Red blood cell

Red blood cells (RBCs), referred to as erythrocytes (from <a href="/facts/Ancient_Greek_language/LIK7NlUh">Ancient Greek</a> erythros 'red' and kytos 'hollow vessel', with -cyte translated as 'cell' in modern usage) in academia and medical publishing, also known as red cells, erythroid cells, and rarely haematids, are the most common type of <a href="/facts/Blood_cell/lf9GA0Dj">blood cell</a> and the <a href="/facts/Vertebrate/tT54FSTT">vertebrate</a>'s principal means of delivering <a href="/facts/Oxygen/acyn6o8r">oxygen</a> (O2) to the body <a href="/facts/Tissue_(biology)/H7CpML7A">tissues</a>—via blood flow through the <a href="/facts/Circulatory_system/WXwudzzc">circulatory system</a>. Erythrocytes take up oxygen in the <a href="/facts/Lung/gTWXI6Fj">lungs</a>, or in fish the <a href="/facts/Gill/FWgM3Jp8">gills</a>, and release it into tissues while squeezing through the body's <a href="/facts/Capillary/4BIzKJAe">capillaries</a>.
The <a href="/facts/Cytoplasm/Wa0sE6xf">cytoplasm</a> of a red blood cell is rich in <a href="/facts/Hemoglobin/RsD1MzYA">hemoglobin</a> (Hb), an <a href="/facts/Iron/QK1JYy8E">iron</a>-containing <a href="/facts/Biomolecule/DGvFzN7R">biomolecule</a> that can bind oxygen and is responsible for the red color of the cells and the blood. Each human red blood cell contains approximately 270 million hemoglobin molecules. The <a href="/facts/Cell_membrane/vAXSD0DT">cell membrane</a> is composed of <a href="/facts/Proteins/Jxmagu3E">proteins</a> and <a href="/facts/Lipids/TdQR87HX">lipids</a>, and this structure provides properties essential for physiological <a href="/facts/Cell_(biology)/bLM9UQvy">cell</a> function such as <a href="/facts/Erythrocyte_deformability/nffVDPfN">deformability</a> and <a href="/facts/Erythrocyte_fragility/GaBDunQM">stability</a> of the blood cell while traversing the circulatory system and specifically the <a href="/facts/Capillary/4BIzKJAe">capillary</a> network.
In humans, mature red blood cells are flexible <a href="/facts/Biconcave_disk/JnQ2AwCV">biconcave disks</a>. They lack a <a href="/facts/Cell_nucleus/D7sFRa3c">cell nucleus</a> (which is expelled during <a href="/facts/Erythropoiesis/HFUbNYAf">development</a>) and <a href="/facts/Organelle/vhDFnGbs">organelles</a>, to accommodate maximum space for hemoglobin; they can be viewed as sacks of hemoglobin, with a <a href="/facts/Lipid_bilayer/CQKQ9l3g">plasma membrane</a> as the sack. Approximately 2.4 million new erythrocytes are produced per second in human adults. The cells develop in the <a href="/facts/Bone_marrow/4dfudk0H">bone marrow</a> and circulate for about 100–120 days in the body before their components are recycled by <a href="/facts/Macrophage/z7hkQu3o">macrophages</a>. Each circulation takes about 60 seconds (one minute). Approximately 84% of the cells in the human body are the 20–30 trillion red blood cells. Nearly half of the blood's volume (<a href="/facts/Hematocrit/wg1UalUh">40% to 45%</a>) is red blood cells.
<a href="/facts/Packed_red_blood_cells/PlmjsB1A">Packed red blood cells</a> are red blood cells that have been donated, processed, and stored in a <a href="/facts/Blood_bank/c3uLSVVc">blood bank</a> for <a href="/facts/Blood_transfusion/fb0Mk6Dx">blood transfusion</a>.

Red blood cell open-in-new

Red blood cell