Erythrocytes are the functional component of blood involved in the transportation of gases and nutrients throughout the human body.

1. Red Blood Cells
or
Erythrocytes
Amjad KhanAfridi
Chapter # 08

2. Erythrocytes
• Also called Red Blood Cells
• Have no nucleus
• Thin plasma membrane
• A lipid bilayer membrane covers the cell’s cytoplasm
• Do not have cell organelles
• Shaped as a biconcave disk
• Primary component hemoglobin (Hb)
• 7.5 µm in diameter
Erythrocytes are the functional component of blood involved in
the transportation of gases and nutrients throughout the human
body.

3. • Because of the lack of a nucleus, erythrocytes cannot
divide and thus need to be continually replaced by
new cells synthesized in the red bone marrow.
• The lifespan of red blood cells is about 120 days, and
the development of red blood cells from stem cells
occurs in about seven days via the process of
erythropoiesis.

4. Structure of Erythrocytes
• The mature human erythrocyte has a biconcave, discoid shape and is
anucleated. They are approximately 7.5 μm in diameter, 2.6-μm thick at the
rim, but only 0.75-μm thick in the center.
• The biconcave shape of the cell provides a large surface-to-volume ratio
and facilitates gas exchange.

5. • The average concentration of erythrocytes in
the blood is approximately 3.9-5.5 million per
microliter (μL, or mm3) in women and 4.1-6.0
million/μL in men.
• Erythrocytes are quite flexible, which permits
them to bend and adapt to the small diameters
and irregular shape of the blood vessels.

6. • The plasmalemma (Plasma membrane) of
erythrocyte, consists of about 40% lipid, 10%
carbohydrate, and 50% protein.
• A phospholipid bilayer membrane supports the
structure of the RBC & also covered the
cytoplasm of RBC, which is maintained by a
network of proteins that make up the
cytoskeleton.

7. • The cytoskeleton is composed of proteins like
spectrin, actin, band 3 (anion exchanger-1),
protein 4.1 (Beatty's Protein), and ankyrin, which
allows for cellular structural integrity as well as
malleability.
• The cytoplasm of erythrocytes lacks all organelles
but is densely filled with hemoglobin, which
allows the transportation of respiratory gases.

8. • The RBC membrane contains integral
and peripheral proteins.
• Integral proteins distinguish individuals in the
form of A, B, O, and AB blood types.
• They also support the internal structure and bind
hemoglobin.
• Peripheral membrane proteins are found on the
inner side of the membrane and help to make the
red blood cell extremely elastic.

9. Functions of Erythrocytes
• RBCs transport oxygen from the lungs to the
peripheral tissues to assist.
• The cells also collect the generated carbon
dioxide from the periphery and return it to the
lungs for elimination from the body.

10. 10th January, 2022