medical Definition of organelle : a specialized cellular part (as a mitochondrion or nucleus) that has a specific function and is considered analogous to an organ Learn More about organelle
RBCs take up oxygen in the lungs or gills and release it into tissues while squeezing through the body's capillaries. The cytoplasm of erythrocytes is rich in hemoglobin, an iron-containing biomolecule that can bind oxygen and is responsible for the red color of the cells.ed blood cells are also known as RBCs, red cells, red blood corpuscles (an archaic term), haematids, erythroid cells or erythrocytes (from Greek erythros for red and kytos for hollow vessel, with-cyte translated as cell in modern usage).
The arterioles then divide further into capillaries. Capillaries are the smallest blood vessels and their walls are only one cell thick which allows diffusion between the blood and cells to occur. Nutrients and oxygen from the blood diffuses through the capillary walls into the tissues that need it. This is aided by the relatively high blood pressure that also squeezes the oxygen and nutrients through the capillary wall and into the cells of the tissue. At the same time carbon dioxide and other waste products re-enter the capillary in order to be processed and removed from the body.