Human Heart: Anatomy, Diagrams, functions and facts

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Overview of the heart

The Human heart is a muscular organ about the size of a fist, located just behind and slightly left of the breastbone. The heart pumps blood through the network of arteries and veins called the cardiovascular system.
We see and hear about hearts everywhere. A long time ago, people even thought that their emotions came from their hearts, maybe because the heart beats faster when a person is scared or excited. Now we know that emotions come from the brain, and in this case, the brain tells the heart to speed up. So what’s the heart up to, then? How does it keep busy? What does it look like? keep reading..
Also read: Cardiac cycle

Anatomy of the heart

The heart muscle is very special as it pumps blood around our body. Normally the blood provides or serves our body with nutrient and oxygen. If something is wrong with our heart, then it can affect the other parts of our body.

Location and size of the heart

Heart is located under the rib-cage into the center of our chest between our right and left lungs. The heart muscular walls generally beat or contract and pumping blood continually to all the parts of our body in human heart diagram. human heart is roughly the size of a large fist. The heart weighs between about 10 to 12 ounces (280 to 340 grams) in men and 8 to 10 ounces (230 to 280 grams) in women. The heart beats about 100,000 times per day (about 3 billion beats in a lifetime)

Borders of the Human heart

Separating the surfaces of the heart are its borders. There are four main borders of the heart:
  • Right border – Right atrium
  • Inferior border – Left ventricle and right ventricle
  • Left border – Left ventricle (and some of the left atrium)
  • Superior border – Right and left atrium and the great vessels

Chambers of the Human heart

The Human heart consists of four chambers: the two atria and the two ventricles.
Blood returning to the heart enters the atria, and is then pumped into the ventricles. From the left ventricle, blood passes into the aorta and enters the systemic circulation. From the right, it enters the pulmonary circulation via the pulmonary arteries.
The heart has four chambers:

  • The right atrium: receives blood from the veins and pumps it to the right ventricle.
  • The right ventricle: receives blood from the right atrium and pumps it to the lungs, where it is loaded with oxygen.
  • The left atrium: receives oxygenated blood from the lungs and pumps it to the left ventricle.
  • The left ventricle:(the strongest chamber) pumps oxygen-rich blood to the rest of the body. The left ventricle’s vigorous contractions create our blood pressure.
chamber of the heart
The coronary arteries run along the surface of the heart and provide oxygen-rich blood to the heart muscle. A web of nerve tissue also runs through the heart, conducting the complex signals that govern contraction and relaxation. Surrounding the heart is a sac called the pericardium.

Human Heart wall

heart wall
The heart wall itself can be divided into three distinct layers: the endocardium, myocardium, and epicardium.

 

Endocardium

The innermost layer of the cardiac wall is known as the endocardium. It lines the cavities and valves of the heart.

Structurally, the endocardium is comprised of loose connective tissue and simple squamous epithelial tissue – it is similar in its composition to the endothelium which lines the inside of blood vessels.

In addition to lining the inside of the heart, the endocardium also regulates contractions and aids cardiac embryological development.

Sub-endocardial layer

The sub-endocardial layer lies between, and joins, the endo-cardium and the myocardium. It consists of a layer of loose fibrous tissue, containing the vessels and nerves of the conducting system of the heart. The purkinje fibres are located in this layer.
As the sub-endocardial layer houses the conducting system of the heart, damage to this layer can result in various arrhythmias.

Myocardium

The myocardium is composed of cardiac muscle and is an involuntary striated muscle. The myocardium is responsible for contractions of the Human heart.

 

Sub-epicardial layer

The subepidcardial layer lies between, and joins, the myocardium and the epicardium.

Epicardium

The epi-cardium is the outermost layer of the heart, formed by the visceral layer of the pericardium. It is composed of connective tissue and fat. The connective tissue secretes a small amount of lubricating fluid into the pericardial cavity. In addition to the connective tissue and fat, the epicardium is lined by on its outer surface by simple squamous epithelial cells.
Also read: Cardiac cycle

Facts about the Human heart

The Heart Is a Muscle

Your heart is really a muscle. It’s located a little to the left of the middle of your chest, and it’s about the size of your fist. There are lots of muscles all over your body — in your arms, in your legs, in your back, even in your behind.

But the heart muscle is special because of what it does. The heart sends blood around your body. The blood provides your body with the oxygen and nutrients it needs. It also carries away waste.

Your heart is sort of like a pump, or two pumps in one. The right side of your heart receives blood from the body and pumps it to the lungs. The left side of the heart does the exact opposite: It receives blood from the lungs and pumps it out to the body.

How the Human Heart Beats

How does the heart beat? Before each beat, your heart fills with blood. Then its muscle contracts to squirt the blood along. When the heart contracts, it squeezes — try squeezing your hand into a fist. That’s sort of like what your heart does so it can squirt out the blood. Your heart does this all day and all night, all the time. The Human heart is one hard worker!

