Skip to Content

What is the color of the human heart?

What is the color of the human heart?

The human heart is an incredibly complex and vital organ that plays a crucial role in circulating blood throughout the body. But have you ever wondered – what color is the human heart? Understanding the color and appearance of the heart can provide insight into its anatomy and function. In this article, we will explore the reasons behind the characteristic color of the human heart.

The Inner Structure and Composition of the Heart

In order to understand the color of the heart, it is important to first consider its internal structure and composition. The heart is made up of three layers:

  • The outer layer, known as the pericardium, is a thin, double-walled sac that encloses and protects the heart. It is made up of fibrous tissue and contains a small amount of serous fluid that lubricates the heart’s movement.
  • The middle layer is the myocardium, which is the muscular wall of the heart. This layer does the main work of pumping blood. It is made up largely of cardiac muscle tissue and contains blood vessels that supply the heart muscle with oxygen.
  • The inner layer is the endocardium, a smooth lining layer that also covers the heart valves. It limits friction as blood flows through the chambers and valves of the heart.

In addition to these three layers, the heart contains four chambers – the left and right atria on top and the left and right ventricles on the bottom. The atria collect blood returning to the heart, while the stronger ventricular chambers pump blood out of the heart to the lungs and body. The heart also contains one-way valves between chambers and major blood vessels connected to the heart that carry blood to and from it.

The Color of Cardiac Muscle

The main contributor to the color of the heart is the thick middle myocardium layer containing cardiac muscle. Cardiac muscle tissue has a natural reddish-brown tint primarily due to the high amount of myoglobin present within the muscle cells.

Myoglobin is an iron and oxygen binding protein related to hemoglobin in red blood cells. Both myoglobin and hemoglobin contain heme groups with iron atoms that can bind to oxygen. This gives them both a red pigmentation. Myoglobin is present at high levels in muscle tissues that need a steady supply of oxygen, like the constantly contracting cardiac muscle. The myoglobin stores and supplies oxygen to the heart muscles, giving cardiac muscle its reddish color.

The Color of Blood in the Heart

In addition to the natural color of the muscle, the blood contained within the chambers and vessels of the heart also significantly contributes to its reddish-brown color. Blood gets its bright red color primarily from the hundreds of millions of red blood cells containing oxygen-carrying hemoglobin that flow through the heart each minute. The blood adds layers of vivid redness to the inside of the heart.

Interestingly, the blood contained in different areas of the heart can be slightly different colors depending on oxygen content. Blood returning to the heart through the veins is darker, more purple-red as it carries waste carbon dioxide back from the body’s tissues. As this blood enters the right atrium, it mixes and passes through the lungs to pick up fresh oxygen. The refreshed, oxygen-rich blood returning to the left atrium and ventricle then takes on a brighter cherry red color. This color difference allows you to see the separations between the oxygen-rich and oxygen-poor sides of the heart.

The Effect of Coronary Artery Blood Flow

The heart has its own dedicated blood supply via a network of coronary arteries on its surface. These arteries supply oxygen and nutrients to the hard-working cardiac muscle tissue. Bright oxygenated blood flows through the coronary arteries, contributing to the redness of the outer surface of the heart. Blockages in these important arteries can starve areas of the heart of oxygen, leading to cardiac ischemia and heart attacks.

Other Contributing Factors

In addition to the major factors described above, other anatomical elements contribute subtly to the overall color of the heart:

  • Yellow adipose tissue around arteries and underneath the pericardium
  • The whiter-colored tendons anchoring the heart valves
  • Brown nerve fibers conducting signals
  • Clear serous fluid around the heart

The complex combination of all these anatomical elements gives the healthy human heart its characteristic reddish-brown hue.

Variation in Heart Color

While the healthy heart is generally some shade of reddish brown, there can be subtle variation in color between individuals. Factors that can affect heart color include:

Factor Effect on Color
Age Hearts can become more grayish with scar tissue as we age
Sex Women tend to have slightly redder hearts
Genetics Gene variants affect myoglobin levels
Physical fitness Athletic hearts may be darker red
Disease state Illness can cause paler or darker discoloration

However, despite some individual variation, the healthy human heart is remarkably consistent in its deep red-brown color.

What a Change in Color Could Indicate

Significant changes to the expected red-brown color of the heart may indicate an underlying problem. Here are some key conditions associated with color changes:

  • Cyanosis (blue color) – often indicates low oxygen levels in the blood or defects in the heart’s structure
  • Pale whitish color – can indicate severe anemia or ischemia
  • Yellowish fat deposits – suggest complications like diabetes or hyperlipidemia
  • Black spots – could be clots in the heart or melanin deposits
  • Bright red blood throughout – linked to increased oxygen use by inflamed heart tissues

In most people though, the heart maintains a healthy reddish-brown tone due to the high myoglobin content and oxygenated blood flowing through it. This consistent natural coloration is essential for normal cardiac function.


The human heart is truly an amazing organ. Its characteristic reddish-brown color provides key insights into its hard-working anatomy and critical function. This complex coloration arises from the iron-containing myoglobin in cardiac muscle fibers, oxygen-rich blood circulating through the heart’s chambers, and the network of coronary arteries on its surface. Subtle variations in color can occur but are normal. Significant shifts away from its natural tone could signify problems. But for the most part, the human heart beats on with its tell-tale red-brown hue, pulsating life through our bodies.