1. What are RBCs?
- RBCs are biconcave,
nucleus-less cells in the blood.
- Their main
function is to carry oxygen from lungs to tissues.
- They
contain a red pigment called hemoglobin (Hb).
2. Normal Count and
Life Span
|
Feature |
Value |
|
Count (Male) |
5–6 million/mm³ |
|
Count (Female) |
4–5 million/mm³ |
|
Life Span |
~120 days |
|
Shape |
Biconcave, round, flexible |
|
Size |
~7.2 microns (diameter) |
Mnemonic: “RBCs live for 120 days in a 7-micron room.”
3. Site of Formation
(Erythropoiesis)
- Before
birth: Yolk sac → Liver → Spleen
- After
birth: Red bone marrow (vertebrae, ribs, sternum)
Hormone: Erythropoietin (EPO)
- Secreted
by kidneys in response to low oxygen.
Mnemonic: "KIDney makes RBCs when O₂ is LOW"
4. Structure of RBC
- No nucleus, no
mitochondria → can’t divide or use oxygen
- Biconcave
shape ↑ surface area for gas exchange
- Flexible
to pass through capillaries
5. Function of RBCs
|
Function |
Explanation |
|
1. Oxygen transport |
Via hemoglobin binding with O₂ |
|
2. CO₂ transport |
Partly by Hb, mostly as bicarbonate (HCO₃⁻) |
|
3. Buffering |
Hb acts as buffer to maintain blood pH |
|
4. Maintain viscosity |
Helps in blood flow |
|
5. Blood group antigens |
Present on RBC membrane |
Mnemonic: “OCBBB”
O – Oxygen
C – CO₂
B – Buffer
B – Blood group
B – Blood viscosity
6. Destruction of RBCs
- Happens
after 120 days
- Old RBCs
are destroyed in spleen (called RBC graveyard)
- Hb breaks
into:
- Heme →
Bilirubin (excreted in bile)
- Iron → Reused
- Globin → Broken
into amino acids
Mnemonic: “Spleen Says Goodbye at 120”
7. Hemoglobin (Hb)
|
Feature |
Value |
|
Normal (Males) |
13–18 g/dL |
|
Normal (Females) |
12–16 g/dL |
|
Function |
Carry O₂ and CO₂ |
|
Structure |
4 globin chains + 4 heme groups |
8. Clinical Conditions
Related to RBCs
|
Condition |
Meaning |
|
Anemia |
↓ RBC count or ↓ Hb (tiredness, pale skin) |
|
Polycythemia |
↑ RBC count (due to hypoxia or bone marrow disorder) |
|
Sickle Cell Anemia |
Abnormal crescent-shaped RBCs |
|
Thalassemia |
Genetic defect in Hb chain production |
Mnemonic: “APe ST”
A – Anemia
P – Polycythemia
S – Sickle cell
T – Thalassemia
Summary for Quick
Revision:
RBC at a Glance:
|
Feature |
Key Point |
|
Shape |
Biconcave, no nucleus |
|
Function |
O₂, CO₂ transport, buffering |
|
Formation |
Bone marrow, hormone: EPO |
|
Life Span |
120 days, destroyed in spleen |
|
Hemoglobin |
13–18 g/dL (M), 12–16 g/dL (F) |
FAQs – Frequently Asked Questions
Q1. What is the normal
RBC count?
Ans:
- Male: 5–6
million/mm³
- Female:
4–5 million/mm³
Q2. What is the main function
of RBC?
Ans: To carry oxygen from lungs to tissues using hemoglobin.
Q3. Where are RBCs
destroyed?
Ans: In the spleen (RBC graveyard), after ~120 days.
Q4. Why do RBCs have a
biconcave shape?
Ans: To increase surface area for oxygen exchange and allow flexibility
in capillaries.
Q5. What stimulates RBC
production?
Ans: Erythropoietin (from kidneys) in response to low oxygen levels.
