A representation of erythropoiesis (red blood cell formation), bone marrow.
includes several stages of cell changes during differentiation. Erythrocytes derive from
that give rise to the F rst recognizable erythrocyte precursor, the
. The proerythroblast is a large cell, which has a large
active nucleus with nucleoli. Each proerythroblast divides into two
. Each basophilic erythroblast divides into
, each of which then divides to form
, which do not divide.
These, in turn, differentiate into
(±ig. 8-11B,C), which F nally become
. There are some general tendencies
accompanying differentiation of erythrocytes: (1) the overall size of the cells decreases, (2) the nucleus size decreases and the condensa-
tion of the chromatin increases, (3) nucleoli disappear, and (4) the color of the cytoplasm changes from blue to gray to pink because
of a reduction of ribosomes and an increase of hemoglobin. When the ribosomes are diluted by cell division and the hemoglobin
concentration rises to a near mature level, the cell becomes an orthochromatophilic erythroblast (or
). When the nucleus
is extruded and only a few organelles (polyribosomes and mitochondria) remain in the cytoplasm, the cell is called a
reticulocyte completes maturation and enters the blood circulation to become a
red blood corpuscle
Thrombopoiesis (platelet formation process), bone marrow.
from left to
are very small fragments of cells that have no nuclei. They are also called
. Their differentiation from a large
, takes place in the bone marrow.
are the precursor cells. They have a large, round nucleus,
undergo mitosis, and become
. These cells have a large, round nucleus and develop through growth and a series
of endomitoses into
. A megakaryocyte has a large, multilobed nucleus with a huge amount of cytoplasm containing
numerous granules. The maturation process includes the development of a demarcation membrane system and the subdivision of
the cytoplasm to form platelets (±ig. 8-12A,B).