28- Development of Reproductive System Flashcards
Describe the timeline for reproductive system development.
Weeks 1-6 = Indifferent embryo
Week 7 = Sexual differentiation begins
Week 12 = Female and Male genitalia can be recognized
Wee 20 = Phenotypic differentiation complete
During week 5, these cells are the progenitor cells of the oogonia and spermatogonia. They are specified within epiblast.
Primordial Germ Cells
After gastrulation and body folding, primordial germ cells end up where?
Yolk Sac Wall
At about week 5, primordial germ cells migrate up the dorsal mesentery of the developing gut to enter the genital ridge of the ________ ________.
Intermediate Mesoderm
At week 6 the gonads are indifferent. Primitive gonads appear initially as a pair of longitudinal swellings in the ________ ________ of the intermediate mesoderm at about axial level _______.
Urogenital Ridges
T10
Primordial germ cells stimulate proliferation and delamination of cells from the coelomic epithelium of the genital ridge to form _______ _______ ________ (sometimes referred to as primitive sex cords).
Somatic Support Cells
Somatic Support Cells in males will eventually differentiate into ______ ______ and in females will eventually differentiate into _______ _______.
Sertoli Cells
Follicle Cells
Two sets of genital ducts form within the intermediate mesoderm of the urogenital ridge. These ducts are…
Mesonephric (Wolffian) Ducts and tubules
Paramesonephric (Mullerian) Ducts
These tubules and ducts form within the urogenital ridge and serve as early collecting ducts for the mesonephric kidney.
Mesonephric (Wolffian) Ducts and tubules
Mesonephric ducts open into the…
Urogenital Sinus
What will the Mesonephric ducts become?
Epididymis
Vas Deferens
Seminal Vesicles
Ejaculatory Duct
These are new ducts forming on both sides from an invagination alone the anterolateral surface of the urogenital ridge.
Paramesonephric (Mullerian) ducts
Cranially, the Paramesonephric ducts open to the coelomic cavity and caudally they meet with each other when attaching to the _______ _______.
Urogenital Sinus
Sexual dimorphism is complex and involves both autosomal and sex genes. The key to sexual dimorphism is the…
Y Chromosome
The Y Chromosome contains the testis-determining factor gene, _______. Presence or absence of this factor has a direct effect on gonadal differentiation and acts as a switch to initiate a cascade of many downstream genes that determine the fate of rudimentary sexual organs.
SRY
***Also called TDF (Testis Determining Factor)
What happens without SRY?
Female development occurs
***Certain genes positively drive female development as well.
Sexual dimorphism is dependent on the SRY gene on the Y chromosome, but it also requires _________.
Autosomes
The SRY gene is actively transcribed on days…
42-52
SRY gene expression turns on _______ expression in Somatic Supporting Cells, driving them toward Sertoli Cell differentiation. SRY also suppresses _______, which is a pro-female gene.
SOX9
WNT4
Sertoli Cells surround primordial germ cells, and by the 4th month these cells together with differentiating myoepithelial cells will organize into _______ _______ (U-shaped loops).
Testis Cords
The Testis Cords will eventually develop into ________ _______ soon after birth.
Seminiferous Tubules
The Testis Cords become connected to the Rete Testis (these are like Testis Cords but do not contain germ cells). The Rete Tests then become connected to ________ ________, which are remnants of Mesonephric tubules during kidney development. This ultimately links the Testis Cords to the developing ________ and _______ _______ (derivatives of the Mesonephric duct).
Efferent Ductules
Epididymis
Vas Deferens
Primordial germ cells proliferate and differentiate into _______ ________ (males) at about 3 months postnatally and then halts at this point until puberty.
Type A Spermatogonia
Subset of intertubular cells differentiate into fetal _______ ______, which are recruited by Sertoli Cells. They begin producing ________ during the 9th-10th week and begin influencing differentiation of genital ducts and external genitalia.
Leydig Cells
Testosterone
Sertoli Cells express _______, which drives regression of Paramesonephric Ducts (weeks 8-10). Remnants of these ducts in males include the appendix testis and prostatic utricle.
AMH (Anti-Mullerian Hormone)
- **Also called Mullerian Inhibitor Substance (MIS)
- **SOX9 stimulates production of these hormones
Leydig Cell-derived testosterone drives the Mesonephric tubules and ducts to form…
Efferent ductules (from remaining mesonephric tubules)
Epididymis
Vas Deferens
Seminal Vesicles
What are the remnants of the Paramesonephric Ducts in males?
Appendix Testis
Prostatic Utricle
A portion of testosterone (from fetal Leydig cells) is converted to _______ by ________. This drives the development of external genitalia (i.e., penis, scrotum, prostate, testicular descent).
