Fetal development of the mesonephric artery in humans with reference to replacement by the adrenal and renal arteries.
According to the classical ladder theory, the mesonephric arteries (MAs) have a segmental arrangement and persist after regression of the mesonephros, with some of these vessels becoming definitive renal arteries. To avoid interruption of blood flow, such a vascular switching would require an intermediate stage in which two or more segmental MAs are connected to a definitive renal artery. To examine developmental changes, especially changes in the segmental distribution of MAs, we studied serial paraffin sections of 26 human embryos (approximately 5-7 weeks). At 5-6 weeks, 1-2 pairs of MAs ran anterolaterally or laterally within each of the lower thoracic vertebral segments, while 2-5 pairs of MAs were present in each of the lumbar vertebral segments, but they were usually asymmetrical. The initial metanephros, extending along the aorta from the first lumbar to first sacral vertebra, had no arterial supply despite the presence of multiple MAs running immediately anterior to it. Depending on increased sizes of the adrenal and metanephros, the MAs were reduced in number and restricted in levels from the twelfth thoracic to the second lumbar vertebra. The elimination of MAs first became evident at a level of the major, inferior parts of the metanephros. Therefore, a hypothetical arterial ladder was lost before development of glomeruli in the metanephros. At 7 weeks, after complete elimination of MAs, a pair of symmetrical renal arteries appeared near the superior end of the metanephros. In conclusion, the MAs appear not to persist to become a definitive renal artery.
Department of Urology, Kobe University School of Medicine, Kobe, Japan. Electronic address: hntnbyk@me.com.
Nobuyuki
N
Hinata
Department of Anatomy, Akita University Graduate School of Medicine, Akita, Japan.
Ryoji
R
Suzuki
Department of Anatomy, Akita University Graduate School of Medicine, Akita, Japan.
Akimitsu
A
Ishizawa
Department of Urology, Kobe University School of Medicine, Kobe, Japan.
Hideaki
H
Miyake
Institute of Embryology, Complutense University, Madrid, Spain.
Jose Francisco
JF
Rodriguez-Vazquez
Division of Internal Medicine, Iwamizawa Asuka Hospital, Iwamizawa, Japan.
Gen
G
Murakami
Department of Urology, Kobe University School of Medicine, Kobe, Japan.
Masato
M
Fujisawa
D000311:Adrenal Glands / Q000098:blood supply / Q000196:embryology*; D000328:Adult; D001158:Arteries / Q000196:embryology*; D005260:Female; D047109:Fetal Development / Q000502:physiology*; D005865:Gestational Age; D006801:Humans; D007668:Kidney / Q000196:embryology*; D007678:Kidney Glomerulus / Q000254:growth & development; D008159:Lumbar Vertebrae / Q000098:blood supply / Q000196:embryology; D008650:Mesonephros / Q000098:blood supply / Q000196:embryology*; D011247:Pregnancy; D012039:Regional Blood Flow; D012077:Renal Artery / Q000196:embryology*; D012079:Renal Circulation; D012445:Sacrococcygeal Region / Q000098:blood supply / Q000196:embryology
Adrenal; Definitive kidney; Human embryo; Mesonephric artery; Metanephros; Renal artery