Development of the Urogenital System

1
Development of theUrogenital System

• Montakarn Tansatit, M.D.
• Department of Anatomy
• Faculty of Medicine
• Chulalongkorn University

2
Urogenital system

• develops from intermediate mesoderm
• Urogenital ridge
• Nephrogenic cord urinary system
• Gonadal (genital) ridge genital system

3
Developmentof theUrinary System
4
Urinary system

• intermediate mesoderm ? urogenital ridge
• Part of the urogenital ridge forms the
  nephrogenic cord
• Nephrogenic cord develops into three sets of
  nephric structures
• 1. Pronephros
• 2. Mesonephros
• 3. Metanephros

5
(No Transcript)
6
Kidneys

• Three sets of excretory organs develop in human
  embryos
• 1. Pronephros
• 2. Mesonephros
• 3. Metanephros

7
Pronephros

• is the cranialmost nephric structure
• pronephric tubules and pronephric duct
• is a transitory structure that regresses
  completely by week 5 of development and is not
  funcitonal in humans

8
Mesonephros

• is the middle nephric structure
• mesonephric tubules and mesonephric duct
  (wolffian duct)
• is partially transitory and is functional for a
  short period

9
Mesonephros

• most of the mesonephric tubules regress, but the
  mesonephric duct persists and opens into the
  urogenital sinus
• mesonephroi degenerate by the end of the first
  trimester

10
(No Transcript)
11
(No Transcript)
12
Metanephros

• develops from an outgrowth of the mesonephric
  duct, the ureteric bud, and from a condensation
  of mesoderm within the nephrogenic cord, the
  metanephric blastema
• is the caudalmost nephric structure

13
Metanephros

• begins to form at week 5 and is functional in the
  fetus at about week 10 of development
• develops into the definitive adult kidney

14
Development of the kidneys

• Ureteric bud
• Ureters
• Renal pelvis
• Major calyces
• Minor calyces
• Collecting tubules

15
Development of the kidneys

• The inductive influence of the collecting
  tubules causes the formation of metanephric
  vesicles

16
Nephron formation

• The metanephric vesicles differentiate into
• Distal tubule
• Loop of Henle
• Proximal tubule
• Bowmans capsule

17
Uriniferous tubule

• consists of two embryologically different parts
  
• 1. Nephron is derived from the metanephric mass
  of mesoderm
• 2. Collecting tubule is derived from the
  ureteric bud (metanephric diverticulum)

18
Nephron formation

• is complete at birth, but functional maturation
  of nephrons continues throughout infancy

19
Fetal kidney

• The fetal kidneys are subdivided into lobes that
  are visible externally
• The lobulation disappears during infancy and is
  obscured in definitive adult kidney

20
Positional changes of the kidneys

• Initially permanent kidneys lie close to each
  other in the pelvis
• gradually come to lie in the abdomen and move
  farther apart
• attain their adult position by the ninth week
• as the kidneys ascend they rotate medially almost
  90 degrees

21
(No Transcript)
22
Anomalies of the Kidney
23
Renal agenesis

• ureteric bud fails to develop
• 1. Unilateral renal agenesis
• 2. Bilateral renal agenesis

24
Unilateral renal agenesis

• is relatively common
• occurs about 1 in every 1,000 newborn infants
• is more common in males
• is asymptomatic
• should be suspected in infants with a single
  umbilical artery

25
Bilateral renal agenesis

• is associated with oligohydramnios
• occurs about 1 in 3,000 births
• is incompatible with life

26
Horseshoe kidney

• 1 in about 500 persons
• 7 of persons with Turner syndrome
• is asymptomatic

27
Development of the urinary bladder

• Division of the cloaca by the urorectal septum
  into
• urogenital sinus ventrally
• rectum dorsally

28
Urogenital sinus

• Vesical part - continuous with the allantois
• Pelvic part - becomes the bladder neck, prostatic
  part of urethra in male and entire female urethra
• Phallic part - grows toward the genital tubercle

