The Heart Is on the Left, but Why?

When I was in high school, a required health course involved a plastic model of the human body with the skin removed and all the organs visible. We named the model “Oscar” and tried to change the arrangement of the organs. We learned that correct internal organ placement is essential, and the heart is on the left.

Getting all the organs into Oscar was difficult because they were hard plastic, and not all organs are symmetrical. We learned that there were reasons for the human body’s design, and the heart is on the left, but we didn’t know why?

We learned there is a reason for the brain to be at the top of the body to avoid a stroke. The pressure in a column of liquid is greater at the bottom than at the top. For that reason, a blood vessel can rupture in our feet but still not be critical to our survival. If our brain were in the lower part of the body, a broken blood vessel would lead to a stroke.

So what determines where our organs are placed? A recent study led by Harvard Medical School researchers gave some answers to that question. In early embryonic development, a cluster of cells called the left-right organizer contains some hair-like structures called motile cilia. They sense the biomechanical forces that shape the body plan. The cilia beat rapidly, moving extracellular fluid in the correct direction to move organs to the proper place to function most efficiently. They are the reason why the heart is on the left side.

Incorrect left-right placement of the internal organs can result in various disorders, including heterotaxy syndrome and primary ciliary dyskinesia. These disorders can cause recurring respiratory infections and congenital heart disease.

In Psalms 139:10-14, David speaks of God’s right hand forming him in the womb. In verse 14, David says, “I will praise you, God, for I am fearfully and wonderfully made…” The more we learn about how our bodies are designed and formed, the more we understand the truth of that statement.

— John N. Clayton © 2023

References: National Science Foundation Research News and the journal Science