The brain is one of the most complex and fascinating organs in the human body. Protected by the skull, it controls everything from breathing and heart rate to cognition and emotion. But what color is the living, functioning brain?
The Appearance of the Living Brain
At first glance, the color of the living brain appears pinkish-gray. The gray matter, made up of neuron cell bodies, gives the brain its grayish hue. The pink color comes from blood vessels on the surface of and within the brain.
The blood flow to the brain gives it a pinkish tint, but the actual color of brain tissue is gray. The brain has a high concentration of blood vessels and gets approximately 20% of the body’s blood supply. All this blood flow is necessary to deliver oxygen and nutrients to the hard-working neurons.
The Colors of Gray and White Matter
There are two main types of tissue in the brain: gray matter and white matter. Each has a distinct color and function.
Gray matter is made up of neuron cell bodies and gives the brain its gray color. It contains the neurons that process information. Gray matter is found in different brain areas like the cerebral cortex, cerebellum, brain stem, and basal ganglia.
White matter contains the nerve fibers or axons that connect neurons. It appears white because the axons are insulated by a fatty substance called myelin. White matter allows different regions of the brain to communicate.
What Makes Gray Matter Gray?
The main reason the gray matter looks gray is because of how dense the tissue is. Gray matter contains tens of billions of neuron cell bodies as well as blood vessels and capillaries.
All these structures packed tightly together make the tissue appear darker. Areas with just nerve fibers and very few neuron cell bodies, like the white matter, look lighter.
The Colors of Specific Brain Structures
While the main color of the brain is pinkish-gray, some structures have their own distinct colors based on what they contain.
The Cerebral Cortex
The cerebral cortex has a very gray color since it is made up almost entirely of neuronal cell bodies. It is divided into four lobes: frontal, parietal, temporal, and occipital. Each lobe controls specific functions but they all have the same grayish hue.
The Brain Stem
The brain stem also contains primarily gray matter and has a similar gray color to the cortex. It connects the rest of the brain to the spinal cord and controls functions like breathing, consciousness, and heart rate.
The cerebellum coordinates movement and is located at the base of the brain. It has a very convoluted surface, giving it a grayish color distinct from the smoother cortex.
The hippocampus is found within the temporal lobe. This structure is involved in memory formation and has a gray color like other gray matter. Its curved shape also gives it a unique look.
The Basal Ganglia
The basal ganglia are a group of structures deep in the brain involved in control of voluntary movements. Like other gray matter, areas like the caudate nucleus and putamen are a grayish color.
Colors Seen During Brain Surgery
For a neurosurgeon operating on the brain, the colors may appear different than a textbook image. Bright lighting, blood flow, and opening of the dura mater can change the brain’s appearance.
When the dura mater is retracted during surgery, the cortex may appear more purple or blue. This color comes from the combination of gray matter with the red blood vessels underneath.
Bleeding during surgery will also cover the brain with vivid red blood. The areas with white matter may also appear more yellow. So the view depends on the type of surgery and amount of blood present.
How Oxygenation Changes Brain Color
The level of blood and oxygen flow also determines the shade of the brain. Areas receiving plentiful oxygen appear more red while poorly oxygenated areas look bluer or purple.
This is why pulse oximetry placed directly on the brain during surgery changes colors. The redder the tissue appears, the better the blood and oxygen supply. A loss of proper oxygenation causes the brain to become a more dusky purple.
Differences Between Dead and Live Brains
The brain’s color and consistency starts changing dramatically soon after death as the tissue breaks down. Here are some of the major differences between living and dead brain tissue:
|Living Brain||Dead Brain|
|Pinkish-gray color||More yellowish or tan|
|Firm, rubbery texture||Softer, more moist appearance|
|Anatomic structures recognizable||Loss of typical anatomic structure|
|Blood continues to circulate||No blood flow or oxygenation|
Changes After Fixation
Fixing and preserving the brain in formaldehyde further alters its appearance. Fixation causes the brain to become firmer and discolored.
The gray matter takes on a deeper gray, even brownish hue. The white matter starts to turn yellowish or tan. Over time, the preserved fixed brain develops a uniform light brown color.
In summary, the color of a living brain is mostly grayish-pink. The neuron-rich gray matter gives the brain its predominant gray color. Blood vessels on the surface and within the tissue impart a pinkish tint.
More specifically, areas with high neuron density like the cortex and cerebellum appear gray. White matter has fewer neurons and more nerve fibers, making it lighter white. Oxygenation levels can also change the brain’s color from red to purple.
After death, lack of blood flow causes the brain to lose its natural pinkish-gray hue, becoming more yellowed and discolored. Fixation also leads to a darker, more uniform brown color throughout the brain matter.
So the next time you picture the human brain, remember that its color results from a combination of grayish neuron bodies intermixed with the red blood supply coursing through it. The living brain’s natural color is like a pinkish-gray palette enabling our amazing minds.