[Morphological observation on 6th-week development of human kidneys and gonads]

The development of kidney and gonad of 3-6th-week human embryos were studied. Their positions at different developing stages were measured in terms of the sequence of neural ganglion according to Felix's method. The 9.5 mm embryo: Pronephrons are seen as 2 epithelial blind tubules on the right side and 1 on the left at the 6th cervical ganglion level. The lateral tubule on the right side and the left one are pronephric ducts, whereas the medial one on the right side is the pronephric tubule. The cranial ends of mesonephrons on both sides level at the 1st thoracic ganglia and run caudally to the 11th thoracic ganglia, their total number amount to 62. The mesonephric ducts on both sides firstly appear opposite to the 1st thoracic ganglia and open caudally into the cloaca. The metanephrons, the ureteric buds are unbranched yet and the metanephric mesoderm appears as clusters of cells on both sides. The gonads are indifferent. The 11 mm embryo: Pronephrons degenerated. The cranial ends of mesonephric tubules locate at the 3rd thoracic ganglia level on both sides and extend caudally to the level of the 11th ganglion in the right side and 12th in the left, their total number amounts to 65. Mesonephric ducts appear opposite to the 4th thoracic ganglia on both sides, running caudally, and open into the cloaca. Metanephrons, the ureteric buds give off 1st grade branches on both sides and metanephric mesoderm remain as clusters of cells. The gonads are indifferent. The 12 mm embryo: Pronephrons degenerated.(ABSTRACT TRUNCATED AT 250 WORDS)