The Heart - Anatomy

Serous pericardium

A parietal layer which adheres to the outermost layer A visceral layer ? outer surface of the heart wall

AV valves

Between the atria and the ventricles Composed of flaps (cusps) of endocardium reinforced by connective tissue Between contractions valves 'flap' open Valves attached by chordae tendineae which are anchored by the papillary muscles Chordae Tendineae prevent inversion of the valves

Pulmonary circulation

Carries deoxygenated blood from the R ventricle via the pulmonary trunk to the lungs and returns oxygenated blood through the pulmonary veins in the L atrium

Systemic Circulation

Carries oxygenated blood from the L ventricle via the aroma to the body and returns the deoxygenated blood to the RA

Left Coronary Artery

Circumflex branch supplies the left atrium and posterior wall of the left ventricle Left anterior descending (LAD) or Anterior Inter-ventricular which supplies anterior walls of both ventricles

Obstruction of coronary arteries

Complete blockage leads to tissue death ANGINA is the severe pain that accompanies temporary deficiency in oxygen in the myocardium MYOCARDIAL INFARCTION results from a prolonged blockage and death of myocardial cells Damage to the left ventricle is the most serious —> it pumps blood to the systemic circulation

Coronary Sinus

Empties into the right atrium where the deoxygenates coronary blood joins with oxygen-depleted blood from the rest of the body

3x layers of the heart

Endocardium Myocardium Pericardium

Coronary arteries

Have many connecting branches to provide detours if one is obstructed Arteries and branches lie in the visceral pericardium and penetrate the myocardium The left ventricle receives most of the blood

Location

In the thoracic cavity mediastinum Medial to the lungs Anterior to the vertebrae Posteriorly to the sternum with 2/3 of its bulk to the L). The base of the heart is tipped medially and posteriorly, while the apex is inferiorly and laterally

Myocardium

Layer of cardiac muscle Thicker in the left ventricle, as it pumps around the body Thinner in the right (—> to the lungs) Thinest in the atria

Semilunar valves

Pulmonary semilunar valves concept of 3 cusps which surround the entrance to the artery from the ventricle Half moon shape with curved surface against the wall of the pulmonary trunk When the ventricle contracts and blood is forced from the ventricle to the artery, the cusps are flattened against the wall of the artery As the ventricle relaxes and pressure inside them falls, the cusps act like pockets and fill with blood, bulge out meeting in the centre, blocking the opening completely, preventing the back flow of blood into the ventricle.

Major veins

Superior / Inferior vena cava 4x pulmonary veins Coronary sinus

Coronary Circulation

Supplies the myocardium with oxygen and nutrients and removes waste. Blood in the chambers doesn't supply the myocardium —> too thick for diffusion Right and left coronary arteries branch from the ascending aorta These are squeezed shut when the heart contracts Blood enters when the heart relaxes

Right Coronary Artery

Supplies the right atrium and nearly all of the right ventricle

Pericardium

Surrounds the heart and covers the roots of the great vessels. Composed of 2 layers: Fibrous pericardium Serous pericardium

Endocardium

Thin smooth lining of the heart. Simple squamous epithelial layer which covers the heart valves and is continuous with the blood vessels Thin layer of connective tissue underneath FUNCTION = minimise surface friction as blood flows through the heart

Heart Valve Fn

is to prevent the back flow of blood. Blood flows through the heart from areas of high pressure to areas of low pressure in a one-way system, valves operate in pairs

Fibrous Pericardium

tough connective tissues that Protects the heart Anchors it to the surrounding structures Prevents over filling