NOTES: UNIT 6- The Circulatory System The Heart

The circulatory system… The cardiovascular system provides oxygen and nutrients to tissues and removes wastes.

STRUCTURE OF THE HEART Size: ● about 14 cm long and 9 cm wide Location: ● 2/3 left of midline ● below 2nd rib and rests on diaphragm Location allows for CPR

STRUCTURE OF THE HEART Heart Covering: the heart is enclosed in a double-walled sac called the pericardium (protects against friction) ● loosely fitting superficial part of the sac: fibrous pericardium ● deep to the fibrous pericardium: serous pericardium *composed of 2 layers *space between the layers = pericardial cavity (cushions and lubricates heart)

STRUCTURE OF THE HEART Heart Wall ● epicardium = outermost layer; in contact with pericardium (older people= infiltrated with FAT  ) ● myocardium = middle layer; thick, muscular (mainly cardiac muscle tissue!) ● endocardium = inner layer; has elastic and collagen fibers (lines the heart chambers)

4 Heart Chambers: (heart is divided into right and left sides) RIGHT ATRIUM receives deoxygenated blood from the superior and inferior venae cavae and coronary sinus pumps blood into the RIGHT VENTRICLE  right ventricle pumps blood out of the heart into the PULMONARY ARTERIES (take blood to the lungs)

● LEFT:  LEFT ATRIUM receives blood from the pulmonary veins (from the lungs)  pumps blood into the LEFT VENTRICLE  left ventricle pumps blood out of the heart into the AORTA (takes blood to all of the body)

Heart Valves: designed to prevent backflow of blood! ATRIOVENTRICULAR VALVES: -TRICUSPID VALVE: separates R atrium from R ventricle -BICUSPID VALVE (a.k.a. MITRAL VALVE): separates L atrium from L ventricle

● Structure of AV valves: -CHORDAE TENDINAE: strong fibrous structures that attach to the flaps of the valves -PAPILLARY MUSCLES: muscles embedded in the endocardium; attach to the chordae tendinae *serve to anchor flaps in their closed position so pressure doesn’t blow them into atria like an umbrella on a windy day Chordae tendinae Papillary muscles

-PULMONARY VALVE: separates R ventricle from pulmonary arteries SEMILUNAR VALVES: -PULMONARY VALVE: separates R ventricle from pulmonary arteries -AORTIC VALVE: separates L ventricle from aorta *ventricle contraction forces these valves open until contraction is over; blood flow backwards closes valves

Path of Blood Through the Heart: ● Blood low in oxygen and high in CO2 enters the RIGHT SIDE through the venae cavae and is then pumped into pulmonary circulation (to the lungs)

Path of Blood Through the Heart: ● After blood is oxygenated in the lungs, it returns to the LEFT SIDE through the pulmonary veins and is then pumped into systemic circulation via the aorta (to the body)

Path of Blood Flow Through the Heart Right side Deoxygenated blood enters the right atrium through the superior and inferior vena cava  right atrioventricular (tricuspid) valve  right ventricle  pulmonary semilunar valve  pulmonary artery lungs Left Side Oxygenated blood returns from the lungs through the pulmonary veins  left atrium  left atrioventricular (bicuspid, mitral) valve  left ventricle  aortic semilunar valve  aorta

Heart Blood Supply: ● The CORONARY ARTERIES supply blood to the myocardium ● Blood returns to the R atrium through the cardiac veins and coronary sinus

**500,000 Americans die per year of coronary artery disease **3.5 million Americans have coronary problems

Cardiac Cycle: *systole: contract *diastole: relax ●Ventricular filling: blood returning to heart passively flows into atria & the open AV valves ● ATRIAL SYSTOLE: atria contract (propels residual blood) while the ventricles relax (VENTRICULAR DIASTOLE) ● VENTRICULAR SYSTOLE: ventricles contract while the atria relax (ATRIAL DIASTOLE) ● all chambers relax for a brief period; cycle repeats!

Heart Poster- start Draw or trace a heart template in the middle of your paper Label the anatomy of the heart Then color code blood flow using arrows through the heart

Conduction System of the Heart The conduction system of the heart is composed of 4 structures Sinoatrial Node (SA Node) Atrioventricular Node Atrioventricular Bundle Purkinje Fibers Each of these structures is composed of modified cardiac muscle cells that only permit the rapid conduction of an impulse through the heart

Initiation of Cardiac Cycle: ● Electrical impulses originate in the SA node: stimulate the atria to contract (pacemaker) ● Impulses pass slowly to the AV node, down the AV bundle, then to the Purkinje fibers: stimulate the ventricles to contract

Animation!- click here

ELECTROCARDIOGRAM (ECG/EKG): ● records the electrical changes in the myocardium during a cardiac cycle ● the pattern has several characteristic waves: 1) P wave: depolarization wave from SA through atria 2) QRS complex: ventricular depolarization; precedes ventricle contraction 3) T wave: ventricular repolarization

Normal EKG/ECG

A 60 year old woman with 3 hours of chest pain. Acute Myocardial Infarction

A 55 year old man with 4 hours of "crushing" chest pain. Acute Myocardial Infarction

Regulation of Cardiac Cycle: ● Heartbeat is affected by: -Physical exercise -Body temperature -Concentration of ions (calcium, potassium) -Emotions

Heart Poster- finish Color code blood flow using arrows through the heart Label the 4 structures in the conduction system on your heart Use yellow highlighter to outline the flow of impulse conduction through the heart

Heart Poster- finish On the left side of the heart, create a flow chart explaining the conduction system

Heart Poster- start Draw or trace a heart template in the middle of your paper Label the anatomy of the heart Then color code blood flow using arrows through the heart Label the structures in the conduction system on your heart Use yellow highlighter to outline the flow of impulse conduction through the heart