Chapter 5. Anatomy and Embryology

1. Chapter 5. Anatomy and Embryology 부산백병원 산부인과 R3 강영미

2. Pelvic Viscera

3. Embryonic development • Female urinary and genital tract • Closely related, anatomically and embryologically • Embryologic urinary system ; important inductive influence on developing genital system • Anomalies in one system are often mirrored by anomalies in another system

4. Embryonic development • Urinary system, internal reproductive organs and external genitalia • Develop synchronously at an early embryologic age(table 5.6)

5. Urinary system

6. Kidney, Renal collecting system, Ureters • Kidney, renal collecting system and ureters from longitudinal mass of mesoderm(nephrogenic cord)

7. Mesonephric(Wolffian) duct • Singular importance for the following reasons • Grows caudally in developing embryo to open an excretory channel into the primitive cloaca and outside world • Serves as starting point for development of the metanephros which becomes definitive kidney • Differentiates into the sexual duct system in male • Although regressing in female fetuses, inductive role in development of the paramesonephric or mullerian duct

8. Metanephros • Development of metanephros

9. 그림 13-8

10. Bladder and Urethra • Cloaca

11. Genital system development

12. Genital system • In embryologic stage, early genital system • Indistinguishable between two sexes • Known as “ indifferent stage” of genital development • Mesodermal epithelium, mesenchyme and primordial germ cell

13. Internal reproductive organs • Primordial germ cells

14. 1. Mullerian duct • Paramesonephric or mullerian ducts • Form lateral to mesonephric ducts • Grow caudally and then medially to fuse in midline • Contact urogenital sinus in region of the post. urethra at slight thickening known as sinusal tubercle

15. Male fetus • TDF • Results in degeneration of gonadal cortex and differentiation of the medullary region of the gonad into Sertoli cells • Sertoli cells • Secrete glycoprotein known as anti-mullerian hormone(AMH) • Cause regression of paramesonephric duct system in male embryo • Signal for differentiation of Leydig cells from the surrounding mesenchyme

16. Male fetus • Leydig cells • Produce testosterone,dihydrotestosterone with 5a-reductase • Testosterone • Responsible for evolution of mesonephric duct system into vas deferens, epididymis, ejaculatory ducts and seminal vesicle • At puberty, leads to spermatogenesis and changes in primary and secondary sex characteristics • DHT • Results in development of the male external genitalia and prostate and bulbourethral glands

17. Female fetus • In the absence of TDF, medulla regresses and cortical sex cords break up into isolated cell clusters(primordial follicles) • in the absence of AMH & testosterone, • Mesonephric duct system degenerates • Then, paramesonephric duct system develops • Inf. fused portion • Uterovaginal canal -> uterus and upper vagina • Cranial unfused portions • Open into celomic cavity(future peritoneal cavity) • Fallopian tubes

20. 3. Accessory genital glands • Female accessory genital glands • Develop as outgrowths from urethra(paraurethral or Skene) and definitive urogenital sinus(greater vestibular or Bartholin) • Ovaries first develop in the thoracic region, but arrive in pelvis by complicated process of descent • This descent by differential growth ; under the control of a ligamentous cord called the gubernaculum

21. Genital system ; 3. Accessory genital glands • Gubernaculum

22. External genitalia

23. Genital system abnormalities • Congenital defects in sexual development, usually arising from a variety of chromosomal abnormalities, tend to present clinically with ambiguous external genitalia • Known as intersex conditions or hermaphroditism • Classified according to the histologic appearance of the gonads

24. (1) True hermaphroditism • Individuals with true hermaphroditism • Have both ovarian and testicular tissue • Most commonly as composite ovotestes • Occasionally with an ovary on one side and a testis on the other • In the latter case, a fallopian tube and single uterine horn may develop on the side with the ovary ∵ absence of local AMH • Extremely rare condition

25. (2) Pseudohermaphroditism • In individuals with pseudohermaphroditism, • Genetic sex indicates one gender • External genitalia has characteristics of the other gender • Caused either by abnormal levels of sex hormones or abnormalities in the sex hormone receptors

26. (2) Pseudohermaphroditism • Males with pseudohermaphroditism • Genetic males with feminized external genitalia • Hypospadias(urethral opening on the ventral surface of the penis) • Incomplete fusion of the urogenital or labioscrotal folds ; m/c manifesting sx. • Females with pseudohermaphroditism • Genetic females with virilized external genitalia • Clitoral hypertrophy • Some degree of fusion of the urogenital or labioscrotal folds

27. Genital Structures

28. Vagina • Hollow fibromuscular tube extending from the vulvar vestibule to the uterus • In dorsal lithotomy, directed posteriorly toward the sacrum • In upright position, almost horizontal • Spaces between the cervix and vagina ; ant, post, and lateral vaginal fornices • Post. vaginal wall ; about 3 cm longer than the ant. wall ∵ vagina is attached at a higher point posteriorly than anteriorly

