A broken heart, learning by heart, from the bottom of my heart — these idioms and many others can be traced back to the early Bronze Age and to ancient Greece, when philosophers believed that the heart was responsible for human intelligence, movement, memory and emotions.
Now that we have a deeper understanding of human anatomy, we know that the brain is actually “at the heart” of these human abilities, and that the veiny, pulsating organ in our chest is actually a pump that feeds oxygenated blood to the rest of our body.
Dr. Christopher Ramnanan, an associate professor at the Faculty of Medicine’s Department of Innovation in Medical Education, shared with us five interesting facts about the heart that might not be common knowledge.
1. Two hearts are better than one
The human heart has four chambers: the left and right atria, which collect blood from the body and organs, and the left and right ventricles, which pump blood away from the heart.
“What might not be as well-known is that these chambers are organized to function essentially as two different hearts, involved in two different systems of blood flow,” says Ramnanan. “So, functionally speaking, we actually have two hearts in our chest, pumping at two different pressures and with two distinct goals.”
The “right heart” collects blood from the body and funnels it from the right atrium to the right ventricle, which then pumps it out to the lungs to be oxygenated. The right ventricle pumps at moderately low pressure, so as not to damage the lungs’ delicate tissue. “It’s a conscientious next-door neighbour,” he says.
The “left heart” gathers the oxygenated blood from the lungs into its left atrium. The blood travels down to the left ventricle and is then pumped out to the rest of the body through the aorta, the body’s largest artery. The left ventricle pumps blood at a higher pressure than the right because it has to work against gravity to bring blood up to the head, while also driving blood all the way down to our toes. Because it’s working harder, the left ventricle is thicker and more muscular than the right.
2. The heart is smack dab in the centre
“During the national anthem, when people put their hand to their heart, they tend to place it way too far to the left,” says Ramnanan. “It’s way more in the centre than popular culture will have you believe. It’s true that the heart veers to the left, but most of its tissue is sitting smack dab in the middle of the chest, comfortably placed behind the bony protection of the sternum, or ‘breastplate’. Not bad in terms of design, right?”
In fact, the heart lives in the mediastinum, a central cavity in our chest that literally means “that which stands in the middle” in Latin. It’s this very design that led thinkers such as Aristotle to identify the heart as the most important organ in the body and as the centre of vitality. Aristotle believed that the brain and the lungs existed merely to cool the heart down.
It wasn’t until 1628, when English physician William Harvey wrote that the heart’s primary function was “the transmission of the blood and its propulsion,” that beliefs began to change. French philosopher René Descartes was one of the first scholars to describe the heart as a mechanical pump in his book Discours de la méthode, published in 1637.
3. The heart starts off tubular
In utero, a baby’s heart grows in the shape of two tubes, like finger traps. At between four and eight weeks, the tubes fuse together and undergo vast transformations.
“Initially, we have one atrium sitting below a ventricle, with one circuit of blood flow,” says Ramnanan. “This one-circuit heart subsequently undergoes substantial growth, looping and folding. Eventually, our original atrium and ventricle are divided in two, giving us a total of four compartments. As the ventricles get bigger, they begin to drop below the atria, giving the organ its final shape.”
4. The most common and dangerous heart attack is nicknamed the “widow maker”
Coronary arteries are the blood vessels that link the aorta to the heart. These arteries nab some of the oxygenated blood destined for your head and body and use it to feed the heart itself, which also needs oxygen to function.
“There’s a right coronary artery and a left, each with several branches feeding specific parts of the heart,” says Ramnanan. “When there’s blockage in one of these branches, it prevents a part of the heart from being fed oxygen. That lack of oxygen leads to damage and the associated pain that we feel in our chest and shoulder. That’s a heart attack. At the heart of it, the issue is one of blood supply, or blockage.”
According to Ramnanan, the left coronary artery and one of its branches in particular, the left anterior descending (LAD) artery, are more prone to blockage than any other heart artery. A heart attack caused by blockage in this critical area is so common and dangerous that people in the medical profession call it a “widow maker.”
This nickname is perhaps a testament to the old misconception that heart disease was mostly a men’s issue. “As a child, I remember thinking that heart attacks happened mainly to dads, not so much to moms,” he recalls. “I think it’s commonly accepted now that heart disease and other heart issues are an ‘everybody’ problem. In fact, recent studies have shown that, statistically, it’s actually more common in women. Important work is currently being done to understand why.”
5. Heart attacks ≠ cardiac arrest
“I’ve heard the terms ‘heart attack’ and ‘cardiac arrest’ used interchangeably,” says Ramnanan. “But they’re actually two different things.”
A heart attack is a blockage in the arteries that interrupts the flow of oxygenated blood to a part of the heart. Cardiac arrest means that the heart stops beating, but not as a result of blood flow issues. “It’s more of an electrical issue,” says Ramnanan.
“The heart has its own electrical wiring within its walls, and for whatever reason, it stops working. It’s usually sudden and drastic, and the sensation might feel more like gasping for air. If there is time to feel anything before losing consciousness, which I’m not sure there always is, you might feel weakness, fatigue, dizziness and shortness of breath, because the pump stopped working all of a sudden and there’s no blood flowing to your brain, organs and limbs.”
Ramnanan says that, as humans, we’re very good at sensing our body wall and our external tissue. Touch the back of our right knee and we’ll be able to pinpoint the precise location of that touch. But we’re very imprecise about sensations in our organs.
"During a heart attack, the pain is usually interpreted by our spinal cord as coming from our arm and the wall of our chest, as opposed to our heart. We typically describe this as ‘referred pain’. Perhaps it’s an evolutionary thing, because we don’t want to be distracted by every little thing happening inside. But it also makes it harder to detect a problem and accurately report it to a doctor. Fortunately, healthcare professionals are well trained to link the common patterns of patients’ referred pain with likely underlying causes.”
The heart remains at the forefront of our minds. It’s one of the organs that fascinates the general public the most. After all, there are no holidays with kidney-shaped candy boxes or liver-shaped chocolates (probably for the best).
That’s why the heart is typically a centrepiece of any outreach activity offered by the Faculty of Medicine’s Division of Clinical and Functional Anatomy. These outreach events are meant to educate the general public about human anatomy, using cadaveric teaching resources from their Body Donation Program. These events are a great opportunity for medical students to acquire some teaching experience and interact with members of their community.
After the pandemic, the Division of Clinical and Functional Anatomy and the medical students at the University of Ottawa look forward to engaging the public in these activities once again. The heart, of course, will remain at the centre of it all.
Consider supporting the University of Ottawa
The Division of Clinical and Functional Anatomy has established a School of Anatomy Fund to help enhance the student experience and make improvements to our program. Donations to the fund will be used to better support student learning activities or purchase teaching tools and technologies such as ultrasound machines and 3-D printers. These tools are critical to medical education and will help our students thrive in this competitive environment.