Physiology of RBC Flashcards
Describe the characteristics of the blood
- Fluid tissue
- Sticky and opaque
- Scarlet when there is an increased amount of O2 and dark red when O2 is low
- 8% of body weight, 5-6L in males and 4-5L in females
- pH of 7.35-7.45
- Saline 0,85%
What are the different functions of the blood?
1) Transportation
- O2
-CO2 - Nutrients
- Metabolic wastes
- Hormones
2) Regulation
- Body temp
- pH
- Fluid volume
3) Protection
- Infection and foreign bodies
What are the different components of the blood?
1) Plasma 52-62%
- Water 92%
- Proteins 7%
- Other 1% (waste, gases, electrolytes, vitamins, etc)
2) RBC 38-48%
3) WBC <1%
- Neutrophils
- Lymphocytes
- Monocytes
- Eosinophils
- Basophils
4) Platelets <1%
What are the different proteins found in the plasma? and what are their functions?
1) Albumin (60% of plasma proteins)
- Normal level is 3.5-5g/dl
- Maintains the osmotic pressure, and transports hormones, fatty acids, bilirubin
2) Globulins (35% of plasma proteins)
- Normal level 1.5-2.5g/dl
- Alfa 1 & 2 transports hormones
- Gamma forms antibodies
3) Fibrinogens
- Normal level: 0.2-0.4g/dl
- Forms blood clots
- Serum means plasma - clotting factors (the yellow liquid that comes out of a wound)
What are the “other” components of the plasma, and what are their functions?
1) Na, K, Ca, Mg, Cl, HCO3:
- Maintains osmotic balance
- pH buffer
- Regulates the membrane permeability
2) Glucose, fatty acids, Amino acids, and Vitamins:
- Energy production
- Maintenance and repair
3) Oxygen:
- Energy production
4) Urea, uric acid, CO2:
- For Disposal (either by the lungs or the kidney’s)
Describe the RBC (erythrocytes)
- Bioconcave for a larger surface area
- It has no mitochondria or nucleus
- They can change their shapes and squeeze into tiny capillaries
- They make ATP via glycolysis (and they do not use the O2 they carry “they are anaerobic ATP)
- They do not make proteins and use the ones produced early on in development, and thus no virus can attack them
- Life span 120 days
Describe the life span and function of the RBC
- After their production, they are always active with no rest
- If a sudden demand for RBCs arises (e.g., going into a hypoxic state), bone marrow has to make RBCs from scratch. It has no reserved army of RBCs
- There is no mature RBC nor Platelets in the bone marrow
- In case of high RBC demand, bone marrow would release premature (large) cells that have nuclei. Seeing nucleated RBCs in the blood is a sign of high demand/ tumor
- RBC are only found in the circulation with no storage, and a life span of 120 days, they are not found in the bone marrow nor in the peripheral tissues
What is the normal RBC count?
1) Males:
- 4.2-5.4 million/mm^3
2) Females:
- 3.6-5 million/mm^3
- It is lower in women due to the loss of blood during menstruation and the low levels of testosterone
What is the function of RBC?
1) Transportation
2) Acid-base balance
- Carbonic anhydrase maintains
Acid-base balance via buffering action
3) Maintains blood viscosity
4) Provides pigments:
- Bilirubin and biliverdin
Describe the structure of hemoglobin (Hb)
- Each hemoglobin molecule is made up of 4 globin chains (2-alpha & 2-beta)
- Each globin chain has a heme molecule attached to it
- Each heme molecule has an iron (Fe) attached to it
- Each Fe atom carries one oxygen
- Compared to O2, carbon monoxide (CO) has a higher affinity for Hb, In CO poisoning, Hb cannot bind O2, and the cause of death is hypoxia.
Describe the mechanism of Oxygen binding to hemoglobin
1) In the lungs:
- There is a high amount of oxygen
- And the pH is high due to the low number of CO2
- Oxygen binds to Hb
2) In the tissues:
- Low oxygen
- Low pH (High CO2)
- Oxygen is released
- CO2 is acidic as it reacts with H2O to make carbonic acid
What are the different types of hemoglobin (Hb)?
