transport in humans Flashcards
double circulation
-in pulmonary circulation, deoxygenated blood is transported away from the heart to the lungs, and returns oxygenated blood back to the heart
-in systemic circulation, oxygenated blood is transported away from the heart to the body, and returns deoxygenated blood back to the heart
advantages of a double circulation
-blood enters lungs at lower pressure, thus allowing sufficient time for blood to be well oxygenated
-heart pumps oxygenated blood at high pressure to the rest of the body to be distributed to the tissues quickly
components of blood
-blood is a fluid tissue
-plasma, red blood cells, white blood cells and platelets
blood plasma
-composed mostly water
-helps to transport ‘substances’ around the body, such as nutrients, excretory waste products, hormones, ions and proteins
-helps distribute heat around the body to maintain constant internal environment
-plays a role in blood clotting by transporting blood clotting proteins fibrinogen and prothrombin
red blood cells
-produced by bone marrow
-lack in nucleus and mitochondria, hence cannot perform cell division
-after about 120 days, they are destroyed in the spleen and liver
adaptations of red blood cell
-circular, biconcave shape increases surface area to volume ratio, for greater diffusion rate of oxygen and carbon dioxide
-presence of haemoglobin allows the red blood cell to bind reversibly with oxygen
-no nucleus allows the red blood cell to carry more haemoglobin to bind to more oxygen
-elastic cell surface membrane allows red blood cells to squeeze through very small lumen of blood capillaries
transport of oxygen by red blood cells
-at the lungs, oxygen diffuses from the alveolus into the red blood cells
-at other body organs, haemoglobin releases its oxygen which diffuses into respiring cells
adaptations at high altitudes
-people living at high altitudes have higher number of red blood cells to compensate for lower oxygen concentration
-increase number of red blood cells increases the concentration of haemoglobin in the blood
-thus, oxygen can be transported to the body cells faster
why carbon monoxide is toxic to humans
-haemoglobin combines permanently with carbon monoxide
-less haemoglobin is available to carry oxygen to respiring cells. as a result, death may occur.
sickle-cell anaemia
-red blood cells having mutated haemoglobin that polymerises into long chains when not bound to oxygen, hence distorting the membrane of red blood cells into distinct sickle shape
-results in decreased oxygen-carrying ability of red blood cells, and sickled red blood cells may occlude blood vessels to form blood clot
white blood cells
-larger than red blood cells, and are usually lesser in numbers
-produced by bone marrow
-lymphocytes and phagocytes
lymphocytes
-large, rounded nucleus
-produce antibodies into the blood plasma that recognises antigens
-an immune response should only be raised when antigens are of foreign sources
functions of antibodies
-antibodies neutralise toxins from bacteria, which later will be destroyed by phagocytes
-antibodies bind to antigens on bacteria/ virus, hence enhancing phagocytosis
phagocytes
-bean-shaped/ multi-lobed nucleus
-squeeze between gaps in the wall/ endothelium of blood capillary to any infected areas
-they engulf and ingest bacteria/ virus via phagocytosis
-phagosome is formed with the bacteria/ virus enclosed. then the lysosome inside phagocyte fuses with the phagosome to form phagolysosome. then enzymes in lysosomes hydrolyse the bacteria/ virus
blood platelets
-fragments of cells produced in bone marrow
-initiate blood clotting to prevent entry of bacteria/ virus and prevent excessive loss of blood
process of blood clotting
-damaged tissues and platelets release thrombokinase
-thrombokinase converts prothrombin into thrombin, with calcium ions present
-thrombin converts soluble fibrinogen into insoluble fibrin threads
-fibrin threads trap red blood cells to form a clot
blood groups
blood group A
-antigen A on red blood cell, antibody b in plasma
blood group B
-antigen B on red blood cell, antibody a in plasma
blood group AB
-antigens A and B on red blood cell, no antibodies in plasma
blood group O
-no antigens A or B on red blood cell, antibodies a and b in plasma
agglutination
-the clumping of red blood cells with antibodies. hence, blood vessels become blocked.
-antigen A and antibody a will agglutinate
-antigen B and antibody b will agglutinate
blood vessels
-artery—> arteriole—> capillary—> venule—> vein
-the heart is a muscular organ that contracts to pump blood
-capillaries are the sites of exchange of ‘substances’ within organs
arteries
-thicker muscular walls/ smaller lumen to withstand the high blood pressure. muscles contract—> artery vasoconstricts—> lumen narrower—> less blood flows through. muscles relax—> artery vasodilates—> lumen wider—> more blood flows through.
-elastic fibres walls to allow stretching and recoiling of artery wall. hence, maintain high blood pressure and push blood along the artery in pulses.
veins
-lesser muscular and less elastic wall than artery/ larger lumen for blood to flow slowly and smoothly
-presence of semi-lunar valves to prevent backflow of blood
-surrounded by skeletal muscles for muscle contractions on the veins to move the blood forward
capillaries
-one-cell thick endothelium to allow movement of substances across quickly and to provide large surface area to volume ratio for exchange of substances between blood and tissue cells quickly
-branched into dense network to increase the total cross-sectional area for blood flow to be very slow, hence more time for the exchange of substances
comparison 1 - nature of walls
artery - thicker muscular and a lot elastic fibres
capillary - one-cell thick endothelium
vein - less muscular and less elastic fibres
comparison 2 - size of lumen
artery - small lumen
capillary - very small lumen
vein - large lumen
