Transcript structure and function of bone marrow

Course title: Hematology (1)
Course code: MLHE-201
Supervisor: Prof. Dr Magda Sultan
Date : 31 / 10/2013
Outcome :
The student will understand :
-The process of hematopoiesis
-The development of mature blood cells
Hematopoiesis
Hematopoiesis is the process by which
immature precursor cells develop into
mature blood cells.
A single type of stem cell gives rise to
all the mature blood cells in the body.
This stem cell is called the pluripotent
stem cell.
SITES OF HEMATOPOIESIS
Age
Site of hematopoiesis
Embryo ------------------------ yolk sac then liver
3rd to 7th month------------ spleen
4th and 5th months-------- marrow cavity - esp. granulocytes and platelets
7th month ------------------- marrow cavity - erythrocytes
Birth---------------------------- mostly bone marrow; spleen and liver when
needed
Birth to maturity number of active sites in bone marrow decreases but
retain ability for hematopoiesis.
Adult--------------------------- bone marrow of skull, ribs, sternum, vertebral
pelvis, proximal ends of femurs
• STRUCTURE AND FUNCTION OF BONE MARROW
Bone marrow has a vascular compartment and an
extravascular compartment.
Hematopoiesis takes place in the extravascular
compartment. The daily output of mature blood
cells in bone marrow is : 2.5 billion erythrocytes,
2.5 billion platelets, 50-100 billion granulocytes.
The numbers of lymphocytes and monocytes is also
very large.
In addition to hematopoiesis , bone marrow is
the site of other activities . These include :
-The removal of aged and defective erythrocytes
-The differentiation of B lymphocytes
-It is also the site of numerous plasma cells.
THE PROCESS OF HEMATOPOIESIS
Pluripotent stem cells multiply to produce
more pluripotent stem cells, thus ensuring the
steady and lasting supply of stem cells. Some of
the pluripotent stem cells differentiate into
precursor cells that are at least partially
committed to become one type of mature blood
cell.
Pluripotent stem cells multiply slowly into one
of five possible unipotential stem cells, which
then multiply rapidly into the precursor of the
specific mature blood cell for which they are
destined.
Although the pluripotent stem cells and the
unipotential stem cells cannot be distinguished
from one another histologically, the precursor
cells can be distinguished with a trained and
practiced eye
Basically an immature, precursor cell goes
from a cell that is making lots of protein to a
cell that is making much less protein.
Thus, a cell that is making a lot of protein will
have a nucleus containing dispersed or active
chromatin.
When this cell is making less protein, the
chromatin is condensed or clumped.
• ERYTHROPOIESIS
As the cells are maturing in the erythrocytic series,
the cells are usually getting smaller, the nucleus is
becoming smaller and more condensed and is
eventually lost, and the cytoplasm is becoming
pinker rather than blue.
The cells in the developing erythrocyte series are as
follows:
• Unipotent stem cell: cannot be distinguished
from other unipotent stem cells by histology
• Proerythroblast: nucleus still rather large, taking up most of the
cell; nucleus not condensed; cytoplasm still very blue or basophilic
• Basophilic erythroblast (early) : very difficult to distinguish from
the proerythroblast
• Polychromatophilic erythroblast (intermediate) : nucleus is more
condensed than that of the proerythroblast; cytoplasm less blue,
more grayish
. Orthochromatophilic erythroblast (late) : nucleus more
condensed, smaller than that of previous cells and looks pyknotic
by comparison; cytoplasm beginning to take on a more pinkish cast
• Reticulocyte: no nucleus; cytoplasm still
stains somewhat bluish due to presence of
remnants of polyribosomes
• Erythrocyte: mature erythrocyte has no
nucleus (in mammals); cytoplasm stains very
pink due to lack of ribosomes and presence of
high amounts of protein, i.e hemoglobin
Myelopoiesies
• Unipotent stem cell: cannot be distinguished from other
unipotent stem cells by histology
• Myeloblast: large cell with blue-staining cytoplasm; large nucleus;
and with nucleolus .
• Promyelocyte: still a rather large cell with azurophilic granules
• Myelocyte: overall cell still rather large; nucleus still round
without indentation; granules staining appropriately for the series,
i.e., pink for eosinophilic, blue for basophilic, neutral for neutrophilic
• Metamyelocyte: cell is about the size of a mature
granulocyte; nucleus with slight indentation; granules
present that stain appropriately for the series, i.e., pink for
eosinophilic, blue for basophilic, neutral for neutrophilic
• Band cell: cell is about the size of a mature granulocyte;
nucleus with definite indentation - looks like a horseshoe;
prominent granules that stain appropriately for the series
• Mature (segmented) granulocyte: cell is mature and looks
like normal, mature granulocytes in the blood with lobed
nucleus and prominent granules that stain appropriatly for
the series .
•
Immune System
This system consists of cells and tissues that have as their main function the
protection of the body from the invasion by microorganisms and disease-.
Components of this system are:
• Lymphocytes
T cells
B cells
• Plasma cells
• Bone marrow
• Thymus
• Lymph Node
• Spleen
The bone marrow and thymus are considered as primary immune/lymphoid
components because they contain the stem cells that will develop into T cells,
B cells and natural killer cells of the functioning immune and lymphatic systems.
Megakaryopoiesis
• Platelets, also called thrombocytes, play an important
role in hemostasis
• Platelets appear as round, oval or biconcave disks and
have a diameter of about 1.5 to 3.5 μm.
• Platelets are formed in the bone marrow from
megakaryocytes (30-100 μm diameter), very large
cells with a polyploid, multilobed nucleus and
granular cytoplasm . Platelets are released from
fragmenting megakaryocytes.
‫‪Student Name‬‬
‫‪Title‬‬
‫سعيد عبد اللطيف عبد الباري‬
‫سلمي عبد الرحمن‬
‫سليم فارس عبد االه‬
‫سهام محمود مهران‬
‫سهي هشام بدر‬
‫سهيله نبيل حامد‬
‫سوزان عبد الحميد‬
‫شاهنده عنتر محمد‬
‫شروق اسامه محمد‬
‫‪Erythropoiesis .‬‬
‫صالح الدين محمد‬
‫صهيب محمد عبد الكريم‬
‫عائشه علي حسن‬
‫عاطف سعيد السيد‬
‫عاطف كمال خميس‬
‫عبد الباري ابراهيم عبد االباري‬
‫عبد الرحمن عوض حسين‬
‫عبد الفتاح محمد انور‬
‫عبد هللا وجيه‬
‫عزيزه حسين عبد الحافظ‬
‫عال حازم علي‬
‫‪Bone marrow structure‬‬
• Training Questions :
- Mention the cells of developing erythrocyte
series .
- What are the components of the immune
system ?
Reference Books :
- Essential Hematology
- Dacie .