4. Hematopoiesis Flashcards
Other term for hematopoiesis
Hemopoiesis
The process of blood cell formation
Hematopoiesis
Classical marker of HSC
CD34
Hematopoiesis is considered to start around the ______ of embryonic development after fertilization
19th day
2 Theories on the origin of hematopoietic progenitor cells
polyphyletic theory
monophyletic theory
This theory suggests that each of the blood cell lineages is derived from its own unique stem cell
Polyphyletic theory
This theory is the most widely accepted theory among experimental hematologists
Monophyletic theory
Monophyletic theory suggests that all blood cells are derived from a single progenitor stem cell called a
pluripotent stem cell
Three phases of hematopoiesis
Mesoblastic/Megaloblastic
Hepatic
Medullary/Intramedullary/Myeloid
Chief site of hematopoiesis in the mesoblastic phase
yolk sac
chief site of hematopoiesis in the hepatic phase
fetal liver
chief site of hematopoiesis during the medullary phase
bone marrow
During the hepatic phase, hematopoiesis can also occur on these sites (3)
spleen
thymus
lymph nodes
The first blood cells in mesoblastic phase are called
primitive erythroblasts
Primitive erythroblasts are formed during the
first 2-8 weeks of life
Primitive erythroblasts are important in the early embryogenesis to produce (3 types of Hgb) that are necessary to supply oxygen to embryonic tissues
Gower-1
Gower-2
Portland
How is yolk sac hematopoiesis different from the hematopoiesis that occurs during the subsequent fetal and adult stages?
Yolk sac hematopoiesis occurs intravascularly
The predominant Hgb during the hepatic phase
Hb F (Fetal Hemoglobin)
The first fully developed organ in the fetus
Thymus
Thymus is the major site for
T cell production
These 2 organs produce B cells during fetal phase
Kidneys
Spleen
Hematopoiesis starts in the bone marrow cavity ______ of fetal development
before the 5th month
The bone marrow becomes the chief site of hematopoiesis by the
end of 24 weeks’ gestation
Hematopoietic tissues of adults are located not only in the bone marrow, but also in the
lymph nodes
spleen
liver
thymus
The bone marrow contains developing (4) cells
erythroid
myeloid
lymphoid
megakaryocytic
The bone marrow is considered to be a primary lymphoid organ with functions equivalent to that of
Bursa of fabricus (birds)
The bone marrow is capable of generating around _____ per kg of body weight daily
2.5 billion rbcs
1 billion granulocytes
2.5 billion platelets
The process of replacing red marrow by yellow marrow during development
Retrogression
Between ages ______, adipocytes become more abundant and start to occupy the spaces in the long bones previously dominated by active marrow
5 and 7 years old
Retrogression ultimately results in the restriction of the red marrow (adult) to the (4)
ribs
sternum, skull, shoulder blades
vertebrae
pelvis and proximal ends of long bones
T/F
Yellow marrow is incapable of reverting back to active marrow in cases of increased demand in the bone marrow.
False
Hematopoietically active marrow
red marrow
The yellow marrow is hematopoietically inactive and is primarily composed of
adipocytes
primary lymphoid organs
bone marrow
thymus
secondary/peripheral (major) lymphoid organs
spleen
lymph nodes
Thymus develops during fetal development and continues until puberty. It then undergoes
atrophy with aging
Lymphoid cells fated to become B cells undergo their early stages of differentiation within the
bone marrow
2 major functions of the secondary/peripheral lymphoid organs
trapping and concentrating foreign substances
main sites of antibody production and induction of Ag-specific T lymphocytes
The largest of the secondary lymphoid organs
Spleen
Lymph nodes are small ovoid, bean-shaped structures measuring
<1 cm in diameter
Spleen is a major organ in the body in which ______ are synthesized and from which they are released into the circulation.
antibodies
Effect of splenectomy to children
increased incidence of bacterial sepsis
causative agents of bacterial sepsis in children who had splenectomy
streptococcus pneumoniae
Neisseria meningitidis
haemophilus influenzae
Effect of splenectomy in adults
> less adverse effects
increase in blood-borne bacterial infections/ bacteremia
Removal of spleen
Splenectomy
Refers to the increased hemolytic activity of the spleen caused by splenomegaly
hypersplenism
Any disorder characterized by a localized/generalized enlargement of lymph nodes/vessels
lymphadenopathy
Solid tumor neoplasm of lymphoid tissue
lymphoma
Minor secondary lymphoid organs (4)
tonsils
appendix
peyer’s patches
MALT
This organ detects and responds to antigens in the respiratory and alimentary secretions
tonsil
These are clusters of lymphocytes distributed in the lining of the small intestine
peyer’s patches
peyer’s patches detect substances that diffuse across the
intestinal epithelium
MALT stands for
mucosa-associated lymphoid tissue
This is a general term for the unencapsulated lymphoid tissues present in regions underlying the mucosal areas
mucosa-associated lymphoid tissue
Bone marrow collection sites (5)
Posterior superior iliac crest
Anterior superior iliac crest
Sternum
Anterior medial surface of the tibia
Spinous process of the vertebrae, ribs, and other red marrow containing tissues
preferred collection site for bone marrow aspiration in adults
posterior superior iliac crest
anterior superior iliac crest
preferred collection site for bone marrow aspiration in children <2 years old
anterior medial surface of the tibia
This organ can maintain hematopoietic stem cells and progenitor cells to generate various blood cells as a response to infectious agents or pathologic myelofibrosis of the bone marrow.
Liver
the largest cell in a normal marrow
megakaryocyte (30-50 um)
normal marrow cells
developing HSCs
macrophages
mast cells
osteoblasts
osteoclasts
macrophage size
40-50 um in diameter
Macrophages are + for this cytochemical stain
nonspecific (alpha napththyl acetate or alpha naphthyl butyrate) esterase
diameter of mast cells
12-25 um
mast cells are + for this cytochemical stain
chloroacetate esterase
these cells synthesize new bone matrix
osteoblasts
osteoblasts appearance
waterbug/comet
These are large, multinucleated cells with >100 um diameter
osteoclasts
M:E ration in leukemia
10:1
normal M:E ratio
2:1 to 4:1
In marrow differential, it is recommended to count
at least 500
preferably 1000 cells (500 cells on each of 2 slides)
myeloid cells will become
wbcs
erythroid cells will become
rbcs
bone marrow aspirate vs bone marrow biopsy
BMA disturbs bone marrow architecture; BMB does not
Bone marrow aspirate is used for
analysis of individual cell morphology
Bone marrow aspirate smears should be retained for
10 years
Advantage of bone marrow biopsy
gives a better picture of the real structure of the bone marrow
blood cell production outside of the bone marrow
extramedullary hematopoiesis
The spleen normally produces
lymphoid cells
Extramedullary hematopoiesis mainly occurs in the
liver
spleen
extramedullary hematopoiesis is often accompanied with
splenomegaly
hepatomegaly
