What is your blood made of? Where is it formed?

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.

Transcript

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)