Cardiovascular System: Heart Structure

• The cardiovascular system (CVS) consists of the heart and blood vessels.
• Types of blood vessels: arteries, veins, and capillaries.

Heart Structure and Location

• Conical muscular pump located behind the sternum and costal cartilages.
• It extends from the 2nd to the 6th costal cartilages.
• About 2/3 lies to the left, and 1/3 to the right of the median plane.
• The heart consists of 4 chambers.
• The heart has 2 atria (right and left).
• The heart has 2 ventricles (right and left).
• It has 4 borders: upper, lower, right, and left.
• It has 4 surfaces: anterior, posterior, right, and left.
• The base of the heart is directed backward.
• The apex is directed downward and to the left.

Right Atrium

• Receives deoxygenated blood from all parts of the body through 2 large veins: the superior and inferior vena cava.
• It sends blood to the right ventricle through the right atrioventricular orifice (tricuspid valve).

Left Atrium

• Receives oxygenated blood from both lungs through 4 pulmonary veins.
• It pumps blood to the left ventricle via the left atrioventricular orifice (mitral valve).

Right Ventricle

• Sends deoxygenated blood through the pulmonary valve to the pulmonary artery.
• The pulmonary artery divides into 2 branches for each lung, where oxygenation occurs.
• The 2 ventricles are separated by the interventricular septum.

Left Ventricle

• Pumps oxygenated blood to all parts of the body through the aortic orifice (valve) to the aorta and its branches.
• The heart contains 4 valves: tricuspid, pulmonary, mitral, and aortic.
• The heart is covered by the fibrous and serous pericardium.

Blood Supply

• The heart gets its blood supply from 2 arteries: the right and left coronary arteries.
• These arteries are branches from the ascending aorta.

Ischemic Heart Disease

• Narrowing of small coronary arteries due to atherosclerosis can lead to angina pectoris.
• Occlusion of main arteries can lead to myocardial infarction (MI).
• Myocardial infarction is associated with elevated cardiac enzymes such as CK and troponin.

Surface Anatomy of the Heart

• Borders are outlined on the body's surface by 4 points.
• Point A: left 2nd costal cartilage, 4 cm from the median plane.
• Point B: right 3rd costal cartilage, 3 cm from the median plane.
• Point C: right 6th costal cartilage, 3 cm from the median plane.
• Point D: (apex of the heart) left 5th intercostal space, 9 cm from the median plane.
• Upper border: between points A and B.
• Right border: between points B and C.
• Lower border: between points C and D.
• Left border: between points D and A.

Surface Anatomy of Valves

• Pulmonary valve: behind the left border of the sternum, opposite the 3rd costal cartilage.
• Aortic valve: behind the left border of the sternum, opposite the 3rd intercostal space.
• Mitral valve: behind the left border of the sternum, opposite the 4th costal cartilage.
• Tricuspid valve: behind the body of the sternum, opposite the 4th intercostal space.

Systemic Circulation

• Begins in the left ventricle, where oxygenated blood passes through the aorta and its branches.
• Reaches all the body's tissues, enabling the exchange of gases and materials.
• Deoxygenated blood is collected by small veins, then large veins, and finally by the superior and inferior vena cava.
• The deoxygenated blood flows into the right atrium. After which, flows into the right ventricle where this circulation cycle ends and a new one starts.

Pulmonary Circulation

• Starts from the right ventricle
• Venous blood passes through the pulmonary artery and its two branches to reach both lungs.
• Exchange of gases occurs in the lungs.
• Oxygenated blood returns to the left atrium via the 4 pulmonary veins, and then to the left ventricle.
• A new cycle then occurs.

Portal Circulation

• Venous blood from the stomach, spleen, pancreas, and intestine is collected into the portal vein.
• The portal vein enters the liver (through the porta hepatis) and divides into many branches that end in liver sinusoids.
• Blood leaves the liver sinusoids via the hepatic veins, which end in the inferior vena cava, and then the right atrium.