haematology: red cell physiology Flashcards
What is erythropoiesis
Production of red blood cells
Where does erythropoiesis in fetus vs adult
Fetus: yolk sac then liver/spleen then bone marrow
Adult: bone marrow
What is the survival time of RBC & how are they removed
120 days
Removed from circulation by macrophages in the spleen
What is the development pathway of RBC
Stem cells becomes pro-erythroblast & ribosome synthesis occur forming early erythroblast
Hemoglobin accumulation occurs forming late erythroblast & nomoblast
Reticulocyte forms as nucleus gets rejected with some DNA fragment
Erythrocyte form once all DNA is removed
What hormone stimulates erythropoiesis
Erythropoietin
What is the pathway of EPO
- Cortical peritubular cells in kidney detect low oxygen
- EPO released & binds to EPO receptors triggering erythropoiesis
- Increase in RBC increase oxygen carrying capacity
- Adequate oxygen levels leading to decreased EPO production & RBC production
What is 4 structure & function relations in RBC
- Biconcave & discoid shape due to constant oxygen exchange over large surface area
- No nucleus due to low oxygen requirement for metabolism & carry oxygen for tissue
- Lipids & protein in cell membrane due to gaseous exchange
- Metabolic pathways due to ATP generation, maintain Hb in reduced state, reduce oxidative stress & generates 2,3-DPG to decrease affinity
What is the structure of hemoglobin in adults vs children <1 years
Tetramer with 2 pairs of globin chains with hemoglobin attached
Adults: HbA
Children: HbF
Where is hemoglobin synthesised
Mitochondria
What is the relaxed state of hemoglobin
Oxyhemoglobin
Release of oxygen at tissue due to decreased partial pressure of oxygen & low pH
What is the tense state of hemoglobin
Deoxyhemoglobin
Binds 2,3 -DPG leading to lower oxygen affinity (not rebind at tissue level) & binds to carbon dioxide & transport to lungs
What 4 things shifts the hemoglobin dissociation curve to the left
Increased pH, decrease 2,3-DPG, HbF, hypothermia
What 4 things shifts the hemoglobin dissociation curve to the right
Decreased pH, increase 2,3-DPG, HbS, hyperthermia
Is oxygen easily released in left or right shift
Oxygen is easily released at right shift due to higher P50 & decrease affinity for oxygen
What nutrients are required for synthesis of haemoglobin
Folate & vitamin B12 for DNA
Iron & amino acids for hemoglobin
What is the life cycle of RBC
- EPO from the kidneys stimulates erythropoiesis
- Erythrocyte is released into vessel & circulate for 120 days
- Spleen macrophages break down old erythrocytes into bilirubin, iron & amino acids
- Amino acids & iron get re-used in erythropoiesis as it circulates back to the bone marrow
- Liver processes bilirubin into bile & some gets excreted in feces & other in urine
What does hemoglobin levels in FBC assess for
Anemia status
What is hemoglobin levels in anemia indicating
Reduced levels leading to reduced oxygen carrying capacity
What does MCV levels in FBC assess for & categories
Size of RBC
Microcytic: smaller than normal
Normocytic: normal
Macrocytic: larger than normal
What does MCH/MCH levels in FBC assess for & categories
Color of red blood cells
Hypochromic: less hemoglobin & less color (bigger pale)
Normochromic: normal amount of hemoglobin
Hyperchromic: more hemoglobin & more color (no pale)
What does MCHC measure
Correlates hemoglobin content with volume of cells (Hb/Hct)
What does MCH measure
Average amount of hemoglobin in single RBC (Hb/RCC)
What does RDW levels in FBC assess for
Variation in size & volume of RBC
What does RCC levels in FBC assess for
Measurement of number of RBC
