Transport in Humans: Answers
Name the different components of blood and their functions.
Blood is made up of four different components:
Red blood cells which transports oxygen around the body for aerobic respiration
White blood cells which detect and destroy pathogens
Platelets which form blood clots - this prevents excessive blood loss from a wound and stops microorganisms from entering the body through the wound
Plasma which contains dissolved carbon dioxide, heat energy, hormones and digested food molecules.
How is a red blood cell adapted for transporting oxygen?
Red blood cells are adapted for efficient transport of oxygen in a number of ways. They are one of the few cells in the human body which does not have a nucleus, providing more space for the cell to carry oxygen. It has a biconcave shape and this curved, dimpled shape gives it a larger surface area so there is more space for the diffusion of oxygen. The haemoglobin within red blood cells binds strongly to oxygen, facilitating oxygen transport. Red blood cells are also small and flexible which allows then to squeeze through small blood vessels (capillaries) easily.
Describe the two ways in which white blood cells destroy pathogens.
A special type of white blood cell called phagocyte can engulf and destroy pathogens in a process called phagocytosis. Once the pathogen is engulfed and encased inside the cell, the pathogen is digested using digestive enzymes such as amylase and proteases. Once the pathogen is digested (and destroyed) the material is removed from the cell. The other way that white blood cells protect us against pathogens is through the production of antibodies. Another type of white blood cell, called plasma cells, produce antibodies which are complementary to molecules called antigens which are expressed on the surface of a pathogen. When an antibody binds to a pathogen, it renders it harmless and acts as a ‘signal’ for phagocytes to destroy it.
How does vaccination protect a person against an infectious disease?
Vaccination involves injecting a dead of weakened form of a pathogen into a person. The dead pathogen is unable to cause disease but our body still produces antibodies and memory cells in response to it. Memory cells are a special type of white blood cell which will produce the right type of antibodies against that specific pathogen if it re-enters our bodies (it ‘remembers’ the pathogen). If re-infection occurs, antibodies are produced much quicker than they would be if encountering the pathogen for the first time, protecting the person from the disease.
Describe the differences between the structure of an artery and a vein.
Arteries have a thick wall of muscle and elastic fibres and a small lumen whereas veins have a thin muscular wall, fewer elastic fibres and a large lumen. This is because arteries carry blood at higher pressure and need a thick wall to withstand the increased pressure. Another difference is that veins have valves which prevent the slow-flowing blood from travelling in the wrong direction.
Why is the heart wall so much thicker on the left side compared to the right?
The blood is pumped from the left hand side of the heart, through the aorta to the rest of the body, whereas the blood from the right hand side is pumped to just the lung through the pulmonary artery. Since the left hand side needs to pump blood to lots more organs, it needs to have a thicker muscular wall to generate a larger contraction.
What is coronary heart disease?
Coronary heart disease occurs when a blood vessel supplying the heart is blocked. The heart muscle can’t receive sufficient amounts of oxygen for aerobic respiration and stops contracting, preventing blood flow to the rest of the body. This condition can be fatal and is influenced by several factors including diet, smoking and high blood pressure.