B5 - Blood Donation and Gaseous Exchnage Flashcards
Why are anticoagulants needed? Why do we need vitamin K?
If you cut yourself, your blood should clot to heal the wound. This prevents bacteria from entering and stops blood loss.
Blood kept in a bag would clot in this way. Chemicals are added to block the chemical reactions and prevent clotting (coagulation).
We need vitamin K to help blood clot. Bacteria in our gut make vitamin K, but we can also get it from green vegetables and cranberries.
What is haemophilia?
In haemophilia the blood does not clot or clots very slowly, so sufferers who cut themselves keep on bleeding.
Who may need a transfusion?
• people who have lost a lot of blood through injury or during surgery
• haemophiliacs
• some cancer patients
Why are some blood transfusions unsuccessful?
If the donor and recipient bloods are not matched properly, agglutination or clumping happens. The blood cannot circulate and the recipient dies.
Why might agglutination occur? Why do doctors need to be careful?
Your red blood cells have proteins called agglutinins (a type of antigen) on their membranes. There are different shaped agglutinins. Your blood plasma has antibodies against the agglutinins. You don’t have antibodies in your plasma that can react with the antigens on your own red blood cells.
When transfusing blood, doctors have to think about the antibodies clumping the red cells together. They need to consider how the antibodies of the recipient will react to the donor’s red blood cells.
Which blood groups can donate to and receive from which blood groups?
• People of group O can donate blood to anyone as their red blood cells do not have any antigens, so the recipient’s antibodies have nothing to react with.
• People of group AB can receive any type of blood as they do not have any antibodies in their plasma to react to donors’ antigens.
• People of group A cannot receive group B blood because their anti B antibodies would coagulate it.
• People of group B cannot receive group A blood because their anti A antibodies would coagulate it.
How are people classified according to the Rhesus factor?
Your blood is rhesus positive if your plasma has a D protein, and rhesus negative if it does not. Rhesus- negative people cannot receive rhesus-positive blood as they would make antibodies against the D protein.
What is gaseous exchange?
If an organism respires aerobically, it has to get oxygen to its cells (and then to the mitochondria in its cells). The waste carbon dioxide from aerobic respiration has to be removed from the organism as it is toxic; it would lower the pH and disrupt enzyme activity. The exchange of these two gases, into and out of the organism, is called gaseous exchange.
Describe the gaseous exchange of single called organisms.
Simple one-celled organisms such as aerobic bacteria and amoebae have a large surface area compared with their volume. There is enough cell surface membrane to allow suf cient oxygen to diffuse into the cell. The carbon dioxide produced can all diffuse out.
Describe the gaseous exchange of earthworms. How do they avoid drying out?
They have a large surface area compared to their volume. Oxygen diffuses through their thin, permeable skin and into their blood vessels. The blood carries oxygen from the skin to respiring cells.
It also carries carbon dioxide from respiring cells to the skin.
Earthworms, like all organisms, contain a lot of water. They do not have waterproof skin, as humans do, so they secrete mucus to stop themselves drying out. They also live in damp places.
Describe the gaseous exchange of amphibians. How do they avoid drying out ?
Most of the gaseous exchange in a frog happens across its skin. Frogs also have simple lungs, and can obtain oxygen from the floor of their mouth.
Because their skin is permeable to gases, frogs are susceptible to excessive water loss. To avoid drying out they need to live in damp places. Some survive in drier habitats by having a layer of slime over the skin.
Describe the gaseous exchange of fish.
• The blood flows from the heart to the gills.
• The gills have filaments which give a very large surface area.
• Each filament is well supplied with blood.
• As the fish swims, it gulps water into its mouth.
• Then with the mouth closed, it raises the floor of its mouth and forces the water out over the gills.
• Oxygen dissolved in the water diffuses into the fish’s blood at the gills.
• Carbon dioxide diffuses from the blood in the gills into the water.
• The oxygenated blood then flows to the fish’s body organs.
