1

1

Chapter 15 Cardiovascular System

2

Size of Heart

Average Size of Heart •  14 cm long •  9 cm wide

3

Location of Heart

• Hollow, cone-shaped muscular pump • posterior to sternum •  medial to lungs •  anterior to vertebral column •  base lies beneath 2nd rib •  apex at 5th intercostal space •  lies upon diaphragm

2

4

Coverings of Heart

• Pericardium - covering that encloses the heart and the proximal ends of the large blood vessels to which it attaches • Fibrous pericardium • Visceral pericardium • Parietal pericardium

5

Wall of the Heart

6

Wall of the Heart

3

7

Heart Chambers

Right Atrium •  receives blood from

•  inferior vena cava •  superior vena cava •  coronary sinus

Left Atrium •  receives blood from pulmonary veins

Right Ventricle •  receives blood from right atrium

Left Ventricle •  receives blood from left atrium

Interatrial and interventricular steptum • Separates the heart into left and right halves

8

Heart Valves

9

Heart Valves

Tricuspid Valve Pulmonary and Aortic Valve

4

10

Skeleton of Heart •  fibrous rings to which the heart valves are attached

11

Path of Blood Through the Heart

12

Blood Supply to Heart

5

13

Angiogram of Coronary Arteries

14

Heart Actions

Atrial Systole/Ventricular Diastole Atrial Diastole/Ventricular Systole

15

Cardiac Cycle

Atrial Systole/Ventricular Diastole

•  blood flows passively into ventricles •  remaining 30% of blood pushed into ventricles •  A-V valves open/semilunar valves close •  ventricles relaxed •  ventricular pressure increases

6

16

Cardiac Cycle Ventricular Systole/Atrial diastole

•  A-V valves close •  chordae tendinae prevent cusps of valves from bulging too far into atria •  atria relaxed •  blood flows into atria •  ventricular pressure increases and opens semilunar valves •  blood flows into pulmonary trunk and aorta

17

Heart Sounds

Lubb •  first heart sound •  occurs during ventricular systole •  A-V valves closing

Dubb •  second heart sound •  occurs during ventricular diastole •  pulmonary and aortic semilunar valves closing

Murmur – abnormal heart sound

18

Heart Sounds

7

19

Cardiac Muscle Fibers

Cardiac muscle fibers form a functional syncytium

•  group of cells that function as a unit •  atrial syncytium •  ventricular syncytium

20

Cardiac Conduction System

21

Cardiac Conduction System

8

22

Electrocardiogram

•  recording of electrical changes that occur in the myocardium •  used to assess heart’s ability to conduct impulses

P wave – atrial depolarization QRS wave – ventricular depolarization T wave – ventricular repolarization

23

Electrocardiogram

24

Cardiac Cycle

9

25

Blood Vessels

•  arteries •  carry blood away from ventricles of heart

•  arterioles •  receive blood from arteries •  carry blood to capillaries

•  capillaries •  sites of exchange of substances between blood and body cells

•  venules •  receive blood from capillaries

•  veins •  carry blood toward ventricle of heart

26

Arteries and Arterioles

Artery •  thick strong wall •  endothelial lining •  middle layer of smooth muscle and elastic tissue •  outer layer of connective tissue •  carries blood under relatively high pressure

Arterioles •  thinner wall than artery •  endothelial lining •  some smooth muscle tissue •  small amount of connective tissue •  helps control blood flow into a capillary

27

Walls of Artery and Vein

10

28

Arteriole

•  smallest arterioles only have a few smooth muscle fibers •  capillaries lack muscle fibers

29

Metarteriole

connects arteriole directly to venule

30

Capillaries •  smallest diameter blood vessels •  extensions of inner lining of arterioles •  walls are endothelium only •  semipermeable •  sinusoids – leaky capillaries

11

31

Capillary Network

32

Regulation of Capillary Blood Flow

Precapillary sphincters

•  may close a capillary •  respond to needs of the cells •  low oxygen and nutrients cause sphincter to relax

33

Exchange in the Capillaries •  water and other substances leave capillaries because of net outward pressure at the capillaries’ arteriolar ends •  water enters capillaries’ venular ends because of a net inward pressure •  substances move in and out along the length of the capillaries according to their respective concentration gradients

12

34

Venules and Veins

Venule •  thinner wall than arteriole •  less smooth muscle and elastic tissue than arteriole

Vein •  thinner wall than artery •  three layers to wall but middle layer is poorly developed •  some have flaplike valves •  carries blood under relatively low pressure •  serves as blood reservoir

35

Venous Valves

36

Characteristics of Blood Vessels

13

37

Blood Volumes in Vessels

38

Arterial Blood Pressure

Blood Pressure – force the blood exerts against the inner walls of the blood vessels

Arterial Blood Pressure •  rises when ventricles contract •  falls when ventricles relax •  systolic pressure – maximum pressure •  diastolic pressure – minimum pressure

39

Pulse •  alternate expanding and recoiling of the arterial wall that can be felt

14

40

Factors That Influence Arterial Blood Pressure

41

Venous Blood Flow

•  not a direct result of heart action •  dependent on

•  skeletal muscle contraction •  breathing •  venoconstriction

42

Pulmonary Circuit

•  consists of vessels that carry blood from the heart to the lungs and back to the heart

15

43

Systemic Circuit

•  composed of vessels that lead from the heart to all body parts (except the lungs) and back to the heart •  includes the aorta and its branches •  includes the system of veins that return blood to the right atrium

44

Life-Span Changes •  cholesterol deposition in blood vessels •  heart enlargement •  death of cardiac muscle cells •  increase in fibrous connective tissue of the heart

•  increase in adipose tissue of the heart •  increase in blood pressure

•  decrease in resting heart rate

45

Clinical Application Arrhythmias

Ventricular fibrillation •  rapid, uncoordinated depolarization of ventricles

Tachycardia •  rapid heartbeat

Atrial flutter •  rapid rate of atrial depolarization

16

46

Clinical Application Atherosclerosis

• Caused by build of plaque on the walls of the arteries • Factors that lead to plaque build up

• Lack of exercise • Poor diet (high in saturated fats and cholesterol) • Smoking • Stress • Genetics

Blood Clots

• Thrombus-blood clot • Embolus • Stroke • Myocardial infarction