*** A&p Ch. 20 Heart

Front 1

List the functions of the heart

Back 1

- generating blood pressure (blood flow)

- routing blood (pulm. & syst. circ.)

- regulating blood supply (rate & force of contraction)

Front 2

Describe the size of the human heart

Back 2

Approximately the size of a closed fist, avg. of 250g in females & 300g in males, and larger in active adults

Front 3

Describe the location of the heart

Back 3

Located in the mediastinum, between the lungs and lies inside the pericardium.

Front 4

What is the base and what is the apex

Back 4

Base: towards top, larger flat part of the heart.

Apex: bottom, blunt rounded tip of the heart, 1" midline from the left nipple.

Front 5

List the layers of the pericardium and their location

Back 5

The pericardium/pericardial sac is a double layered closed sac that surrounds the heart.

1. Fibrous pericardium: OUTER LAYER, though fibrous conn. tissue layer that prevents over distention of the heart and anchors it within the mediastinum.

2. Serous pericardium: INNER LAYER, further divided into 2 layers:

2a. Parietal pericardium: lines the fibrous pericardium.

2b. Visceral pericardium/epicardium: covers the surface of the heart. Closest to the heart.

* Pericardial cavity is between the parietal and visceral pericardia and is filled with pericardial fluid and is known for decreasing friction.

Front 6

List and describe the layers of the heart wall

Back 6

- Epicardium/visceral pericardium: (visceral layer of the epicardium) is the thin OUTER LAYER. Is called the epicardium when considered a part of the heart and called the visceral pericardium when considered a part of the pericardium.

- Myocardium: (cardiac muscle cells/responsible for hearts ability to contract) is the thick MIDDLE LAYER.

- Endocardium: (endothelial layer) is the DEEP LAYER to the myocardium. Lines heart chambers and also covers cardiac skeleton of heart valves.

Front 7

List the chambers and valves of the heart

Back 7

Chambers of the heart:

- Each atrium (left and right) has a superior chamber (2) (receiving chambers)

- Each ventricle (left and right) has a inferior chamber (2) (discharging chambers)

Valves of the heart: ensure a one way flow of blood through the heart. 2 types: Atrioventricular valves and semilunar valves.

AV valves:

- Tricuspid valve: (right AV valve) has 3 cusps.

- Bicuspid valve/mitral valve: (left AV valve) has 2 cusps.

Semilunar valves:

- Pulmonary valve: in opening between right ventricle and pulmonary trunk.

- Aortic valve: in opening between left ventricle and aorta.

Front 8

List the great vessels of the heart

Back 8

- inferior vena cava

- aorta

- pulmonary artery

- superior vena cava

- pulmonary vein

- aortic valve

- ascending aorta

- aortic arch

- descending aorta

- brachiocephalic artery

- descending thoracic artery

- venae cavae

Front 9

Compare and contrast AV valves and Semilunar valves

Back 9

AV valves: (Tricuspid and Bicuspid)

AV valves open- atrial pressure greater than ventricular pressure. The semi lunar valves are shut and blood is forced into the ventricles.

1. Blood returning to the heart fills atria, pressing against the AV valves. The increased pressure forces AV valves open.

2. As ventricles fill, AV valve flaps hang limply into ventricles.

3. Atria contract, forcing additional blood into ventricles.

AV valves closed- atrial pressure less than ventricular pressure. The semilunar valves open, forcing blood into the aorta and pulmonary artery.

1. Ventricles contract, forcing blood against AV valve cusps.

2. AV valves close

into atria.

SV valves: (Pulmonary and Aortic)

Semilunar valves open:

3. Pappilary muscles contract and chordae tendineae tighten, preventing valve flaps from everting into atria.

Semilunar valves open: As ventricles contract and intraventricular pressure rises, blood is pushed up against SV valves forcing them to open. Semilunar valves closed: As ventricles relax and interventricular pressure falls, blood flows back from arteries, filling cusps of SV valves forcing them to close.

Semilunar valves closed:

As ventricles relax and interventricular pressure falls, blood flows back from arteries, filling cusps of SV valves forcing them to close.

Front 10

Define papillary muscles, chordae tendineae, pectinate muscles and trabeculae carneae

Back 10

Pectinate muscles:

Mark the ATRIAL walls and are responsible for contraction of the atria.

Papillary muscles and Trabeculae carneae: Mark the VENTRICULAR walls and maintain opening of the ventricles. (Pressure makes them open). Are attached to the cusps of AV valves only (tricuspid/bicuspid) by

Chordae tendineae: (heart strings) Anchor valves to papillary muscles and are responsible for contraction of ventricles.

Front 11

Trace the flow of blood through the heart

Back 11

- vena cava (superior & inferior)

- right atrium

- tricuspid AV valve

- right ventricle

- pulmonary semilunar valve

- 1. pulmonary trunk, 2. Pulmonary arteries.

