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Y2 RNU block > Development of Reproductive Tract > Flashcards

Development of Reproductive Tract Flashcards

1
Q

where does the urogenital tract originate from

A

INTERMEDIATE MESODERM

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2
Q

In humans, there are 3 sets of kidney structures during development, Name them.

A

PRONEPHROS – cervical region
MESONEPHROS – abdominal region
METANEPHROS – pelvic region (definitive kidney)

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3
Q

what order are the 3 sets of kidneys formed

A

They are formed in a cranial to caudal and chronological sequence

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4
Q

describe pronephros

A
  • Rudimentary and non functional
  • intermediate mesoderm clumps and you get 7-10 solid cell groups in the cervical region
  • Regresses (disappears) by week 4
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5
Q

where is the mesonephros derived from

A

Derived from intermediate mesoderm from the upper thoracic and upper lumbar segments

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6
Q

when do the first excretory tubules of the mesonephros first appear

A

Week 4 after regression of the pronephros

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7
Q

mesonephros contributes supporting cells to the _______ _______

A

Genital

ridge

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8
Q

what is the definitive kidney

A

METAnephros

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9
Q

when does the metanephros appear and when does it become functional

A

week 5

becomes functional at week 11

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10
Q

how does the metanephros develop

A

Pronephros- rudimentary and then disappears
Mesonephros- appears at week 4 after regression of pronephros
Metanephros- mesonephros disappears and metanephros appears at week 5

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11
Q

Metanephros is formed from 2 parts that are at the bottom of the developing mesoderm, what are they?

A

Ureteric bud and metanephric cap/mesenchyme

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12
Q

How does the metanephric cap/ mesenchyme form

A

Mesoderm around the ureteric bud becomes metanephric cap or metanephric mesenchyme

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13
Q

Ureteric bud is an outgrowth of ________

A

mesonephric duct

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14
Q

what is the function of the cloaca

A

Posterior orifice that serves as the only opening for the intestinal, reproductive and urinary tracts at early stages. Anything collected from the developing kidneys will drain through the cloaca.

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15
Q

definitive kidney/ Metanephros arises from 2 sources:
- Metanephric cap
- Ureteric duct
what do both of these structure provide

A

Metanephric mesoderm- Provides the excretory units

Ureteric duct- Collecting system

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16
Q

When is the fetus able to produce urine

A

Kidney becomes functional at week 11 or 12 so since then

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17
Q

Do nephrons form until birth?

A

yes

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18
Q

what is the cloaca BEFORE it was divided to become cloaca

A

hindgut (endodermal lining)

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19
Q

What divides the cloaca by fusion with cloaca membrane

A

Urogenital septum

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20
Q

What forms after division of the cloaca

A

ANTERIOR UROGENITAL SINUS

POSTERIOR RECTAL/ANAL CANAL- forms anal canal

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21
Q

when does cloacal division occur

A

week 4-7

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22
Q

what forms the bladder

A
  • From cranial parts of urogenital sinus (division of cloaca)- anterior urogenital sinus
  • EXCEPT, Trigone region comes from the mesonephric duct
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23
Q

What germ layer is the bladder lined with

A

Endoderm

24
Q

What happens in the indifferent stage

A

2 gonads form- neither ovaries or testes
2 pairs of genital ducts surrounding the gonads form
- The paramesonephric ducts (Mullerian) FEMALE (more lateral than males)
- The mesonephric (Wolffian) ducts MALE

see pics for understanding
BOTH DUCTS IN A FOETUS REGARDLESS OF SEX

25
Q

when does the indifferent stage occur

A

weeks 5-6

26
Q

What is the function of the mesonephric duct

A

Drain urine from the mesonephric kidney

27
Q

How does the mesonephric (wolffian) duct play a huge role in the development of the male reproductive system

A

Under the influence of testosterone, duct forms the ductus deferens and ejaculatory duct, and also forms the epididymis when mesonephros vanishes

28
Q

What happens to the mesonephric (wolffian) duct in the female

A

almost completely disappears, leave a few non functional remnants

29
Q

How does the PARAmesonephric (mullerian) duct play a huge role in the development of the female reproductive system

A
  • Ends of the ducts widen to form funnel shaped cranial ends which open into the peritoneal cavity and the ducts approach each other in the midline
  • Cranial portion forms the uterine tubes
  • Caudal portion fuse to form the uterovaginal primordium (To form Uterus and superior vagina)
30
Q

What happens to the PARAmesonephric (mullerian) duct in the males

A

Degeneration of (paramesonephric) Mullerian ducts due to the action of anti-mullerian hormone (AMH).

