Chapter 2 - HEMATOPOIESIS Flashcards
refers to the formation and development of blood cells.
Hematopoiesis
It is a continuous, regulated process of blood cell production that includes cell renewal, proliferation, differentiation, and maturation.
Hematopoiesis
These processes result in the formation, development, and specialization of all of the functional blood cells that are released from the bone marrow to the circulation.
Hematopoiesis
During embryonic and fetal development, hematopoiesis occurs in the (?) then in the (?) (also in the spleen and thymus).
yolk sac
liver
In normal adults, hematopoiesis occurs mostly in the (?).
bone marrow and peripheral lymphatic tissues
PHASES of HEMATOPOIESIS
A. INTRAUTERINE PHASE
B. EXTRAUTERINE PHASE
A. INTRAUTERINE PHASE:
- Mesoblastic or Megaloblastic Phase
- Hepatic Phase
- Myeloid / Medullary Phase
Chief site: yolk sac
Mesoblastic or Megaloblastic Phase
Primitive RBC (megaloblas of Ehrlich) first develop within the blood island followed by leukopoiesis & megakaryopoiesis
Mesoblastic or Megaloblastic Phase
Embryonal hemoglobins are synthesized during this phase.
Mesoblastic or Megaloblastic Phase
This phase starts on the 3rd month of fetal life
Hepatic Phase
Chief site: Liver
Hepatic Phase
Fetal hemoglobin (HbF) is synthesized during this phase
Hepatic Phase
Chief site: Bone Marrow
Myeloid / Medullary Phase
This starts on the 5th month of fetal life. It increases during the last trimester and remains the chief site at birth.
Myeloid / Medullary Phase
Production of adult hemoglobins (HbA) starts during this phase
Myeloid / Medullary Phase
B. EXTRAUTERINE PHASE
- Myeloid / Medullary Phase
- Extramedullary hematopoiesis
First 3 weeks postpartum, the bone marrow becomes the only normal site of blood cell production
Myeloid / Medullary Phase
Red marrow is present in all fetal skeletal structures, until the age of 2 - 3 years
Myeloid / Medullary Phase
Fourth year: Rate of BM growth exceeds need for blood cells resulting to the replacement of active marrow space by areas of fatty reserves. marrow space by areas of fatty reserves.
Myeloid / Medullary Phase
Locations of red marrow
Children:
18 years and older:
skull, clavicle, ribs, vertebra, pelvis & long bones
skull, clavicle, ribs, vertebra, pelvis & at the proximal ends of long bones
Occurs normally and in certain disease states when the BM is unable to produce sufficient numbers of hematopoietic cells.
Extramedullary hematopoiesis
Liver and Spleen
Extramedullary hematopoiesis
THEORIES ON THE ORIGIN OF BLOOD CELLS
- Monophyletic / Unitarian Theory
- Polyphyletic Theory
- Complete Theory
states that blood cells come from one stem cell which is totipotent, giving rise to any series of cell types.
Monophyletic / Unitarian Theory
states that there are two to three cell origins. There is a separate and distinct stem cell compartment
Polyphyletic Theory
Polyphyletic Theory Sub-theories:
a. Dualistic
b. Trialistic
Lymphoblast and myeloblast
a. Dualistic
Reticuloendothelial cells give rise to monocytes
b. Trialistic
believes that there is a separate stem cell for each cell series
Complete Theory