Blood

There is no major changes to blood with age, but there is a reduction of red bone marrow.  This means that there is a diminished capacity for blood cell formation in the elderly.

Heart

In the absence of heart disease the heart remains essentially the same size, or diminishes slightly in size.  The is a reduction in the number and size of cardiac muscle cells with aging and an increase in fibrous tissue.

Blood Vessels

Blood vessels reduce in elasticity with age.  This is due to a reduced elastic fiber content in the wall of the arteries.