Hematopoiesis

Question 1

Red marrow

Answer 1

Network of vascular sinuses (specialized blood vessels) & hematopoietic cells.

Organized into sacs (alveoli) within which hematopoietic cells develop in nests or foci.

Supported by reticular cells and reticular fibers.

Question 2

In red marrow, cells meant to become RBCs develop ___ the sinus wall in nests with an associated macrophage which contains iron.

Megakaryocytes (makes platelets) develop ___ the sinus

Cells meant to become granulocytes develop ___ the sinus.

Answer 2

RBC & megakaryocytes - near the sinus

Granulocytes - away from the sinus

Question 3

Yellow marrow is filled with ____ and essentially excludes ____.

Where is it?

Answer 3

Filled with adipocytes and excludes hematopoietic cells.

Housed in the diaphysis of long bone

Question 4

Erythropoiesis stages

Answer 4

Proerythroblast divides

Basophilic erythroblast divides

Polychromatophilic erythroblast divides

Orthochromic erthyroblast

Reticulocyte

Erythrocyte

Question 5

Name these

Answer 5

Proerythroblast: large

Basophilic erythroblast: smaller, very basophilic cytoplasm

Polychromatophilic erythroblasts basophilic & acidophilic cytoplasmic regions

Orthochromatophilic erythroblast: cytoplasm similar to that of a mature RBC

Reticulocyte: lost their nuclei, but not he polyribsoomes to make globin

Question 6

Control of erythropoiesis (wk long process)

Answer 6

Erythropoietin (EPO): glycoprotein released from kidneys in response to hypoxia

Dietary iron, vitamin B12, and folic acid are also crucical

Question 7

What’s the first step of granulopoiesis that doesn’t divide?

Answer 7

metamyelocyte.

Question 8

Granulopoiesis: formation & differentiation of granulocytes

Answer 8

Question 9

At what stage of granulopoiesis do you start seeing azurophilic granules? Specific granules?

Answer 9

Azurophilic granules - promyelocyte

Specific granules - myelocyte

Question 10

What is MB? 1-5?

Answer 10

mb- myeloblast (no granules)

1- promyelocyte (blue azurophilic granules)

2- myelocytes (some azurophilic, some specific)

3 & EM - late myelocyte (more specific)

4 & EMm- metamyelocyte (specific granules)

5- band cells (band nucleus)

6-nearly mature segmented neutrophils

Question 11

Control of granulopoiesis

Answer 11

Colony stimulating factors (CSF): substances relased by macrophage/monocyte community; release stimulated by increased cell migration into tissues, such as in an infection

Question 12

Neutrophils pass through 4 compartments:

Answer 12

1. Granulopoietic: in bone marrow w/developing progenitor cells
2. Storage: in red marrow; buffer system that releases large #s of mature neutrophils into blood as needed
3. Circulating: blood
4. Marginating: cells accumulate temporarily at the surface of the endothelium in venules & small veins

Question 13

The ___ and __ compartments of granulopoiesis are ~equal size and there is a constant interchange of cells between them.

Answer 13

Circulating & marginating

Question 14

Process of thrombopoiesis: platelet formation

Answer 14

1. Megakaryoblast (Mb): has big nucleus (4n) close to sinuses
2. Promegakaryocyte: has 8n nucleus
   
   1. Develops platelet demarcation channels
3. Megakaryocyte (M): giant cell w 32n-64n nucleus
   
   1. Very distinct platelet demarcation channel
   2. Massive protrustion of the cell penetrates a sinus and fragments into platelets
4. Thrombocyte (platelet): final end product that circulates in blood; responsible for primary hemostasis (clot formation)

Question 15

How can you tell that the middle picture is a megakaryocyte and not a megakaryoblast?

Answer 15

It’s less intensely basophilic.

S= sinusoids

Question 16

Control of thrombopoiesis

Answer 16

Thrombopoietin: serum glycoprotein from liver that simulates megakaryotcytes and platelet production

Autoregulated by platelets, which bind & degrade thrombopoietin

Question 17

Other red marrow cells

Answer 17

Macrophages/histiocytes: tissue counterparts of monocytes in the blood; perform phagocytosis & iron storage

Structural cells: adipocytes, reticular cells, endothelial cells

Lymphocytes

Mast cells: releases histamine; also has heparin, PAF, etc

Question 18

G-CSF

Answer 18

Glycoprotein produced in endothelial cells, fibroblasts, and macrophages in different parts of the body to treat neutropenia after cancer chemotherapy or bone marrow transplanatation

Question 19

If you have a chronic reneal disease, your kidney isn’t making EPO, so you can administer it then monitor the effectiveness by an increase in ___ in circulating blood

Answer 19

Reticulocytes

Question 20

GM-CSF

Answer 20

Glycoprotein produced by endothelial cells, T cells, fibroblasts, and monocytes that stimulates the formation of neutrophils, eosinophils, basophils, monocytes, and dendritic cells.

Not as effective as G-CSF for neutropenia

Question 22

Deficiency in vitamin B₁₂ and folic acid causes

Answer 22

megaloblastic anemia: development of large megaloblasts that develop into large RBCs (macrocytes)

Question 23

Microcytic anemias (small RBCs) are due to a decrease in hemoglobin production caused by:

Answer 23

Lack of hemoglobin product (e.g. thalassemia)

Limited iron availability and suppression of EPO production in inflammation

Lack of iron delivery to the heme group (most common)

Defects in the synthesis of the heme group (sideroblastic anemias, characterized by ringed sideroblasts)

Question 24

All blood cell types arise from common or pluripotent stem cells, then they can become lymphoid cells that go to the ___ or myeloid cells that develop in the ____.

Answer 24

Lymphoid cells - lymphocytes- leave the marrow to go to the thymus, lymph nodes, spleen, and other lymphoid tissue

Myeloid cells - granulocytes, monocytes, RBCs, megakaryotcytes - develop in bone marrow