- Lungs (pulmonary circulation)

- pulmonary veins

- left atrium

- bicuspid/mitral AV valve

- left ventricle

- aortic semilunar valve

- aorta to coronary arteries to heart tissue (coronary circulation) to coronary sinus cardiac veins to right atrium.

Or aorta to body (systemic circulation) to vena cava (superior and inferior)

Front 12

Explain how blood is supplied to the myocardium; the function and position of coronary vessels

Back 12

- Blood is supplied to the myocardium by the left & right coronary arteries which come off the aorta & branch. Both encircle heart in the coronary sulcus.

- The function and position of coronary vessels:

The LEFT CORONARY ARTERY branches anterior into the interventricular artery & circumflex artery. Supplies interventricular septum, anterior ventricular walls, left atrium & posterior wall of left ventricle.

The RIGHT CORONARY ARTERY branches right marginal artery & posterior interventricular artery. Supplies right atrium & most of right ventricle.

Front 13

Describe the structure and function of cardiac muscle cells

Back 13

Cardiac muscle cells (Cardiomyocytes) are branching cells with one centrally located nuclei. The cells are joined to one another by intercalated discs.

Gap junctions in the intercalated discs allow APs to pass from one cardiac muscle cell to the next, thus cardiac muscles function as a UNIT.

Cardiac muscle cells are striated by Sarcomeres which are formed by myofibrils (actin & myosin).

Desmosomes stop separation during contraction by binding filaments, joining cells together.

SR and T-tubules are visible but not as numerous as in skeletal muscle.

Calcium: normal contraction depends on extracellular Ca2+.

Cardiac muscle cells rely on Aerobic respiration for ATP production. Many mitochondria in cardiac muscle cells provides ATP for contraction.

Cardiac muscle cells involve the cardiac skeleton: crisscrossing, interlacing layer of connective tissue. It anchors cardiac muscle fibers, supports great vessels and valves, as well as limits spread of APs to specific paths.

Front 14

Explain the conducting system of the heart

Back 14

1. APs originate in the SA node (pacemaker) & travel across the wall of the atrium from the SA node to the AV node.

2. APs pass through the AV node & along the atrioventricular bundle, which extends from the AV node, through the fibrous skeleton, into the interventricular septum.

3. The AV bundle divides into right & left bundle branches & APs descend to the apex of each ventricle along the bundle branches.

4. APs are carried by the purkinje fibers from the bundle branches to the ventricular walls & papillary muscles.

Front 15

What is an electrocardiogram?

Back 15

An electrocardiogram (ECG/EKG) can detect electrical currents (APs) generated by the heart, by nodal & contractile cells at a given time. Electrodes placed to measure voltage differences. Usually a 12 lead.

Front 16

Describe what is occurring in the heart during each section of an ECG trace

Back 16

3 waves:

P wave: atrial depolarization. SA node to atria. SA node fires, atria depolarize & contract. (Atrial systole begins 100msec after SA signal)

QRS complex: ventricular depolarization & atrial repolarization. (Complex shape of spike due to different thickness & shape of 2 ventricles).

T wave: ventricular repolarization & relaxation.

ST segment: ventricular systole. Entire ventricular myocardium depolarized. Plateau in myocardial AP.

P-R interval: beginning of atrial excitation to beginning of ventricular excitation.

Q-T interval: beginning of ventricular depolarization through ventricular repolarization.

Front 17

Recognize abnormal ECG traces and predict a possible cause

Back 17

Enlarged R waves: may indicate enlarged ventricles.

Elevated or depressed S-T segment: indicates cardiac ischemia.

Prolonged Q-T interval: reveals a repolarization abnormality that increases risk of ventricular arrhythmias.

Tachycardia: elevated body temp., excessive sympathetic stim., toxic conditions.

VT;Ventricular tachycardia: often assoc. w/ damage to AV node or ventricular muscle.

Atrial flutter: ectopic APs in the atria.

Atrial fibrillation: ectopic APs in the atria.

Ventricular fibrillation: ectopic APs in the ventricles.

Bradycardia: elevated SV in athlete's, excessive vagal stim., carotid sinus syndrome.

Sinus arrhythmia: cause not always known, occasionally caused by ischemia or inflammation or assoc. w/ cardiac failure.

SA node block: ischemia, tissue damage due to infarction.

AV node block: 1st, 2nd, 3rd degree. Inflammation of AV bundle, excessive vagal stim., ischemia of AV nodal fibers or compression of AV bundle.

PVCs; premature atrial contractions: excessive smoking, lack of sleep, too much caffeine, alcoholism.

PVCs; premature ventricular contractions: ectopic foci in ventricles, lack of sleep, too much caffeine, irritability, occasionally occurs w/ coronary thrombosis.