29. Vagina • Post. vaginal wall ; separated from post. cul-de-sac and peritoneal cavity by the vaginal wall and peritoneum • This proximity ; clinically useful • Culdocentesis • Intraperitoneal hemorrhage, pus, other intraabdominal fluid • Posterior colpotomy • As an adjunct to laparoscopic excision of adnexal masses

30. Cervix • Endocervical canal • About 2-3cm in length, opens proximally into the endometrial cavity at the internal os • In early childhood, during pregnancy, or with oral contraceptive use, • Columnar epithelium may extend from the endocervical canal onto the exocervix -> eversion or ectopy • Cervical mucus production • Under hormonal influence • Around the time of ovulation - profuse, clear, thin • In the postovulatory phase of the cycle ; scant and thick mucus

31. Corpus • At birth, cervix and corpus are about equal in size • In adult women, corpus has grown to 2-3 times the size of the cervix • Position ; flexion and version • Flexion - angle between the long axis of the uterine corpus and cervix • Version - angel of the junction of the uterus with the upper vagina

32. Corpus • Divided into several different regions ; • Isthmus or lower uterine segment • The area where the endocervical canal opens into the endometrial cavity • Uterine cornu • On each side of the upper uterine body, funnel-shaped areareceives the insertion of the fallopian tubes • Fundus • Uterus above this area(cornu)

33. Fallopian tubes • Fallopian tubes and ovaries ; referred to as the adnexa • Vary in length from 7 to 12 cm • Function • Ovum pickup • Provision of physical environment for conception • Transport and nourishment of the fertilized ovum

34. Fallopian tubes • Divided into several regions ; • Interstitial • Narrowest portion of the tube, lies within the uterine wall and forms the tubal ostia at the endometrial cavity • Isthmus • Narrow segment closest to the uterine wall • Ampulla • Larger diameter segment lateral to the isthmus • Fimbria(infundibulum) • Funnel-shaped abdominal ostia of the tubes

35. Ovaries • Paired gonadal structures that lie suspended between the plevic wall and the uterus by the infundibulopelvic ligament laterally and uteroovarian ligament medially • Varies in size with measurements up to 5*3*3cm • Consists of a cortex and medulla • Cortex - specialized stroma and follicles • Medulla - primarily of fibromuscular tissue and blood vessels

36. Urinary tract

37. Ureters • 25cm in length • Totally retroperitoneal in location • Pathway of lower half of each ureter • Traverses the pelvis after crossing the common iliac vessels at their bifurcation, just medial to the ovarian vessels • Descends into the pelvis adherent to the peritoneum of the lateral pelvic walland the medial leaf of the broad ligament • Enter the bladder base anterior to the upper vagina, traveling obliquely through the bladder wall

38. P. 772

39. Bladder • divided into two areas ; • Base of the bladder • Consists of the urinary trigone posteriorly and a thickened area of detrusor anteriorly • Trigone - two ureteral orifices and opening of the urethra into the bladder • Receives a-adrenergic sympathetic innervation • Is the area responsible for maintaining continence • Dome of the bladder • Parasympathetic innervation • Is responsible for micturition

40. Urethra • Female urethra ; about 3 to 4 cm in length • Extends from the bladder to the vestibule, traveling just anterior to the vagina • Lined by nonkeratinized squamous epithelium that is responsive to estrogen stimulation • Contains as inner longitudinal layer and outer circular layer

41. Abdominal Wall

42. Abdominal wall • 1. Skin • 2. Muscles • Five muscles and their aponeuroses(fig 5.16)

43. 3. Fascia ; (1) Superficial fascia • Consists of two layers • Camper fascia • Most superficial layer, which contains a variable amount of fat • Scarpa fascia • Deeper membranous layer continuous in the perineum withcolles fascia(superficial perineal fascia) and with deep fascia of the thigh(fascia lata)

44. 3. Fascia ; (2) Rectus sheath • Aponeuroses of the external and internal oblique and the transversus abdominis ; Combine to form a sheath for the rectus abdominis and pyramidalis, fusingmedially in the midline at the linea alba and laterally at the semilunar line(fig 5.16)

46. 3. Fascia ; (3) Transversalis fascia and endopelvic fascia • Firm membranous sheet on the internal surface of the transversus abdominismuscle • Like peritoneum, divided into a parietal and a visceral component • Transversalis fascia • Continues along blood vessels and other structures leaving and entering theabdominopelvic cavity • Contributes to the formation of the visceral (endopelvic) pelvic fascia • Pelvic fascia • Invests the pelvic organs and attaches them to the pelvic side walls, thereby playing a critical role in pelvic support

47. Perineum • Situated at the lower end of the trunk between the buttocks • Its bony boundaries • Lower margin of the pubic symphysis anteriorly • Tip of the coccyx posteriorly • Ischial tuberosities laterally • Diamond shape of the perineum • Divided by imaginary line joining the ischial tuberosities immediately in front of the anus, at the level of the perineal body, into an ant. urogenital and a post. anal triangle(fig 5.18)