The color of the human heart is commonly debated, with some believing it is red and others insisting it is actually black. This confusion stems from the fact that the heart changes color depending on whether it contains oxygenated or deoxygenated blood.
What Gives Blood Its Color?
Blood obtains its red color from the hemoglobin protein in red blood cells. Hemoglobin contains iron, which binds to oxygen molecules and allows the blood to transport oxygen throughout the body. Oxygenated blood traveling from the lungs back to the heart has a bright red color.
However, after the oxygen is delivered to tissues and organs, the blood returns to the heart deoxygenated. The deoxygenated blood has a much darker reddish-purple or maroon color. This color difference allows us to easily distinguish arteries (bright red oxygenated blood) from veins (darker deoxygenated blood).
The Color of the Heart Itself
The muscle tissue of the heart itself is never truly red. The interior surface of the chambers of the heart features endocardium tissue, which is a smooth membrane layer that is pale gray or white in color. The bulk of the heart wall consists of myocardium tissue, which has a brownish or tan color.
The red appearance of illustrations and models of the heart is for visualization purposes only. The true color of the heart muscle itself is not red. The brownish myocardium provides contrast against the red blood filling the chambers.
Heart Color In Situ
When observing a beating heart in the body, the color again depends on whether it is filled with oxygenated or deoxygenated blood:
- Oxygenated blood returning from the lungs to the left side of the heart makes it appear cherry red.
- Deoxygenated blood returning from the body to the right side of the heart makes it appear a very dark burgundy or purple.
So while the heart muscle itself is never truly red, the color red is associated with the heart because of the oxygenated blood flowing through its chambers.
Common Descriptions of Heart Color
Given the complexities of heart color, there are a few common shorthand ways people describe its appearance:
- “Red heart” – referring to the oxygenated blood filling its chambers.
- “Blue heart” – referring to deoxygenated blood pools in the heart.
- “Black heart” – referring to potential dried blood accumulating on the exterior surface.
- “Purple heart” – referring to areas of bruising or infarction.
But these descriptions are somewhat inaccurate or simplified. The heart muscle itself is never blue or black. And only certain conditions would make portions of the heart appear blue, black or purple.
When Does the Heart Appear Black?
There are a few situations that can make portions of the heart appear dark or black:
- Dried blood on the exterior – Blood clotting on the outer surface of the heart after surgery or trauma can appear black when dried.
- Bruising from trauma – Hematomas caused by chest trauma can cause purple-black bruising on the surface.
- Infarcted heart muscle – Heart attacks kill off areas of myocardium tissue, which turn black/dark purple.
- Deoxygenated blood – Poor circulation allows blood pools in the heart to become very dark purplish-black.
But these black portions are from blood, bruising, or dead tissue – not the healthy heart muscle itself underneath.
Conclusions on Heart Color
In summary:
- The heart muscle itself is never actually red, blue, black, or purple.
- The endocardium surface tissue is pale grayish-white.
- The myocardium muscle tissue is brownish-tan in color.
- Oxygenated blood filling the chambers makes the heart appear bright cherry red.
- Deoxygenated blood makes the heart appear very dark burgundy or purple.
So while artistic depictions show a bright red heart, the real color of the human heart is more complex. The confusion stems from the fact that the color we associate with the heart – red – comes from the blood flowing through it rather than the muscle itself. Saying the heart is “red” is a simplification referring to the oxygenated blood that makes it appear that color.
Interesting Facts About Heart Color
- Human hearts are never actually blue – only deoxygenated blood appears blue/purple.
- Hearts can appear darker or bruised during myocardial infarction heart attacks.
- Fetal hearts pump more deoxygenated blood and appear darker than adult hearts.
- Arteries carry bright red oxygenated blood, while veins carry darker deoxygenated blood.
- Cardiologists can diagnose heart conditions based on variations in normal heart coloring.
Cultural Associations of Heart Color
The symbolic red heart is used extensively in culture and tradition:
- Red hearts are an icon and symbol for love and romance.
- Ancient Egyptians associated the heart with emotion due to its red color.
- Red heart shapes are used on Valentine’s Day cards and decorations.
- Heart art is commonly rendered in red and pink hues.
- “Purple Heart” is a U.S. military award for those wounded or killed in service.
However, the real human heart is never fully red or purple. Cultural associations with heart color are based on the blood filling the chambers rather than the muscle itself.
Summary of Key Points
- The heart muscle itself is not red – the endocardium is pale and the myocardium is brownish.
- Oxygenated blood filling the chambers makes the heart look bright cherry red.
- Deoxygenated blood makes the heart look very dark purple-red.
- The “red heart” is a simplification referring to oxygenated blood flow through the organ.
- Discolorations like black, blue, or purple only occur under abnormal conditions.
- The cultural symbol of the red heart comes from blood color, not the muscle itself.
So in summary, the human heart is never fully black or blue – these are misconceptions. The red color we associate with the heart comes from the oxygenated blood flowing through it. So technically the heart is multiple colors, even though “red” is the shorthand color term used culturally and artistically.
