6 Hematology of the Fetus and the Newborn Flashcards
The appearance of primitive erythroid cells in blood islands of the yolk sac begin at ________ of gestation
Day 18 of gestation
Primitive erythroblasts have extremely large size, with an estimated mean cell volume (MCV) of greater than 400 fL/cell, yolk sac erythroblasts have been termed
Megaloblasts
In humans, primitive erythroblasts begin to enter the embryo proper at days ________of gestation with the onset of cardiac contractions and circulate until approximately _______weeks of gestation
Days 21–22 of gestation
12 weeks of gestation
The initial wave of primitive hematopoietic progenitors is followed by a second wave of yolk sac–derived definitive erythroid progenitors, termed
Burst-forming units–erythroid (BFU-E)
BFU-E are present in the human yolk sac as early as ______ weeks’ gestation and are found in the fetal liver by ______ weeks’ gestation
Yolk sac: 4 weeks gestation
Fetal liver: 5 weeks gestation
Between 7 and 15 weeks of gestation, _______% of the liver cells are hematopoietic.
60%
The liver serves as the primary source of red cells from the ____________week of gestation
9th to the 24th week of gestation
Are smaller than yolk sac–derived primitive megaloblasts and contain one-third the amount of hemoglobin
Fetal liver–derived definitive “macrocytes”
TRUE OR FALSE
Fetal liver–derived erythroid progenitors can differentiate in vitro with erythropoietin alone, in contrast to adult marrow–derived BFU-E, which requires erythropoietin plus interleukin (IL)-3 or stem cell factor.
TRUE
Fetal liver–derived erythroid progenitors can differentiate in vitro with erythropoietin alone, in contrast to adult marrow–derived BFU-E, which requires erythropoietin plus interleukin (IL)-3 or stem cell factor.
Erythropoietin transcripts also are present in the developing human kidney as early as
17 weeks’ gestation
Megakaryocytes are present in the liver by __________weeks of gestation, and platelets are first evident in the circulation at ________ weeks of gestation
6 weeks of gestation
8–9 weeks of gestation
69
Granulopoiesis is present in the liver parenchyma as early as ______ weeks of gestation, and small numbers of circulating leukocytes are present at the ______ week of gestation.
7 weeks of gestation
11th week of gestation
7-11
G-CSF is expressed by hepatocytes at ______ weeks gestation.
14 weeks gestation
B-cell progenitors are present in the fetal liver by ___weeks of gestation, and circulating lymphocytes are present at ____weeks’ gestation.
7 weeks of gestation
9 weeks gestation
7-9
T lymphocytes are found only rarely before _______ weeks’ gestation
12 weeks’ gestation
Hematopoietic cells are first seen in the marrow of _______week embryos, and they remain confined to the ______________ until 15 weeks’ gestation
10- to 11-week
Diaphyseal regions of long bones
Myeloid cells predominate by ______ weeks’ gestation, and the myeloid-to-erythroid ratio approaches the adult level of 3:1 by______weeks’ gestation.
12 weeks’ gestation
21 weeks’ gestation.
TRUE OR FALSE
Macrophage cells in the fetal marrow, but not in the fetal liver, express the lipopolysaccharide receptor CD14.
TRUE
Macrophage cells in the fetal marrow, but not in the fetal liver, express the lipopolysaccharide receptor CD14.
A massive expansion of B-cell progenitors occurs in the fetal marrow between __________ weeks of gestation.
11 and 20 weeks of gestation
The marrow becomes the major site of hematopoiesis after the ________ week of gestation and remains so throughout the remainder of fetal life.
24th week of gestation
Chromosome location
α-globin gene cluster:
β-globin gene cluster:
α-globin gene cluster: Chromosome 16 (ζ , α)
β-globin gene cluster: Chromosome 11(ε-γ A-γ G-δ-β)
The major hemoglobin in embryos younger than 5 weeks’ gestation
Hgb Gower-1 (ζ2ε2)
Found in embryos with a gestational age as young as 4 weeks and is absent in embryos older than 13 weeks.
Hgb Gower-2 (α2ε2)
Found in young embryos but persists in infants with homozygous α-thalassemia
Hgb Portland (ζ2γ2)