1) Alpha (a-chains are synthesized both pre- and post- natal life, from the first trimester)
2) Gamma (Y-chain is synthesized from the 2nd trimester and starts to disappear after birth, to be replaced by b-chains, from the first trimester till the age of six)
3) Epsilon & zeta (e-chains &z-chains, are synthesized during the first trimester only)
4) Delta (d-chains, synthesized throughout adult life at low levels, starts to be produced during the third trimester and continuous through adult life but in small amounts)
5) Beta (b-chains, synthesized after birth mainly)
- After birth, you see alpha and beta chains mostly and a small amount of delta
1) Gower’s Hb:
- the predominant Hb in the first trimester of the prenatal period (any two of a, e, or z chains)
2) Fetal Hb:
- Dominant in 2nd and 3rd trimester
- Two alpha (a) and two gamma (Y) chains
3) Adult Hb (Hb-A):
- 2 alpha, and 2 beta
- predominant in adults >95%
4) Delta Hb (HbA2)
- two alpha and two delta
- Small amounts
What is the amount of Hb in the RBC?
35% of RBC is Hb
270 million Hb molecules/RBC
1) Men:
- 14-17g/dl
2) Woman:
- 13-16g/dl
What is the site of RBC production during the first trimester?
Yolk Sac
What is the source of RBC formation during the 2nd trimester?
Liver and Spleen
What is the source of RBC production from the 3rd trimester onwards?
The bone marrow
Describe the RBC cycle
1) Bone marrow produces RBC while the spleen destroys it
2) The synthesis and destruction of RBC is remarkably balanced
3) The destruction of RBC produces 3 products:
1) Pigments (bilirubin and biliverdin)
2) Iron
3) Amino acids
- Both the iron and amino acids are reused to synthesize new RBCs
Describe the erythropoiesis process
1) RBCs starts as a single type (pluripotent cell)
- A blast is an immature RBC
- A cyte is a mature cell
2) With each successive stage the nucleus becomes smaller and the Hb content increases
3) During the reticulocyte stage the cell passes from the bone marrow to the circulation
- Proerythrocyte - Basophil erythrocyte - polychromatophil erythroblast - orthochromatic erythroblast - reticulocyte - erythrocyte
Which hormone stimulates the production of RBC’s?
Erythropoietin (secreted by the kidneys and some from the liver)
- Erythropoietin activates pluripotent stem cells in the bone marrow to make more pro-erythroblasts which through various stages make more RBCs
- Patients with renal failure needs an EPO injection
What are the stimulants of erythropoietin?
1) Poor oxygenation
2) High altitude
3) Heart failure
4) Anemia
5) Pulmonary disease
6) Androgens
What are the nutritional requirements for the production of erythropoiesis?
1) Fe (heme synthesis)
2) Amino acids (globin synthesis)
3) Vitamin B12 & Folate (Maturation of RBC)
4) Vitamin C (iron absorption)
- Iron and Amino acids from destroyed RBCs are reused to make new RBCs
What are the different RBC disorders?
1) Anemia
2) Polycythemia
What is anemia?
It is a total reduction in:
1) RBC count
2) Hb content
3) O2 carrying capacity
What are the types of anemia?
1) Low MCV:
- <80 fL
- Iron deficiency anemia
- Thalassemia
- Chronic diseases
- Sideroblastic anemia
2) Normal MCV:
- 80-99 fL
- G6PD deficiency
- Hereditary spherocytosis
- PNH “Paroxysmal Nocturnal Hemoglobinuria” (your complement part of the immune system attacks and destroys RBCs due to deficiency of a protein on the RBC surface)
3) High MCV:
- >100 fL
- Folate deficiency
- B12 deficiency
What is meant by polycythemia?
Increase in the count of RBCs
- It is a malignant condition (like a cancer for the production of RBCs)
-
What are the different types of polycythemia?
1) Absolute
- Increased RBC
1a) Primary
- It is independent of EPO = Polycythemia vera
2a) Secondary
- Due to the increased amount of EPO
1) Could be physiological cause (hypoxia)
2) Pathological cause (renal tumor “increasing the EPO production)
2) Relative
- Water loss dehydration
- The amount of RBC is not increased but the blood is concentrated, so in those cases, RBCs relative to plasma look high
