Development of Reproductive System

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3 Component organs of a Reproductive System:: 1. Gonads
2. Reproductive Ducts
3. External genitalia
2 Processes involving Gonads:: -Gamete production
-Steroid hormone production
2 Processes involving Reproductive Ducts:: -Gamete transport
-Embryo nurturing
2 Processes involving External Genitalia:: -Gamete delivery/reception
2 steps in establishing sex:: 1. Sex determination (genetic sex)
2. Sex differentiation (phenotypic sex)
3 Cell types in both Female and Male Gonads:: -Germ cells
-Supporting cells
-Interstitial cells
What are Germ cells derived from?: Primordial germ cells in the yolk sac
What are the supporting cells in -Males -Females: Males: Sertoli cells
Females: Granulosa/Follicle cells
What are the interstitial cells in males vs females?: Males: Leydig
Females: Theca
What do the interstitial cells do?: Produce Steroid Hormones - Androgens or Estrogen
What DETERMINES Sex?: Fertilization - whether the egg is XX or XY
What causes sex DIFFERENTIATION?: Genetic and Epigenetic Factors
-Hormones
-Environmental factors
What 2 hormones are mainly responsible for sex differentiation?: -Androgens
-Mullerian inhibitory substance
What does Androgen do?: Influences differentiation in the male direction by MAINTAINING THE MESONEPHRIC DUCT
What does MIS do?: Promotes regression of the female Paramesonephric Ducts (PMD) by inducing apoptosis.
What in the Brain also plays a role in sex differentiation?: Gonadotropins
-Females cyclic release
-Males noncyclic
What GENE is essential for male development to occur?: SRY - on the Y chromosome.
When is testosterone first produced in the male? Where?: Week 8 - in the developing testis.
When and Where do PGCs first appear in the Embryo?: -Fourth Week of Devo
-Wall of Yolk Sac
How do PGCs get to the developing Gonad?: By migrating from the yolk sac to the gonad via the Dorsal Mesentery of the intestine.
What are the attachments of the primitive gonad? -Cranially -Caudally -Dorsally: Cranial: Suspensory ligament
Caudal: Gubernaculum
Dorsal: UG Ridge attachment
What does the Suspensory ligament become in males/females?: Males: Spermatic cord
Females: Suspensory ligament of the ovary
What does the Gubernaculum become in Males/Females?: Males: anchors testis to floor of scrotum
Females: Proper ligament of ovary and round ligament of uterus
What happens to the dorsal attachment to the UG ridge in males?: It disappears as the testis descends into the scrotum.
What does the dorsal attachment to the UG ridge become in females?: Broad Ligament
Where are the gonads devloping?: Retroperitoneally
What are the 2 pairs of ducts that form in the Int Mesoderm?: -Mesonephric - Wolffian
-Paramesonephric - Mullerian
What gives the inductive signal for PMDS to form?: MDs
What makes the MD stay in the male and disappear in the female?: Testosterone
How do the PMDs to form?: Coelomic epithelium invaginates and covers the intermediate mesoderm LATERAL to the MD
How do the PMDs not stick around in males?: They are induced to ATROPHY by Mullerian Inhibitory Substance
Where is MIS from again?: Secreted by the testis.
How does the PMD connect to the outside?: It fuses with the Cloaca - as the lower 1/3 of each tube fuses together too.
What results from the PMD fusing to the cloaca backside?: A genital tubercle that will form the lower vagina.
3 Primordia of External Genitalia:: -Genital tubercle
-Urethral folds
-Labioscrotal swellings
What is the Genital Tubercle?: An elevation superior to the cloacal membrane; unpaired midline structure.
What is the adult deriv of the Genital Tubercle in -Males -Females: Males: Glans and Penis

