Blood returning from the lungs enters:

The right AV valve is the:

Papillary muscles function to:

The ductus arteriosum allows blood to bypasses fetal lungs.

Impulses from the SA node spread through contractile myocytes through:

Sympathetic stimulation increases:

Blood vessels include all except:

Systemic circulation is provided blood from the left ventricle.

Deoxygenated blood returns to the heart via the:

A portal system involves: