Your question makes no sense - The amniotic sac is the sac in which a foetus develops and is filled with amniotic fluid.
This therefore has nothing to do with the heart or cell division rates.
Most of the myocardium is composed of cardiac myocytes.
Cardiac muscle is a striated, involuntary muscle. Cardiac muscle cells usually contain 1 or 2 nuclei.
Cardiac muscle
The heart is made mostly of cardiac muscle.
The cardiac muscle is arranged spirally around the heart to make it more efficient.
I think it's smooth muscle, which makes up the heart.
Basically, yes. All muscle (skeletal, cardiac and smooth) are made of muscle fibers.
cardiac
It consists of a maximum of 2 nuclei per fiber so no it can't be considered multinucleated. Only skeletal is multinuke.
Smooth cardiac muscle.
cardiac muscle cells are joined by intercalated disks.
Cardiac muscle is involuntary striated muscle. The cells of cardiac muscle have only one nucleus. The layer of the heart that contains cardiac muscle is called the myocardium.
Most of the myocardium is composed of cardiac myocytes.
cardiac muscles/involuntary muscle
cardiac muscle is striated cardiac muscle is not voluntary
Cardiac muscle.
Cardiac muscle forms the muscular wall of the heart. Cardiac muscle is involuntary muscle.