29
Development of the urinary bladder

• is formed from the upper end of the urogenital
  sinus (vesical part) which is continuous with the
  allantois
• The allantois becomes a fibrous cord, the urachus
  (median umbilical ligament in adult)

30
Anomaliesof theUrinary Bladder
31
Extrophy of the bladder

• occurs about 1 in every 10,000 to 40,000 births
• the posterior wall of the urinary bladder is
  exposed to the exterior
• is caused by a failure of the anterior abdominal
  wall and anterior wall of the bladder to develop
  properly

32
Extrophy of the bladder

• is associated with urine drainage to the exterior
  and epispadias

33
Urachal cyst or sinus

• a remnant of the allantois persists
• is found along the midline on a part from the
  umbilicus to the apex of the urinary bladder
• is often associated clinically with urine
  drainage from the umbilicus

34
Development of the urethra

• Epithelium is derived from endoderm of the
  urogenital sinus
• distal part of the urethra in male is derived
  from the glandular (urethral) plate

35
(No Transcript)
36
Developmentof theReproductive System
37
Reproductive System
38
Indifferent stage

• The initial period of genital development which
  the early genital system in the two sexes are
  similar.

39

• Phenotypic sexual differentiation may result in
  individuals with
• Female phenotype
• Intersex phenotype
• Male phenotype

40

• The components of the indifferent embryo that
  are remodeled to form the adult female or male
  reproductive systems are
• 1. Gonads
• 2. Genital duct systems
• 3. Primordium of the external genitalia

41
Gonads

• The indifferent embryo has one pair of gonads
  that develop into either the ovaries or testes
• The gonads are derived from three sources
• mesothelium
• underlying mesenchyme
• primordial germ cells

42
Indifferent gonads

• Gonadal (genital) ridge
• primary sex cords grow into the underlying
  mesenchyme
• consist of
• cortex
• medulla

43
Indifferent gonads
44
Primordial germ cells

• Primitive sex cells
• are among the endodermal cells of the yolk sac
  near the origin of the allantois
• migrate along the dorsal mesentery of the hindgut
  to the gonadal ridge and enter the underlying
  mesenchyme

45
(No Transcript)
46
(No Transcript)
47
Genital duct systems

• The indifferent embryo has 2 separate genital
  duct systems
• 1. Paramesonephric (Mullerian) ducts
• play a major role in the female
• 2. Mesonephric tubules and mesonephric (Wolffian)
  ducts
• play a major role in the male

48
Primordium of the external genitalia

• The indifferent embryo has one primordium of
  the external genitalia, which will differentiate
  along either female or male lines

49
(No Transcript)
50
Sex determination

• SRY gene on short arm of chromosome Y
• Testis-determining factor (TDF)
• Two X chromosome are required for the development
  of the female phenotype

51
(No Transcript)
52
Developmentof theFemale Reproductive System
53
Gonad

• Intermediate mesoderm ? urogenital ridge ?
  gonadal ridge
• primary sex cords ? rete ovarii ? degenerate
• secondary sex cords ? primordial follicles
  (contain oogonium)

54
Ovary
55
(No Transcript)
56
Oogenesis

• Primordial germ cells ? oogonium
• active mitosis of oogonia occurs during fetal
  life
• no oogonia form posnatally

57
Genital duct systems

• Paramesonephric ducts
• uterine tubes
• hydatid of Morgagni
• uterovaginal primordium
• uterus
• cervix
• superior third of the vagina

58
Development of the uterus
59
Uterus

• Paramesonephric ducts
• unfused cranial parts uterine tubes
• fused caudal parts uterovaginal primordium

60
Development of the vagina
61
Vagina

• Sinovaginal bulbs fuse to form a vaginal plate

62
Development of the vagina

• Endoderm of urogenital sinus vaginal epithelium
• Surrounding mesenchyme fibromuscular wall

63
(No Transcript)
64
(No Transcript)
65
(No Transcript)
66
(No Transcript)
67
Genital duct systems

