RBC Production, Function, and Morphology & Hemoglobin Function

• pluripotent stem cells in bone marrow

• erythropoietin (EPO) from the kidneys

What do RBCs originate from and what stimulates their production?

• cell size decreases

• nuclear cytoplasm ratio decreases

• chromatin becomes more condensed

• cytoplasm changes color

• loss of nucleus (becomes anucleate)

What 5 changes do red blood cells go through in maturation?

1. pronormoblast

2. basophilic normoblast

3. polychromatophilic normoblast

4. orthochromic normoblast

5. reticulocyte

6. mature red blood cell

What are the 6 maturation stages of red blood cells (from most premature to mature)?

• size: 18-20 micrometers

• NC ratio: 6:1 (big nucleus)

• chromatin: fine texture, deep violet color

• Cytoplasm: dark blue, purple

List the size, N:C ratio, and cytoplasm color for pronormoblasts.

• size: 16 micrometers

• NC ratio: 6:1 (large nucleus)

• cytoplasm: blue, with areas of clearing

List the size, N:C ratio, and cytoplasm color for basophilic normoblasts.

• size: 13 micrometers

• NC ratio: 4:1

• cytoplasm: blue, with tinges of red-orange

List the size, N:C ratio, and cytoplasm color for polychromatophilic normoblast.

• size: 8 micrometers

• NC ratio: 1:1

• cytoplasm: red-orange tinges with slight blue

• chromatin: very round and dense

List the size, N:C ratio, and cytoplasm color for orthochromic normoblasts.

• size: 8 micrometers

• appearance: large, bluish red cells, reminants of RNA visualized with methylene blue stain

List the size and appearance for reticulocytes (polychromatic macrocyte).

• Embden-Meyerhof pathway

  • produces 90% of ATP and NAD⁺

• Phosphogluconate pathway

  • provides 5-10% of ATP

• Methemoglobin reductase pathway

  • maintains iron in the ferrous state (Fe²⁺)

RBC metabolism is anaerobic

What are the 3 pathways of RBC metabolism?

• outer layer

  • made of glycolipids and glycoproteins

• middle layer

  • made of cholesterol and phospholipids

• inner layer

  • cytoskeleton

Describe the 3 layers of the RBC membrane

• size: 6-8 micrometers

• MCV: 80-100 fL

• MCHC: 32-36%

What is the normal size, MCV, and MCHC of red blood cells?

• microcytic

  • less than 6 micrometers

  • caused by iron deficiency anemia, thalassemia, sideroblastic anemia, and iron overload disorders

• macrocytic

  • larger than 9 micrometers

  • caused by vitamin B12 deficiency, folic acid deficiency, liver disease, and megaloblastic anemia

What are the two variations in size (anisocytosis) of RBCs?

• polychromasia

  • often seen when the bone marrow responds to anemic stress and releases immature cells into circulation (reticulocytes and orthochromic normoblasts)

  • appearance: gray-blue and large

• hypochromasia

  • has a larger central pallor

  • Hgb synthesis is impaired and MCHC is less than 32%

  • conditions causing: thalassemia, sideroblastic anemia, and IDA (iron def anemia)

What are the two variations in color of RBCs?

• abnormally dark and compacted cells

• MCV is nearly normal, but MCHC is greater than 32%

• results from hereditary spherocytosis or autoimmune hemolytic anemia

Describe the following abnormal cell shape: spherocytes

• two types:

  • reversible - rounded, half moon shaped (can revert back to normal RBC)

  • irreversible - crescent shaped and pointed (cannot revert back)

• those with sickle cell have the abnormal hemoglobin S, which forms tactoids (sickles) under hypoxic stress

Describe the following abnormal cell shape: sickle cells

• egg-shaped and disc-shaped (respectively)

• caused by thalassemia or megaloblastic anemia

• elliptocytes stem from abnormal spectrin (an RBC membrane protein), and in serious cases, anemia

Describe the following abnormal cell shape: ovalocytes and elliptocytes

• bull’s-eye shaped cells

• happens due to an artifact, decreased Hgb, or increased red cell surface membrane

• seen in those with IDA, hemoglobin C disease, liver disease, and a splenectomy

Describe the following abnormal cell shape: target cells

• small red cells surrounded by uneven thorn-like spikes

• found in those with liver disease, autoimmune hemolytic anemia, and LCAT deficiency

Describe the following abnormal cell shape: acanthocytes

• bite cells

• burr cells (in dehydrated patients)

• schistocytes

List 3 types of fragmented RBCs (pieces of RBC membranes)

• remnants of DNA that look like a dark purple dot inside cells

• can be seen in postsplenectomy patients when responding to anemic conditions (erythropoiesis is rushed, no spleen = no removal of abnormal cells)

What are Howell-Jolly Bodies inclusions?

• small, light purple beaded inclusions

• seen in iron loading anemias (excessive iron)

What are Pappenheimer bodies inclusions?

• composed of RNA and mitochondrial remnants

• course-looking in appearance, granular

• caused by lead intoxication or thalassemia

What are basophilic stippling inclusions?

