1. The Cardiovascular System: The Heart

2. Structure and Organization
Structure & Organization
Location
Between the lungs in the thoracic cavity
2/3 of mass to the left of midline
Size: about the same as your closed fist
Pointed end (apex) rests on diaphragm
Wide end (base) is superior to the apex

4. Figure 15.01 Position of the Heart and Associated Blood Vessels in Thoracic Cavity

5. Cardiac Muscle Tissue Cardiac Muscle Unique features Properties
Intercalated disks – thick connections between fibers
Properties
Forms 2 networks: atrial and ventricular
Each network works as a single functional unit
Long contraction (10-15x longer than skeletal muscle)
Long refractory period – no tetanus

6. Figure 15.02 Pericardium and Heart Wall

7. Chambers
Chambers
Left and Right Atria – 2 superior “receiving” chambers
Interatrial septum – tissue between the atria
Auricles – wrinkled structure on anterior side of atria; increase atrial capacity.
Left and Right Ventricles – 2 larger inferior chambers
Interventricular septum – tissue between the ventricles

9. Major Vessels Major Blood Vessels Veins – carry blood to the heart
Superior vena cava – carries deoxygenated blood from above the heart
Inferior vena cava – carries deoxygenated blood from below the heart
Coronary sinus – carries deoxygenated blood from the heart itself
Pulmonary veins – carries oxygenated blood from the lungs
Arteries – carry blood away from the heart
Pulmonary trunk – splits into right & left pulmonary arteries; carries deoxygenated blood to the lungs
Aorta – carries oxygenated blood to the rest of the body.
Coronary arteries – carry blood to the heart itself

10. Figure 15.03a Structure of the Heart – Anterior External View

11. Figure 15.03b Structure of the Heart – Posterior External View

12. AV Valves Valves (one-way)
Atrioventricular (AV) valves Atria to Ventricles
Tricuspid valve – 3 cusps; right atrium to right ventricle
Bicuspid (mitral) valve – 2 cusps; left atrium to left ventricle
Papillary muscles contract to keep valves from blowing out under pressure.

13. Cow Heart – Internal Anatomy

14. Semilunar Valves Semilunar valves  ventricles to Lungs/Aorta
Pulmonary valve – right ventricle to the lungs
Aortic valve – left ventricle to the aorta
Pressure of the ventricular contraction open valves
Blood flowing back towards the heart fills cup-like cusps, closing valves.
Valve order: Tricuspid, Pulmonary, Bicuspid, Aortic
“Try Pulmonary before you Buy Aoric”

15. Figure 15.03c Structure of the Heart – Anterior View

16. Figure 15.04 Atrioventricular (AV) Valves

17. Blood Flow Blood flow through the heart From high to low pressure
R. Atrium → R. Ventricle → Pulmonary trunk → Lungs → Pulmonary veins → L. Atrium →L. Ventricle → Aorta

18. Figure 15.05 Blood Flow Through the Heart

20. The Cardiac Cycle Cardiac Cycle
All of the events associated with 1 heart beat
Systole: Contraction
Diastole: Relaxation
1 Cardiac cycle = 1 atrial systole & diastole + 1 ventricular systole & diastole

21. Figure Cardiac Cycle

22. Sounds Heart sounds “Lubb” “Dupp” Normal beat: Lubb-Dupp-Pause
First, longer sound
AV valves closing during ventricular systole
“Dupp”
Second, shorter, sharper sound
Semilunar valves closing at the end of ventricular systole
Normal beat: Lubb-Dupp-Pause
Heart murmur – abnormal rushing/gurgling heart noise, usually indicates a valve disorder

26. AP Conduction Action Potential Conduction
Pacemaker: about 1% of cardiac muscle cells initiate APs, setting the heart rhythm.
Conduction system: the route for sending APs throughout the heart.

27. Conduction System Steps
The sinoatrial (SA) node initiates the AP and spreads it through the atria, causing them to contract together.
The AP reaches the atrioventricular (AV) node, which slows the AP down.
The AP travels to the AV bundle (bundle of His) and is conducted to the ventricles.
The AP travels through the right and left bundle branches toward the apex.
AP travels quickly through Purkinje fibers from the apex through the ventricles; the ventricles then contract together.

28. Figure 15.06 conduction System of the Heart

29. Electrical Conduction System

30. Variations Pacemaker variations Normally the SA node
Capable of up to 100 beats/min (bpm)
Usually about 75 bpm at rest
Diseased/damaged SA node…
AV node takes over (40-60 bpm)
AV bundle or bundle branch (20-35 bpm) can take over for AV node…but aren’t fast enough
Ectopic pacemakers – other cardiac muscle becomes the pacemaker, disrupting heart beat. Artificial pacemaker is then needed.

31. Electrocardiogram Electrocardiogram (ECG or EKG)
A recording of the electrical changes accompanying a heart beat.
3 waves
P wave: atrial depolarization
QRS complex: ventricular depolarization
T wave: ventricular repolarization
Depolarization occurs just before contraction; atrial repolarization is masked by the QRS complex.

32. Figure 15.07 Normal ECG of a Single Heartbeat

33. Phases of the Cardiac Cycle
Relaxation
All 4 chambers in diastole
Repolarization of the ventricles (T wave)
AV valves open; 75% of ventricle filling occurs
Atrial systole
AP from SA node causes atrial depolarization (P wave)
Last 25% of blood enters ventricles
AV valves open; semilunar valves closed
Ventricular systole: ventricles contract
Ventricular depolarization (QRS complex) & contraction
AV valves close; semilunar valves open

34. Cardiac Output Cardiac Output (CO) A measure of cardiac efficiency
CO = stroke volume x heart rate
Stroke volume (SV) = amount of blood pumped into the aorta during contraction
Example
CO = 75 mL/beat x 70 beats/min
CO = 5250 mL/min
CO = 5.25 L/min

35. Disorders Heart Disorders Coronary Artery Disease
Atherosclerosis – blockage of arteries
Myocardial ischemia – insufficient blood supply to the myocardium
Angina pectoris – pain caused by myocardial ischemia
Myocardial infarction (heart attack) – blockage of coronary arteries leading to myocardial cell death

36. Disorders Congenital Defects Arrhythmias
Atrial septal defect (ASD) – foramen ovale fails to close
Ventricular septal defect (VSD) – incomplete closure of septum
Valvular stenosus – narrowing of a valve
Arrhythmias
Atrial fibrillation – uncoordinated atrial contraction
Ventricular fibrillation – uncoordinated ventricular contraction; may result in death