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Chapter 19 A&P
| Question | Answer |
|---|---|
| Heart located in | mediastinum, between lungs |
| Base | wide, superior portion of heart, large vessels attach here |
| Apex | tapered inferior end, tilts to the left |
| In adult hearts... | weighs 10 ounces, 3.5 in. wide at base, 5 in. from base to apex |
| At any age, heart is size of | fist |
| Pericardium | double-walled sac that encloses the heart |
| Functions of pericardium (2) | - Allows heart to beat without friction, provides room to expand, yet resists excessive expansion - Anchored to diaphragm inferiorly and sternum anteriorly |
| Parietal pericardium | pericardial sac |
| what is parietal pericardium made of (2) | - Superficial fibrous layer of connective tissue - Deep, thin serous layer |
| Visceral pericardium (epicardium) | Serous membrane covering heart |
| Pericardial cavity | space inside the pericardial sac filled with 15 to 30 mL of pericardial fluid |
| Pericarditis | painful inflammation of the membranes |
| Heart wall has three layers | - epicardium - myocardium - endocardium |
| Epicardium (visceral pericardium) (3) | - Serous membrane covering heart - Adipose in thick layer in some places - Coronary blood vessels travel through this layer |
| Endocardium (2) | - Smooth inner lining of heart and blood vessels - Covers the valve surfaces and is continuous with endothelium of blood vessels |
| Myocardium (2) | - Layer of cardiac muscle proportional to work load - Fibrous skeleton of the heart: |
| What is the fibrous skeleton of the heart in the myocardium layer | framework of collagenous and elastic fibers |
| What does the cardiac muscle do in the myocardium layer | Muscle spirals around heart which produces wringing motion |
| Functions of the fibrous skeleton in the myocardium layer (2) | - Provides structural support and attachment for cardiac muscle and anchor for valve tissue - Electrical insulation between atria and ventricles; important in timing and coordination of contractile activity |
| Four chambers (2) | - Right and Left atria - Right and Left ventricles |
| Right and left atria (3) | - Two superior chambers - Receive blood returning to heart - Auricles (seen on surface) enlarge chamber |
| Right and left ventricles (2) | - Two inferior chambers - Pump blood into arteries |
| Heart Anatomy (6) | - Atrioventricular (coronary) sulcus - Interventricular sulcus - Interatrial septum - Pectinate muscles - Interventricular septum - Trabeculae carneae |
| Atrioventricular (coronary) sulcus | separates atria and ventricles |
| Interventricular sulcus | overlies the interventricular septum that divides the right ventricle from the left |
| Sulci contain | coronary arteries |
| Interatrial septum | Wall that separates atria |
| Pectinate muscles | Internal ridges of myocardium in right atrium and both auricles |
| Interventricular septum | Muscular wall that separates ventricles |
| Trabeculae carneae (2) | - Internal ridges in both ventricles - May prevent ventricle walls from sticking together after contraction |
| Valves ensure one-way flow of | blood through heart |
| Types of valves (2) | - Atrioventricular (AV) valves - Semilunar valves |
| Atrioventricular (AV) valves | control blood flow between atria and ventricles |
| Right AV valve has | three cusps (tricuspid valve) |
| Left AV valve has | two cusps (mitral valve, formely 'bicuspid') |
| Chordae tendineae | cords connect AV valves to papillary muscles on floor of ventricles |
| Functions of chordae tendineae (2) | - Prevent AV valves from flipping or building into atria when ventricles contract - Each papillary muscle has 2-3 attachments to heart floor to distribute physical stress, coordinate timing of electrical conduction, and provide redundancy |
| Semilunar valves | control flow into great arteries; open and close because of blood flow and pressure |
| Pulmonary semilunar valve | in opening between right ventricle and pulmonary trunk |
| Aortic semilunar valve | in opening between left ventricle and aorta |
| Blood flow through the chambers ( first 4 steps) | 1) Blood enters right atrium from superior and inferior venae cavae 2)Blood flows through right AV valve into right ventricle 3) Right ventricle contracts, opening pulmonary valve 4) Blood flows into pulmonary trunk |
