CH 3 Structure/Function of Hematopoietic Organs

What are the 3 stages of hematopoiesis, what organs are associated with it, and what types of Hgb are produced in each stage?

1. Mesoblastic (embryonic): In the yolk sac. Gower 1, Gower 2, Portland

2. Hepatic (fetal): From the liver. Hgb F, A, and A₂

3. Medullary (Myeloid): From bone marrow. Hgb A

What is the cite of cell development for all blood cells?

Bone marrow

What is the M:E ratio normally in bone marrow? What are the terms for excess and deficiency of the M:E progenitors?

3:1

excess: hyperplasia

deficiency: hypoplasia

What are the 3 organ sites for later lymphoid development?

Thymus, Spleen, and Lymph Nodes

Checkpoint

BM aspirate is found to have a M:E ratio of 1:2. How could we describe the causes of this finding?

Could be caused by a hypoplasia of myeloid cells while also caused by hyperplasia of erythroid cells

What are the 3 cells that can be found in the endosteum (endosteal compartment)?

Hematopoetic stem cells (HSC), osteoblasts, and osteoclasts

Why are HSC’s bound to the osteoblasts in the endosteal compartment?

Because they are precious and act as storage

Describe how adipocyte proportions change within a person at;

1. first four years of life

2. after four years of age

3. by age 25

1. nearly all marrow cavities composed of hematopoietic cells (red marrow)

2. red marrow in shafts of long bones gradually replaced by adipocytes

3. hematopoiesis limited to marrow in skull, ribs, sternum, clavicles, vertebrae, pelvis, and proximal ends of long bones

What is the definition of medullary hematopoiesis? Extramedullary hematopoiesis?

blood cell production in bone marrow

blood cell production in other tissues (spleen, then liver, then lymph nodes)

What four deficiencies/symptoms can result in extramedullary hematopoiesis?

1. marrow failure

2. marrow displacement

3. hypo/hyperplasia

4. increased hematopoietic demand

What are the 2 primary factors that regulate release of blood cells (BM-blood cell egress) from BM?

GCSF (granulocyte-colony stimulating factor)

GMCSF (granulocyte monocyte-colony stimulating factor)

What ability must cells have in order to pass into circulation?

ability to deform (the flexible ability to change shape to fit through small pores)

Checkpoint

True/False: Erythroblasts should be plentiful in peripheral circulation?

False

What are the primary and secondary lymphoid tissues?

Primary: BM and thymus (T-cell in thymus)

Secondary: Spleen and lymph nodes (late B-cell differentiation site)

What type of T/B cells come from the primary and secondary lymphoid tissues? (relate to activity/functionality)

Primary: develop from nonfunctional precursors

Secondary: possess immunocompetent T and B cells

Checkpoint

True/False: Splenectomy only affects lymphocyte production

False, other blood cells could be formed in the spleen via extramedullary hematopoiesis

What are the 4 functions of the spleen?

1. Culling: removes senescent RBC’s (aged, damaged, abnormal) from circulation through macrophage activity

2. Pitting: Macrophages remove RBC nuclear remnants/inclusions w/out destroying cell

3. Immune defense: protect against blood-borne infections

4. Storage: Stores ~ 1/3 of body’s platelets

Checkpoint

Is there evidence of splenectomy/spleen dysfunction on a Wright Stain?

?

What else does the spleen filter thats not senescent RBC’s?

encapsulated bacteria (s. pneumoniae, haemophilus influenzae, neisseria meningitidis)

What is the primary purpose of the thyroid in regards to hematopoiesis?

Serve as a compartment for maturation of T-lymphs

What are the four functions of the lymph nodes?

1. act as filters removing foreign particles via dendritic cells/macrophages

2. dendritic cells stimulate T+B cells

3. Stimulated B cells reside as plasma cells & secrete Ab’s

4. provide immune defense against pathogens in all tissues

What is lymphadenopathy and what are the 4 potential causes of it?

enlargement of lymph nodes by tissue expansion within the node

1. inflammation of lymph node

2. prolonged immune responses

3. malignant transformation of lymphocytes

4. metastatic tumors

Checkpoint

What do erythroblastic islands consist of?

erythroid precursors and macrophages