Function of the RBCs, WBCs, platelets and Bone Marrow

Question 1

What is haematopoiesis?

Answer 1

Formation of blood components

It includes the processes of erythropoiesis, thrombopoiesis, and granulopoiesis.

Question 2

What regulates erythropoiesis?

Answer 2

Erythropoietin (EPO) synthesized by kidneys

EPO stimulates the formation of erythrocytes.

Question 3

What is thrombopoiesis?

Answer 3

Formation of thrombocytes/platelets

It is regulated by thrombopoietin (TPO) synthesized by the liver.

Question 4

What are the steps involved in thrombopoiesis?

Answer 4

1. Pluripotent stem cells stimulated by TPO to differentiate into megakaryocytes
2. Megakaryocyte develops extra cytoplasm and forms pro-platelets
3. Platelets bud off from pro-platelets into circulation

The megakaryocyte remains in the bone marrow.

Question 5

What regulates granulopoiesis?

Answer 5

Granulocyte colony stimulating factor (GCSF) synthesized by endothelium

GCSF stimulates the formation of granulocytes.

Question 6

What are hematopoietic stem cells?

Answer 6

Multipotent stem cells capable of differentiation or self-renewal

Their differentiation is influenced by growth factors and the microenvironment.

Question 7

What is the differentiation timeline for blood cell types?

Answer 7

Takes 2-3 weeks and occurs in different areas as age increases

Initial formation in foetus occurs in the yolk sac, then lymph nodes, liver, and spleen.

Question 8

Where does haematopoiesis occur in infants and children?

Answer 8

In red marrow, which is present in all bones

Red marrow is responsible for the formation of blood cells.

Question 9

Where does haematopoiesis occur in adults?

Answer 9

In red marrow of axial bones: sternum, vertebrae, ribs, pelvis, proximal long bones, cranial

All other bones develop yellow marrow.

Question 10

What do haematopoietic stem cells differentiate into?

Answer 10

Myeloid or lymphoid stem cells

Myeloid stem cells further differentiate into various blood cell precursors.

Question 11

What do myeloid stem cells differentiate into?

Answer 11

Megakaryoblasts, proerythroblasts, monoblasts, myeloblasts

Myeloblasts further differentiate into granulocytes: neutrophils, eosinophils, basophils.

Question 12

True or False: Erythropoiesis occurs primarily in the liver.

Answer 12

False

Erythropoiesis is regulated by EPO from the kidneys.

Question 13

What do lymphoid stem cells differentiate into?

Answer 13

Lymphoblasts, which further differentiate into NK cells, T lymphocytes, and B lymphocytes.

Question 14

What is a multipotent hematopoietic stem cell also known as?

Answer 14

Hemocytoblast.

Question 15

What are the two paths a remaining cell can take after division?

Answer 15

Myeloid stem cell or lymphoid stem cell.

Question 16

What are the products of myeloid stem cells?

Answer 16

Megakaryoblast, proerythroblast, reticulocyte, myeloblast, monoblast, basophil, neutrophil, eosinophil, monocyte.

Question 17

What are the products of lymphoid stem cells?

Answer 17

Lymphoblast, natural killer cell, small lymphocyte, T lymphocyte, B lymphocyte, plasma cell, macrophage.

Question 18

Where do myeloblasts and lymphoblasts remain?

Answer 18

In the bone marrow; they should never enter peripheral blood circulation.

Question 19

What can cause Bone Marrow Failure (BMF)?

Answer 19

Stress can cause yellow marrow to revert back to haematopoiesis.

Question 20

What is extramedullary hematopoiesis?

Answer 20

Formation of blood components outside the bone marrow, e.g., in the liver and spleen.

Question 21

What condition can cause myelofibrosis?

Answer 21

It causes red bone marrow to become filled with fibrotic tissue, leading to haematopoiesis occurring elsewhere.

Question 22

What is self-renewal in the context of hematopoietic stem cells?

Answer 22

The ability to maintain proliferation and block differentiation, increasing the number of hematopoietic stem cells.

Question 23

What is self-renewal in haematopoietic stem cells?

Answer 23

Self-renewal allows haematopoietic stem cells to maintain their ability to proliferate and block differentiation, increasing their numbers.

Question 24

What is the normal blood volume in males and females?

Answer 24

Normal blood volume is 5-6 litres in males and 4-5 litres in females, increasing by ~50% during pregnancy.

Question 25

What are the components of centrifuged blood?

Answer 25

In centrifuged blood:
- Top: 55-60% volume plasma
- Middle: Less than 1% volume WBCs and platelets (buffy coat)
- Bottom: 40-45% volume RBCs

Question 26

What happens to cell lineage counts with overactive and failed stem cells?

Answer 26

Overactive stem cells cause cell lineage counts to increase, while failed stem cells cause cell lineage counts to decrease.

Question 27

What is the structure of bone marrow?

Answer 27

Bone marrow is soft, spongy, and flexible.

Question 28

What does a bone marrow trephine biopsy show?

Answer 28

A bone marrow trephine biopsy shows cells with pink/orange cytoplasm and purple nuclei, dispersed around large white circles (fat spaces in bone marrow).

Question 29

What does a bone marrow aspirate reveal?

Answer 29

A bone marrow aspirate shows individual cells in more detail but cannot show bone marrow architecture.