Flashcards in Hematologic Conditions of the Newborn Deck (97)
When does early hematopoiesis begin?
one of the earliest systems to achieve some fx capactity
- begins in the yolk sac at 12-15d
When does circulation begin?
by 22days with primitive cells arising intravascularly from vessel walls
* circulation is vital for the well-being of the fetus for transport of nutrients, O2 and removal of waste products
From where do blood cells arise?
all blood cells come from the pluripotent hematopoietic stem cell that divides into a myeloid or lymphoid stem cell
When is the pluripotent hematopoietic stem cell present in the yolk sac?
at 16 days
What happens to the pluripotent hematopoietic stem cell?
becomes unipotent stem cells (colony forming cells) which develop into specific cells. When they divide, they are committed to making only one kind of cell; structural differentiation occurs
following yolk sac hematopoiesis, when and where does this activity take place?
migration of pluripotent stem cells from yolk sac to the liver where hepatic hematopoiesis is established by 9 weeks; peak fx at 4-5mo GA
As hepatic hematopoiesis regresses, where is the primary site of this function?
medullary (bone marrow) hematopoiesis becomes dominant at 22 wk GA
Why is extra-medullary hematopoiesis necessary?
as the long bones mature, extra-medullary hematopoiesis aids the process
What are the extra-medullary sites for hematopoiesis?
spleen, lymph nodes, thymus and kidneys
What are the formed elements present in a CBC in order from greatest to least?
erythrocytes, plt and leukocytes
What is included in the differential of a CBC?
- Granulocytes: Neutrophils (40-70%); Eosinophils (1-4%) and Basophils (0-1%)
- Agranulocytes: Lymphocytes (20-45%) and Monocytes (4-8%)
What is the process of erythropoiesis?
production of erythrocytes
1) pluripotent stem cell
2) myeloid stem cell
3) proerythroblasts cells
What does erythropoietin regulate?
erythropoiesis and the synthesis of hemoglobin
Where is erythropoietin produced?
in the kidneys post natally, however, it is produced in the liver and submandibular glands during fetal life
What stimulates erythropoietin production?
anemia and decreased O2 availability to the tissues
What are the 2 major components of a RBC?
heme and globin (95%)
Describe an erythrocyte.
- biconcave discs and flexible
- plasma membrane but no nuclei or organelles
- packed with hemoglobin molecules
What is a hemoglobin molecule?
- O2 carrying CO2 is carried a well (carries from lungs to tissues)
- a conjugated protein consisting of an Fe containing pigment called heme and a simple protein, globin
- composed of 4 chains of AA, each with Fe which is a binding site for O2
What are young erythrocytes carrying ribosomes called?
What is the life span of a RBC?
what do fetal RBCs contain relative to adult RBCs?
more fetal hgb; newborns have more fetal hgb. the more mature the baby the less fetal hgb
At 10 weeks GA, what is the major component of RBC?
When does production shift from HbF to HbA?
at the end of fetal life; 70-90% HbF in RBC at birth
What is the importance of 2,3 diphophglycerate?
binds with hgb and causes a release of O2 to the tissues as a result
What is the composition of HbA?
the globin, or protein portion of each HbA molecule consists of 2 identical alpha chains and 2 identical beta chains
What is the composition of HbF?
normal HbF has 2 alpha chains and 2 gamma chains; these gamma chains increase hgb's attraction to O2 and facilitates transfer of maternal O2 across the placenta, but reduces release to the tissues; net result hgF more readily holds onto O2
Where is HbF primarily produces and at what GA?
- predominant from 10-12 weeks and increases rapidly to 90-95% by 30-32 wk
- slow decrease to 84% by 34 weeks and to 60-80% by FT
Where is HbA2 primarily produces and at what GA?
- bone marrow
- appear after6-8 weeks and increase rapidly after 16-20
- levels simultaneously rise as HbF decreases along with total body hgb mass
Where is HbA primarily produces and at what GA?
- bone marrow
- by 6 mos of age, the switch from HbF to HbA synthesis is r/t postconceptual age, not post birth age
- not significantly affected by intrauterine transfusions or exchange transfusions after birth