In capillaries, the outer tunics of smooth muscle cells are absent and only the endothelium is present. Capillaries are often invested in pericapillary contractile cells called pericytes. The layer of endothelial cells is a type of epithelium and is bounded at its outer surface by a basement membrane.
Answer:
High pressure systems entail sinking air, while lows entail rising air. High pressure systems form where air converges in the higher levels of the atmosphere. The converging air has nowhere to go and is forced to sink toward the ground. ... In contrast, low pressure systems form where air near the ground converges.
Explanation:
Hope this helps :)
Genetic variation can be caused by mutation. Hope this helped. ;)
Answer 4th sentence Hope this helps