DHT (Dihydrotestosterone)
5-Alpha Reductase
Adult Leydig cells generate ________ that initiate and maintain spermatogenesis, masculinization of the brain, and male sexual behavior.
Androgens
Origin of adult Leydig cells is unclear but somehow requires the presence of testicular ________. At puberty, _______ regulates testosterone production.
Macrophages
LH
These are formed from buds emanating from Mesonephric ducts, hence they are derived from intermediate mesoderm of urogenital ridge.
Seminal Vesicles
These are formed from buds emanating from endoderm of urogenital sinus within the future membranous region of the pelvic urethra.
Prostate Gland
These glands from from endodermal buds.
Bulbourethral Glands
During external genitalia development at the indifferent stage, this is an ectodermal-covered mesodermal swelling at the ventral (distal) end of the phallic portion of the urogenital plate. How extensive it outgrows depends on DHT levels.
Genital Tubercle
With rupture of the cloacal membrane, the floor of the phallic segment of the urogenital sinus is lost, whereas the roof of the phallic segment expands along the lower surface of the genital tubercle as the genital tubercle enlarges. This endodermal extension forms the…
Urogenital Plate
A pair swellings called _______ _______ develops on either side of the urogenital plate through an expansion of mesoderm underlying the ectoderm.
Urogenital Folds (Cloacal Folds)
At the distal end of the Urogenital Folds, remnants of the cloacal membrane adjacent to the genital tubercle remain as the _______ _______.
Glans Plate
A new pair of swellings, the ________ (genital) swellings appear on either side of the urethral folds.
Labioscrotal
A _______ groove forms along the ventral surface of the urogenital plate as the genital tubercle elongates. Distally, this and the urogenital plate terminate at the solid glans plate.
Urethral
For development of the male external genitalia, initially the urethral groove and urogenital folds extend only part of the way along the shaft of the elongating phallus. As the phallus and urogenital plate continue to elongate, the urogenital folds grow toward one another and fuse in the midline, beginning proximally in the perineal region and extending distally toward the _______ _______. This converts the urethral groove into a tubular _______ _______.
Glans Penis
Penile Urethra
_______ drives the lengthening and growth of genital tubercle and fusion of labioscrotal swellings forming the scrotum.
DHT
This ligament is involved in testis descent and contains gonadal vessels, nerves, and lymphatics. Connections are made at T10 level.
Suspensory Ligament
This is the structure connecting developing gonad to the base of the labioscrotal swellings. This will shorten eventually pulling the testes into the scrotum.
Gubernaculum
Failure of the testes to descend leads to _________ (incidence 4-5% at birth, with 1-1.5% at 3 months). Most self-resolve within the year but must be watched as incidence of testicular cancer is greatly increased.
Cryptorchidism
This is the most common male birth defect after Cryptorchidism (0.5% of all births in US). It is due to failure of urethral folds to close properly, and have various degrees of severity.
Hypospadias
This is rare, with an incidence of 1:40,000 to 120,000. The cause is unknown but may be due to improper ventral body closure or formation of too large of a cloacal membrane to be covered when it ruptures.
Epispadias
In the absence of the SRY gene, Somatic Support Cells express _______ (pro-female) and _______.
WNT4
FOXL2
FOXL2 continually suppresses any _______ expression, thereby maintaining female gonad differentiation (by continually suppressing Sertoli cell and Leydig cell differentiation).
SOX9
Primordial germ cells differentiate into oogonia, proliferate and differentiate into ________.
Oocytes
The developing oocytes induce surrounding Somatic Support Cells to become ________ cells.
Follicular
The follicle cells surrounding individual oocytes are responsible for arresting the primary oocytes in _________ of meiosis until puberty.
Prophase I
In the absence of Sertoli cells, there is no AMH so the _________ _________ are retained.
Paramesonephric Ducts
In the absence of Leydig cells, the Mesonephric Duct system is lost. Remnants found include the ________ and ________ near the ovary and Gartner’s cyst.
Epoophoron
Paraoophoron
Paramesonephric Ducts become fused at proximal/caudal (week 9-10) and are attached to the _______ _______.
Urogenital Sinus
Fusion of the inferior proximal end of the Paramesonephric ducts forms the ________ with the un-fused portion forming the _______ _______.
Uterus
Uterine Tubes
Uterus anomalies occur due to improper or failed fusion of…
Paramesonephric Ducts
This is the term for a double uterus (occurs in 1:30,000).
Didelphys
This is the term for a uterus with two bodies and one cervix.
Bicornate Uterus
This is the term for when only one uterine tube forms.
Unicornate Uterus
Contact of the Paramesonephric Duct to the urogenital sinus stimulates proliferation and formation of ________ ________ (endodermal thickening).