| Blood flow through the chambers (steps 5-8) | 5) Blood goes to lungs via pulmonary arteries (releases CO₂, picks up O₂) 6) Blood returns to left atrium via pulmonary veins 7) Blood flows through left AV valve into left ventricle 8) Left ventricle contracts, opening aortic valve |
| Blood flow through the chambers (steps 9-11) | 9) Blood flows into ascending aorta 10) Blood goes to body (delivers O₂, picks up CO₂) 11) Blood returns to right atrium via venae cavae |
| Types of circuits (3) | - Pulmonary circuit - Systemic circuit - Coronary circuit |
| Pulmonary circuit path and function | path: Right ventricle → Pulmonary artery → Lungs (gas exchange) → Pulmonary veins → Left atrium. function: Picks up oxygen and releases carbon dioxide. |
| Systemic circuit path and function | path: Left ventricle → Aorta → Body tissues (capillaries) → Veins → Right atrium. function: Delivers oxygen and nutrients to cells, removes waste. |
| Coronary circuit path and function | path: aorta → heart → Right Atrium function: supply the heart muscle with oxygen and nutrients |
| 5% of blood pumped by heart is pumped to the heart itself through the | coronary circulation, to sustain its strenuous workload |
| How much blood does the coronary circulation pump per minute | 250 mL |
| what does coronary circulation need | O2 and nutrients |
| Left coronary artery (LCA) branches off the | ascending aorta |
| Two branches of the left coronary artery (LCA) | - Anterior interventricular branch - Circumflex branch |
| Anterior interventricular branch | Supplies blood to both ventricles and anterior two- thirds of the interventricular septum |
| Circumflex branch (3) | - Wraps around left side in coronary sulcus - Gives off left marginal branch, ends on back of heart - Supplies left atrium and posterior left ventricle |
| Right coronary artery (RCA) branches off the | ascending aorta |
| Function of right coronary artery (RCA) and the two branches | - Supplies right atrium and sinoatrial node (pacemaker) - Right marginal branch - Posterior interventricular branch |
| Right marginal branch | Supplies lateral aspect of right atrium and ventricle |
| Posterior interventricular branch | Supplies posterior walls of ventricles |
| Flow through coronary arteries is greatest when | heart relaxes |
| Contraction of the myocardium | compresses the coronary arteries and obstructs blood flow |
| Opening of the aortic valve flap during ventricular systole | covers the openings to the coronary arteries blocking blood flow into them |
| During ventricular diastole | blood in the aorta surges back toward the heart and into the openings of the coronary arteries |
| 5% to 10% of coronary blood drains directly into | heart chambers (mostly right ventricle) by way of the thebesian veins |
| Most coronary blood returns to right atrium by way of the coronary sinus which has three main inputs | - great cardiac vein - Middle cardiac vein (posterior interventricular) - small cardiac veins |
| Great cardiac vein (3) | - Travels alongside anterior interventricular artery - Collects blood from anterior portion of heart - Empties into coronary sinus |
| Middle cardiac vein (posterior interventricular) (3) | - Found in posterior sulcus - Collects blood from posterior portion of heart - Drains into coronary sinus |
| Small cardiac vein | Empties into coronary sinus |
| Coronary sinus (2) | - Large transverse vein in coronary sulcus on posterior side of heart - Collects blood and empties into right atrium |
| Cardiac Cells Categories (2) | - Autorhythmic cells - Contractile cells |
| Autorhythmic cells (2) | - Conduction system - modified cardiac muscle cells |
| Conduction system functions (2) | - Coordinates the heartbeat - Generates and conducts rhythmic electrical signals |
| The conduction system generates and conducts rhythmic electrical signals in the following order (5) | - Sinoatrial (SA) node - Signals spread throughout atria - Atrioventricular (AV) node - Atrioventricular (AV) bundle (bundle of His) - Subendothelial conduction networks |
| Sinoatrial (SA) node | modified cardiomyocytes |
| Pacemaker initiates | each heartbeat and determines heart rate |
| Pacemaker is in | right atrium near base of superior vena cava |
| Atrioventricular (AV) node (3) | - Located near the right AV valve at lower end of interatrial septum - Electrical gateway to the ventricles - Fibrous skeleton |
| Atrioventricular (AV) bundle (bundle of His) (2) | - Bundle forks into right and left bundle branches - Branches pass through interventricular septum toward apex |
