Pneumococcal infections are caused by Streptococcus pneumoniae, a gram-positive, catalase-negative organism commonly referred to as pneumococcus.
Blood pressure is a measure of the changing fluid pressure within the circulatory system. It varies. from a peak pressure produced by contraction of the left ventricle, to a low pressure, which is. maintained by closure of the aortic valve and elastic recoil of the arterial system. The peak.
Venous blood pressure changes very little during the cardiac cycle, and is low, reflecting cumulative effects of peripheral resistance (17 mm Hg in venules dropping to almost 0 mm Hg at the termini of the venae cavae). Venous return is aided by both structural modifications and functional adaptations.