Parts of the Human Heart

The Human heart is made up of four different blood-filled areas, and each of these areas is called a chamber. There are two chambers on each side of the heart. One chamber is on the top and one chamber is on the bottom. The two chambers on top are called the atria (say: AY-tree-uh). If you’re talking only about one, call it an atrium. The atria are the chambers that fill with the blood returning to the heart from the body and lungs. The heart has a left atrium and a right atrium.

The two chambers on the bottom are called the ventricles (say: VEN-trih-kulz). The heart has a left ventricle and a right ventricle. Their job is to squirt out the blood to the body and lungs. Running down the middle of the heart is a thick wall of muscle called the septum (say: SEP-tum). The septum’s job is to separate the left side and the right side of the heart.

The atria and ventricles work as a team — the atria fill with blood, then dump it into the ventricles. The ventricles then squeeze, pumping blood out of the heart. While the ventricles are squeezing, the atria refill and get ready for the next contraction. So when the blood gets pumped, how does it know which way to go?

Well, your blood relies on four special valves inside the heart. A valve lets something in and keeps it there by closing — think of walking through a door. The door shuts behind you and keeps you from going backward.

Also read: Cardiac cycle

Two of the heart valves are the mitral (say: MY-trul) valve and the tricuspid (say: try-KUS-pid) valve. They let blood flow from the atria to the ventricles. The other two are called the aortic (say: ay-OR-tik) valve and pulmonary (say: PUL-muh-ner-ee) valve, and they’re in charge of controlling the flow as the blood leaves the heart. These valves all work to keep the blood flowing forward. They open up to let the blood move ahead, then they close quickly to keep the blood from flowing backward.

How Blood Circulates

You probably guessed that the blood just doesn’t slosh around your body once it leaves the heart. It moves through many tubes called arteries and veins, which together are called blood vessels. These blood vessels are attached to the heart. The blood vessels that carry blood away from the heart are called arteries. The ones that carry blood back to the heart are called veins.

The movement of the blood through the heart and around the body is called circulation (say: sur-kyoo-LAY-shun), and your heart is really good at it — it takes less than 60 seconds to pump blood to every cell in your body.

Your body needs this steady supply of blood to keep it working right. Blood delivers oxygen to all the body’s cells. To stay alive, a person needs healthy, living cells. Without oxygen, these cells would die. If that oxygen-rich blood doesn’t circulate as it should, a person could die.

The left side of your heart sends that oxygen-rich blood out to the body. The body takes the oxygen out of the blood and uses it in your body’s cells. When the cells use the oxygen, they make carbon dioxide and other stuff that gets carried away by the blood. It’s like the blood delivers lunch to the cells and then has to pick up the trash!

The returning blood enters the right side of the heart. The right ventricle pumps the blood to the lungs for a little freshening up. In the lungs, carbon dioxide is removed from the blood and sent out of the body when we exhale. What’s next? An inhale, of course, and a fresh breath of oxygen that can enter the blood to start the process again. And remember, it all happens in about a minute!

Listen to the Lub-Dub

When you go for a checkup, your doctor uses a stethoscope to listen carefully to your heart. A healthy heart makes a lub-dub sound with each beat. This sound comes from the valves shutting on the blood inside the heart.

The first sound (the lub) happens when the mitral and tricuspid valves close. The next sound (the dub) happens when the aortic and pulmonary valves close after the blood has been squeezed out of the heart. Next time you go to the doctor, ask if you can listen to the lub-dub, too.

Pretty Cool — It’s My Pulse!

Even though your heart is inside you, there is a cool way to know it’s working from the outside. It’s your pulse. You can find your pulse by lightly pressing on the skin anywhere there’s a large artery running just beneath your skin. Two good places to find it are on the side of your neck and the inside of your wrist, just below the thumb.

You’ll know that you’ve found your pulse when you can feel a small beat under your skin. Each beat is caused by the contraction (squeezing) of your heart. If you want to find out what your heart rate is, use a watch with a second hand and count how many beats you feel in 1 minute. When you are resting, you will probably feel between 70 and 100 beats per minute.

When you run around a lot, your body needs a lot more oxygen-filled blood. Your heart pumps faster to supply the oxygen-filled blood that your body needs. You may even feel your heart pounding in your chest. Try running in place or jumping rope for a few minutes and taking your pulse again — now how many beats do you count in 1 minute?

