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.
These arteries that receive blood directly from the heart-the aorta and the pulmonary artery.: These need to be elastic because: They are relatively thin compared to their diameter. When the heart contracts, and ejects blood into these arteries, the walls need to stretch to accommodate the blood surge, storing energy. The arterial hydrostatic pressure that results from ventricular contraction is the 'systolic blood pressure' (systole is greek for contract).