Cardiovascular Organization and the Heart

Circulatory Circuits

Pulmonary circuit - carries blood to and from the lungs

Systemic circuit - carries blood to and from the rest of the body

Pulmonary Arteries - carry blood away from the heart to the lungs

Pulmonary Veins - carry blood from the lungs to the heart

Systemic Arteries - carry blood from heart to other organs

Systemic veins - carry blood from other organs to the heart

Lymphatic vessels - carry lymph from tissues to systemic veins

 

Microcirculation

Interstitial space - space between cells and between cells and the smallest blood vessels (the capillaries)

Interstitial fluid - fluid surrounding cells of tisues

fluid moves between blood and the interstitial space, and between the interstitial space and cells

Blood Capillaries

thin walled vessels between the smallest arteries and veins where exchange of oxygen, nutrients, wastes and other substances occurs between the blood and the interstitial fluid.

Lymphatic Capillaries

recovers plasma lost from the blood capillaries for return to the systemic venous circulation (lymphatic system also collects, captures and destroys pathogens in the body)

 

Relationship between the Heart and Blood Vessels

Right atrium - receives blood from the systemic circuit via the Inferior and Superior Vena Cava

Right ventricle - discharges blood into pulmonary circuit via the Pulmonary Trunk and Pulmonary Arteries

Left atrium - receives blood from the pulmonary circuit via the Pulmonary Veins

Left ventricle - discharges blood into systemic circuit via the Aorta

Right atrioventricular valve - controls movement of blood between the right atrium and right ventricle (tricuspid valve)

Pulmonary semilunar valve - controls movement of blood between the right ventricle and the pulmonary circuit

Left atrioventricular valve - controls movement of blood between the left atrium and the left ventricle (bicuspid valve, mitral valve)

Aortic semilunar valve - controls movement of blood between the left ventricle and the systemic circuit

The Heart as a Pump

Cardiac cycle - period between one heart beat and the next

Systole - during contraction

Diastole - during relaxation

Blood moves from one chamber to the next only if the pressure in the first chamber exceeds that in the second.

Atrial Relaxation

leads to a decrease in atrial pressures.

As the atrial pressures become less than the venous pressures, blood moves from the veins to the atria.

Ventricular Relaxation

leads to a rapid decrease in ventricular pressure.

As the ventricular pressures become less than the arterial pressures, the semilunar valves close.

As the ventricular pressures become less than the atrial pressures, the atrioventricular valves open and blood moves from the atria to the ventricles.

The diastolic pressure differences between the atria and the ventricles leads to about 70% of ventricular filling.

Atrial Contraction

leads to a rapid increase in atrial pressures.

As the atrial pressures increase, more blood moves from the atria to the ventricles

Ventricular Contraction

leads to a rapid increase in ventricular pressure

As the ventricular pressures exceed the atrial pressures, the atrioventricular valves close.

As the ventricular pressures exceed the arterial pressures, the semilunar valves open and blood moves to the arteries.

 

David G. Ward, Ph.D.  Last modified by wardd 23 May, 2006