Chapter 18: Anatomy of the Cardiovascular System Summary: Anatomy of the Heart is: 4 chambers 4 valves 4 great vessels 3 layered covering 3 layered wall 3 circuits

The Heart is a muscular PUMP with 4 Chambers (size and shape of a fist) with 4 Chambers The upper chambers ( R atrium, L atrium ) are for receiving Blood The lower chambers (R Ventricle, L Ventricle) are for pumping blood LA Right Atrium Left Atrium Right Ventricle Left Ventricle RA RV LV

Right and Left Atria separated by the membranous ATRIAL SEPTUM Located in the MEDIASTINUM of the THORACIC CAVITY, between the Right and Left Lungs, posterior to the body of STERNUM, Anterior to Thoracic Vertebrae 5-8. Sits atop the diaphragm Right and Left Atria separated by the membranous ATRIAL SEPTUM (valves separate RA/RV, LA/LV) Ventricles separated by the muscular INTERVENTRICULAR SEPTUM RA LA --- -- --- -- -- - --- --- --- RV LV

4 CARDIAC VALVES important in regulating the filling & flowing The Heart has 4 valves, important in regulating the filling & flowing of the chambers of the blood TRICUSPID VALVE (Right Atrium / Right Ventricle) MITRAL VALVE (Left Atrium / Left Ventricle) PULMONIC VALVE (right Ventricle / Pulmonary trunk {artery} ) AORTIC VALVE (Left Ventricle / Aorta)

LA LV RV The Atrioventricular valves (tricuspid and mitral) The Pulmonic and the Aortic Valves are semilunar valves, Each with three billowy, pocket-like leaflets The Atrioventricular valves (tricuspid and mitral) are composed of flat flaps (cusps), are connected to the interior ventricular walls via Connective tissue chords -- (CHORDAE TENDONAE), and PAPILLARY MUSCLES. Pulmonic valve Aortic valve LA RA Mitral valve LV Chordae tendonae Tricuspid valve RV Papillary muscle Chordae tendonae

Auricles of Right and Left Atria On both the Right & the Left Atrium, there is an ear-like extension called the Auricle these are visible on the external surface of the heart: Auricle of right atrium RA Auricle of right atrium RV Left ventricle Apex of the heart

The HEART and GREAT VESSELS Each of the 4 cardiac chambers is associated with Major Blood vessel/s: (entering or exiting) Right Atrium : (in) Superior & Inferior Vena Cavae Right ventricle: Pulmonary Trunk (R & L pulm. arteries) (out) Left Atrium: (in) Pulmonary veins Left Ventricle: Aorta

R & L Pulmonary arteries Superior Vena Cava Aorta Pulmonary Trunk: R & L Pulmonary arteries Superior Vena Cava Aorta (Anterior view) Pulmonary veins Ventricles make up most of volume of heart. The right ventricle forms most of the heart’s anterior surface. The left ventricle forms most of the posterior/inferior surface. Inferior Vena Cava (more on these to follow) Note: red oxygenated, blue unoxygenated blood

vena cavae, aortic arch, pulmonary trunk, pulmonary veins To remember great vessels: in order VC, AA, PT, PV

Heart: posterior view

Triple layered Covering of the heart: PERICARDIAL SAC Heart coverings protect against friction Fibrous Pericardium: the thick, tough outer sac, which is lined By the Serous Pericardium: a thin, moist double membrane, the parietal layer, which lines the fibrous pericardium, and the visceral layer, which adheres to & covers the heart, it is also known as THE EPICARDIUM

Serous pericardium (two-layered) Coverings of the Heart Fibrous pericardium Serous pericardium (two-layered) Parietal layer lines fibrous pericardium Visceral layer (epicardium) forms outermost part of heart wall Fibrous pericardium composed of dense connective tissue & functions to: Protect the heart. Anchor heart to surrounding structures. Prevent overfilling of heart with blood. Serous pericardium is a two-layered serous membrane (secretes serous fluid) Pericarditis? Inflammation of the pericardium. Hinders production of serous fluid & roughens serous membrane surfaces. Over time may lead to adhesions that impede heart activity. In severe cases may cause cardiac tamponade. Cardiac tamponade – heart is compressed by fluid (inflammatory fluid that seeps into the pericardial cavity). Treatment – drain off excess fluid.

3 Layers of the heart wall Epicardium: thin , moist - is the visceral pericardial membrane MYOCARDIUM - the Heart Muscle, the left ventricular wall is three times as thick as the right ventricle ENDOCARDIUM - the inner lining, made up of single layer of ENDOTHELIUM, ( endothelium also lines the blood vessels of the entire CVS)

Ventricles ( FYI ) Two lower chambers known as pumping chambers because, upon contraction, they push blood into the large network of vessels Ventricular myocardium is thicker than the atrial myocardium because great force must be generated to pump the blood a large distance, against systemic resistance. Myocardium of left ventricle is thicker than the right for same reasons – distance and increased resistance.

2 3 CIRCUITS B. SYSTEMIC CIRCUIT: A. PULMONARY CIRCUIT: Right heart: unoxygenated blood from SVC & IVC Right Atrium >>> Right Ventricle>>> Pulmonary Trunk Right and left Pulmonary arteries, into the LUNGS, for gases exchange; then to Heart via Pulm veins B. SYSTEMIC CIRCUIT: Left heart: oxygenated blood from PULM Veins Left atrium >>> Left Ventricle >>> Aorta , and the systemic arterial, capillary, venous network C. CORONARY CIRCULATION: blood flow to the heart

Right side of heart is pulmonary circuit pump ***Flow of Blood Through Heart*** Right side of heart is pulmonary circuit pump Left side of heart is systemic circuit pump right atrium (tricuspid valve) -> right ventricle (pulmonary SL valve) -> lungs -> left atrium (bicuspid (mitral) valve) -> left ventricle (aortic SL valve) -> body tissues Pulmonary circuit – blood vessels that carry blood to and from the lungs. Systemic circuit – blood vessels that carry blood to and from all body tissues.

Systemic & Pulmonary Circuits

Lung Bypasses in Fetal Heart Foramen ovale – opening between right &left atria; after birth closes to form fossa ovalis. Ductus arteriosus – connection between pulmonary trunk & aorta; closes to form ligamentum arteriosum. These 2 shunts allow blood to bypass the deflated, nonfunctional lungs. Foramen ovale & ductus arteriosus close at or shortly after birth.

CORONARY ARTERIES: BLOOD SUPPLY TO THE HEART THE FIRST BRANCHES off the AORTA, immediately superior to the Aortic valve: RIGHT CORONARY ARTERY, LEFT MAINSTEM CORONARY ARTERY, with its 2 quick branches: LEFT CIRCUMFLEX, LEFT ANTERIOR DESCENDING. Coronary blood flow actually occurs when the aortic valve cusps are closed, during back-flow; not during the powerful “systolic” pulsation of blood out of the ventricle during contraction.

(systole) (diastole)

CORONARY VEINS Veins of the coronary circulation As a rule, veins follow a course that closely parallels that of coronary arteries. After going through cardiac veins, blood enters the CORONARY SINUS to drain into the right atrium Several veins drain directly into the right atrium

posterior anterior

posterior