The reason why some internal organs are located on one side of the body is due to their increased efficiency in that position. For instance, the heart is situated on the left side to optimize blood circulation throughout the body.
As we grow older, we become more familiar with our body’s external appearance. However, this familiarity primarily stems from our external observations. In other words, although we are aware of our vital organs, we may not have a precise understanding of their exact locations. For instance, I have spent a significant portion of my life believing that my kidneys were positioned near my hips, at the front of my body. In reality, each kidney is located on either side of the spine, towards the back of my torso, beneath the rib cage!
Some of our organs, both internal and external, exist in pairs and exhibit symmetry in the body. Examples include the lungs, kidneys, eyes, and ears. Conversely, some organs lack a matching pair and can be found on either the left side, right side, or center of our bodies. The question is, what determines this placement, and is there a specific reason why certain organs tend towards the right or left side?
Before delving into an explanation, it is important to review the anatomy of the body and familiarize ourselves with the most crucial organs and organ systems.
Overview of Human Anatomy
When observing a human being externally, one of the first things we notice is the bilateral symmetry, meaning our body appears symmetrical from the outside in most cases. If we were to draw a line down the center of our body, starting from the top of our head and extending down between our legs, each side would feature one ear, one eye, one arm, one leg, and so on. Some of our features come in pairs, such as nostrils, eyes, and ears, while others exist as singular entities, like our mouth, bellybutton, and nose.
When it comes to organs or features that exist in pairs versus those that are singular, there is usually a logical explanation. For example, having two ears and eyes allows for more accurate detection of sensory input, resulting in a more comprehensive understanding of the world around us. On the other hand, only one mouth is necessary since it is directly connected to a separate organ system where duplication is unnecessary – one mouth, one esophagus, one small intestine, one stomach, one large intestine, and so forth.
Internally, the body does not exhibit the same bilateral symmetry as our external appearance might suggest. Instead, the focus is on maximizing space efficiency, which does not always result in a visually pleasing, evenly divided arrangement. Some internal organs do display symmetry or pairing, such as the kidneys and lungs, while others, like the liver, brain, heart, and gallbladder, do not.
Some organs in our body are present in pairs to ensure survival. For example, we have two ovaries and two testicles in case one of them stops functioning. Having two lungs provides a reserve capacity for oxygen, allowing us to be active without running out of oxygen. Similarly, having two kidneys makes it easier to remove waste from the body compared to having only one.
However, certain organs like the brain and the heart are singular because they consume a lot of energy and play critical roles in the body. Although they are singular, they still have some duality in their structure, such as the left and right ventricles in the heart, the left and right lobes in the liver, and the left and right hemispheres in the brain.
Understanding why some organs come in pairs while others don’t helps explain the asymmetry of our internal body. Now, let’s explore what controls and determines the placement of our organs.
Organ Position In The Body
During embryo development, the early stages remain symmetrical. However, around six weeks, the heart and stomach start shifting to the left, and the liver migrates to the right. This change is known as left-right symmetry breaking and has puzzled scientists for years.
Embryo development (Photo Credit: Julia Dolovanuk/Shutterstock)
Recent research has identified some genes and transcription factors that regulate the development of organs and their positioning. In a specific area of the embryo called the node, specialized cilia behave in a unique way. They rotate in a controlled clockwise direction, guiding fluid flow around the embryo. This rotation triggers the expression of certain genes on the left side and others on the right, disrupting the previous symmetrical growth. If these cilia don’t function properly or rotate in the opposite direction, organs may grow randomly or on the wrong side, leading to potential health issues.
One significant gene involved in this process is the Pitx2 gene, which codes for a protein acting as a transcription factor. Impairment or mutation of this gene can severely affect human growth development, causing cranio-facial deformities, impaired tooth growth, and problems with human growth hormone production. Ongoing research aims to identify other transcription factors that influence organ placement and development, as Pitx2 alone cannot account for all cases of left/right determination issues.
Once the organs start growing in an asymmetrical way, if everything goes well, a healthy child will be born with all their organs in the right place, in the correct number, and intact. However, there are various defects and syndromes that can occur when the left/right symmetry breaking is incorrect. These include the absence of certain organs, the duplication of some organs, or the organs being in a mirrored position compared to the average human. Some of these disorders are harmless and may go unnoticed until later in life, while others require immediate medical attention as they can be potentially fatal!
A Final Word
Despite the seemingly chaotic arrangement of our internal body, there is a method behind the madness. Through the intricate interplay of genes and millions of years of natural selection and evolution, we have evolved into complex beings with intricate blueprints that are not always perfectly executed. Fortunately, our body has backup mechanisms for most organs in case of errors. Although we still don’t have a precise explanation for the specific left-right placement of organs, the efficient utilization of internal space and the proximity of interactive organ systems suggest that there is a good reason behind it!