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).
Capillaries. Capillaries, the smallest and most numerous of the blood vessels, form the connection between the vessels that carry blood away from the heart (arteries) and the vessels that return blood to the heart (veins).The primary function of capillaries is the exchange of materials between the blood and tissue cells.apillaries. Capillaries, the smallest and most numerous of the blood vessels, form the connection between the vessels that carry blood away from the heart (arteries) and the vessels that return blood to the heart (veins).