Where is your heart and what does it look like?
The heart is located under the rib cage, to the left of the breastbone (sternum) and between the lungs. Your heart is an amazing organ. Shaped like an upside-down pear, this fist-sized powerhouse pumps five or six quarts of blood each minute to all parts of your body.
Outside the heart
Looking at the outside of the heart, you can see:
- that the heart is made of muscle. The strong muscular walls contract (squeeze), pumping blood to the arteries.
- the major blood vessels that enter the heart:
- aorta
- superior vena cava
- inferior vena cava
- pulmonary artery takes oxygen-poor blood from the heart to the lungs
- pulmonary vein -- brings oxygen-rich blood from the lungs to the heart
- the coronary arteries
Inside the heart
The heart is a four-chambered, hollow organ.It is divided into the left and right side by a muscular wall called the septum. The right and left sides of the heart are further divided into:
two atria - top chambers, which receive blood from the veins and
two ventricles - bottom chambers, which pump blood into the arteries
The atria and ventricles work together, contracting and relaxing to pump blood out of the heart.
The normal aortic valve
As blood leaves each chamber of the heart, it passes through a valve. There are four heart valves within the heart:
mitral valve
tricuspid valve
aortic valve
pulmonic valve (also called pulmonary valve)
The tricuspid and mitral valves lie between the atria and ventricles. The aortic and pulmonic valves lie between the ventricles and the major blood vessels leaving the heart.
The heart valves work the same way as one-way valves in the plumbing of your home, preventing blood from flowing in the wrong direction.
Each valve has a set of flaps, called leaflets or cusps. The mitral valve has two leaflets; the others have three. The leaflets are attached to and supported by a ring of tough, fibrous tissue called the annulus. The annulus helps to maintain the proper shape of the valve.
The leaflets of the mitral and tricuspid valve are also supported by tough, fibrous strings called chordae tendineae. These are similar to the strings supporting a parachute. The chordae tendineae extend from the valve leaflets to small muscles, called papillary muscles, which are part of the inside walls of the ventricles
Your coronary arteries
Like all organs, your heart is made of tissue and requires a supply of oxygen and nutrients. Although its chambers are full of blood, the heart receives no nourishment from this blood. The heart receives its own supply of blood from a network of arteries, called the coronary arteries.
Two major coronary arteries branch off from the aorta near the point where the aorta and the left ventricle meet:
the right coronary artery (RCA) which supplies the right atrium and right ventricle. It branches into the posterior descending artery which supplies the bottom portion of the left ventricle and back of the septum.
the left main coronary artery, which branches into:
the circumflex artery, which supplies blood to the left atrium, side and back of the left ventricle
the left anterior descending artery (LAD), which supplies the front and bottom of the left ventricle and the front of the septum
What is collateral circulation?
Collateral circulation is a network of tiny blood vessels, and, under normal conditions, not open. When the coronary arteries narrow to the point that blood flow to the heart muscle is limited (coronary artery disease), collateral vessels may enlarge and become active. This allows blood to flow around the blocked artery to another artery nearby or to the same artery past the blockage, protecting the heart tissue from injury.
How does the heart beat?
The atria and ventricles work together, alternately contracting and relaxing to pump blood through your heart. The electrical system of your heart is the power source that makes this possible.
Your heartbeat is triggered by electrical impulses that travel down a special pathway through your heart:
SA node (sinoatrial node) – known as the heart’s natural pacemaker
The impulse starts in a small bundle of specialized cells located in the right atrium, called the SA node. The electrical activity spreads through the walls of the atria and causes them to contract. This forces blood into the ventricles.
The SA node sets the rate and rhythm of your heartbeat. Normal heart rhythm is often called normal sinus rhythm because the SA (sinus) node fires regularly.
AV node (atrioventricular node)
The AV node is a cluster of cells in the center of the heart between the atria and ventricles, and acts like a gate that slows the electrical signal before it enters the ventricles. This delay gives the atria time to contract before the ventricles do.
His-Purkinje Network
This pathway of fibers sends the impulse to the muscular walls of the ventricles and causes them to contract. This forces blood out of the heart to the lungs and body.