• Mesonephric tubules and ducts
• regress completely in the female after formation
  of the metanephric kidney
• vestigial remnants persist as the
• appendix vesiculosa
• epoophoron
• paroophoron
• Gartners duct

68
Primordium of the external genitalia

• Genital tubercle ? phallus
• Urethral folds
• Genital swelling

69
(No Transcript)
70
(No Transcript)
71
Primordium of the external genitalia
72
Developmentof theMale Reproductive System
73
Gonad

• Intermediate mesoderm ? urogenital ridge ?
  gonadal ridge
• Testes determining factor (TDF) (on Y chromosome)
• primary sex cords containing primordial germ
  cells (XY genotype)

74
Testes

• TDF induces the primary sex cord to condense and
  extend into the medulla of the indifferent gonad
• The development of the dense tunica albuginea is
  the characteristic and diagnostic feature of
  testicular development

75
Testes

• Primary sex cords
• seminiferous cords
• tubuli recti
• rete testes
• Seminiferous cords are made up of spermatogonia
  and Sertoli cells secrete mullerian-inhibiting
  factor (MIF)

76
Seminiferous tubules

• Sertoli cells are derived from the surface
  epithelium of the testes
• Spermatogonia are derived from the primordial
  germ cells

77
Testes

• The mesoderm between the seminiferous cords gives
  rise to the interstitial (Leydig) cells, which
  secrete testosterone
• Seminiferous cords remain as solid cords until
  puberty when they acquire a lumen and are then
  called seminiferous tubules

78
(No Transcript)
79
Testes

• Sertoli cells begin producing mullerian
  inhibiting substance at 6-7 weeks
• Interstitial cells begin producing testosterone
  in 8th week
• Testosterone production is stimulated by hCG

80
Descent of the testes

• is associated with
• Enlargement of the testes and atrophy of the
  mesonephroi
• Atrophy of the paramesonephric ducts
• Enlargement of the processus vaginalis

81
2 months
82
After birth
83
Genital duct systems

• Paramesonephric ducts
• Under the influence of MIF, the cranial portions
  of the paramesonephric ducts and the uterovaginal
  primordium regress completely
• A vestigial remnant may persist the appendix
  testis

84
Genital duct systems
85
(No Transcript)
86
Primordium of the external genitalia
87
(No Transcript)
88
Intersexuality (Hermaphroditism)

• True intersexuality
• Female pseudointersexuality
• Male pseudointersexuality

89
True intersexuality

• has both ovarian and testicular tissue
  (ovotestes)
• ambiguous genitalia
• usually have a 46,XX genotype (70)

90
Female pseudointersexuality

• has only ovarian tissue histologically
• masculinization of the female external genitalia
• have a 46,XX genotype
• most common cause is
• congenital adrenal hyperplasia (excess androgens)

91
Congenital adrenal hyperplasia(CAH)

• Excessive androgen production during fetal period
• causes masculinization of the external genitalia
  and enlargement of the clitoris in females

92
Congenital adrenal hyperplasia(CAH)

• autosomal recessive disorders
• mutation in cytochrome P450c21-steroid
  21-hydroxylase gene

93
Male pseudointersexuality

• has only testicular tissue histologically
• various stages of stunted development of the male
  external genitalia
• have a 46,XY genotype
• most common cause is
• inadequate production of testosterone and MIF by
  the fetal testes

94
Androgen insensitivity syndrome(AIS)

• Testicular feminization syndrome
• 1 in 20,000 live births
• are normal-appearing females
• 46,XY genotype
• testes are present
• results from a defect in the androgen receptor
  mechanism

95
Hypospadias

• Most common anomaly of the penis
• 1 in every 300 male infants
• there are 4 types
• glandular hypospadias
• penile hypospadias
• penoscrotal hypospadias
• perineal hypospadias

80 of cases
96
Cryptorchidism(undescended testes)

• 30 of premature males 3-4 of full-term males
• failure of development and atrophy are detectable
  by the end of the first year
• may result from deficiency of androgen production

97
The End