The main function of erythrocytes is to transport oxygen in the blood.
They are flat disc-shaped cells indented in the middle; this shape helps them perform the major
function in two ways: 1) The biconcave shape provides a larger surface area for the diffusion of
oxygen and 2) the thinness of the shape allows oxygen to rapidly diffuse across the exterior of
Hemoglobin is the main component which allows red blood cells to transport oxygen and
hemoglobin is only found in erythrocytes.
Hemoglobin molecule has two components: 1) The globin portion which is a protein made up of
4 highly folded polypeptide chains and 2) four iron containing non protein heme groups each of
which is bound to one polypeptide chain.
Oxygen is poorly soluble in plasma therefore the majority of oxygen is bound to hemoglobin.
Hemoglobin is red because of the combination of iron and oxygen and when it is deoxygenated
it is blue like venous blood.
Besides oxygen, hemoglobin can bind to:
H from carbonic acid, hemoglobin acts like a buffer to prevent this ion from causing big
changes in pH of the blood
Erythrocytes contain no nucleus, organelles or ribosomes because during their development the
majority of the space is taken up by hemoglobin.
Erythrocytes contain only two enzymes:
Glycolytic enzymes which are used to generate the energy required to fuel the active
transport mechanisms used to maintain the proper ionic concentration levels. They
don’t possess mitochondria so they rely on glycolysis for all their ATP.
Carbonic Anhydrase is critical for carbon dioxide transport. This enzyme converts
carbon dioxide to the bicarbonate ion which is the major form of carbon dioxide that is
Erythrocytes have a short life span and the meet their final demise in the spleen
Erythrocytes cannot divide to give rise to more erythrocytes therefore they must continually
replenished by the bone marrow Erythropoiesis. Young children have red bone marrow that
is capable of producing red blood cells however as you grow older you start to develop yellow
bone marrow that has fat deposits on them, these bone marrows are incapable of
Red bloods also give rise to leukocytes and platelets.
Low oxygen levels do not stimulate erythropoiesis by acting on the bone marrow instead it acts
on kidneys which causes them to secrete erythropoietin into the blood and this hormone stimulates red blood cell production by the bone marrow. This increases the number of
circulating red blood cells which in turn increases the oxygen carrying capacity of the blood.
Once normal oxygen levels are delivery to the kidneys then erythropoietin production is turned
When demands for red blood cells is high the bone marrow might release some immature rbcs
which are known as reticulocytes, this reticulocytes can develop into mature red blood cells
Refers to a below normal oxygen carrying capacity of the blood and it is characterized by a low
hematocrit. It is usually caused by a decreased rate of erythropoiesis, excessive losses of
erythrocytes or a deficiency in the hemoglobin content. There are six main causes of anaemia:
Pernicious-inability to absorb nutrients like B12
Haemorrhagic- caused by a loss of a lot of blood
Harmolytic- which is caused by the rupture of a lot of red blood cells. Sickle cell
The larger the bloods viscosity the larger the reduction of blood flow, so if the number of red
blood increases a lot the viscosity is created by the drag between the blood red blood cell and
the vessel wall.
Increasing hematocrit (red blood cell volume) helps by increases hemoglobin and oxygen
carrying capacity but it is also bad because it reduces the hearts ability to circulate the blood
because of the increased friction thereby decreasing the timely delivery of oxygen to tissues.
Polycythemia is characterized by too much circulating red blood cells and an elevated
hematocrit. There are two types:
Primary- is caused by a tumor like condition of the bone marrow in which erythropoiesis
proceeds at an uncontrolled rate, the excessive number of red blood cells increases the
viscosity causing the blood flow to be sluggish and it might also increase the blood
Secondary- is an adaptive mechanism which is used to improve the bloods oxygen
carrying capacity and it usually occurs in people living at high altitudes.
Relative polycythemia is when the number of red blood cells doesn’t increase it just that
they take up