The Circulatory System

The Anatomy of the Circulatory System

• The circulatory system includes:- Heart- Blood vessels (arteries, veins, capillaries)

- Blood

The movement of blood around the body relies heavily on the heart which acts like a pump.

The Heart• Organ made of muscle tissue• The top part is larger than the bottom part• Located between the two lungs • Protected by the rib cage

The heart has 4 chambers: 2 atria and 2 ventricles

Both atria contract at the same time to empty their contents into the ventricles which then contract at the same time to move the blood out of the heart.

• Valves control the bloodflow between each chamber.

The walls of the left ventricle are larger than those of the right because the left ventricle pumps blood around the entire body, whereas the right ventricle only pumps blood to the lungs.

The blood vessels of the heart

Superior Vena Cava:• Carries deoxygenated blood from the upper body to the right atrium.

Inferior Vena Cava:• Carries deoxygenated blood from the lower body to the right atrium.

Pulmonary Trunk:• Separates into the right and left pulmonary arteries.• Sends deoxygenated blood to the lungs

Pulmonary Veins:• Carry oxygenated blood to the left atrium.

Aorta:• Carries oxygenated blood to the arteries around the body.

**Coronary arteries supply oxygenated blood to the heart tissue and coronary veins carry deoxygenated blood back to the right ventricle**

Blood vessels of the bodyArteries:-Carry blood away from the heart’s ventricles to the arterioles.-Thick elastic walls which withstand high pressures-Aorta is the largest artery

Arterioles:Carry blood from the arteries to the capillaries.

Capillaries:-Smallest blood vessel in the body (1mm) where diffusion of oxygen, carbon dioxide,

simple nutrients and water takes place. Blood is then sent to the venules.

-White blood cells and exit and enter capillaries to destroy bacteria outside the circulatory system.

Venules:-Carry blood towards the veins.

Veins:-Carry blood towards the heart’s atriums.-not very elastic as the blood pressure is weaker than in the arteries-Contain valves to prevent blood from flowing “backwards”

Diffusion at the Capillaries

Pulmonary circulation vs. Systemic circulation

Pulmonary Circulation• Pathway of deoxygenated blood from the heart to the

lungs, where it gets rid of CO2 and is resupplied with oxygen, back to the heart.

Right Ventricle

Pulmonary Artery

Pulmonary Arterioles

Pulmonary Capillaries

Pulmonary Venules

Pulmonary Veins

Left Atrium

Systemic Circulation• Pathway of oxygenated blood from the

heart to the body cells to supply them with oxygen and nutrients, and back to the heart.

Left Ventricle

Aorta

Arteries

Arterioles

Systemic Capillaries

Venules

Veins

Inferior/Superior Vena Cava

Right Atrium

Blood Pressure• Measuring the force witch which blood pushes against the walls of

the arteries.• Unit: millimetres of mercury (mm Hg)• Measured with a sphygmomanometer

Blood pressure is at its maximum during the contraction of the ventricles (ventricular systole). When this happens, blood is rushed into the arteries which must expand.

The pressure measured during systole is called systolic pressure.

Blood pressure is at its lowest when the heart is not contracting (diastole).

The pressure measured during a lack of contraction is called diastolic pressure.

Blood pressure = Systolic pressure / Diastolic pressure

Normal Blood Pressure is 120 / 80 mm Hg