Reproductive System Development Flashcards
what weeks are the organogenetic period of development?
4-8
when does maturation of the organ systems occur?
week 9 +
name the 3 sets of developmental “kidney”
pronephros
mesonephros
metanephros
where and functionality of the pronephros?
cervical region
vetigial
where and functionality of the mesonephros
thoracolumbar region
briefly functional
where and functionality of the metanephros?
pelvic region
functional
describe the development of the urinary system?
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
describe the genital (gonadal) ridge formation
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.
what happens at week 6 in regards to genitals
- 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
how does the paramesonephric duct form?
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
another name for the mesonephric duct
Wolffian duct
another name for the paramesonephric duct
mullerian duct
in males: what do the gonads form?
testis
in males: what do the mesonephric duct form?
epididymis
vas deferens
seminal vesicle
in males: what do the paramesonephric duct do?
degenerates
in males: what do the urogenital sinus form?
bladder
urethra
prostate
in females: what do the gonads form?
ovary
in females: what do the mesonephric duct do?
degenerates
in females: what do the paramesonephric ducts form?
fallopian tube
uterus
cervix part of vagina
in females: what do the urogenital sinus form?
bladder
lower part of vagina
how does the indifferent gonad know whether to develop into a testis or ovary?
see notes
describe testis development
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
how do the seminal vesicles form?
outgrowth from caudal end of mesonephric duct
how does the prostate form?
outgrowth(s) from urethar (from urogenital sinus)
what are male external genitalia formed under the influence of?
testosterone
describe the development of the ovary (prenatal)
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
describe the postnatal development of the ovary
~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
where do the tubular components of the female reproductive system come from?
Absence of testosterone causes degeneration of mesonephros and mesonephric duct
Paramesonephric ducts develop to give rise to female genital tract
describe the descent of the male gonads
- 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)
describe the descent of the female gonads
- Week 7 – Level of T10
- Week 12 – Broad ligament
- Round ligament drawn through inguinal canal to attach to labrum majorum
types of cryptochidism
undescended
ectopic
retractile teses
absent testes
complications fo undescended testis?
infertility
malignant transformation (germ cell tumours)
testicular torsion
name some anomalies of the female repro tract
complete duplication
septate uterus
bicornate uterus
arcuate uterus