1. The Heart
Circulatory System

2. The Cardiovascular System
A closed system of the heart and blood vessels
The heart pumps blood
Blood vessels allow blood to circulate to all parts of the body
The function of the cardiovascular system is to deliver oxygen and nutrients and to remove carbon dioxide and other waste products

3. Closed system?
What does it mean to be a “closed system?”

4. The Heart Location: About the size of your fist In the thorax
Between the lungs
Pointed apex directed toward left hip
About the size of your fist
Less than 1 lb.

5. The Heart
Figure 11.1

6. The Heart: Coverings
Pericardium – tissue like sac surrounding the heart
A double membrane made of:
A. Visceral pericardium – thin layer of tissue that hugs the heart
B. Parietal pericardium – fibrous outer layer to protect heart
Fluid fills the space between the layers of pericardium and allows the heart to beat without friction

7. The Heart: Heart Wall 3 layers of heart tissue Epicardium
Outside layer of connective tissue
Myocardium
Middle layer made mostly of cardiac muscle
This is the layer that actually contracts
Endocardium
Thin inner layer that lines heart chambers

9. External Heart Anatomy

10. The Heart: Chambers Right and left side act as separate pumps
Atria (2) - Receiving chambers
Right atrium
Left atrium
Ventricles (2) - discharging chambers
Right ventricle
Left ventricle

11. The Heart: Associated Great Vessels
Vena cava – deoxygenated blood enters right atrium
Superior and Inferior
Pulmonary arteries – deoxygenated blood leaves right ventricle
Pulmonary veins (four) – oxygenated blood enters left atrium
Aorta – oxygenated blood leaves left ventricle

12. Blood Circulation

13. The Heart: Valves
Each of the hearts 4 chambers has its own valve
Valves allow blood to flow in only one direction
A. Atrioventricular (AV) valves – located between atria and ventricles
1. Bicuspid or mitral valve (left side) – made of two flaps of endocardium
2. Tricuspid valve (right side) – made of three flaps
B. Semilunar valves – located at the base of two large arteries leaving the ventricles
3. Pulmonary semilunar valve – made of 3 leaflets
4. Aortic semilunar valve – made of 3 leaflets

14. How they work…
AV valves are open when the heart is relaxed and blood is passively filling into the ventricles
Held in place by tendon-like cords
As the ventricles contract, they press on the blood in their chambers which closes the AV flaps
This prevents backflow into the atria
The semilunar valves then open during ventricle contraction

16. So, does the heart need its own blood for nutrients and oxygen?
We know that the heart pumps blood, but does the heart need blood for itself too?
YES! Of course it does
BUT….
Blood in the heart chambers DOES NOT nourish the myocardium (heart muscle cells)
So where does the heart get blood?

17. Cardiac Circulation
The heart has its own nourishing circulatory system
The blood supply that oxygenates and nourishes the heart is provided by:
Coronary arteries
Cardiac veins
Waste products in the blood are then emptied into the right atrium via the coronary sinus

18. The Heart: Conduction System
Intrinsic Conduction System - Heart muscle cells contract, without action potentials, in a regular, continuous way
1. Sinoatrial node (SA): group of myocytes in the right atirum that conduct AP’s
Also called the “Pacemaker” – generator of heart rhythm
2. Atrioventricular node (AV) – myocytes located at the junction between the atria and ventricle

19. Heart Contractions
Figure 11.5

20. The Heart: Conduction System
3. Bundle of His - a collection of heart muscle cells that transmits AP’s from the AV node to the bundle branches
4. Bundle branches – long muscle fibers that travel down the inner ventricular walls
5. Purkinje fibers – muscle fibers located on the lower ventricular walls that allow the ventricles to contract

21. Heart Contractions
Figure 11.5

22. Electrocardiograms (EKG/ECG)
An interpretation of the electrical activity of the heart captured and recorded by skin electrodes
Three formations:
P wave: impulse across SA node (P)
QRS complex: spread of impulse down AV node (Q), towards Bundle of His (R), down bundle branches, and around ventricles in Purkinje fibers (S)
T wave: end of electrical activity in ventricles

23. Electrocardiograms (EKG/ECG) (cont.)