Red blood cell synthesised by the kidney. Just before and after leaving the bone marrow, the developing cells are known as reticulocytes; these constitute about 1% of circulating red blood cells. The functional lifetime of a red blood cell is about 100–120 days, during which time the red blood cells are continually moved by the blood flow push (in arteries), pull (in veins) and a combination of the two as they squeeze through microvessels such as capillaries. They are also recycled in the bone marrow. The aging red blood cell undergoes changes in its plasma membrane, making it susceptible to selective recognition by
Great arteries of the aortic arch. The 5th pair of vessels only form in some cases without any known contribution to the final structure of the great arteries. The right 6th almost completely regresses with only the proximal part contributing to the base of the pulmonary arteries, while the left 6th forms the ductus arteriosus, which disappears after birth. Abnormalities in the development of the great arteries during embryonic development may lead to congenital cardiovascular defects, such as: Some of these defects can be asymptomatic and cause no complications in patients, with others being more severe and require immediate surgery right after