Transport in Humans Flashcards
Description of plasma
- Liquid part of blood
- Mainly water
Function of plasma
- Carries blood cells around the body
- Carries dissolved nutrients, hormones, carbon dioxide and urea
- Distributes heat around the body
Description of erythrocytes
Biconcave, disc-like cell with no nucleus; Millions in each mm cubed of blood
Function of erythrocytes
Transport oxygen - contain mainly haemoglobin
Description of lymphocytes
About the same size as red cells with a large spherical nucleus
Function of lymphocytes
- Produced antibodies to destroy microorganisms
- Some persist in our blood after infection and give us immmunity
Description of phagocytes
Much larger than red cells with a spherical or lobed nucleus
Function of phagocytes
Digest and destroy microorganisms that have infected our bodies
Description of platelets
The smallest cells -really fragments of other cells
Function of platelets
Release chemicals to make blood clot when we cut ourselves
Describe an immune response
- A pathogen enters the body
- Antigens on the microbe’s surface alert the white blood cells
- Lymphocytes release Y-shaped antibodies against the microbe
- Antibodies stick to the antigens and either stick microbes together so that phagocytes can ingest them more easily; mark microbes for attack by phagocytes; cause microbes to burst open or neutralise poisons (toxins) produced by the pathogen
- Phagocytes surround and engulf the microbe
- Phagocytes use digestive enzymes to destroy the microbes
- Memory cells remain in the blood after the attack, ready to produce a fast response if the same microbe infects the body again
- Once memory cells have been made, we are said to be immune to this disease
How does a vaccine work?
It injects an inactive pathogen to activate an immune response and produce memory cells
How does exposure to air stimulate platelets to clot the blood?
Platelets produce a chemical which causes the soluble plasma protein fibrinogen to change into insoluble fibres of fibrin. The fibrin forms a network across a wound, in which red blood cells get trapped forming a clot and preventing further blood loss and the entry of microorganisms
Describe a heart beat
- Blood enters the atria though cannot pass into the ventricles because the atrio-ventricular valves are closed
- The walls of the atria constrict, easing the blood pressure which forces the atrio-ventricular valves open and blood passes into the ventricles
- When the ventricles are full, they contract, increasing the blood pressure and closing the atrio-ventricular valves, preventing blood from returning to the atria
- The ventricles continue to contract and the blood pressure increases, forcing open the semi-lunar valves and ejecting blood into the pulmonary artery and the aorta
- As the ventricles empty, higher pressure in the arteries closes the semi-lunar valves and the cycle begins again
What does adrenaline do?
Increase heart rate