Page 448 - First Aid for the USMLE Step 1 2020, Thirtieth edition [MedicalBooksVN.com]_Neat

404 SectIon III Hematology and oncology ` hematology and oncology—emBRyology Hematology and oncology ` hematology and oncology—emBRyology

` hematology and oncology—emBRyology

Fetal erythropoiesis Fetal erythropoiesis occurs in: Young Liver Synthesizes Blood.
ƒ Yolk sac (3–8 weeks)
ƒ Liver (6 weeks–birth)
ƒ Spleen (10–28 weeks)
ƒ Bone marrow (18 weeks to adult)
Hemoglobin Embryonic globins: ζ and ε.
development Fetal hemoglobin (HbF) = α γ . From fetal to adult hemoglobin:
2 2
Adult hemoglobin (HbA ) = α β . Alpha Always; Gamma Goes, Becomes Beta.
1
2 2
HbF has higher affinity for O due to less avid
2
binding of 2,3-BPG, allowing HbF to extract
O from maternal hemoglobin (HbA and
1
2
HbA ) across the placenta. HbA (α δ ) is a
2 2
2
2
form of adult hemoglobin present in small
amounts.
BIRTH
Site of Yolk
erythropoiesis sac Liver Spleen Bone marrow
50 α

40
Fetal (HbF) γ Adult (HbA ) 1
% of total 30
globin synthesis
20 β
ε Embryonic globins
10 ζ

Weeks: 6 12 18 24 30 36 6 12 18 24 30 36 42 >>
EMBRYO FETUS weeks POSTNATAL months ADULT >>

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