PLMS 3

The _______ is the major structure of the circulatory system.

• brain

• heart

• lungs

• blood

The heart is surrounded by a thin fluid-filled sac called the ________.

• muscular organ

• pericardium

• Arteries

• Capillaries

The thin outer layer of the heart

The right and left chambers are separated from each other by partitions called _____

The middle muscle layer of the heart is called _____.

The thin inner layer of the heart is called _____.

The upper chambers on each side of the heart are called ______

The lower chambers on each side of the heart are called ______

The valves at the entrance to the ventricles are called _____

The valves at the exit to the ventricles are called _____