Females: Clitoris
Why is the SRY gene ESSENTIAL for male differentiation?: Because it encodes a protein called TESTICULAR DETERMINING FACTOR that results in the testes forming.
What does TDF do and where is it expressed?: -Expressed in UG ridge cells
-Tells the indifferent gonad to become a testes by directing cell differentiation.
What do the 3 precursor cells in the indifferent gonad differentiate into in males?: PGC -> spermatogonia
Sertoli cells
Leydig cells
What is the role of Sertoli cells?: To associate with PGCs as they become spermatogonia and become SEMINIFEROUS CORDS.
What is the role of Leydig cells?: Secrete testosterone
What cells give rise to the Sertoli and Leydig cells?: Coelomic epithelial cells
So the 2 main secretions of the Male Testes are:: -Testosterone
-Mullerian inhibiting factor
What is the active form of Testosterone?: Dihydrotestosterone
What happens when the SRY gene is not present?: Ovarian development occurs by default.
What causes the SRY gene to not be present?: No Y chromosome
What do the PGCs become in females?: Oocytes
How does PGC maturation differ between males and females?: -Females oocytes progress to Meiosis Prophase 1 then arrest.
-Males spermatogonia DON'T.
What is the role of Follicle cells in the developing ovary?: Associate with oocytes to form primordial follicles.
What happens to the Genital Tubercle that makes it become a penis?: It elongates into a Primordial Phallus
What influences the indifferent Primordial phallus to become male?: Dihydrotestosterone
What is on the Ventral side of this Phallus?: Urethral folds - they become fused overtop the Urethral groove
What type of tissue is the urethral groove?: Endoderm - it becomes the lining of the penile urethra.
What type of tissue is the distal penis? How does it form?: ECTODERM - ingrowth forms GLANS.
How does the Scrotum form?: The labial scrotal swellings approach each other and fuse.
What happens to the female primordial phallus if no androgen is around?: It doesn't enlarge/elongate.
What does the primordial phallus become in the female?: Clitoris
How does the development of urethral folds differ in females compared to males?: They DON'T fuse - instead become labia minora.
What happens to the labioscrotal swellings in the female?: They also don't fuse, becoming labia majora. UNZIPPED
What is EPISPADIUS?: Condition where penile urethra is open dorsally
What is epispadius commonly associated with?: Exstrophy of the bladder.
What is hypospadius?: Opening of the penile urethra on the VENTRAL side PROXIMAL TO THE GLANS TIP.
What causes hypospadius?: Incompete fusion of the urethral folds.
What usually causes abnormal development of the uterus?: Failure of the lower 1/3 of the PMDs to fuse together and with the uterus.
What happens when the lower 1/3 of the PMDS fail to fuse?: Duplex uterus
What happens if there is PARTIAL fusion of the distal 1/3 of the PMDs?: Bicornuate uterus - only the superior part of the uterus is unfused.
What would result if the wall between 2 successfuly fused PMDs failed to atrophy?: A midline septum would be present in the uterus.
What is the most common cause of ambiguous genitalia?: Abnormal testosterone representation in utero.
What is the definition of a true hermaphrodite?: -Gonadal tissue from each sex
-Either separate ovaries/testes
-Or a combined ovitestis
What is a Pseudohermaphrodite?: A person with the genotype of one sex, and variable expressions of the phenotype of the other sex.
What are the features of a male pseudohermaphrodite?: -XY chromosome
-Testes, no uterus
-variable feminine features
What is usually the cause of Male pseudohermaphroditism?: Testicular feminization - insensitivity to testosterone
What do individuals with complete androgen insensitivity develop?: Breasts and female external genitalia - but they don't have a uterus and do have testes.
What is the cause of testicular feminization?: A defect in the androgen receptor mechanism
Features of a female pseudohermaphrodite:: -XX chromosome
-No testes
-Uterus
-MAsculine phenotype
What is a common cause of Female pseudohermaphroditism?: Congenital adrenal hyperplasia
What is Turner Syndrome?: Monosomy X
What is the Phenotype of Turner Sydnrome individuals?: Female
Where do the testes end up in the end, and how do they get there?: Retroperitoneal, in the deep inguinal rings; during week 26, pass through the inguinal ring to enter scrotum.
Where do the ovaries end up in the end, and how do they get there?: End in Pelvis, inferior to pelvic brim; attached to Gubernaculum -> round ligament of the uterus/ovarian ligament.
What is from the Gubernaculum -Cranial part -Caudal part: Cranial = ovarian ligament
Caudal = round ligament of ovary
Where on the uterus is the gubernaculum attached?: Near the uterine tube.
Where is the termination of the Round ligament of the uterus?: Passes through the Inguinal canal and terminates in Labia Majora

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