Answer:
It is both a barrier keeping unwanted things out, and a gate for nutrients to be brought in.
Answer:
millions of years
Explanation:
Takes a long time to form, so millions of years.
<h2>Blood is forced upward and toward</h2>
Explanation:
- In the cardiovascular cycle, the autonomous withdrawal and unwinding of heart cells are facilitated through the movement of the heart's characteristic conduction framework and by cell-to-cell correspondence by means of the hole intersections in the myocardial cells themselves.
- The natural conduction arrangement of the heart comprises of nodal tissue, whose specific cells have both apprehensive and solid qualities. Nodal tissue is restricted in explicit areas of the heart.