1- Paleozoic era
2- mesozoic era
3- Cenozoic era
The superior vena cava is located in the upper chest region and is formed by the joining of the brachiocephalic veins. These veins drain blood from the upper body regions including the head, neck, and chest. It is bordered by heart structures such as the aorta and pulmonary artery.
The superior vena cava (and inferior vena cava) are veins that return deoxygenated blood from circulation in the body and empty it into the right atrium.
Live in crowded, unsanitary conditions
Answer:
selectively permeable
Explanation:
cell memebranes conteol the flow of butrients in and out of the cell, this meaning that they can keep some out of the cell. they SELECT what goes in and out.
