Figure 1.
(A–H) Panoramic view of chicken yolk sacs between E3 and E19.
The embryonic day (E) is indicated in the upper right corner in each picture. Histological sections of yolk sacs show endoderm (End), vessels (Art), and areas of hematopoietic foci (arrows). (A–E) The areas occupied by these foci are shown gradually increasing in the photomicrographs between E3 and E12, and (F–H) decreasing in onwards stages. (G, H) Atrophic vessels (arrowheads). (F–H) Yolk (Y). Hematoxylin-eosin. Bars 100 µm.
Figure 2.
(A–K) Erythropoiesis (Ery) and (E–L) granulopoiesis (Gr) in chicken yolk sac between E3 and E20.
The embryonic day (E) is indicated in the upper right corner in each picture. Thin arrows show mitosis in erythrocytes (A, D, E, I, K) and in a granulocyte (H). (A) Predominance of basophilic cells with a slight acidophily. (B, C) Numerous pro-erythroblasts and basophilic erythroblasts (Ery) between artery (Art) and endoderm (End). (C) Note a cell band leukocyte (arrowhead). (D) Erythrocytic (Ery) focus showing mature erythrocyte (arrowhead). (F, G) Cell band leukocyte (arrowhead). (H) Eosinophil granules into granulocytic cells at different stages of maturation show the cytoplasm of these cells in red-orange color. (I) Promyelocyte (arrowhead). (J, K) Foci of erythrocytic (white asterisks) and granulocytic (black asterisks) differentiation are present in equivalent numbers at this stage. (K) Mature leukocyte (arrowhead). (L) Myelocyte (arrowhead). (E–K) Note that granulocytic and erythrocytic lineages do not mix. End, endoderm; Art, artery. (A–E, G, I, L) Lennert's Giemsa, (F, J, K) Hematoxylin-eosin, and (H) Sirius Red stains at pH 10.2. Bars 20 µm.
Figure 3.
Chicken liver development without hematopoietic activity from E3 to E8.
The embryonic day (E) is indicated in the upper right corner in each picture. (A, C, D) Numerous mitosis (arrows) are seen in hepatoblasts (Hp). (B) Mitosis in circulating erythrocyte (arrow). (E) Immature hematopoietic circulating cells (arrows) in sinusoidal capillaries (vessels located between hepatoblast cords, Hp). Note the large and irregular lumen of the sinusoidal capillaries. (F) Foci of immature erythropoietic cells in circulation (limited by arrows). Hp, hepatoblasts; VD, venous duct; sinusoidal capillaries (asterisks). (A, C, F) Hematoxylin-eosin and (B, D, E) Lennert's Giemsa stains. Bars 20 µm.
Figure 4.
Chicken liver development without hematopoietic activity from E9 to E 14.
The embryonic day (E) is indicated in the upper right corner in each picture. Hp, hepatoblasts; CV, central vein; sinusoidal capillaries (asterisks); PV, portal vein; CT, connective tissue. (A) Lennert's Giemsa and (B–F) Hematoxylin-eosin stains. Bars 20 µm.
Figure 5.
Liver development with hematopoietic activity (E15 to E19 and E21).
The embryonic day (E) is indicated in the upper right corner in each picture. Granulopoiesis (limited by arrows) is demonstrated in connective tissue (CT) in the liver portal spaces (PV, portal vein; BD, biliary duct; V, vessel). (F) Promyelocyte (black arrowhead). Myelocyte (white arrowhead). (A–C) Hematoxylin-eosin and (D–F) Lennert's Giemsa stains. Bars 20 µm.
Figure 6.
Establishment of hematopoiesis in the diaphysis of long bones during chickens' developmental period.
The embryonic day (E) is indicated in the upper right corner in each picture. (A) Leukocytes with eosinophil granules (arrowheads) are shown in the marrow stroma (St) in the beginning of the bone marrow formation. Metamyelocyte (black arrow) into vessel (V). Osteoclast (white arrow). (B) Granulocytes (white arrows) and basophilic cells with eccentric nucleus and prominent nucleolus (black arrows) are shown in the marrow stroma. Mitosis in erythrocyte (arrowhead). (C) Basophilic cell (arrowhead). Granulocytes at different stages of maturation in the stroma including promyelocytes (arrows). (D) These cells are shown in high magnification (arrows). (E) Granulocytes in the stroma (St) and erythropoiesis (limited by arrows) in sinusoidal capillaries, shown (F) in high magnification. (G) Panoramic view of a transversal section of diaphysis. The bone marrow (limited by arrows) shows areas of erythropoiesis (blue color) and granulopoiesis (red color). (H) Erythropoiesis (Ery) in sinusoidal capillaries showing immature hematopoietic cells (arrows) and mitosis in erythrocyte (arrowhead). Granulopoiesis (Gr) in the marrow stroma. HC, hypertrophic cartilage; SC, sinusoidal capillary; BT, bone tissue. (A) Sirius Red at pH 10.2, and (B–H) Lennert's Giemsa stain. Bars 20 µm.
Figure 7.
Scheme of hematopoiesis in the yolk sac, liver, and bone marrow during chicken development.
Bars indicate the temporal distribution of this activity in the AGM region, yolk sac (YS), liver (L), and bone marrow (BM). Black dotted lines indicate the presence of both erythropoiesis and granulopoiesis in the YS (C–F) and BM (E–G). The blue dotted line is to draw attention to the granulopoiesis in the L. (A) At E4, immature erythropoietic cells, incomplete erythropoietic foci, and rare granulocytes are distributed in the YS. (B) From E6, the YS shows complete erythropoietic foci (all maturation stages are seen) and some granulocytes. (C) From E7, complete erythropoietic and granulopoietic foci are distributed in the YS. (D) At E10, erythropoietic and granulopoietic foci are seen in the YS. Granulocytes at different stages of maturation are noted in the BM. At E11, basophilic cells are also seen in the BM. (E) At E15, both erythropoietic and granulopoietic foci are frequently observed in the YS and BM. In this phase, granulopoiesis begins in the L around the portal vessels. (F) At E17, hematopoiesis is reduced in the YS. Granulopoiesis persists in the L portal spaces, and both erythropoietic and granulopoietic activities are noted in the BM. (G) At E21, granulopoietic foci are seen in L connective tissues, both erythrocytic and granulocytic activities are observed in the BM, and the YS is no longer a hematopoietic site.