The hand is the most versatile part of the skeleton. It enables people to grasp and manipulate objects. The hand is comprised of the wrist (carpals), palm (metacarpals), and fingers (phalanges). There are three main nerves which travel to the hand; the median nerve, the ulnar nerve, and the radial nerve. Each of these three nerves connects with a specific part of the hand to permit movement and sensation. Intricate hand movements are achieved by using the small muscles that are contained entirely within the hand (the intrinsic muscles), and the much larger forearm muscles. The forearm muscles are connected to the bones of the hand by long tendons. Tendons and ligaments are often confused with one another. A tendon is the fibrous attachment of a muscle to a bone. A ligament is a fibrous attachment between bones.
CThe Digital Hand
The hand is the most versatile part of the skeleton. It enables people to grasp and manipulate objects. The hand is comprised of the wrist (carpals), palm (metacarpals), and fingers (phalanges). There are three main nerves which travel to the hand: the median nerve, the ulnar nerve, and the radial nerve. Each of these three nerves connects with a specific part of the hand to permit movement and sensation. Intricate hand movements are achieved by using the small muscles that are contained entirely within the hand (the intrinsic muscles), and the much larger forearm muscles. The forearm muscles are connected to the bones of the hand by long tendons. Tendons and ligaments are often confused with one another. A tendon is the fibrous attachment of a muscle to a bone. A ligament is a fibrous attachment between bones.
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The Heart
The heart is a powerful pump that beats continuously during life to circulate the blood throughout the body. The heart has four separate chambers. There are two atria to receive the blood returning to the heart, and two ventricles to pump the blood back out. Each of these four chambers has a one-way valve to ensure that blood flow is always in the forward direction. The heart is actually better described as two pumps that act in series. With each beat, the right ventricle pumps deoxygenated blood to the lungs, and the left ventricle pumps oxygenated blood to the body. The two sides of the heart are not identical, however. The left ventricle is much thicker and stronger than the right ventricle. Why is this so? It is easy to see that the right and left sides of the heart must always pump the same volume of blood. If they didn't, serious bottlenecks would develop in the circulation. However, the resistance to blood flow is much greater in the body than it is in the lungs. The left ventricle thus has to work harder and contract more forcefully to keep up with the right ventricle. This explains why the left ventricle has much thicker muscular walls than the right ventricle.
Let us follow the course of a single red blood cell in more detail as it moves through the heart. At the outset of the journey, the blood cell returns from the body via the vena cava and enters the right atrium. The right atrium contracts and pumps the blood cell across the tricuspid valve and into the right ventricle. Soon after that, the right ventricle contracts and pumps the blood cell across the pulmonic valve and into the pulmonary artery. The blood cell can then go either right or left to enter one of the lungs. While in the lungs, the blood cell unloads carbon dioxide and picks up oxygen. Next the blood cell returns to the left atrium via one of the pulmonary veins. The blood cell then crosses the mitral valve to enter the left ventricle. At this point, the left ventricle contracts forcefully to send the blood cell across the aortic valve and out into the body. After unloading its oxygen somewhere in the body, the blood cell enters a vein and returns via the vena cava to the right atrium where it can begin the cycle once again. On average, this whole journey takes about two minutes.
Red blood cells only last about 4 months before they wear out, but the heart never rests. During an average lifetime, the heart beats approximately 2.5 billion times. The heart is a very well designed pump indeed. It is more reliable and energy efficient than any pump ever created by man.
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The Heart
The heart is a powerful pump that beats continuously during life to circulate the blood throughout the body. The heart has four separate chambers. There are two atria to receive the blood returning to the heart, and two ventricles to pump the blood back out. Each of these four chambers has a one-way valve to ensure that blood flow is always in the forward direction. The heart is actually better described as two pumps that act in series. With each beat, the right ventricle pumps deoxygenated blood to the lungs, and the left ventricle pumps oxygenated blood to the body. The two sides of the heart are not identical, however. The left ventricle is much thicker and stronger than the right ventricle. Why is this so? It is easy to see that the right and left sides of the heart must always pump the same volume of blood. If they didn't, serious bottlenecks would develop in the circulation. However, the resistance to blood flow is much greater in the body than it is in the lungs. The left ventricle thus has to work harder and contract more forcefully to keep up with the right ventricle. This explains why the left ventricle has much thicker muscular walls than the right ventricle.
Let us follow the course of a single red blood cell in more detail as it moves through the heart. At the outset of the journey, the blood cell returns from the body via the vena cava and enters the right atrium. The right atrium contracts and pumps the blood cell across the tricuspid valve and into the right ventricle. Soon after that, the right ventricle contracts and pumps the blood cell across the pulmonic valve and into the pulmonary artery. The blood cell can then go either right or left to enter one of the lungs. While in the lungs, the blood cell unloads carbon dioxide and picks up oxygen. Next the blood cell returns to the left atrium via one of the pulmonary veins. The blood cell then crosses the mitral valve to enter the left ventricle. At this point, the left ventricle contracts forcefully to send the blood cell across the aortic valve and out into the body. After unloading its oxygen somewhere in the body, the blood cell enters a vein and returns via the vena cava to the right atrium where it can begin the cycle once again. On average, this whole journey takes about two minutes.
Red blood cells only last about 4 months before they wear out, but the heart never rests. During an average lifetime, the heart beats approximately 2.5 billion times. The heart is a very well designed pump indeed. It is more reliable and energy efficient than any pump ever created by man.
│ Index
Welcome to the Body Adventure index. Just click on a letter to access a subject of interest. It is also possible to go directly to a subject by typing the word at any time.
┌ 3-D Body Adventure
Click directly on the rotataing body to bring up either the heart or the digital hand. Zoom inside the heart.
In the full 3-D Body Adventure, there are are dozens of models and hundreds of screens to learn from.
┌ 3-D Body Adventure
Click directly on the rotataing body to bring up either the heart or the digital hand. Zoom inside the heart.
In the full 3-D Body Adventure, there are are dozens of models and hundreds of screens to learn from.
