Human anatomy systems

Cardiovascular system

Anatomy

The human cardiovascular system consists of the heart , blood vessels and blood . The heart is located in the mediastinum on the left side of the thorax , posterior to the sternum and is divided into four chambers . Two atria (left and right ) are located superiorly in the heart , and inferior to these are the powerful left and right ventricles (Vickers . A ventricular septum divides the left and right ventricles , and the atrial septum separates left and right atria . The heart and lungs are contained within the pericardium , a membranous

sac filled with a serous fluid that serves to reduce friction during heart contractions

Physiology

Deoxygenated blood is returned from the body via the large vena cavae and enters the right atrium . During diastole , blood flows downwards through a one-way atrioventricular valve to the right ventricle Systolic heart contractions eject blood from the right ventricle into the cardio-pulmonary circuit . Blood is oxygenated in the lungs and returns to the left atrium via the pulmonary vein . Oxygen rich blood is sent to the muscular left ventricle , where it is ejected into the body during systole . Twenty major arteries carry blood into the tissues branching into smaller vessels called arterioles and capillaries . As blood in the capillaries becomes nutrient-deprived , it is collected by venules , which join to form the larger veins that transfer blood back to the heart , where the cycle begins again (Vickers

Contraction of the heart is controlled by electrical impulses (action potentials ) which are generated by the sinoatrial (SA ) node . Located superior to the right atrium , the SA node initiates impulses that cause the myocardium of the atria to contract . The impulses are propagated through bundles of nervous tissue to the atrioventricular (AV ) node . The AV node checks the integrity of the signals and passes them on to the ventricular myocardium , which then contracts . Whilst electrical impulses occur at a standard rate , hormonal changes , stress or physical demands may cause the heart rate to increase or decrease

Pathology

Since the cardiovascular system provides oxygen and nutrients to all body tissues , pathologies of the cardiovascular system are serious and have wide-reaching consequences . All the components of the cardiovascular system are subject to pathology . Congenital abnormalities , such as valvular or septal defects are relatively common and affect the structural integrity of the heart . These are often corrected surgically . Cardiac arrhythmias are a group of conditions that occur when the heartbeat is irregular , faster (tachycardia ) or slower (bradycardia ) than usual . Fibrillation occurs when the contractile units of the myocardium do not operate in synchronicity . Atrial fibrillation often indicates a serious underlying pathology , but is not typically life-threatening . By contrast , ventricular fibrillation can lead to cardiac arrest and should be treated as a medical emergency

Cardiovascular disease is the leading cause of death in the United States . The condition refers to disease of the entire cardiovascular system , however the major pathology is a chronic inflammatory response (atherosclerosis ) in the walls of the arteries . This inflammation occurs in response to the deposition of...