Reproductive System Development

Question 1

what weeks are the organogenetic period of development?

Answer 1

4-8

Question 2

when does maturation of the organ systems occur?

Answer 2

week 9 +

Question 3

name the 3 sets of developmental “kidney”

Answer 3

pronephros
mesonephros
metanephros

Question 4

where and functionality of the pronephros?

Answer 4

cervical region

vetigial

Question 5

where and functionality of the mesonephros

Answer 5

thoracolumbar region

briefly functional

Question 6

where and functionality of the metanephros?

Answer 6

pelvic region

functional

Question 7

describe the development of the urinary system?

Answer 7

Cloaca divides to form rectum (GI tract) and anteriorly the Urogenital Sinus.
The mesonephric duct drains into the urogenital sinus
The urogenital sinus later forms the urinary bladder and its caudal end forms the urethra

Question 8

describe the genital (gonadal) ridge formation

Answer 8

week 5-6
mesonephros forms a long ovoid structure in association with thoracic and upper lumbar vertebrae
Medial part of mesonephric ridge becomes thickened to form a genital/ gonadal ridge.

Question 9

what happens at week 6 in regards to genitals

Answer 9

• Week 6 - Germ cells migrate from yolk sac, via dorsal mesentery, and embed into primitive sex cords (formed from mesenchyme of genital ridges
• This structure known as the indifferent gonad
• No migration of germ cells - no gonads

Question 10

how does the paramesonephric duct form?

Answer 10

Epithelium of the mesonephros invaginates to form a tube.
Develops lateral to developing gonads and mesonephric duct
Funnel shaped cranial end opens into peritoneal cavity
Caudally, cross ventral to mesonephric ducts
This projects into dorsal wall of urogenital sinus

Question 11

another name for the mesonephric duct

Answer 11

Wolffian duct

Question 12

another name for the paramesonephric duct

Answer 12

mullerian duct

Question 13

in males: what do the gonads form?

Answer 13

testis

Question 14

in males: what do the mesonephric duct form?

Answer 14

epididymis
vas deferens
seminal vesicle

Question 15

in males: what do the paramesonephric duct do?

Answer 15

degenerates

Question 16

in males: what do the urogenital sinus form?

Answer 16

bladder
urethra
prostate

Question 17

in females: what do the gonads form?

Answer 17

ovary

Question 18

in females: what do the mesonephric duct do?

Answer 18

degenerates

Question 19

in females: what do the paramesonephric ducts form?

Answer 19

fallopian tube
uterus
cervix part of vagina

Question 20

in females: what do the urogenital sinus form?

Answer 20

bladder

lower part of vagina

Question 21

how does the indifferent gonad know whether to develop into a testis or ovary?

Answer 21

see notes

Question 22

describe testis development

Answer 22

Wk 5 – primary sex cords, medulla and cortex
Wk 6 primordial germ cells incorporated into primary sex cords
Wk 7 – TDF stimulates primary sex cords –> extend into medulla –> seminiferous cords –> tubules
Seminiferous cords branch, ends anastomose –> rete testis of medulla
Surface epithelium (mesothelium) lost when thick capsule forms (tunica albuginea of adult testis)
Mesenchyme between cords gives rise to Interstitial cells of Leydig (Endocrine gland that is not derived from epithelium)
By week 8, Leydig cells produce testosterone and other hormones which stimulate masculine differentiation of mesonephric ducts and external genitalia

Question 23

how do the seminal vesicles form?

Answer 23

outgrowth from caudal end of mesonephric duct

Question 24

how does the prostate form?

Answer 24

outgrowth(s) from urethar (from urogenital sinus)

Question 25

what are male external genitalia formed under the influence of?

Answer 25

testosterone

Question 26

describe the development of the ovary (prenatal)

Answer 26

Primary sex cords degenerate (leaving the primordial germ cells)
By 10 weeks secondary sex cords develop from surface epithelium
Primordial germ cells become incorporated into them
Primordial germ cells then bud off with single surrounding layer of cortical cord cells to form primordial follicles (from ~16 weeks)
Active mitosis of these early primordial follicles to form additional follicles
By 7th month all follicles have formed
Oocytes enter meiosis and arrested in prophase 1st meiotic division
Some follicular atresia by birth

Question 27

describe the postnatal development of the ovary

Answer 27

~2 million primordial follicles at birth
Many follicles become atretic before puberty
After puberty, hormonal
influences stimulate 12-15 follicles, per 28 day cycle, to develop
Only one follicle (normally) reaches maturity and ovulation
Continues until the menopause

Question 28

where do the tubular components of the female reproductive system come from?

Answer 28

Absence of testosterone causes degeneration of mesonephros and mesonephric duct
Paramesonephric ducts develop to give rise to female genital tract

Question 29

describe the descent of the male gonads

Answer 29

• Week 7 – Level of T10 (Diaphragm undescended)
• Week 12 – Level of deep inguinal ring (remains until 7th month)
• Enters scrotum just prior to birth (39 weeks)

Question 30

describe the descent of the female gonads

Answer 30

• Week 7 – Level of T10
• Week 12 – Broad ligament
• Round ligament drawn through inguinal canal to attach to labrum majorum

Question 31

types of cryptochidism

Answer 31

undescended
ectopic
retractile teses
absent testes

Question 32

complications fo undescended testis?

Answer 32

infertility
malignant transformation (germ cell tumours)
testicular torsion

Question 33

name some anomalies of the female repro tract

Answer 33

complete duplication
septate uterus
bicornate uterus
arcuate uterus