Ch 20 – The Heart

Anatomy

I. Size- clenched fistII. Location

A. in the mediastinum- area between the lungs B. inside a sac named the pericardium1. pericardium has layersa. fibrousb. parietalc. 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

B. 4 chambered1. Atria(um)- Top

a. Right- blood from the body cells via the systemic system

- enters via vena cavab. Left- blood from the lungs via the pulmonary

system- enters via pulmonary veins

2. Ventricles -bottoma. Right- blood exits to the lungs- via pulmonary arteriesb. 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.

AnatomyD. Evidence of Walls1. Externala. Coronary sulcus- fills with

fat2. Internal= septaa. 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 valveb. Left-= Mitral valve

(bicuspid)2. Opening and closing –

a. controlled by papillary muscles on ventricular wallsb. 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 chestc. thrombosis- clot

Treated w/- catheters, angioplasty, CABGSee 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. HeartbeatA. Involves 2 cell types

1. Contractile Cellsa. propel bl.b. 99% of heartc. respond to action potentiald. invol.e. striated (z lines)f. branched w/ intercalated discsg. all together act like 1 giant cell called

synctium2. 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 cells1.Sinoatrial node- SA node

a. called pacemakerb. initiates the heart beatc. 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 & ventricleb. impulse delays here(due to smaller diameter) to give atria time to completely contract

4. Atrioventricular bundlea.also called Bundle of Hisb. carries impulse to ventricular muscle walls via. Interventricular septumc. @ bottom impulse branches out

5. Purkinje Fibersa. spread impulse through ventricleb. 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 contractionsB. 2 main parts

1. Systole- contraction a. bl. pushed out of chamber b. top # in B.P.2. Diastole- relaxationa. bl. fills chamberb. 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.