The Size
A human being's heart is about the size of that human being's fist. As the body develops, the heart grows at the same rate as the fist. So an infant's heart and fist are about the same size at birth. In the womb, however, that similarity was not always true. During the first few weeks after conception, the fetal heart occupies most of the fetus' mid-section. The heartsize to bodysize ratio is nine times greater in the fetus than in the infant. During those first few weeks, the fetal heart lies high in the chest. Soon, it moves down to occupy its position in the chest cavity.
The heart you see drawn on the average Valentine is only a rough representation of the actual structure of the heart. Your heart is actually shaped more like an upside-down pear.
Source : http://www.ynhh.org/heart-and-vascular-center/heart_works.aspx?source=/cardiac/heart/index.html
The human heart is primarily a shell. There are four cavities, or open spaces, inside the heart that fill with blood. Two of these cavities are called atria. The other two are called ventricles. The two atria form the curved top of the heart. The ventricles meet at the bottom of the heart to form a pointed base which points toward the left side of your chest. The left ventricle contracts most forcefully, so you can best feel your heart pumping on the left side of your chest.
The left side of the heart houses one atrium and one ventricle. The right side of the heart houses the others. A wall, called the septum, separates the right and left sides of the heart. A valve connects each atrium to the ventricle below it. The mitral valve connects the left atrium with the left ventricle. The tricuspid valve connects the right atrium with the right ventricle.
The top of the heart connects to a few large blood vessels. The largest of these is the aorta, or main artery, which carries nutrient-rich blood away from the heart. Another important vessel is the pulmonary artery which connects the heart with the lungs as part of the pulmonary circulation system. The two largest veins that carry blood into the heart are the superior vena cava and the inferior vena cava. They are called "vena cava" because they are the "heart's veins." The superior is located near the top of the heart. The inferior is located beneath the superior.
View the structure of a preserved heart here.
How It Works
- Deoxygentated blood returning to the heart from veins all over the body flows into the right atrium via the vena cava.
- From there the blood flows into the right ventricle, which pumps it out to the lungs for oxygenation via the pulmonary vein.
- The oxygen-rich blood returns to the left atrium by the pulmonary artery.
- From there the blood flows into the left ventricle, which pumps it at high pressure into the arteries.
This entire process constitutes one heartbeat.
The pumping, or
contraction, of the left ventricle must be very powerful because that is what
keeps the blood flowing throughout the body.
The strength of the heart muscle depends on the oxygen and
nutrient supply coming via the coronary arteries.
These arteries are usually strong, elastic, and quite flexible.
http://www.fi.edu/learn/heart/
7 comments:
Good work wif the pictures and video and stuffs wakakaka
Quote "The pumping, or contraction, of the left ventricle must be very powerful because that is what keeps the blood flowing throughout the body."
Question:What diff between left and right allows left to do so?
Question: what makes the heart pump?
People usually say:
"Prevention is better than cure"
Therefore, is there anyway to prevent from having those heart problems/sickness ? (^_^)
Does cardiac muscles reach fatigue stage ?
To anonymous,
To answer your first question, the muscles in the left ventricle wall is thicker to withstand the higher pressure produced and it also has stronger muscles. This is vital as the contraction of the left ventricle pumps blood to all parts of the body (except the lungs). In contrast, the right ventricle has a much thinner wall and is less muscular as it contracts to pump blood (deoxygenated blood) from the heart to the lungs via the coronary artery.
As to your 2nd question, the cardiac muscle is myogenic (which means it contracts and relaxes without stimulation by nerve impulses). The sino-atrial node(SAN), located at the right atrial wall, acts like a pacemaker to initialize the heartbeat. The electrical impulses generated by the SAN is relayed to the atrio-ventricular node and then to the Purkinje fibres. These electrical impulses will first cause the atrium, then the ventricles to contract and pump blood to all parts of the body.
Dear Churchill, indeed prevention is better than cure. Thus, to prevent the onset of cardiovascular diseases, one should :
1). Practice a healthy lifestyle, i.e. having a balanced diet
2). Exercise regularly
3). Steer away from smoking
For further information regarding this matter, kindly refer to the posts on prevention on this blog. Thanks!
Dear JeLee,
Since the heart has to beat continuously during the lifetime of an individual, a long refractory period gives the heart "time to rest and recover" in between beats and so hence they do not get fatigued as skeletal muscles do.
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