泌尿生殖發(fā)生ppt課件-資料下載頁
2025-03-22 01:39本頁面
【正文】 hra. In female, these ducts and tubules regress. The metanephros or permanent kidneys appear in the fifth week. The metanephros develop from two sources：ureteric bud(an outgrowth of the mesonephric duct ) and metanephrogenic tissue. Metanephrogenic tissue forms renal capsules and renal tubules. And the collecting system originates from the ureteric bud. This bud also gives rise to the ureter, renal pelvis, calyces. Connection between renal tubule and the collecting tubule is important for normal development. The genital system consists of gonads or primitive sex glands, genital ducts, and external genitalia. All three ponents go through an indifferentiation stage in which they may develop into either a male or a female. Sex differentiation is a plex process that involves many genes. The key to sexual dimorphism is the Y chromosome, which contains the SRY(sexdetermining region on Y) gene on its short arm. The SRY protein is the testisdetermining factor。 under its influence male development occurs。 in its absence female development is established. The testisdetermining factor causes development of the testis. Absence of the testisdetermining factor stimulates formation of the ovary. When primordial germ cells fail to reach the indifferent gonad, the gonad remains indifferent or is absent. There are two types of ducts in the early embryo: a pair of mesonephric ducts and a pair of paramesonephric ducts. In male the mesonephric ducts develop into genital ducts. In female the paramesonephric ducts develop. QUESTIONS 1. Illustrate the development of kidney. 2. Explain the formation of polycystic kidney, horseshoe kidney and double ureter. is cloaca? what ans will it further develop into? do the primordial germ cells migrate from? 5. Describe the development of testis and ovary. 6. How do the mesonephric ducts and paramesonephric ducts develop in male or female?
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