Also read: Cardiac cycle

Human Heart Conditions

  • Coronary artery disease: Over the years, cholesterol plaques can narrow the arteries supplying blood to the heart. The narrowed arteries are at higher risk for complete blockage from a sudden blood clot (this blockage is called a heart attack).
  • Stable angina pectoris: Narrowed coronary arteries cause predictable chest pain or discomfort with exertion. The blockages prevent the heart from receiving the extra oxygen needed for strenuous activity. Symptoms typically get better with rest.
  • Unstable angina pectoris: Chest pain or discomfort that is new, worsening, or occurs at rest. This is an emergency situation as it can precede a heart attack, serious abnormal heart rhythm, or cardiac arrest.
  • Myocardial infarction (heart attack): A coronary artery is suddenly blocked. Starved of oxygen, part of the heart muscle dies.
  • Arrhythmia (dysrhythmia): An abnormal heart rhythm due to changes in the conduction of electrical impulses through the heart. Some arrhythmias are benign, but others are life-threatening.
  • Congestive heart failure: The heart is either too weak or too stiff to effectively pump blood through the body. Shortness of breath and leg swelling are common symptoms.
  • Cardiomyopathy: A disease of heart muscle in which the heart is abnormally enlarged, thickened, and/or stiffened. As a result, the heart’s ability to pump blood is weakened.
  • Myocarditis: Inflammation of the heart muscle, most often due to a viral infection.
  • Pericarditis: Inflammation of the lining of the heart (pericardium). Viral infections, kidney failure, and autoimmune conditions are common causes.
  • Pericardial effusion: Fluid between the lining of the heart (pericardium) and the heart itself. Often, this is due to pericarditis.
  • Atrial fibrillation: Abnormal electrical impulses in the atria cause an irregular heartbeat. Atrial fibrillation is one of the most common arrhythmias.
  • Pulmonary embolism: Typically a blood clot travels through the heart to the lungs.
  • Heart valve disease: There are four heart valves, and each can develop problems. If severe, valve disease can cause congestive heart failure.
  • Heart murmur: An abnormal sound heard when listening to the heart with a stethoscope. Some heart murmurs are benign; others suggest heart disease.
  • Endocarditis: Inflammation of the inner lining or heart valves of the heart. Usually, endocarditis is due to a serious infection of the heart valves.
  • Mitral valve prolapse: The mitral valve is forced backward slightly after blood has passed through the valve.
  • Sudden cardiac death: Death caused by a sudden loss of heart function (cardiac arrest).
  • Cardiac arrest: Sudden loss of heart function.
  • Abdominal Aortic Aneurysm: Abdominal aortic aneurysms (AAA) are dilatations of the abdominal aorta that are greater than 3 cm. The abdominal aorta is a major blood vessel that connects the heart to the lower extremities. The prevalence of this illness increases with age. It is not common in persons who are younger than 50 years old.

Heart Treatments

  • Exercise: Regular exercise is important for heart health and most heart conditions. Talk to your doctor before starting an exercise program if you have heart problems.
  • Angioplasty: During cardiac catheterization, a doctor inflates a balloon inside a narrowed or blocked coronary artery to widen the artery. A stent is often then placed to keep the artery open.
  • Percutaneous coronary intervention (PCI): Angioplasty is sometimes called a PCI or PTCA (percutaneous transluminal coronary angioplasty) by doctors.
  • Coronary artery stenting: During cardiac catheterization, a doctor expands a wire metal stent inside a narrowed or blocked coronary artery to open up the area. This lets blood flow better and can abort a heart attack or relieve angina (chest pain).
  • Thrombolysis: “Clot-busting” drugs injected into the veins can dissolve a blood clot causing a heart attack. Thrombolysis is generally only done if stenting is not possible.
  • Lipid-lowering agents: Statins and other cholesterol (lipid) lowering drugs reduce the risk for heart attack in high-risk people.
  • Diuretics: Commonly called water pills, diuretics increase urination and fluid loss. This reduces blood volume, improving symptoms of heart failure.
  • Beta-blockers: These medicines reduce strain on the heart and lower heart rate. Beta-blockers are prescribed for many heart conditions, including heart failure and arrhythmias.
  • Angiotensin-converting enzyme inhibitors (ACE inhibitors): These blood pressure medicines also help the heart after some heart attacks or in congestive heart failure.
  • Aspirin: This powerful medicine helps prevent blood clots (the cause of heart attacks). Most people who have had heart attacks should take aspirin.
  • Clopidogrel (Plavix): A clot-preventing medicine that prevents platelets from sticking together to form clots. Clopidogrel is especially important for many people who have had stents placed.
  • Antiarrhythmic medications: Numerous medicines help control the heart’s rate and electrical rhythm. These help prevent or control arrhythmias.
  • AED (automated external defibrillator): If someone has sudden cardiac arrest, an AED can be used to assess the heart rhythm and send an electrical shock to the heart if necessary.
  • ICD (Implantable cardioverter defibrillator): If a doctor suspects you are at risk for a life-threatening arrhythmia, an implantable cardioverter defibrillator may be surgically implanted to monitor your heart rhythm and send an electrical shock to the heart if necessary.
  • Pacemaker: To maintain a stable heart rate, a pacemaker can be implanted. A pacemaker sends electrical signals to the heart when necessary to help it beat properly.
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