6 — transport in humans Flashcards
Blood transports
- Digested food substances
- Excretory products (e.g. urea and carbon dioxide)
- Hormones
- Heat
- Oxygen
Measures to prevent Tissue Rejection
- the immune system may recognise a donated organ or blood as foreign tissue and cause tissue rejection.
- Tissue matching avoids tissue rejection -> Donor and recipient should be genetically close
- The use of immunosuppressive drugs that inhibit the immune system to reduce risk of tissue rejection (side effect: lowered resistance to infections
Blood clotting (coagulation)
Platelets involved in converting soluble protein, Fibrinogen (plasma protein) -(enzymes)-> insoluble fibrin threads -> entangles blood cells n forms a clot -> seals wound n prevents excessive loss of blood + entry of bacteria
Plasma appearance + function
- Contains mainly water (90% of plasma volume)
- Yellowish liquid in blood
- consists of 55% of blood
Function
Transports dissolved substances in blood such as
- excretory products to excretory organs for removal (e.g. urea, creatinine, uric acid)
- Nutrients from SI such as glucose, amino acids, fats
- Blood cells around the body
- Hormones from endocrine glands to target organs
Red blood cells adaptations + functions
Adaptations
- Contains haemoglobin that can combine reversibly with oxygen to form oxyhaemoglobin to release O2 to tissue cells
- Has circular biconcave shape to ^SA:V -> ^diffusion of O2 rate into + out of cell
- Absence of nucleus to max space available for haemogoblin
- Flexible and can change into a bell-shaped structure so that they can flow easily through narrow capillaries. Slows down due to tumbling action hence more time for absorption or release of oxygen.
Function
Transport oxygen from the lungs to other parts of the body
White blood cells structure + function
Phagocytes:
- carry out phagocytosis to engulf and ingest foreign particles such as bacteria
Phagocytosis is the process by which a white blood cell engulfs and ingests foreign particles such as bacteria.
Lymphocytes:
produce antibodies that:
- cause pathogens to agglutinate (clump together) for easy engulfing and ingestion by phagocytes
- neutralise toxins produced by bacteria (antitoxin function)
Platelets structure + function
Structure:
Fragments of cytoplasm. They contain an enzyme that catalyses the conversion of fibrinogen to fibrin threads.
Function:
Promotes blood clotting (coagulation) to prevent excessive blood loss n entry of harmful organisms into bloodstream
Explain how the blood clots at a wound. [4]
- Damaged tissues and platelets release an enzyme known as thrombokinase. [1]
- Thrombokinase converts prothrombin in blood plasma to thrombin in the presence of calcium ions. [1]
- Thrombin converts soluble fibrinogen to insoluble fibrin threads. [1]
- which form a mesh to entangle blood cells and form a clot to seal the wound, thus preventing pathogens entering the wound causing infections / disease. [1]
Explain why heart rate increases during exercise. [3]
- Vigorous contraction of muscles require increasing energy demand. [1]
- More blood transported to muscles to supply more oxygen and glucose [1]
- for aerobic respiration to release more energy to meet energy demand [1]
Antigens definition
Identifiable surface features of pathogens that WBCs learn to recognise
Why is blood type O the universal donor
Blood type O is the universal donor: no antigens on the donor’s red blood cells -> antibodies in recipient’s blood plasma will not react with the red blood cells.
Why is blood type AB the universal acceptor
Blood type AB is the universal acceptor -> no blood type antibodies in the blood plasma -> no agglutination of red blood cells in donor’s blood will occur.
Explain why it is impossible for a person of blood type A to receive B type blood during blood transfusion. [3]
- Blood type A has A antigen on the surface of the RBC, thus the blood plasma contain B antibodies [1].
- Blood type B has B antigen on the surface of the RBC, upon transfusion, the B antibodies in plasma will bind with the transfused B antigen RBCs and cause agglutination. [1].
- Agglutination of RBCs will cause blockage in blood vessels resulting in heart attack / stroke / organ failure. [1]
Adaptations of arteries
Walls r thick muscular and elastic to withstand the high blood pressure flowing within and recoil of the elastic layer helps maintain the pressure of the blood as it travels further away from heart.
Function of arterioles and blood capillaries and veins
A: Transports oxygenated blood (except pulmonary arteries) from the heart to other parts of the body
BC: To facilitate exchange of substances between blood and tissue cells in the body.
V: Transport deoxygenated blood (except pulmonary veins) back to the heart.
Adaptations of blood capillaries
Walls partially permeable, one-cell thick endothelium, made up of single layer of flattened cells – minimize diffusion distance for faster rate of diffusion.
Numerous branches of capillaries
- ^surface area for exchange of substances betw blood n tissue cells
- ^total cross-sectional area of the blood vessels, lowering the blood pressure and thereby slowing blood flow to give more time for exchange of substances
Continuous blood flow thru capillaries: maintain steep conc gradient for ^rate of exchange of substances
Adaptations of veins
Blood in vein has lower pressure and speed, thus blood tends to backflow -> have valves to prevent backflow of blood.
In the veins, blood lower in pressure n spd compared to in the arteries -> walls of veins are relatively thinner compared to the walls of the arteries.
Tissue fluid
Colourless liquid present in tiny spaces betw tissue cells that transports dissolved substances betw tissue cells n the blood capillaries.
Transfer of substances betw capillaries n tissue fluids
- Dissolved food substances n O2 diffuse from blood -> blood capillaries -> tissue fluid -> tissue cells .
- Metabolic waste products diffuse from cells into tissue fluid -> blood capillary walls -> blood -> excretory organs for removal.
Advantages of double circulation
During pulmonary circulation, (from heart to lungs to heart) the right ventricle has thinner walls that pumps deoxygenated blood to the lungs at lower pressure, allowing blood to flow thru lungs at lower spd, allowing sufficient time for blood to be fully oxygenated and CO2 to diffuse out before returning to the heart.
In systemic circulation (from heart to rest of the body back to heart), blood is pumped by the left ventricle which has thick walls, at high pressure, ensuring oxygenated blood and nutrients is quickly distributed to all the tissues in the body
Compare and contrast between the structures of artery and vein. [4] (2S2D)
Similarities:
- Muscular and elastic tissue present [1]
- One cell thick endothelium present [1]
Differences:
- Vein has wider lumen than artery [1]
- Vein has semi-lunar valves along the vessel while artery don’t have [1]
- /Vein has thinner muscular and elastic layer compared to artery [1]
Describe how a molecule of oxygen is transported from the alveoli to the heart muscles. [6]
- Molecule of oxygen dissolves in the layer of moisture on the surface of the alveolus and diffuse from alveoli into blood down the concentration gradient. [1]
- Binds with haemoglobin to form oxyhaemoglobin and transported in the blood capillaries. [1]
- Oxygenated blood from the lungs enters the left atrium and left ventricle through the pulmonary veins via passive filling. [1]
- Atrial systole, muscles in left atrium contracts forcing more oxygenated blood into left ventricle. [1]
- Ventricular systole, muscles in left ventricle contracts and pressure in the ventricle becomes higher than in the aorta, forcing open the semi-lunar valve and forces oxygenated blood into the aorta. [1]
- The oxygenated blood flows into coronary artery to supply the heart muscles with oxygen. [1]
