The cardiovascular system consists of the heart and blood vessels. The heart is hollow and located in the thorax, protected by the pericardium. It pumps blood through the circulatory system via contraction and relaxation in a cardiac cycle. Blood flow is regulated by arteries, veins and capillaries which allow for gas and nutrient exchange. Blood pressure and flow are influenced by many factors including the heart, blood properties and vessel dynamics.

1. Cardiovascular System

2. Heart Structure
• Hollow
• Located within the mediastinum of the thorax.
• Base is attached to several large blood vessels.
• Distal end extends downward and to the left
forming a blunt apex at the fifth intercostal
space.

3. Pericardium or
pericardial sac covers
the heart.

5. The inner layer of the pericardium is called the visceral pericardium (epicardium)
which covers the heart.
The parietal pericardium forms the inner lining of the fibrous pericardium.
The fibrous pericardium is tough and composed of mostly connective tissue.
Between the layers is the pericardial cavity which has pericardial fluid that
lubricates the membranes to reduce friction when the heart moves.

6. The heart consists of three different layers

10. Mitral Valve Closed

11. Mitral Valve Open

12. Semilunar Valve Function

13. Tricuspid Valve
Chordae Tendineae

14. Pulmonary
and
Systemic
Bloodflow

16. Circumflex artery – supplies the blood to the walls of the left atrium and left
ventricle.
Left anterior descending artery – supplies the walls of both ventricles.
Posterior interventricular artery – supplies the walls of both ventricles.
Marginal artery – supplies the walls of the right atrium and right ventricle.

17. Heart Actions
• Atrial systole is when the atria contract while
the ventricles relax which is called ventricular
diastole.
• Thus systolic and diastolic blood pressure.
• This series of contraction and relaxation is
called a cardiac cycle.

18. Cardiac Cycle

19. Heart Sounds
• “Lubb” heart sound occurs during the
ventricular contraction when the A-V valves
are closing.
• “Dubb” heart sound occurs during ventricular
relaxation when the pulmonary and aortic
valves are closing.
• A heart murmur is when the heart valves fail
to close completely causing leakage.

20. Sinoatrial Node
AtrioVentricular Node
Atrioventricular Bundle
Purkinje Fibers
Heart Conduction System

26. Sympathetic & Parasympathetic
Nervous Systems
• Physical exercise, body temperature, and
concentration of various ions affect heartbeat.
• Branches of sympathetic and parasympathetic nerve
fibers innervate the S-A and A-V nodes.
• Parasympathetic impulses decrease heart action,
sympathetic increases heart action.
• Cardiac center in the medulla oblongata regulates
autonomic impulses to the heart.

28. Effects of K+ & Ca2+
• Potassium and calcium are two ions that
influence heart action and are the most
important.
• Potassium affects the electrical potential of the
cell membrane.
• Calcium ions are needed more for cardiac muscles

29. Conditions
• Hyperkalemia (excessive potassium ions) decreases
the rate and force of cardiac contractions.
• Very high amounts may block cardiac impulses.
• Hypokalemia is low potassium and can cause an
abnormal arrhythmia.
• Hypercalcemia increases heart action causing a
prolonged contraction.
• Hypocalcemia depresses heart action.

30. Arteries are strong, elastic
vessels adapted for carrying
blood away from the heart
under high pressure.
Three distinct layers:
Endothelium – Inner most
layer. Rich in elastic and
collagenous fibers. Called the
tunica interna.
Middle layer – Tunica media.
Smooth muscle fibers, thick
layer of elastic connective
tissue.
Outer layer – Tunica externa.
Attaches the artery to tissues.
Contains vasa vasorum that gives
Rise to capillaries

31. • Vasomotor fibers stimulate smooth muscle to contract, thus
reducing the diameter of the vessel.
• This is called vasoconstriction.
• Vasodilation changes the diameter of the vessel that
influences the blood flow and pressure.
• Arterioles are microscopic continuations of arteries that give
off branches called metarterioles that join capillaries.
• If arteries are cut they spurt blood due to the high pressure of
the heart.

32. Venules are microscopic vessels
That continue from capillaries into
To form veins.
Veins have valves and are
Pushed back if blood begins
To back up in a vein.
Valves aid in the return of
Blood to the heart.
Arterial blood loss will cause
a sympathetic nerve impulse
to stimulate vein walls to
return more blood to the
heart to maintain blood
pressure.

33. Capillaries exchanges nutrients, gases, and metabolic by-products between the
Capillary blood and tissue fluid.
Diffusion provides the most important means of transport. The pathways depend
on lipid solubilities.
Filtration causes a net outward movement of fluid at the arteriolar end of a
capillary.
Osmosis causes a net inward movement of fluid at the venular end of a capillary.
Plasma proteins generally stay in the blood.

35. Blood Pressure
• Arterial blood pressure is produced by heart action; it rises
and falls with phases of the cardiac cycle.
• Systolic pressure occurs when the ventricle contracts;
diastolic pressure occurs when the ventricle relaxes.
• Heart action, blood volume, resistance to flow and blood
viscosity influence arterial blood pressure.
• Blood pressure is controlled by cardiac output.
• The more blood that enters the ventricle the greater the
stroke volume and the greater the cardiac output.

36. Venous Blood Flow
• Not a direct result of heart action.
• Skeletal muscle contraction, breathing
movements and vasoconstriction influence
the flow.
• Venous constriction can increase venous
pressure and blood flow.