In adults, blood is formed in short, flat bones like the ribs and sternum. This week's viewer question comes from Monica
Bustos in Colombia.
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00:00 What is our blood made of? And where is it formed?
00:06 Every adult has between 5 and 6 litres of blood.
00:10 Because it enables all of the other important bodily functions,
00:14 blood is sometimes called a liquid organ.
00:17 Almost half of it, though, is made up of solid components.
00:21 Red blood cells give it the characteristic colour.
00:24 They supply the body with oxygen
00:26 and transport gaseous carbon dioxide waste to the lungs to be exhaled.
00:31 The platelets, on the other hand,
00:34 play an important role in clotting and healing wounds.
00:38 And the white blood cells are able to recognise and ward off pathogens.
00:44 The cells and platelets are suspended in what's called blood plasma.
00:49 This clear yellowish fluid is made up of water,
00:52 nutrients, hormones, minerals and proteins.
00:57 Through a branching circulatory system that is almost 100,000 kilometres long,
01:03 the blood is distributed to the farthest reaches of the body.
01:07 Besides oxygen and CO2,
01:10 blood carries and distributes hormones, nutrients and also heat.
01:14 Its cells form in the so-called red bone marrow,
01:17 a net-like tissue that itself has a plentiful blood supply.
01:21 In adults, blood is mostly produced in short, flat bones like the ribs and sternum.
01:27 In children, formation occurs in bones all over the body.
01:33 The red bone marrow is home to special stem cells
01:36 that are able to produce all the different types of blood cells.
01:40 Many blood cells live only a few days.
01:49 They have to be replenished constantly.
01:52 And by the way, before birth, blood is produced mainly in the liver and spleen.
01:59 And these organs can resume the task even in adults,
02:03 if for some reason the red bone marrow is damaged.
02:07 (water splashing)
02:09 (water bubbling)