Today I bring you a few interesting images from the world of science:
I'm sure you'll agree with me when I say that the world of science is a wonderful and truly varied world indeed.
Monday, 14 February 2011
The heart is said to be myogenic, in that it is self stimulating. This is due to the cells of the sinoatrial node being designed to release electrical impulses at set intervals. These impulses spread rapidly through the heart muscle cells of the atria using gap junctions, until they reach the non-conducting connective tissues, where a 0.1 second delay occurs. During which, the atria contract, forcing blood into the ventricles and the impulses gather around the atrioventricular node. From here, impulses travel through the bundle of His to the Apex of the heart and then, move upwards and outwards through purkyne tissues, causing the ventricles to contract with force.
The non-conducting connective tissue is vital for causing the delay because it allows the atria to contract before the ventricles, ensuring the one-way flow of blood through the heart.
The heart is a muscular organ located in the upper body (chest area) with the following structural components:
- A ventricular septum separates the left and right side of the heart.
- The right ventricle supplies blood to the lungs, which are close by for oxygenation.
- The left ventricle can be two to thee times more muscular than the right, due to the need to build up sufficient pressure to overcome the resistance of systemic circulation.
- The muscle of the atria is very thin, due to the fact that these chambers do not create much pressure when pushing blood into the ventricles.
- Coronary arteries lie over the surface of the heart, carrying oxygenated blood to the heart muscle.
- Veins take blood into the atria; arteries take blood from the ventricles.
- The vena cava carries deoxygenated blood into the right atrium. The pulmonary vein carries oxygenated blood into the left atrium. From here, blood flows into the ventricles via the atrioventricular valves.
- Chordae tendineae attach to the walls of the ventricles and are kept in position by papillary muscles. These tendinous chords prevent inversion of bicuspid and tricuspid valves.
- Valves prevent the backflow of blood. Atrioventricular valves prevent the backflow of blood from the ventricles to the atria. Semilunar valves prevent blood returning to the heart as the ventricles relax.