Module 9: Reproductive System Flashcards Preview

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Flashcards in Module 9: Reproductive System Deck (224)
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31

(Male Gonadal Development )
• embryonic __ enlarges to become the testis and embryonic cortex regresses

medulla

32

(Male Gonadal Development )

• formation of seminiferous tubules and Sertoli cells at 6 to 7 weeks

• formation of Leydig cells at 8 to 9 weeks
- secrete testosterone in response to HCG
- at 9 weeks, a definitive testes is present and secretion of testosterone established

• at 7 to 9 months gestation
- testes normally descend through inguinal ring

33

Female Gonadal Development (1)

• embryonic cortex proliferates to become the ovaries
- at weeks 11 and 12, primordial follicles are discernible
- reaches maximal development by weeks 20 to 25

34

Female Gonadal Development (2)

• embryonic medulla regresses and becomes the hilum of mature ovaries
• embryonic ovary does not secrete hormones
• development starts during 9th week gestation in the absence of a signal for testis formation

35

Phenotypic Sex development requires:

- differentiation of genital ducts (internal genitalia)
- differentiation of external genitalia
- hypothalamic differentiation

36

• differentiation of the internal and external genitalia requires presence of hormones or chemical messengers

Phenotypic Sex

37

(Control Mechanisms in Development of Phenotypic Sex)

• cells in distant endocrine gland secrete hormones into bloodstream to regulate or induce differentiation in distant target tissues  
• EXAMPLE: testosterone, secreted by fetal Leydig cells, induces differentiation of anlagen of external genitalia

CLASSIC ENDOCRINE MECHANISM

38

(Control Mechanisms in Development of Phenotypic Sex)

• dissemination of hormone by local diffusion through the nearby target tissue
• EXAMPLES: action of MIF on Mullerian duct, action of Testosterone on Wollfian duct

LOCAL PARACRINE REGULATORY MECHANISM

39

(Differentiation of Internal Genitalia)
• at 7 weeks, fetus contains both male and female primordial genital ducts:

1. Wolffian ducts (mesonephric duct)
2. Mullerian ducts (paramesonephric ducts)

40

- have the potential of differentiating into:
• epididymis
• vas deferens
• seminal vesicles

Wolffian ducts (mesonephric duct)

41

- serves as the anlagen of the:
• uterus
• fallopian tube
• cervix
• upper vagina

Mullerian ducts (paramesonephric ducts)

42

• it doesn't mean that because you are a female you will have a uterus; you might have a congential absence of the uterus
• you did not have a mullerian duct
• 2nd/3rd common cause of the absence of menses in a teenage girl

Mayer-Rokitansky-Küster-Hauser syndrome

43

(Hormones Involved in Sex Differentiation)

• responsible for differentiation of Wolffian ducts to male internal genitalia at 9 to 10 weeks
• secreted by fetal Leydig cells
• does NOT have to be converted to its active product (dihydrotestosterone) to act on the Wolffian ducts
*5- reductase activity is required for conversion of testosterone to dihydrotestosterone
*cells do not develop 5- reductase activity until they have fully differentiated

TESTOSTERONE

44

(Hormones Involved in Sex Differentiation)
• other names: Anti-Mullerian Hormone (AMH), Mullerian Regressing Factor (MRF)
• glycoprotein hormone produced by Sertoli cells
• induces dissolution of Mullerian ducts, therefore inhibiting differentiation of female internal genitalia

MULLERIAN INHIBITING FACTOR (MIF)

45

Differentiation of External Genitalia

• in contrast to internal genitalia, external genitalia in both sexes develop from common anlagen
• growth and development of the male external genitalia require dihydrotestosterone

46

(Anlagen of External Genitalia)

• in males: becomes glans penis, corpus cavernosum and corpus spongiosum
• in females: becomes clitoris and vestibular bulb

GENITAL TUBERCLE

47

(Anlagen of External Genitalia)

• in males: fuse around the urethral groove to form the penis (ventral shaft)
• in females: genital folds do not fuse and develop into labia minora

GENITAL FOLDS or URETHRAL FOLDS

48

(Anlagen of External Genitalia)

• in males: fuse to form scrotum and prepuce
• in females: do not fuse but develop into labia majora

GENITAL SWELLING or LABIO SCROTAL SWELLING

49

(Anlagen of External Genitalia)

• in males: develops into male urethra, Cowper’s glands and prostate gland
• in females: develops into female urethra, lower vagina, Bartholin’s glands and Skene’s glands

UROGENITAL SINUS

50

Special Considerations

• in normal females, hormones may not be essential for differentiation
• growth of labia to normal size requires estrogen

51

Special Considerations (2)

• exposure of normal female fetus to excess testosterone during differentiation causes virilization
*if exposed early, male pattern can result
*if exposed after differentiation is completed, enlargement of clitoris may occur

• for newborn with ambiguity of external genitalia
*postpone signing of birth certificate
*do screening test

52

(Hypothalamic Differentiation)
• control of gonadal function is mediated by 2 gonadotropins:

o follicle-stimulating hormone (FSH)
o luteinizing hormone (LH)

53

(Hypothalamic Differentiation)
• gonadotropins differ in pattern of secretion:

o in males: pulsatile but relatively constant, sustained manner (tonic release)
o in females: pulsatile but cyclic (cyclic release)

54

(Hypothalamic-Pituitary-Gonadotropin Unit)
• includes the following:

o pulsatile secretion of (Luteinizing Hormone Releasing Hormone) LHRH by hypothalamus
o pulsatile secretion of Follicle stimulating hormone (FSH) and Luteinizing Hormone (LH) by pituitary

55

(Hypothalamic-Pituitary-Gonadotropin Unit)
• characteristics:

o matures in the fetus
o suppressed during childhood
o reactivated at onset of puberty

56

Gonad (Cortex)

Male: Regresses
Female: Ovaries

57

Gonad (Medulla)

Male: Testis
Female: Regresses

58

Wolffian Duct (mesonephric duct)

Male: Epididymis, Vas Deferens, Seminal Vesicle
Female: Regresses

59

Mullerian Duct (paramesonephric duct)

Male: Regresses
Female: Fallopian tubes, uterus, cervix, vagina (upper 1/3)

60

Genital Tubercle

Male: Glans penis, corpus cavernosum/ spongiosum
Female: clitoris, vestibular bulb