The SA node fires another impulse and the cycle begins again.
At rest, a normal heart beats around 50 to 99 times a minute. Exercise, emotions, fever and some medications can cause your heart to beat faster, sometimes to well over 100 beats per minute.
How fast does the normal heart beat?
How fast the heart beats depends on the body's need for oxygen-rich blood. At rest, the SA node causes your heart to beat about 50 to 100 times each minute. During activity or excitement, your body needs more oxygen-rich blood; the heart rate rises to well over 100 beats per minute.
Medications and some medical conditions may affect how fast your heart-rate is at rest and with exercise.
Medications and some medical conditions may affect how fast your heart-rate is at rest and with exercise.
How do you know how fast your heart is beating?
You can tell how fast your heart is beating (your heart rate) by feeling your pulse. Your heart-rate is the amount of times your heart beats in one minute.
You will need a watch with a second hand.
Place your index and middle finger of your hand on the inner wrist of the other arm, just below the base of the thumb.
You should feel a tapping or pulsing against your fingers.
Count the number of taps you feel in 10 seconds.
Multiply that number by 6 to find out your heart-rate for one minute:
Pulse in 10 seconds x 6 = ____ beats per minute (your heart-rate)
When feeling your pulse, you can also tell if your heart rhythm is regular or not.
Learn about abnormal heart rhythms
How does blood flow through the heart?
The right and left sides of the heart work together.
Right Side:
Blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium.
Left Side:
The pulmonary vein empties oxygen-rich blood, from the lungs into the left atrium.
Atrial contraction:
Right Side:
blood flows from your right atrium into your right ventricle through the open tricuspid valve. When the ventricles are full, the tricuspid valve shuts. This prevents blood from flowing backward into the atria while the ventricles contract (squeeze).
Left Side:
blood flows from your left atrium into your left ventricle through the open mitral valve. When the ventricles are full, the mitral valve shuts. This prevents blood from flowing backward into the atria while the ventricles contract (squeeze).
Ventricular contraction:
Right Side:
blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs.
Left Side:
blood leaves the heart through the aortic valve, into the aorta and to the body.
This pattern is repeated over and over, causing blood to flow continuously to the heart, lungs and body.
How does blood flow through your lungs?
O
nce blood travels through the pulmonic valve, it enters your lungs. This is called the pulmonary circulation. From your pulmonic valve, blood travels to the pulmonary artery to tiny capillary vessels in the lungs. Here, oxygen travels from the tiny air sacs in the lungs, through the walls of the capillaries, into the blood. At the same time, carbon dioxide, a waste product of metabolism, passes from the blood into the air sacs. Carbon dioxide leaves the body when you exhale. Once the blood is purified and oxygenated, it travels back to the left atrium through the pulmonary veins.How does blood travel through your body?
As the heart beats, it pumps blood through a system of blood vessels, called the circulatory system. The vessels are elastic tubes that carry blood to every part of the body.
Blood is essential.
It carries oxygen and nutrients to your body's tissues
It takes carbon dioxide and waste products away from the tissues.
It is needed to sustain life and promote the health of all the body's tissues.
There are three main types of blood vessels:
Arteries
Arteries begin with the aorta, the large artery leaving the heart.
They carry oxygen-rich blood away from the heart to all of the body's tissues.
They branch several times, becoming smaller and smaller as they carry blood further from the heart.
Capillaries
Capillaries are small, thin blood vessels that connect the arteries and the veins.
Their thin walls allow oxygen, nutrients, carbon dioxide and waste products to pass to and from the tissue cells.
Veins
These are blood vessels that take oxygen-poor blood back to the heart.
Veins become larger and larger as they get closer to the heart.
The superior vena cava is the large vein that brings blood from the head and arms to the heart, and the inferior vena cava brings blood from the abdomen and legs into the heart.
This vast system of blood vessels - arteries, veins, and capillaries - is over 60,000 miles long. That's long enough to go around the world more than twice!
Blood flows continuously through your body's blood vessels. Your heart is the pump that makes it all possible.
