Regarding the structure and types of circulation, which statements are true?
a. The heart is protected by a double-walled membranous bag, the pericardium.
b. The bicuspid valve is also known as the mitral valve and is on the right side of the heart.
c. Purkinje fibres are minute fibres distributed throughout the atrial musculature.
d. The SAN is called the pacemaker and is located in the left atrium.
e. Open circulatory system is present in arthropods and molluscs.
f. Incomplete double circulation, where mixed blood is pumped out, is seen in amphibians and reptiles (except crocodiles).
g. Double circulation involves two separate pathways: pulmonary and systemic.