Sinuvaginal Bulb
The Sinuvaginal (Vaginal) Plate proliferates and lengthens and is eventually canalized. The entire vagina, with possible exception of the upper vaginal fornix, is derived from _________.
Endoderm
This occurs due to failure of normal sinuvaginal bulb development or canalization. Also due to agenesis of the Paramesonephric Ducts (1:5000 to 10,000).
Vaginal Agenesis
Phallic segment of urogenital sinus, like the male, has a urogenital plate, glans plate, and genital tubercle. In absence of testosterone and hence DHT, there is no lengthening of the genital tubercle and no fusion of urogenital folds or labioscrotal swellings. The urogenital folds will form the _______ ______ and labioscrotal folds form the _______ _______.
Labia Minora
Labia Majora
Midline fusion of Paramesonephric Ducts drags the lower urogenital ridge, which is covered with developing peritoneum, into the pelvic cavity. With completion of uterus and uterine tubes, the remaining tissue thins and forms a double fold of peritoneum that supports the uterus and ovary which becomes the…
Broad Ligament
Mesovarian
Mesosalpinx
Ovaries also descend, and like the testis it has a _______ _______ and ________ connecting the gonad to labioscrotal swelling.
Suspensory Ligament
Gubernaculum
This is the portion of the gubernaculum between the gonad and uterus.
Round Ligament of ovary
This is the portion of the gubernaculum between the uterus and base of labioscrotal swellings (future labia majora).
Round Ligament of uterus
In some disorders of sex development (DSDs) the (PHENOTYPIC/GENOTYPIC) sex is masked by (PHENOTYPIC/GENOTYPIC) appearance resembling the opposite sex or having reproductive organs of the opposite genotypic sex.
Genotypic
Phenotypic
***This means if your genes are for example female (XX) you are genotypically female but you have a WEEN like a dude phenotypically.
Describe 46, XY DSDs.
Person has testes but phenotype appears female.
Causes include:
- Inadequate testosterone synthesis
- Androgen insensitivity syndrome
- 5 alpha-reductase deficiency
- Mutations in AMH or AMH receptor
46, XY DSDs due to inadequate testosterone synthesis is because of the deficiency of this enzyme, which converts androstenedione to testosterone.
17 ß-hydroxysteroid dehydrogenase-3
46, XY DSDs due to androgen insensitivity syndrome is most commonly from loss of functional androgen receptors (X-linked recessive). Person has testes but no _________ and _________ levels may be elevated due to lack of negative feedback.
Spermatogenesis
Testosterone
The elevated testosterone due to androgen insensitivity syndrome is metabolized to ________ initiating female secondary sexual characteristics.
Estradiol
For 46, XY DSDs caused by androgen insensitivity, the testes will produce _______ so the Paramesonephric system is suppressed resulting in the absence of a uterus or uterine tubes and the vagina is short and ends blindly (amenorrhea).
AMH
For 46, XY DSDs caused by androgen insensitivity, testis usually found in inguinal or labial regions increasing the risk of ________ formation in the gonads. 25-35% develop malignancies before age 50 without treatment.
Tumor
For 46, XY DSDs caused by the deficiency in this enzyme will develop normal testis and duct system as there is AMH and testosterone. However, there is underdeveloped male external genitalia. The degree of which depends on the level of deficiency of the DHT, but they can exhibit an external female phenotype.
5-alpha reductase
***Converts testosterone to DHT
For 46, XY DSDs caused by mutations in AMH or AMH receptors, there is retention of ________ ________ so individual has uterus and uterine tubes along with male ducts and external genitalia.
Paramesonephric Ducts
The most common type of 46, XX DSD is ________ _______ ________.
Congenital Adrenal Hypoplasia
Congenital Adrenal Hypoplasia involves mutations in genes involved in adrenocortical steroid biosynthesis such as deficient in __________ (90% of time) leading to excess ACTH production (due to lack of negative feedback). Excess ACTH causes adrenal hyperplasia and excessive production of _________.
21-hydroxylase
Androgens
For 46, XX DSDs, people have ovaries. Female external genitalia will undergo masculinization and may exhibit fusion of _______ _______ and an enlarged _________ with what may look like hypospadias.
Labioscrotal Swellings
Clitoris
In Ovotesticular disorders, 70% of the time the karyotype is _______. People have both testicular and ovarian tissue with ambiguous external genitalia or it is predominantly female. Usually have a uterus.
46XX
What are causes of Ovotesticular disorders (46XX)?
– Translocation of piece of Y chromosome onto X chromosome (Barr body causes mosaicism)
– Subset of cells may have mutation in Y chromosome
– Anomaly in sex determination and differentiation of primordial germ cells