31
Q

What makes the anti-mullerian hormones

A

This is a protein made by the Sertoli cells of the testis

32
Q

When does sex determination start

A

week 7

33
Q

How do the gonads initially appear as

A
  • Pair of longitudinal ridges (Urogenital or gonadal ridges)

- Also has a mesoderm structure – projecting into the coelomic cavity

34
Q

Describe the journey of the Primordial Germ cells for gonadal development

A
  • Primordial germ cells (arrive as a subset of epiblast cells)– move out of the yolk sac and into the gonadal ridge
  • Move to the genital/gonadal ridge via dorsal mesentery
  • -> Forms the primitive gonads
35
Q

why do the primordial germ cells move out of the yolk sac

A

due to the constant signalling occurring in this stage for development of the nervous system.
–> SO keeps the gonads undifferentiated.

36
Q

What happens if the primordial germ cells dont arrive into the gonadal ridge by week 6

A

the ridges develop no further and the gonads do not develop

37
Q

Primordial germ cells form in a “cord like” structure called the _______ ____ _____

A

primitive sex cords

38
Q

what is the function of the SRY (Sex determining Region of Y chromosome)

A

if the embryo is male, the Y chromosome encoded this gene- SRY. This acts on the somatic cells of the developing gonads:
- to carry out proliferation of the primitive sex cords

39
Q

What happens to the primitive sex cords after proliferation?

A
  • Cords become horseshoe shaped
    Primitive germ cells move into the somatic cells
  • Cords break up into tubules and results in differentiation of somatic cells
40
Q

What happens after differentiation of somatic cells and when the dense connective tissue forms

A
  • Leydig cells begin to produce testosterone
  • Sertoli cells produce anti-Mullerian hormone

Dense connective tissue forms and separates the cord from the surface epithelium
- Forms Tunica albuginea

41
Q

Testis cords are solid till puberty, what happens to them after reaching puberty?

A
  • Acquire a lumen forming the seminiferous tubules
  • Join with the rete testis
  • Join with efferent ductules
  • Rete testis and mesonephric duct link to form the epididymis and ductus deferens
42
Q

What gene is known to be the ‘ovary determining gene’ in females

A

Wnt 4

43
Q

What happens in FEMALES after the primordial germ cells reach the genital ridge

A

PGCs divide by mitosis → pool of oogonia

  • Oogonia enter meiotic arrest at 4th month of gestattion and become oocytes
  • oocytes become associated with follicular cells- primordial follicles
44
Q

When does development of the external genitalia occur

A

week 3 after fertilisation

45
Q

describe the development of the genital tubercle and function of genital tuebrcle

A
  • a pair of cloacal folds develop around cloacal membrane
  • they join to form the genital tubercle at the CRANIAL end

Genital tubercle- forms penis in males and clitoris in females

46
Q

what happens to the cloacal folds in the caudal side

A
  • urethral folds in front - forms labia minora in female
  • anal folds behind
  • genital swellings then appear on either side of the urethral folds to form scrotal swellings in male, labia majora in the female
47
Q

how does the urethra form in males

A

From middle pelvic part of urogenital sinus

  • In males, androgens from fetal testis cause genital tubercle to elongate into phallus
  • phallus pulls urethral folds forward
  • they form lateral walls of urethral groove and close over urethral plate to form penile urethra
48
Q

what is the terminal part of male urethra (external urethral meatus) formed from and why is it open

A

forms from the surface ectoderm

it is open for ejaculation and peeing

49
Q

how does the prostate gland develop

A

develops as outgrowths from the prostatic urethra

50
Q

how does the bulbourethral gland develop

A

develop as outgrowths from penile urethra

51
Q

how does the upper part of vagina form

A

comes from paramesonephric duct

52
Q

how does the lower part of vagina form

A

forms from two outgrowths from urogenital sinus called the sinovaginal bulbs, these bulbs fuse to form a vaginal plate, and hollows to form a cavity

53
Q

what happens when there is a failure of fusion of uterus in females

A

DOUBLE UTERUS

  • bicornuate uterus – only upper body of uterus involved
  • bicornuate uterus with rudimentary horn
54
Q

what is vaginal atresia

A

failed canalisation (no hollow tube)

55
Q

how does absence of vagina and the uterus occur

A
  • failure of sinovaginal bulbs

- formation of bulbs is normally induced by uterus so uterus is usually also absent

56
Q

what is hypospadias and treatment

A
  • Urethra opening is not at the end of the penis but opens on the underside of the penis
  • Affects 1:300 boys (common) and 70% of cases are mild
  • Surgical correction necessary to enable urination whilst standing, often at around 12 months of age- fine after that

Y2 RNU block (12 decks)

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