• large cells appear bright blue due to staining

  • a dot is visible on the edge of the cell

• results from denatured hemoglobin (Hgb has become unstable)

• can only be visualized with supravital stains (such as brilliant cresyl blue)

• mostly seen in G6PD deficiency

What are Heinz bodies inclusions?

• best way of assessing bone marrow function, RBC generation, and response to anemia

• reference range:

  • 0.5% - 2.0% in adults, 2.0% - 6.0% in newborns

What is the purpose of reticulocyte counts and what is the normal reference range?

• reticulocytosis

  • elevated reticulocyte count

  • body’s response to anemic stress, accompanied by erythroid hyperplasia

• reticulocytopenia

  • decreased reticulocyte count

  • aplastic conditions

  • DECREASED RBC PRODUCTION

What is reticulocytosis and reticulocytopenia?

target cells

Which RBC morphology may form as a result of excess cholesterol on the cell’s membrane?

a decrease in hemoglobin content in red blood cells

Hypochromasia is used to define:

• heme

  • 4 atoms of iron

• globin

  • 2 pairs of globin chains made up of amino acids

What two things make up hemoglobin?

• embryonic Hgb

  • contains zeta and epsilon chains

  • Hemoglobin Gower One, Hemoglobin Gower 2, and Hemoglobin Portland

• fetal Hgb

  • 3 months of fetal development

  • hemoglobin F (contains alpha and gamma chains)

• adult Hgb

  • contains alpha and beta chains

  • adult Hgb is 95%-98% Hemoglobin A, 3%-5% Hemoglobin A₂, and <2% Hemoglobin F

What are the three types of hemoglobin synthesized in RBC production?

• carry oxygen (known as oxyhemoglobin) to tissues

• pull CO₂ away from tissues

• keep a balanced blood pH

What are the three functions of hemoglobin?

Hgb A, Hgb A₂, and Hgb F

What are the three normal adult hemoglobins?

• a substance produced via the Embden-Meyerhof pathway of RBC metabolism

• helps with oxygen affinity of hemoglobin

What is 2,3-DPG?

synthesis begins in the polychromatic normoblast stage of RBC development

What is the origin of hemoglobin?

• four heme molecules with one iron inside

• the heme is lodged in the two globin chains

Describe the structure of a hemoglobin molecule

the Hgb loses its gamma chains and instead, the amount of beta chains increase

• adult hemoglobin has a lot of alpha and beta chains

What changes occur when hemoglobin shifts from fetal Hgb to adult Hgb?

4

one oxygen for each heme

How many molecules of oxygen can one hemoglobin carry?

• in the lungs, Hgb has a high affinity for oxygen, so they become saturated (4 oxygen per Hgb)

  • Hgb become oxyhemoglobin

• Hgb carries oxygen to the tissues and unloads

• in areas where there is low concentration of oxygen, Hgb’s affinity for oxygen decreases, and increases for carbon dioxide

• Hgb picks up CO₂ and transports it to the lungs to be eliminated

Hgb can change shape depending on if it’s oxygenated or not: tense Hgb is not oxygenated, relaxed Hgb is oxygenated

How does hemoglobin deliver oxygen to tissues and eliminate carbon dioxide?

• right

  • Hgb has less attraction to oxygen, releases oxygen more easily

• left

  • Hgb holds on to oxygen, does not release easily

What does right shift and left shift mean in the oxygen dissociation curve?

anemia, acidosis, or fever

• right shift causes RBCs to act more efficiently in delivering oxygen to tissues (compensatory mechanism)

What conditions cause a right shift on the OD curve?

abnormal hemoglobin, alkalosis, or decreased body temp

What conditions cause a left shift in an OD curve?

• methemoglobin

  • iron can no longer bind oxygen

  • can be causes by drugs or Hgb M (an amino acid substitution)

• carboxyhemoglobin

  • Hgb has a higher affinity for CO2

  • can lead to carbon monoxide poisoning (no oxygen to tissues)

  • increased in smokers and industrial workers

  • can be reversed

• sulfhemoglobins

  • affinity for oxygen is 100 times lower than normal Hgb

  • caused by exposure to sulfa-containing drugs or sulfonamides

  • can be toxic at low levels

What are the three abnormal hemoglobins?

• the premature lysis of RBCs

• two types: intravascular and extravascular

What is hemolysis?

• intravascular

  • occurs when RBCs are lysed directly in blood vessels

  • results in low Hgb, Hct, and RBC count

  • high bilirubin, low serum haptoglobin, hemoglobinemia (free hemoglobin), hemoglobinuria, high reticulocytes and LDH, and schistocytes

• extravascular

  • RBCs are destroyed and their contents are phagocytized in the spleen, liver, lymph nodes, and bone marrow

  • low Hgb, Hct, and RBC count, increased reticulocyte count, polychromasia, increased serum bilirubin, low haptoglobin, high LDH, and spherocytes

What is intravascular and extravascular hemolysis?

• PB PORE

  • Pronormoblast

  • Basophilic normoblast

  • Polychromatophilic normoblast

  • Orthochromic normoblast

  • Reticulocyte

  • Erythrocyte

mnemonic to remember RBC maturation stages