white blood cells

  • platelets

Components of the blood

Plasma

• Plasma is the straw-coloured liquid part of the blood in which the cells are suspended

• It transports dissolved substances, including carbon dioxide (from respiring cells to the lungs), glucose and amino acids (from the small intestine to cells), urea (from the liver to the kidneys), hormones, antibodies and ions

• It also carries the blood cells and transfers heat around the body

• Always name the substance: 'nutrients' and 'waste' do not get the mark

Red blood cells

• Red blood cells carry oxygen around the body

• They have several features that aid their function:

  • a biconcave disc shape

    • The biconcave shape gives red blood cells a large surface to volume ratio; this is a key adaptation to maximise the efficiency of diffusion of gases into and out of the cell

  • haemoglobin

    • This is a protein that binds to oxygen, allowing it to be transported around the body

  • no nucleus

    • This maximises the space available for haemoglobin

White blood cells

• White blood cells are part of the immune system, responsible for defending the body from infection by recognising and destroying pathogens

• white blood cells defend the body by:

  • phagocytosis

  • antibody production

  • producing antitoxins, which neutralise toxins released by pathogens

Platelets

• Platelets are fragments of cells (they contain cytoplasm but no nucleus)

• When damage to a blood vessel occurs, the platelets are involved in forming a blood clot to prevent blood loss

Use this image

Recognising blood cells

• An exam question may include a photograph or diagram and ask the identity of the types of blood cell present

• Observing and drawing cells under the microscope is an important skill to develop

• To identify the cells: white blood cells are larger than red blood cells and are the only blood cells with a nucleus (often lobed); red blood cells are biconcave discs with no nucleus; platelets are much smaller cell fragments with no nucleus

Use this image