These granules, composed of proteins and lipids, make their first appearance by age 20 and increase gradually, so that by age 80 they may occupy as much as 5–10 percent of the volume of a muscle fibre.
The heart also shows a gradual reduction in performance with advancing age.
This occurs because of the formation of collagen, a primary constituent of connective tissue, and between adjacent collagen fibres.
These changes in blood vessels occur even in the absence of the deposits on the arterial wall characteristic of While both systolic and diastolic blood pressures (blood pressures at contraction and dilation of the heart, respectively) increase with age, the rate of systolic increase exceeds that of diastolic so that the pulse pressure widens.
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