If blood is red, why are veins blue?

Question

When and how does it change color?

Answer 1

Our Blood is red because our blood cells are red but because our veins are blue is because our viens carry out oxygen and our oxygen mixed with our blood turns to a blueish shade.

Answer 2

thats a simple question.

Blood is a bright red in its oxygenated form (i.e., leaving the lungs), when hemoglobin is bound to oxygen to form oxyhemoglobin. It's a dark red in its deoxygenated form (i.e., returning to the lungs), when hemoglobin is

bound to carbon dioxide to form carboxyhemoglobin.

Veins appear blue because light, penetrating the skin, is absorbed and reflected back to the eye. Since only the higher energy wavelengths can do this (lower energy wavelengths just don't have the *oomph*), only higher energy wavelengths are seen. And higher energy wavelengths are what we call "blue."

In an experiment, glass tubes were filled with blood and immersed in milk, milk having a similar ratio of fat, proteins, and water in emulsion as skin. At a certain depth, the tubes appeared blue.

As a phlebotomist (a person who draws blood) at the local university hospital, I drew hundreds of samples of venous blood. Almost all samples were dark red. Those that weren't were usually because people were on enriched oxygen systems.

At the same time, respiratory therapists drew blood from an artery, not a vein. These samples were characteristically bright red, unless the patient was having difficulty breathing (asthma, people with one lung, pneumonia, emphysema, whatever).

So, your veins may look blue, but even a blueblood will bleed red.

also just so you know

NO. blood is NOT blue.

people seem to think that..

'well blood is inside and its deoxygenated and when it hits oxygen (through wound exposure) it turns red'

that is most definately not true.

blood is red because of hemoglobin.

and there is hemoglobin in blood BEFORE its exposed through a cut.

the only reason veins are blue is because the light is being diffused by the skin.

Answer 3

Blood that has oxygen in it is red, but the blood in veins has given its oxygen to your bodies cells and is on its way back to the heart and lungs to take in more oxygen.

Answer 4

Because blood is blue before it's exposed to oxygen! :D

Answer 5

well when blood is inside your body its blue,but as soon as it hits oxygen it turns red.

thats why when you get a cut its red.

Answer 6

blood changes color when exposed to oxygen

Answer 7

because skin is brown so veins are blue.

Answer 8

Right. This question gets asked all the time, and every single time people answer that it is only red on meeting the air. This is WRONG!!

Blood is ALWAYS red!

In the arteries it is oxygenated, and is a bright red. In the veins it is deoxygenated, and is a darker red - but it is STILL red.

Our veins appear blue because of pigments in the vein wall, and in the fat layer between the vein and the skin. The blood inside the veins is red.

If you have ever had a blood sample taken with one of those evacuated tubes that just "suck" the blood out without needing a syringe, you'll notice the blood entering the tube (which does not contain any oxygen) is red. It hasn't suddenly changed colour on meeting the air because there is no air in the tube.

Answer 9

Its blood that has little or no O2.

Answer 10

The blood that pass through our venes is without oxigen...

Answer 11

donno

Answer 12

Blood is blue till it hits the air and combines with oxygen.  Then it turns red.

Answer 13

Ive heard that immediatley when oxygen is exposed to the blood thats what makes it red.

Answer 14

their is no oxgen in the blood, so this changes the color from red to blue.

Answer 15

Blood is blue when it hasn't reacted with oxygen to make Oxyhaemoglobin. Haemoglobin in a pigment in the red blood cells that resacts with oxygen so that it can be carried around the body. haemoglobin in blue but when reacted with oxygen to form oxyhaemoglobin, turns red. Thats why you have blue and red veins, - blue is blood with no oxygen in, red is blood carrying oxygen.

Answer 16

When blood is oxygenated in the lungs, it is red. This red, oxygenated blood is pumped by the heart through arteries to different parts of the body. You can't see these arteries, because they are deeper inside the body.

When blood gives up oxygen to the different parts of the body, it becomes blue. The veins take blood back to the heart and lungs. They are near the surface of the skin, so you can see them.

Answer 17

Blood is blue until it is carrying oxygen then it turns red.

Answer 18

I think it is something to do with a chemical reaction to hitting air

Answer 19

Nothing really has a colour. White light is made up of a variety of frequencies or wavelengths, we call these red, orange, yellow, green, blue, indigo, and violet. When light hits an object, some of those frequencies are absorbed by the object, and some are reflected. We see what is reflected.

So veins appear blue because of the amount of light that is reflected and blood appears red.

Answer 20

blood is red because of oxygen...arteries bring oxgenated blood around the body from the heart and lungs while veins bring the deoxygenated blood back to the heart and lungs for more oxygen...

Answer 21

Human blood is made up of a liquid part and a solid part.

The liquid part, when it is still in the body, is called plasma.It is yellowish in color. It makes up about 50 - 60 % of our blood.The solid part is made up of cells; red blood cells, white blood cells

and platelets.

White blood cells and platelets have no color but appear white when they are grouped together, as when blood is separated in a centrifuge.

Red blood cells (RBCs) are always red. Since RBCs make up about 40-45% of our blood, the blood is definitely red. Red blood cells are red because they have a protein called hemoglobin which contains iron. Iron likes to bind oxygen. Oxygen combined with iron is red. The more oxygen iron has bound to it, the redder it is.

It is true the veins are blue but some people may think that blood can be blue which is probably because of the

color of our veins, which may be visible near the skin's surface. This is why they are blue. They appear blue because they do not get as much oxygen as the other tissues. When a living tissue lacks enough oxygen it turns blue.

When the red blood cells go to the lungs, the iron in them picks up oxygen. That is why our blood is not blue due to lack of oxygen, it is rather red because of what the iron does by picking up oxygen.

BLOOD IS RED AND NOT BLUE.

Answer 22

It only seems blue under the skin.

Blood that hasn't been oxygenated(or is on it's way to either the heart or lungs) is actually dark red in color, and appears to be a blueish tint under the skin.

Blood leaving the heart with oxygen is bright red in color.

Answer 23

blood is never blue! it's always red, it's just as it is in veins, it is de-oxygenated so it is a darker red color, but never blue

Answer 24

blood only turns red when exposed to air... then it starts to oxidize...

Answer 25

blood is  never blue it looks that way because we see it through our skin

http://www.globalclassroom.org/blublud.h...

Answer 26

When blood contains oxygen, it is red.  When it is deoxygenated, it is a darker, more blue color.  The arteries carry blood away from the heart, while veins take it back to be oxygenated.

Answer 27

Blood is never blue, deoxygenated blood are a darker shade of red but still red nonetheless. Veins appeared blue because the blue wavelength penetrates deeper and that is the colour reflected out by the veins.

Answer 28

he is right