Archive for category Anatomy
The cardiovascular system features the heart, the blood and the blood vessels. The heart pumps blood, and the blood vessels channel and supply it across the body. Blood vessels are of three forms. The first type i.e. arteries carry blood filled up with nutrients away from the heart to all regions of the body. The blood is usually compared to a river, but the arteries are more like a river in invert. Arteries are thick-walled tubes with a spherical overlaying of yellow, elastic fibers, which possess a stuffing of muscle that absorbs the fantastic stress wave of a heartbeat and slows the blood down. This pressure can be experienced in the arm and wrist. In the end arteries separate into smaller arterioles and then into even smaller capillaries, the tiniest of all blood vessels, which make the second type of blood vessels.
One arteriole can deliver a hundred capillaries. Here, in each tissue of every organ, blood’s work is done when it gives up what the cells demand and removes the waste products that they don’t want. Now the river consideration really does apply. Capillaries join together to form small veins, the third type of blood vessels, which flow into much bigger major veins, and these deliver deoxygenated blood back to the heart. Veins, contrary to arteries, have thinner, slack walls, because the blood has lost the pressure which forced it out of the heart, so the dark, reddish-blue blood which runs through the veins on its way to the lungs oozes along very slowly on its way to be oxygenated. Back at the heart, the veins enter a particular vessel, called the pulmonary arteries, into the wall at right area of the heart. It streams along the pulmonary arteries to the lungs to get oxygen, then back to the heart’s left side to begin its voyage all-around the body once more.
The heart itself is tough muscular pumping organ that has of four chambers. It is very tough and hardly rests throughout the existence of individuals. Microscopically, the heart is made of special type of muscle fibers that are distinctive from all the muscle fibers observed in the body. These muscle fibers are known as cardiac muscles. The cardiac muscle makes the mass of the heart. On a larger point, the heart can be taken into consideration as consisting of three layers. The outermost layer is known as epicardium. The middle layer is the myocardium and the innermost layer is the endocardium. Read the rest of this entry »
Heart is a hollow muscular organ, which is somewhat pyramidal in shape. It lies within the pericardium in the mediastinum. It lies free within the pericardium except at its base where it is connected to great blood vessels.
Surfaces of heart:
Because of its shape, the heart has three surfaces: anterior, inferior and posterior. Often the surfaces are referred to as: sternocostal (anterior), diaphragmatic (inferior) and base (posterior). The apex of the heart is directed downward, forward and to the left.
* Anterior (Sternocostal) surface: It is formed mainly by the right atrium and right ventricle. They are separated from each other by the vertical atrioventricular groove. The right border of the anterior surface is formed by the right atrium while the left border is formed by left atrium and part of left auricle.
* Inferior (Diaphragmatic) surface: It is formed mainly by the right and left ventricles separated by the posterior interventricular groove. The inferior surface of the right atrium into which the inferior vena cava opens, also forms part of this surface.
* The base of the heart (posterior surface): It is formed mainly by the left atrium, into which the four pulmonary veins drain. It lies opposite to the apex. Often, the beginners think of the diaphragmatic surface of the heart as its base because of the fact that the heart rests on it, however, it should be kept in mind that the heart does not rest on its base. It rests on the diaphragmatic surface which is not the base. The posterior surface is called the base because it lies opposite to the apex of the pyramidal shaped heart.
Apex of the heart: It is formed by the left ventricle and is directed downward, forward and the left. It lies at the level of the fifth intercostals space, about 3.5 inches from the midline. The apex beat can be palpated in the region of apex of the heart.
Borders of the heart:
Because of pyramidal nature of its shape, the heart has three borders: right, left and lower. Right border is formed by the right atrium. The left border is formed by the left auricle and left ventricle. The lower border is formed by right ventricle, however, some part of it is also formed by the right atrium.
Wall of the heart:
As it was stated earlier, the heart is a hollow muscular chamber. It has strong wall that are composed of three main layers. The bulk of the wall of the heart is formed by cardiac muscles called the endocardium. On the outer side, the endocardium is covered with visceral layer of serous pericardium, known as epicardium. On the inner side, the endocardium is line with a layer of endothelium known as endocardium.
Chambers of the heart:
Human heart is not a simple hollow pump. It has been divided by vertical septa into four chambers: two atria (right and left) and two ventricles (right and left). The atria lie superior to the ventricles. In anatomic position, the right atrium lies anterior to the left atrium and the right ventricle lies anterior to the left ventricle.
It consists of two regions: the main concavity and a small outpouching called auricle. At the region of junction between these two parts, on the outer side, there is a vertical groove called sulcus terminalis, which on the inner side forms a ridge known as crista terminalis. The main part of the atrium lies posterior to crista terminalis and is derived embryologically from sinus venosus. The part of the atrium, which lies in front of crista terminalis, is roughened by bundles of muscle fibers, the musculi pectinati. This anterior part is derived embryologically from primitive atrium. Read the rest of this entry »