Cardiovascular system

The heart has four chambers: right and left atria and right and left ventricles. The atria are receiving chambers that pump blood into the ventricles (the discharging chambers). The wall of each heart chamber consists of three layers Endocardium Myocardium Epicardium

Borders and surfaces

Anterior surface of heart Superior vena cava Aorta Pulmonary trunk Anterior interventricular sulcus Right atrium Right ventricle Left ventricle Atrioventricular sulcus Inferior vena cava

The apex of the heart Is formed by the inferolateral part of the left ventricle. Lies posterior to the left 5th intercostal space in adults, usually approximately 9 cm (a hand's breadth) from the median plane.

Anterior (sternocostal) surface, formed mainly by the right ventricle. Right pulmonary surface, formed mainly by the right atrium. Left pulmonary surface, formed mainly by the left ventricle; it forms the cardiac impression of the left lung.

Posterior surface of heart Atrioventricular sulcus Aorta Superior vena cava Left pulmonary veins Pulmonary trunk Right Pulmonary veins Left Atrium Atrioventricular sulcus Left ventricle Right atrium Inferior vena cava Right ventricle

Borders of the heart

Right border formed by the right atrium and extending between the SVC and the IVC. Inferior border formed mainly by the right ventricle and slightly by the left ventricle. Left border formed mainly by the left ventricle and slightly by the left auricle. Superior border, formed by the right and left atria and auricles in an anterior view;

Right atrium It is separated from the left atrium by the interatrial septum. The right atrium is composed of two main parts, a smooth posterior portion and a rough walled anterior portion. The large smooth part presents the following orifices : 1- The inferior vena cava: Opens into the lower posterior part. It brings blood from the lower limbs and abdomen to the right atrium. 2- The superior vena cava: Opens into the upper posterior part. It brings blood from head, neck, upper limbs and thorax. 3- Tricuspid valve: It connects the right atrium with the right ventricle. It is guarded by three cups. 4- The coronary sinus: It conveys venous blood from the heart wall to the right atrium.

Left atrium The left atrium forms the greater part of the base of the heart. It wall presents a smooth surface except for a small rough part (the left auricle) which lies to the left and in front of the pulmonary trunk. The left atrium shows the following orifices: 1- The four pulmonary veins two from each lung. 2- The mitral valve connects the left atrium with the left ventricle

Right ventricle It is separated from the left ventricle by interventricular septum. Its wall is muscular and is thicker than the atrial wall. The pulmonary trunk arises from the right ventricle and divides into two pulmonary arteries one to each lung. There are three papillary muscles attached to the wall of the ventricle. From the apices of the papillary muscles, fibrous cords (chorda tendinae) pass to the cusps of the tricuspid valve.

Left ventricle: The left ventricle is longer than the right ventricle and forms the apex of the heart. Its wall is nearly three times thicker than the right. The ascending aorta arises from it. Its cavity presents two papillary muscles which are attached to the two cusps of the mitral valve by chorda tendinae.

circulation

Conducting system of the heart: The conducting system of the heart consists of modified cardiac muscle fibers which are responsible for initiation and maintenance of cardiac rhythm. The conducting system is formed of: 1- Sino-atrial node (SAN). 2- Atrioventricular node (AVN). 3- Atrioventricular bundle (AVB).

The aorta and its main branches :  The ascending aorta arises from the left ventricle. It gives two coronary arteries, right and left. The coronary arteries supply the heart.  Ascending aorta arches to give the aortic arch. The aortic arch gives 3 arteries: 1- Brachiocephalic artery which gives the right subclavian and right common carotid arteries. 2- Left common carotid artery. 3-Left subclavian artery.