what is special about tissue present in the heart?

What is the special feature present in a human heart which does not allow mixing of blood when oxygen-rich and carbon dioxide-rich blood reach the heart?

Pigment tissue is present in

Read the following statements ( A-C ) about the human heart : A. The SA node is a specialized mass of cardiac tissue present in the lower-left corner of the right atrium close to the AV septum. B. The body has the ability to alter the heart rate, cardiac output but not stroke volume. C. The end of the T- wave in ECG marks the end of the systole. How Many statements is /are correct from the above?

Collenchyma tissue is present in

Tissue present only in dicot plants is

What kind of muscle fibre is present in the heart /

Transfusion tissue is present in the leaves of