Anemia

Anemia is a group of conditions that occurs when there is a reduced number of healthy functional red blood cells or RBCs in the blood.

Now, RBCs are primarily responsible for carrying and delivering oxygen to the body's tissues. They are produced through erythropoiesis which occurs within the bone marrow under the direction of erythropoietin.

A hormone produced in the kidneys. Here, stem cells called pro erythroblasts.

Differentiate into erythroblasts. A type of immature RBC that synthesizes hemoglobin.

Hemoglobin is a protein that binds and carries oxygen and is made up of four polypeptide chains called globins, which consist of two alpha and two beta chains.

Each chain contains a heme group which includes an iron atom where oxygen can bind one oxygen molecule can bind to each protein chain allowing one hemoglobin molecule to carry up to four oxygen molecules.

And each RBC can contain 100s of hemoglobin molecules. Eventually, erythroblasts differentiate into reticulocytes.

Another type of immature RBC. The bone marrow releases reticulocytes into the bloodstream where they ultimately become mature rbcs, which are called erythrocytes.

Erythrocytes are especially effective in gas exchange due to their flexible biconcave shape which makes them able to fit through narrow blood vessels while increasing surface area to conduct gas exchange.

Now, anemia can result from underproduction, increased destruction or excessive loss of RBC S. First underproduction can occur if the kidneys don't produce enough erythropoietin, which can happen in chronic kidney disease without enough erythropoietin stimulating the bone marrow, not enough rbcs are produced.

Also if there's not enough building blocks to support erythropoiesis such as iron, vitamin B12 and folate less fully functional rbcs can be produced.

So for example, lack of iron can lead to iron deficiency anemia. Additionally, if the bone marrow is damaged from conditions like autoimmune disorders or certain types of cancer.

Erythropoiesis can be inhibited. For instance, an autoimmune disorder may cause the immune system to attack bone marrow.

So it's unable to produce new blood cells resulting in aplastic anemia. Next destruction or hemolysis of RBCs occurs when rbcs are broken down faster than theyre produced.

This is seen with inherited conditions like sickle cell anemia where a genetic mutation alters hemoglobin leading to rbcs that are inflexible, sickled and short lived rbcs can also be destroyed by certain medications like penicillin or methyldopa infections like malaria, autoimmune disorders, like systemic lupus, erythematosus or lupus or physical damage by medical devices like mechanical heart valves.

Lastly, anemia can occur from acute blood loss because of trauma, injury or surgery and from chronic blood loss from conditions like a gastric ulcer.

Risk factors for anemia include nutritional deficiencies, presence of chronic disease, family history of anemia, older age and pregnancy.

Now, regardless of the mechanism, if there are not enough healthy rbcs in circulation, oxygen carrying capacity is reduced and tissue hypoxia results when this happens, there are several compensatory mechanisms.

The body can initiate to help increase the supply of oxygen to the tissues to expand the volume of fluid in circulation.

Interstitial fluid can move into the bloodstream in the kidneys. The renin angiotensin aldosterone system is activated causing salt and water retention, which results in increased blood volume.

Also an increased heart rate and cardiac output can boost circulation of blood to vital organs like the heart and brain.

And there may even be selective shunting of blood to these organs in the short term to help them perfuse as long as possible.

In addition, hypoxia induced dilation of capillaries, arterioles and venules increases the flow of blood through these vessels.

Lastly, an increased rate and depth of respiration and increased release of oxygen from hemoglobin can make more oxygen available to the tissues.

Clinical manifestations occur as a result of tissue hypoxia and depend on the severity and type of anemia. In general, with mild cases of anemia, individuals can be asymptomatic.

However, others may experience fatigue, weakness, headache, dizziness, confusion, and dyspnea and their vital signs may reflect tachycardia and tachypnea.

Skin and mucous membranes are often pale due to reduced hemoglobin. And if hemolysis is present, the end products of RBC destruction may cause jaundice or yellowing of the skin and mucous membranes.

In severe cases, heart murmurs, chest pain and even heart failure may occur. All right.

As a quick recap anemia is a group of conditions that occurs when there's a reduced number of healthy functional red blood cells.

In the blood mechanisms that lead to anemia include underproduction, destruction and blood loss. Common clinical manifestations are related to tissue hypoxia and can include weakness, fatigue, headache, dizziness and dyspnea.