NOTES: UNIT 6- The Circulatory System The Heart

The circulatory system… The cardiovascular system delivers 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 ● divided into right and left sides Divided by interventricular septum

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; lines the heart chambers

one-way valves to prevent “backflow” as blood moves through the heart each side is divided into an atrium and a ventricle (blood always flows from atrium to ventricle) ATRIA: chambers that receive blood returning to the heart VENTRICLES: chambers that pump blood out of the heart one-way valves to prevent “backflow” as blood moves through the heart R and L AV valves (tricuspid/bicuspid) Pulmonary & aortic semilunar valves

Left AV valve (bicuspid) Right AV valve

● Structure of AV valves: -CHORDAE TENDINAE: strong fibrous structures (“heart strings”) that attach to the flaps of the valves  hold AV valves closed while ventricles contract -PAPILLARY MUSCLES: muscles embedded in the endocardium; attach to the chordae tendineae  contract to hold valves closed *serve to anchor flaps in their closed position so pressure doesn’t blow them into atria like an umbrella on a windy day

Blood Vessels & Blood Flow ● RIGHT SIDE: RIGHT ATRIUM receives deoxygenated blood from the superior and inferior vena cava and coronary veins (sinus) pumps blood into the RIGHT VENTRICLE  right ventricle pumps blood out of the heart into the PULMONARY ARTERIES (takes blood to the lungs to get O2)

● LEFT SIDE:  LEFT ATRIUM receives oxygenated blood from the pulmonary veins (coming 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)

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

2 Types of Circulation blood leaves from right side of heart ● pulmonary circulation: to the lungs & back blood leaves from right side of heart

2 Types of Circulation: ● systemic circulation: out to the body & back blood leaves from the left side of the heart *coronary circulation: supplies the heart muscle (myocardium) shortest systemic circuit: blood branches off aorta to coronary arteries, supplies oxygen to myocardium, and then returns through coronary veins & coronary sinus to Right atrium

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

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

Let’s label!

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

Heart Poster- start Label the anatomy of the heart Then color code blood flow using arrows through the heart BLUE: deoxygenated blood RED: oxygenated blood

Conduction System of the Heart The conduction system of the heart is composed of 4 structures Sinoatrial Node (SA Node): initiates contraction; PACEMAKER Electrical message passes throughout R & L atria  atrial systole Atrioventricular Node (AV node): receives message from SA Node & slows it down for 1/10 second before passing it through AV bundle (bundle of His)

Conduction System of the Heart Atrioventricular (AV) Bundle: passes electrical impulse to Purkinje fibers on left and right sides of ventricles Purkinje Fibers: stimulates the right & left ventricles to contract together  ventricular systole

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 Color code blood flow using arrows through the heart BLUE: deoxygenated blood RED: oxygenated blood Label heart Anatomy Label the 4 structures in the conduction system on your heart Use yellow highlighter to outline the flow of impulse conduction through the heart