Development of the Urogenital System

1. Development of the Urogenital System

2. The urinary and reproductive systems develop from a common mesodermal ridge ( intermediate mesoderm) along the posterior wall of the abdominal cavity.

3. Neural tube Developing spine notochord 后肠 urogenital ridge（尿生殖嵴） inside：生殖腺嵴(gonadial ridge) outside：生肾嵴(nephrogenic ridge) nephrogenic ridge gonadial ridge

4. Development of the Urinary System

6. Development of the Kidneys and Ureters Three sets of kidneys develop in human embryos: Pronephros(前肾)： is rudimentary, and the structures are never functional. Mesonephros (中肾): is well developed and functions briefly. Metanephros (后肾) becomes the permanent kidneys.

7. Pronephros（前肾） pronephric tubule(前肾小管)→degenerate pronephric duct(前肾管)→run caudally and open into the cloaca pronephric duct pronephric tubule nephrogenic ridge Early the fourth week

8. Mesonephros（中肾） mesonephric tubule(中肾小管)→degenerate mesonephric duct, Wolffian duct(中肾管) Nephrogenic ridge late the fourth week

9. Mesonephros（中肾） They have function until the permanent kidneys develop. Most of the system disappears. In male: Wolffian duct form the efferent duct, epididymal duct and ductus deferens. In female: these tubules and ducts regress.

10. Metanephros（后肾）-permanent kidney Ureteric bud（输尿管芽） Is a small outgrowth appearing at the cloacal end of each mesonephric. Metanephrogenic blastema（生后肾原基） Under the inductive influence by the terminal branches of the ureteric bud, the intermediate mesoderm form into metanephrogenic blastema. Early the fifth week

11. Ureteric bud（输尿管芽） Give rise to the ureter(输尿管), the renal pelvis(肾盂), the major and minor calyces(肾大盏、肾小盏), and collecting tubules(集合管)

12. Metanephrogenic blastema（生后肾原基） Under the inductive influence by the terminal branches of the ureteric bud, the cells of the metanephrogenic tissue form : Metanephric tissue cap→nephric vesicle→S-shaped tubule S-shaped tubule

13. Metanephrogenic blastema（生后肾原基） S-shaped tubule One end：connection with collecting duct One end：indent→Bowman’s capsule S-shaped tubule Renal corpuscle capillary→glomerulus Renal tubules nephron

14. Positional changes of the kidneys Ascend: in the pelvis → on the posterior abdominal wall Rotate：hilum of the kidney faces ventrally →anteromedially

15. rectum Development of the Urinary Bladder Urorectal septum

16. rectum ①cranial vesical part: forms most of bladder, is continuou s with the allantois ②middle pelvic part：becomes the urethra in the bladder neck Female→the entire urethra Male→the prostatic part of the urethra ③caudal phallic part：grows toward the genital tubercle Female →primordium of clitoris Male→primordium of penis

18. As the bladder enlarges, distal parts of the mesonephric ducts are incorporated into its dorasal wall. As the mesonephric ducts are abosrbed, the ureters come to open separately into the urinary bladder.

19. 膀胱

20. polycystic kidney（多囊肾） Result of failure of the collecting duct to join the distal convoluted tubules. Many hundreds of small cysts results in renal insufficiency.

21. Ectopic kidney（异位肾） One or both kidneys may be in an abnormal position. Most of them are located in the pelvis. Horseshoe kidney（马蹄肾） The poles of the kidneys are fused. Normal ascent of these fused kidneys is prevented.

22. Renal Agenesis（肾缺如） Ureteric buds fail to develop or failure of ureteric bud to penetrate the metanephrogenic balstema results in failure of kidney development. (unilateral or bilateral)

23. 双输尿管（double ureter） Results from division of the ureteric bud.

24. urachal fistula（脐尿管瘘） The entire urachus(脐尿管)remains patent. Urine escapes from its umbilical orifice(脐孔) bladder

25. Development of the genital system

26. （一）Development of the Gonads(生殖腺) The gonads(testes and ovaries) are derived from three sources ● Mesothelium lining the posterior abdominal wall. ● Underlying mesenchyme ● Primodial Germ Cells Primodial Germ Cells(原始生殖细胞) In the fourth week, on the yolk sac near the allantois. During the six week, PGCs migrate to gental ridge

29. Sex determination Testis Determining Factor, TDF（睾丸决定因子）is localized in the short arm region of the Y chromosome. Male：PGCs have Y chromosome→TDF gonad→Testes Female：PGCs have no Y chromosome →without TDF gonad →ovaries

30. Development of the Testes Seminiferous cord Gonadal cord→testicular cord mesonephric duct(中肾管) Tunica albuginea(白膜) Mesenchyme→interstitial cells Seminiferous tubules Gonadal cord →Sertoli cell PGCs→spermatogonia

31. Development of the ovaries Gonadal cords degenerating Cortical cords(皮质索) Tunica albuginea(白膜) Degenerating mesonephric duct Primordial follicles oogonia←PGCs Follicular cells← Cortical cords

33. （二）Development of Genital Ducts生殖管道的发生 mesonephric duct(中肾管) Paramesonephric ducts(中肾旁管) urogenital sinus

34. Development of the Male Genital Ducts Leyding cells testosterone mesonephric duct the efferent duct, epididymal duct, ductus deferens Sertoli cells MIS Paramesonephric ducts degenerate

35. Development of the Female Genital Ducts Paramesonephric ducts Uterine tubes Uterus and vagina Mesonephric ducts degenerate

36. 阴道板 窦结节 处女膜

37. Cryptorchidism（隐睾） crypotorchid testes may be in the abdominal cavity or anywhere along the usual pathe of descent of the testis. congenital inguinal hernia（先天性腹股沟疝） The connection between the abdominal caivity and the processus vadinalis in the scrotal sac normally clouses in the first year after birth. If thhis passageway remains open, intestinal loops may descend into the scrotum, causing … 鞘膜腔

38. ①double uterus (双子宫) ②bicornuate uterus (双角子宫) ③uterus septus (中隔子宫) Results from failure of fusion of the inferior parts of the paramesonephric ducts vaginal atresia（阴道闭锁） Failure of canalization of the vaginal plate results in atresia of the vagina.

39. Hermaphroditism(两性畸形) 共性：外生殖器介于男女之间 （1）真两性畸形： 同时有卵巢和睾丸， 性染色体为嵌合型 （2）假两性畸形： a.男性假两性畸形： 体内有睾丸（46，XY） b.女性假两性畸形： 体内有卵巢（46，XX）

40. testicular feminization syndrome（睾丸女性化综合征） 外生殖器及第二性征均呈女性 有睾丸（46，XY），能产生雄激素 体细胞及中肾管细胞缺乏雄激素受体 →中肾管未发育 支持细胞产生抗中肾旁管激素 →抑制中肾旁管发育