File:Arey1924 fig202.jpg

Fig. 202. Developmental stages of the human spleen

(redrawn from Kollman and Tonkoff). A, 10.5 mm.; B, 20 mm.

Embryos of 9 mm. exhibit a swelling on the left side of the dorsal mesogastrium, near the dorsal pancreas (Fig. 202 A). The thickening is due to a temporary proliferation and invasion of mesothelial cells into the underlying mesenchyme, which, meanwhile, has also undergone local enlargement and vascularization. These cells from the peritoneal epithelium give rise to a large part, at least, of the future spleen. The union of the splenic anlage with the mesogastrium (Fig. 202 B) is ultimately reduced to a narrow band.

At first the blood vessels constitute a closed system. The peculiar adult circulation is acquired relatively late. Lymphoid tissue first appears as ellipsoids about the smallest arteries in fetuses of four months. At seven months, the ovoid splenic corpuscles form nodules about the larger arteries. The capsule, trabeculce, and reticulum differentiate from the cells of the common anlage. During the last half of fetal life, red blood corpuscles are developed actively in the splenic capillaries.

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Developmental Anatomy 1924: 1 The Germ Cells and Fertilization | 2 Cleavage and the Origin of the Germ Layers | 3 Implantation and Fetal Membranes | 4 Age, Body Form and Growth Changes | 5 The Digestive System | 6 The Respiratory System | 7 The Mesenteries and Coelom | 8 The Urogenital System | 9 The Vascular System | 10 The Skeletal System | 11 The Muscular System | 12 The Integumentary System | 13 The Central Nervous System | 14 The Peripheral Nervous System | 15 The Sense Organs | C16 The Study of Chick Embryos | 17 The Study of Pig Embryos | Figures

Reference

Arey LB. Developmental Anatomy. (1924) W.B. Saunders Company, Philadelphia.

Cite this page: Hill, M.A. (2024, April 27) Embryology Arey1924 fig202.jpg. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/File:Arey1924_fig202.jpg

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