The Heart OBJECTIVES:

OBJECTIVES Structure of the Heart Heart Valves Pathway of Blood Through the Heart Cardiac Muscle Tissue Blood Supply to the Heart Disorders of the Heart

Location and Orientation within the Thorax Heart – typically weighs 250–350 grams (healthy heart) Largest organ of the mediastinum Located between the lungs Apex lies to the left of the midline Base is the broad posterior surface(facing toward left shoulder)

Location and Orientation within the Thorax Figure 18.2

Structure of the Heart – Coverings Figure 18.3

Structure of the Heart – Coverings Pericardium – two primary layers Fibrous pericardium Strong layer of dense connective tissue Serous pericardium Formed from two layers Parietal pericardium Visceral pericardium

Structure of Heart Wall Left ventricle – three times thicker than right Exerts more pumping force Flattens right ventricle into a crescent shape Figure 18.7

Structure of the Heart – Layers of the Heart Wall Figure 18.4 This muscle arrangement is very efficient to squeeze out all of the blood

The Heart A muscular double pump (left and right) Pulmonary circuit (right side) – takes blood to and from the lungs Systemic circuit (left side) – vessels transport blood to and from body tissues Atria – receive blood from the pulmonary and systemic circuits Ventricles – the pumping chambers of the heart

The Pulmonary and Systemic Circuits Figure 18.1 This is very sylized!

Four “Corners” of the Heart Superior right At costal cartilage of third rib and sternum Inferior right At costal cartilage of sixth rib lateral to the sternum Superior left At costal cartilage of second rib lateral to the sternum Inferior left Lies in the fifth intercostal space at the midclavicular line

Heart Chambers Right and left atria Superior chambers Right and left ventricles Inferior chambers Internal divisions Interventricular septa Interatrial septa External markings Coronary sulcus posterior interventricular sulcus

Heart Chambers Figure 18.5b Must know all of this!

Right Atrium Forms right border of heart Receives blood from systemic circuit Pectinate muscles Ridges inside anterior of right atrium-associated with auricle Crista terminalis Landmark used to locate veins entering right atrium Fossa ovalis Depression in interatrial septum Remnant of foramen ovale

Right Ventricle Receives blood from right atrium through the tricuspid valve Pumps blood into pulmonary circuit via Pulmonary trunk Internal walls of right ventricle Trabeculae carneae Papillary muscles Chordae tendineae

Left Atrium Makes up heart’s posterior surface Receives oxygen-rich blood from lungs Opens into the left ventricle through Mitral valve (left atrioventricular valve)

Left Ventricle Forms apex of the heart Internal walls of left ventricle Trabeculae carneae Papillary muscles Chordae tendineae Pumps blood through systemic circuit via Aortic semilunar valve (aortic valve)

Heart Chambers Figure 18.5e Must know all of this!

Posterior View of the Heart Figure 18.5d Must know all of this!

Blood Flow Through the Heart Figure 18.6

Heartbeat 70 – 80 beats per minute at rest Systole – contraction of a heart chamber Diastole – expansion of a heart chamber Systole and diastole also refer to Stage of heartbeat when ventricles contract and expand

Heart Valves – Valve Structure Each valve composed of Endocardium with connective tissue core Atrioventricular (AV) valves Between atria and ventricles Aortic and pulmonary valves At junction of ventricles and great arteries

Fibrous Skeleton Surrounds all four valves Composed of dense connective tissue Functions Anchors valve cusps Prevents overdilation of valve openings Main point of insertion for cardiac muscle Blocks direct spread of electrical impulses

Heart Valves – Valve Structure Figure 18.8a

Function of the Atrioventricular Valves Figure 18.9a

Function of the Atrioventricular Valves Figure 18.9b

Function of the Semilunar Valves Figure 18.10a, b

Microscopic Anatomy of Cardiac Muscle Figure 18.12a, b

Cardiac Muscle Tissue Figure 18.12c, d

Cardiac Muscle Tissue Not all cardiac cells are innervated Will contract in rhythmic manner without innervation Inherent rhythmicity Is the basis for rhythmic heartbeat

Conducting System Cardiac muscle tissue has intrinsic ability to Generate and conduct impulses Conducting system A series of specialized cardiac muscle cells Sinoatrial (SA) node sets the inherent rate of contraction (overrides autorhythmicity)

Conducting System Figure 18.14

Innervation Heart rate is altered by external controls Nerves to the heart include Visceral sensory fibers Parasympathetic branches of the vagus nerve Sympathetic fibers – from cervical and upper thoracic chain ganglia Figure 18.15

Heart Sounds “Lub-dup” – sound of valves closing First sound “lub” The AV valves closing Second sound “dup” The semilunar valves closing

Heart Sounds Each valve sound – best heard near a different heart corner Pulmonary valve – superior left corner Aortic valve – superior right corner Mitral (bicuspid) valve– at the apex Tricuspid valve – inferior right corner

Heart Sounds Figure 18.11

Blood Supply to the Heart Functional blood supply Coronary arteries Arise from the aorta Located in the coronary sulcus Main branches Left and right coronary arteries

Blood Supply to the Heart Figure Know all of these!

Disorders of the Heart Coronary artery disease Atherosclerosis – fatty deposits Angina pectoris – chest pain Myocardial infarction – blocked coronary artery Heart attack Silent ischemia – no pain or warning

Disorders of the Heart Heart failure Progressive weakening of the heart Cannot meet the body’s demands for oxygenated blood Congestive heart failure (CHF) Heart enlarges Pumping efficiency declines Cor pulmonale Enlargement and potential failure of right ventricle