Heart Facts
- Your system of blood vessels - arteries, veins and capillaries - is over 60,000 miles long. That's long enough to go around the world more than twice!
- The adult heart pumps about 5 quarts of blood each minute - approximately 2,000 gallons of blood each day - throughout the body.
- When attempting to locate their heart, most people place their hand on their left chest. Actually, your heart is located in the center of your chest between your lungs. The bottom of the heart is tipped to the left, so you feel more of your heart on your left side of your chest.
- The heart beats about 100,000 times each day.
- In a 70-year lifetime, the average human heart beats more than 2.5 billion times
- An adult woman's heart weighs about 8 ounces, a man's about 10 ounces
- A child's heart is about the size of a clenched fist; an adult's heart is about the size of two fists.
- Blood is about 78 percent water.
- Blood takes about 20 seconds to circulate throughout the entire vascular system.
- The structure of the heart was first described in 1706, by Raymond de Viessens, a French anatomy professor.
- The electrocardiograph (ECG) was invented in 1902 by Dutch physiologist Willem Einthoven. This test is still used to evaluate the heart's rate and rhythm.
- The first heart specialists emerged after World War I.
Simple Clues to Your Heart
Your heart doctor will use some standard and simple techniques to gain the first clues to your heart's function.
Feel your pulse
Your doctor feels your pulse in order to check your heart's rate, rhythm and regularity. Each pulse matches up with a heartbeat that pumps blood into the arteries. The force of the pulse also helps evaluate the amount (strength) of blood flow to different areas of your body.
You can tell how fast your heart is beating (heart rate) by feeling your pulse. Your heart rate is the amount of times your heart beats in one minute.
To measure your pulse, you need a watch with a second hand.
- Place your index and middle finger of your hand on the inner wrist of the other arm, just below the base of the thumb.
- You should feel a tapping or pulsing against your fingers.
- Count the number of taps you feel in 10 seconds.
- Multiply that number by 6 to find out your heart-rate for one minute
(pulse in 10 seconds x 6 = ____ beats per minute)
When feeling your pulse, you can also tell if your heart rhythm is regular or not.
Listen to your heart
Your doctor listens to your heart with the aid of a stethoscope. The opening and closing of your valves make sounds ("lub dub") known as the heart sounds. The doctor can evaluate your heart and valve function and hear your heart's rate and rhythm by listening to your heart sounds.
Check your blood pressure (BP)
Blood pressure is the force or pressure exerted in the arteries by the blood as it is pumped around the body by the heart. It is recorded as two measurements:
- Systolic pressure:
pressure in the arteries during the period of the heart's contraction (the higher number) - Diastolic pressure:
pressure in the arteries when the heart is relaxed, between heartbeats (the lower number)
A doctor or nurse can listen to your blood pressure by placing a stethoscope on your artery and pumping up a cuff placed around your arm. The blood pressure is read on a special meter called a sphygmomanometer.
Blood pressure is measured in millimeters of mercury (mm Hg), which refers to how high the pressure in the arteries can raise a column of mercury in the sphygmomanometer.
BP facts:
- Normal blood pressure, for those not taking blood pressure medications, should be less than 120/80.
- Your blood pressure recording is not always the same. When you are exercising or excited, your blood pressure goes up. If you are at rest, your blood pressure will be lower. This is a normal response to changes in activity or emotion. Age, medications, and changes in position can also affect blood pressure.
- One high blood pressure reading does not mean you have high blood pressure. It is necessary to measure your blood pressure at different times, while resting, to find out if your typical blood pressure reading.
Illustrations of the heart
The heart and blood vessels
- Large red vessel = the aorta; large artery that carries blood from of the left ventricle to the arteries of the body
- Large blue vessel = vena cava (includes the superior and inferior vena cava); large vein that empties blood into the right atrium of the heart.
- How does blood travel through your body?
Learn more about Prevention Topics:
Cholesterol
High Blood Pressure
Integrative- Healing Heart Therapies
Weight Management
Diabetes
Evaluation of Risk Factors
Stress & Emotion
Women & Prevention
more
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