| Subendothelial conducting networks (2) | - Nerve-like processes spread throughout ventricular myocardium - Cardiomyocytes then pass signal from cell to cell through gap junctions |
| Conduction system (5) steps | 1) SA nodes fire 2) Excitation spreads through atrial myocardium 3) AV node fires 4) Excitation spreads down AV bundle (His bundle) 5) Subendothelial conducting network distributes excitation through ventricular myocardium |
| Sympathetic nerves | increase heart rate and contraction strength |
| In sympathetic nerves, fibers terminate in (5) | - SA and AV nodes - Atrial and ventricular myocardium - Aorta - Pulmonary trunk - Coronary arteries |
| Parasympathetic nerves | slow heart rate |
| In parasympathetic nerves, fibers (3) | - Fibers of right vagus nerve leads to the SA node - Fibers of left vagus nerve lead to the AV node - Little or no vagal stimulation of the myocardium |
| Electrical and Contractile Activity of the Heart, Cycle of events in heart (2) | - Systole - Diastole |
| Systole | contraction |
| Diastole | relaxation |
| Systole and diastole refer to | the action of the ventricles |
| The Cardiac Rhythm (2) | - Sinus rhythm - Ectopic focus |
| Sinus rhythm | - normal heartbeat triggered by the SA node - Adult at rest is typically 70 to 80 bpm (vagal tone) |
| Ectopic focus | - a region of spontaneous firing other than the SA node - May govern heart rhythm if SA node is damaged - Nodal rhythm |
| Nodal rhythm | if SA node is damaged, heart rate is set by AV node, 40 to 60 bpm |
| Contractile Cells (3) | - Purkinje fibers distribute the stimulus here - make up most of the muscles cells in the heart - resting potential |
| resting potential of ventricular cell and atrial cell | Ventricular cell: about -90 mV Atrial cell: about -80 mV |
| Events in an action potential in a ventricular muscle cell (3) | 1) Rapid Depolarization 2) The Plateau 3) Repolarization |
| Rapid Depolarization (Cause, Duration, Ends with) | Cause: Na+ entry Duration: 3-5 msec Ends with: Closure of voltage gated fast sodium channels |
| The Plateau (Cause, Duration, Ends with) | Cause: Ca2+ entry Duration: 175 msec Ends with: Closure of slow calcium channels |
| Repolarization (Cause, Duration, Ends with) | Cause: K+ loss Duration: 75 msec Ends with: Closure of slow potassium channels |
| Length of cardiac action potential in ventricular cell | 250-300 msec |
| Length of cardiac action potential in ventricular cell is how many times longer than skeletal msucle fiber | 30 times |
| long refractory period prevents | summation and tetany |
| SA node generate | 60–100 action potentials per minute |
| AV node generates | 40–60 action potentials per minute |
| Purkinje fibers depolarize at a rate of | 20-40 |
| Abnormal Pacemaker Function (3) | - Bradycardia - Tachycardia - Ectopic pacemaker |
| Bradycardia | abnormally slow heart rate (<60/min) |
| Tachycardia | abnormally fast heart rate (>100/min) |
| Ectopic pacemaker (4) | - Abnormal cells -Generate high rate of action potentials - Bypass conducting system - Disrupt ventricular contractions |
| Electrocardiogram (ECG or EKG) (3) | - A recording of electrical events in the heart - Obtained by electrodes at specific body locations - Abnormal patterns diagnose damage |
| Standard Electrodes (12 lead EKG) (2) | - Limb leads (total 6) - Chest leads (total 6) |
| Limb leads (2) | - standard leads: I,II,III - augmented leads: aVL, aVR, aVF |
| Chest leads | V1-V6 |
| Features of an ECG (3) | - P wave - QRS complex - T wave |
| P wave | atria depolarize |
| QRS complex | ventricles depolarize |
| T wave | Ventricle repolarize |
| Time Intervals between ECG Waves (2) | - P-R interval - Q-T interval |
| P-R interval | - From start of atrial depolarization - To start of QRS complex |
| Q-T interval | - From ventricular depolarization - To ventricular repolarization |
| There are 3 basic types of Heart block | - First degree AV block - Second-degree AV block - Third-degree AV block |
| First degree AV block | Delayed AV conduction |
| Second-degree AV block (2) | - Type 1 - Type 2 |
| Type 1 second degree AV block (2) | - also known as Wenckeback block - Gradual elongation of PR interval leading to a dropped QRS wave |
| Type 2 second degree AV block | Random or fixed ratio dropped QRS waves |
| Third degree AV block | complete heart block |
Created by:
JessicaKim1230