Ch 20 – The Heart

Anatomy I. Size- clenched fist II. Location A. in the mediastinum- area between the lungs B. inside a sac named the pericardium 1. pericardium has layers a. fibrous b. parietal c. visceral -also forms the outer layer of the heart called epicardium

Anatomy III. Description of heart A. Hollow, muscular Outer layer- epicardium Middle layer- myocardium Inside layer- endocardium

Anatomy 1. Atria(um)- Top B. 4 chambered 1. Atria(um)- Top a. Right- blood from the body cells via the systemic system - enters via vena cava b. Left- blood from the lungs via the pulmonary system - enters via pulmonary veins 2. Ventricles -bottom a. Right- blood exits to the lungs - via pulmonary arteries b. Left- blood exits to all other body parts - so there is a thick muscular wall - exits heart via aorta

C. Summary-human heart is a double pump having two separated sides 1. Right receives deoxygenated blood and sends it to the lungs. 2. Left receives oxygenated blood and sends it to the body.

Anatomy D. Evidence of Walls 1. External a. Coronary sulcus- fills with fat 2. Internal= septa a. Interatrial- thin muscle Fossa ovalis- hole that shows connection of atria in fetus b. Interventricular- thick muscle

Anatomy F. Valves- connect chambers 1. Atrioventricular valves; a. Right= tricuspid valve b. Left-= Mitral valve (bicuspid) 2. Opening and closing – a. controlled by papillary muscles on ventricular walls b. Attach to cusps of valves via chordae tendineae (heart strings) c. make “lub” sound when closing

G. Valves –connect to bl.v leading out of heart -make “dub” sound when closing 1. pulmonary (semilunar) valve- between right ventricle and pulmonary artery 2. aortic (semilunar) valve -between left ventricle and aorta -Color Plate # 49, and 50

IV. Coronary Circulation A. Coronary Arteries- branch off aorta and take oxygenated bl. to heart tissue 1. corona = crown 2. right and left coronary arteries

IV. Coronary Circulation 3. Clinical considerations a. ischemia- reduced coronary circulation due to plaque, can lead to… b. angina- pain in chest c. thrombosis- clot Treated w/- catheters, angioplasty, CABG See page 667-668 and discuss.

IV. Coronary Circulation B. Cardiac Veins- return deoxygenated bl. collected in heart tissue via great cardiac vein to coronary sinus 1. Sinus a. on posterior side b. between right atrium and vena cava C. Color plate #52

V. Heartbeat A. Involves 2 cell types 1. Contractile Cells a. propel bl. b. 99% of heart c. respond to action potential d. invol. e. striated (z lines) f. branched w/ intercalated discs g. all together act like 1 giant cell called synctium 2. Specialized Cells of Conducting System 1. control and coordinate contractile cells

VI. Cardiac Conduction- A. heart beats out of body! Intrinsic- has its own system of stimulating muscle cells 1.Sinoatrial node- SA node a. called pacemaker b. initiates the heart beat c. in rt. atrial muscle 2.Internodal Fiber bundles a. carries impulse to next node thru conduction cells in atria

VI. Cardiac Conduction- 3.Atrioventricular Node a. located b/t/w rt. atrium & ventricle b. impulse delays here(due to smaller diameter) to give atria time to completely contract 4. Atrioventricular bundle a.also called Bundle of His b. carries impulse to ventricular muscle walls via. Interventricular septum c. @ bottom impulse branches out 5. Purkinje Fibers a. spread impulse through ventricle b. cause muscle cells to contact *See plate 51

Sequence the following parts of the conduction system from impulse generation to ventricular contraction AV node, perkinje fibers, internodal tracts, interventricular fibers, SA node

VII. Cardiac Cycle A. Repeated contractions B. 2 main parts 1. Systole- contraction a. bl. pushed out of chamber b. top # in B.P. 2. Diastole- relaxation a. bl. fills chamber b. bottom # in B.P.

VIII. Impulse Conduction A. measured w/ electrocardiograph 1. reading is electrocardiogram ECG or EKG 2. see plate 51 3. x axis= time Y axis= depolarization B. Basic Features 1. P wave- depolarization of atria 2. QRS complex- depolarization of ventricle 3. T wave- repolarization of ventricles C. Other features 1. QT interval- vent. Contraction + relaxation +atria relax 2. ST interval- time to repolarize ventricles

D. Arthymias- abnormal cardiac activity 1. bradycardia- slow 2. tachycardia- fast - Due to a. damage to myocardium b. pacemaker damage c. drugs d. electrolyte imbalance

IX. Calculating Cardiac output A. Cardiac Output- Vol. of bl. pumped from heart in one min B. Stroke Volume- Amt of bl. fr. 1 ventricle in 1 heart beat C. Calculate Cardiac Output Stroke vol. X beats/min=C.O.