<unk> s <unk> s), also referred to as<unk> <unk> s,<unk>  blood corpuscles (in humans or other animals not having nucleus in<unk> s), haematids, erythroid<unk> s or erythrocytes (from Greek erythros for "red" and kytos for "hollow vessel", with -cyte translated as "cell" in modern usage), are the most common type of blood<unk>  and the vertebrate's principal means of delivering oxygen (O2) to the body tissues—via blood flow through the circulatory system.<unk> s take up oxygen in the lungs, or in fish the gills, and release it into tissues while squeezing through the body's capillaries. The cytoplasm of a<unk>  is rich in hemoglobin, an iron-containing biomolecule that can bind oxygen and is responsible for the<unk>  color of the<unk> s and the blood. Each human<unk>  contains approximately 270 million hemoglobin molecules. The<unk>  membrane is composed of proteins and lipids, and this structure provides properties essential for physiological<unk>  function such as deformability and stability of the blood<unk>  while traversing the circulatory system and specifically the capillary network. In humans, mature<unk> s are flexible biconcave disks. They lack a<unk>  nucleus and organelles, to accommodate maximum space for hemoglobin; they can be viewed as sacks of hemoglobin, with a plasma membrane as the sack. Approximately 2.4 million new erythrocytes are produced per second in human adults. The<unk> s develop in the bone marrow and circulate for about 100–120 days in the body before their components are recycled by macrophages. Each circulation takes about 60 seconds (one minute). Approximately 84% of the<unk> s in the human body are 20–30 trillion<unk> s. Nearly half of the blood's volume (40% to 45%) is<unk> s. Packed<unk> s (pRBC) are<unk> s that have been donated, processed, and stored in a blood bank for blood transfusion.
Red blood cell
Agranulocyte
Blood cell
Monocyte
White blood cell
Thymocyte
Podocyte
Lymphoblast