Development of the Genital System Flashcards
What type of mesoderm gives rise to the urogenital system? Describe the position and organization of the urogenital ridges
intermediate mesoderm
position: retroperitoneal
urogenital ridge has 2 portions
- nephrogenic cord (purple)
- lateral in postion
- develops first
- gonadal ridge (yellow)
- medial in postion
What is the origin of the primordial germ cells? Describe the migratory path PGCs take to reach the gonadal ridges
origin: yolk sac
path: begin migrating at week 4, arrive at ridges at week 6
- from the yolk sac they travel thru umbilical cord thru dorsal mesentery of hind-gut to enter the gonadal ridge
Describe the general characteristics that male and female genital systems share during the “indifferent phase” of sexual development (weeks 1-6). What determines the genetic sex of an individual? What determines the phenotypic sex of an individual?
indifferent phase: week 1-6
both sets present
- mesonephric (Wolffian) ducts (m)
- paramesonephric (Mullerian) ducts (f)
genetic sex: determined at conception via chromosomes
- (SRY of “Y” chromosome)
phenotypic sex: determined by hormone secretion
- testosterone
Note: no visible differences in male vs. female gonads/genital duct system/external genitalia until week 7
What are gonadal cord cells, and what role do they play in the development of the testes and ovaries?
defined: mesothelial cells or gonadal ridge = gonadal cord cells
Week 5:
- Intermediate mesoderm thickens bilaterally,
- forming the gonadal ridges
- Mesothelium lining each gonadal ridge thickens (mesothelial cells = gonadal cord cells)
- Cord cells form solid gonadal (cortical) cords that sink into underlying mesenchyme to “welcome” (envelop) PGCs
role: gonadal cord cells develop into
- the caretakers of PGCs
- sertoli cells(m)
- follicular cells (f)
Describe the effects of TDF on the male genital system.
TDF (testes determining factor):
- signals development of Leydig cells
- from mesenchyme of gonadal ridge
- signals gonadal cords to separate from cortex
- extend into the medulla of testicles and form
- seminiferous tubules
- Rete testes
- extend into the medulla of testicles and form
cord cells become sertoli cells under TDF
How do the mesonephric tubules contribute to the male genital duct system?
become efferent ductules
Describe the process of testicular descent and the formation of the spermatic cord. What is the gubernaculum?
testicular descent: weeks 26-32
- descend anterior inferior
- follow gubernaculum
- ligament that attaches to inferior pole of testes on one end and labioscrotal swelling on other
- pulls testes, ductus (vas) deferens and testicular vessels down thru the inguinal canal and eventually into the scrotal sac
- testes pull internal spermatic fascia
spermatic cord: consists of
- internal spermatic fascia
- from transversalis facsia
- cremasteric fascia
- from internal oblique
- external spermatic fascia
- from external oblique
invagination of internal spermatic fascia is known as process vaginalis
Describe the role that the paramesonephric (Müllerian) ducts play in the development of the female genital tract.
the cranial ends form the
- uterine tubes
The caudal ends of the Müllerian ducts fuse to form
- uterovaginal primordium
- which will form the
- uterus
- superior portion of the vaginal canal
- which will form the
How is the urogenital sinus involved with the formation of the vagina?
it provides endothermal cells which give rise to vaginal plate which gives rise to the inferior portion of the vagina
The uterovaginal primordium comes into contact with the dorsal wall of the urogenital sinus and induces the formation of a pair of endodermal outgrowths
- the sinovaginal bulbs.
These separate from the urogenital sinus and fuse with the uterovaginal primordium, forming a
- vaginal plate (the inferior portion of the vagina).
- The central endodermal cells of the plate degenerate, forming
- the vaginal canal (inferior vagina)
- The central endodermal cells of the plate degenerate, forming
What are the ligamentous derivatives of the gubernaculum in the female?
- ovarian ligament
- round ligament of the uterus (anchors into the labia majora)
gubernaculum is attached to inferior pole of gonad and the labiascrotal swell
interacts with the uterus and forms the above ligments
List the vestigial remnants of the mesonephric and paramesonephric ducts in the male and female
male
- appendix testes
female
- epoophoron
- paaophoron
- gartner duct cyst
Compare and contrast the development of male and female external genitalia
both:
- labial scrotal swelling as embryo
- genital tubercle
- urethral folds
males
- genital tubercle: glans penis (head of penis)
- Ectoderm-lined distal spongy urethra
- labial scrotal swelling: the sac
- urethral folds: shaft of penis (fold under ventrally and fuse)
- endoderm-lined proximal spongy urethra
females
- genital tubercle: the clit
- labial scrotal swelling: unfused portions are labia majora
- urethral folds : remain fused as labia minora
Describe the effects of testosterone on the male genital system. What cells produce testosterone?
- Leydig cells (stromal CT cells) produce testosterone
- testosterone produced during week 8
- stimulates formation of male genital ducts (mesonephric duct and mesonephric tubules) and external genitalia
Describe the effects of MIH (MIF/MIS/AMH) on the male genital system. What cells produce the MIH?
- Sertoli cells produces MIH (Müllerian-inhibiting hormone)
- MIH causes Müllerian (Paramesonephric) ducts to degenerate
- Müllerian Duct Remnant in males = Appendix Testis
What structures does the mesonephric duct rise to? What does the mesonephric tubules give rise to? what do the gonadal cords give rise to?
Mesonephric duct:
- Epididymis (superior end)
- Ductus (vas) deferens
- Seminal Vesicle
- Ejaculatory duct
Caudal ends of mesonephric ducts develop seminal vesicles + form the ejaculatory ducts
- will open into prostatic urethra
Mesonephric tubules:
- Efferent ductules
Gonadal cords:
- Seminiferous tubules
- Rete testes
intermediate mesoderm becomes…
retroperitoneal
urogential ridge
Describe the following
- Congenital inguinal hernia
- Hydrocoele of the testes/spermatic cord
- Cryptorchidism
Congenital inguinal hernia
- Patent processus vaginalis
Hydrocoele of the testes/spermatic cord
- Development of fluid-filled cysts
Cryptorchidism
- Failure of the testes to descend
