Bone Marrow and Hemopoiesis Flashcards
1
Q
Objectives
A
- Understand the structure of bone marrow as a tissue
- Know what cells are normally located in the bone marrow
- Describe the difference between red and yellow marrow
- Understand general changes that occur as blood cells progress through the developmental stages and what cellular compnents contribute to staning properties
- Be able to describe the differences between RBC and WBC precursors in marrow smears
- Understand that there are several different nomenclature systems used to descibe hemopoietic stages
- Recognize these specific stages of RBC development:
- Rubricyte, metarubricyte and reticulocyte
- Recognize these specific stages of WBC development:
- Myelocyte, metmyelocyte and band cell
- Know whch red and white blood cell stages normally circulate in peripheral blood
- Descibe the significance of a “left shift” in neutrophil dynamics
2
Q
Myeloid tissue (Bone Marrow)
A
- Reticular connective tissue supporting blood cell development
- Delicate type of connective tissue with a network of reticular fibers, made of type 3 collagen
- Found around the kidney, liver, spleen, and lymph nodes, Peyer’s patches as well as in bone marrow
- Variable amounts of fat
- yellow marrow is nearly all fat
- Large sinusoidal capillaries
- Very cellular - hard to ID individual cells
- usually studied by making a smear from a drop of aspirated bone marrow
3
Q
Myeloid Tissue - Red Marrow
A
- Tissue actively producing erythrocytes, platelets, and most leukocytes
- Blood cells are continuously renewing cell population
- Contains developing blood cells suspended in a reticular connective tissue stroma, andlarge sinusoids with many macrophages near the sinusoids
- Some fat cells
- Yellow marrow has fat that replaces most of the developing blood cells
- Has very large cells called megakaryocytes
4
Q
Distribution of Myeloid Tissue
A
- Fetus:
- All bone marrow is red marrow
- Hemopoiesis also occurs in liver, kidney and spleen
- Adult:
- Some bone marrow is normally hemopoietic even in the adults
- Pelvis, sternum, ribs, vertebrae, cranial bones, femur and humerus, some short bones
- In severe need for blood cells:
- Yellow marrow can become hemopoietic
- Liver, kidney or spleen can become hemopoietic (extramedullary hemopoiesis)
- Some bone marrow is normally hemopoietic even in the adults
5
Q
Hematopoietic Cell Populations
A
- Bone marrow contain several cell populations:
- Stem cells are totipotent or pluripotent, and capable of self renewal
- Committed progenitor cells for a specific lineage or lineages
- Matureing cells are the cells resulting from differentiation of the committed progenitor cell population
- Stromal cells of various types
6
Q
Hematopoietic Stem Cells
A
- Develp in the mesenchyme associated with the fetal yolk sac
- migrate to the liver first, then to the spleen and bone marrow
- Circulate in very small numbers in adult peripheral blood
- 1 stem cell / 10,000 nucleated cells
- Resemble small lymphocytes
- 7 - 10 um in size
7
Q
Overview of Blood Cell Development
(General Concepts)
A
- As differentiated from progenitor cells proceeds:
- The cells become smaller
- Nucleus becomes smaller and less euchromatic
- nucleoli disappear
- For RBC’s: cytoplasm changes from basophilic to palely eosinophilic (loss of ribosomes; accumulation of hemoglobin)
- For granulocytes: specific granules appear in the cytoplasm
8
Q
Lumen Bone Marrow Smear
A
- Lots of nucleated cell
- Any degree of non-round nucleus = not an RBC
- Granules in the cytoplasm = not an RBC
- Most developing granulocytes are PMN’s (neutrophils)
9
Q
Erythropoisis - Quick Overview
A
- Stages of RBC development become progressively smaller
- All stages have a round nucleus that becomes progressively smaller and heterochromatic
- Cytoplasm starts out very basophilic (ribosomes) and becomes eosinophilic (hemoglobin)
- NO GRANUELS in the cytoplams at any stage
10
Q
Erythropoiesis
A
- Rubriblast (Prerythroblast)
- Large cells
- Cytoplasm: scant, deeply basophilic
- Nucleus: large, vesicular
- Prorubicyte (Basophilic erythroblast)
- Cytoplasm: deeply basophilic
- Nucleaus: Less vesicular
- Rubricyte (polychormatophilic erythroblast)
- Cytoplasm: both acidophilic and basophilic
- may appear mottled
- Nuleus: heterochromatic
- Cytoplasm: both acidophilic and basophilic
- Metarubricyte (acidophilic or orthochromtic erythroblast or normoblast)
- Size: near mature RBC
- Cytoplasm: slightly more basophlic than RBC
- Nucleus: dense, round and oten essentrically placed
- Reticulocyte (polychromatophilic erythrocyte)
- Youngest RBC precursor to circulate Normally
- No nucleus
- Size: near mature RBC, slightly bigger
- Cytoplasm: slightly more basophilic than mature RBC
- With special stains, observe clumps of polyribosomes
11
Q
Anemia
A
- Reduction in RBC numbers, hemoglobin content, or both
- One of the most frequent fematologic disorders encountered in practice
- Not a disese, but a reflection of a diease state
- Some causes of anemia: Blood loss, hemolysis, decreased RBC production
12
Q
Regenerative Anemia
A
- The marrow responds by relasing more immature RBC’s
- Reticulocyte count goes up - best indicator of regeneration, but happens rarely in horses
- Mean corpuscular volume (MCV) goes up because reticulocytes have greater volume
- Mean corpuscular hemoglobin concentration (MCHC) goes down because reticulocytes have less concentrated hemoglobin
13
Q
Granulocytopoiesis - Quick Overview
A
- All granulocytes go through the same developmental stages
- Stages become progressively smaller
- Nucleus is round or oval early, and becomes indented or multi-lobed in later stages
- Abudant cytoplasm with granules
14
Q
Granulocytopoiesis
A
-
Myeloblast
- Size: larger than rubriblast
- More cytoplasm
-
Promyelocyte
- Non-specfic granules first appear
-
Myelocyte
- Nucleus is round or oval
- Specific granules appear, can identify 3 lines of granulocytes based on the granules
- Eosinophilic myelocytes - eosinophilic granules
- Basophilic myelocytes - basophilic granules
- Neutrophilic myelocytes - neutrally-staining granules
-
Metamyelocyte
- Nucleus is bean-shaped
- Juvenile: neutrophilic metamyelocyte
-
Band cell (stab cell)
- A horseshoe-shaped nucleus
- If he indentation goes more than halfway across the nucleus it is a band cell
- Mature neutrophil, eosinophil or basophil
- Nucleus: progressive indentation; lobes connected by thin strands
- Neutrophil has a more lobulated nucleus than other granulocytes
15
Q
Neutrophil Dynamics
A
- Total neutrophil count is a reflection of balance between:
- Marrow production
- Release into ciculation
- Tissue demand
- Left Shift:
- More immature neutrophils are seen in a blood smear
- A “regenerative” if associated with neutrophilia, or “degnerative” if without neutrophilia, or with neutropenia, or if here are more nonsegmented forms as compared to mature
