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121 terms

Embryo lec 6: Genital System

Savion, 3/15 Also know stages of folliculogenesis, oogenesis, etc.
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External genitalia; genital ducts; gonads
The genital system is composed of these three general parts
Epididymis; ejaculatory duct; vas deferens
The adult derivatives of male genital ducts (3)
Uterine tubes; uterus; vagina
The adult derivatives of female genital ducts (3)
Genital ducts (connect gonads to external genitalia)
This part of the genital system connects the other two parts (general)
Female
This sex is the default mechanism
Male
This sex requires a signal for the production of its genital system
Urogenital ridges
Two ridges formed in fourth week by intermediate mesoderm being pushed ventrally by lateral folding into intraembryonic coelom
Intermediate; lateral; intraembryonic coelom
The urogenital ridges are form in week 4 by ____ mesoderm being pushed ventrally by (head/lateral) folding into the ____
Intermediate
Urogenital ridges are composed of ____ mesoderm
Urogenital ridges
The genital and urinary system are derived from these folds created in the fourth week
Genital
The (genital/urinary) system is derived from the medial edge of the urogenital ridge
Urinary
The (genital/urinary) system is derived from the lateral urogenital ridge
Primary sex cords (for testes/ovary); primordial germ cells (PGC)
The indifferent gonad contains these two different cell types/clusters in week 5-6
Primordial germ cells
PGC
Primary sex cords (gonadal cords)
At medial edge of urogenital ridge, mesoderm proliferates producing these finger-like projections; composed of inner medulla and outer cortex
Males
In (females/males), the medulla develops into the gonads and the cortex regresses
Females
In (females/males), the cortex develops into the gonads and the medulla regresses
Cortex
The (cortex/medulla) develops into ovaries in females while the other regresses
Medulla
The (cortex/medulla) develops into testes in males while the other regresses
Males (Wolffian = mesonephric ducts)
In (females/males), the Wolffian ducts develop into the genital ducts and the Mullerian ducts regress
Females (Mullerian = paramesonephric ducts)
In (females/males), the Mullerian ducts develop into the genital ducts and the Wolffian ducts regress
Mullerian (paramesonephric ducts)
The (Mullerian/Wolffian) develops into the uterine tubes and uterus in females while the other regresses
Wolffian (mesonephric ducts)
The (Mullerian/Wolffian) develops into the epididymis, vas deferens, efferent ducts in males while the other regresses
Paramesonephric
The Mullerian ducts are the (mesonephric/paramesonephric) ducts; give rise to female genital ducts
Mesonephric (also drain temporary kidney)
The Wolffian ducts are the (mesonephric/paramesonephric) ducts; give rise to male genital ducts
Primitive streak (from the epiblast)
Primordial germ cells are derived from this
Yolk sac (gut)
In the 5-6th week, the PGC migrate from the ____ through the dorsal mesentery to the developing gonads where they wait for a signal
Paramesonephric
The (mesonephric/paramesonephric) ducts are more lateral
Mesonephric (Wolffian) ducts; paramesonephric (Mullerian) ducts
At the indifferent stage, an embryo contains these two sets of ducts
At fertilization
When sex is determined
SRY (region and protein)
This is necessary for development of male genital system; cause medullary sex cord cells to become AMH (anti-Mullerian hormone) producing sertoli cells
SRY
The sex-determining gene for males
AMH
Production of SRY protein by medullary sex cord cells results in their differentiation to sertoli cells which then secrete this; this induces degeneration of paramesonephric ducts
Sertoli cells
These cells differentiate from medullary sex cord cells; produce AMH (anti-Mullerian hormone); form seminiferous tubules
Sertoli; leydig
The SRY protein has two effects, causes differentiation of: medullary cord cells to ____ cells; mesenchymal cells between cords to ____ cells
Leydig cells
SRY signals the mesenchymal cells between the seminiferous tubules to differentiate into these; produce testosterone
Testosterone
This hormone gives rise to most of male genital system; in puberty, initiates spermatogenesis and development of secondary sex characteristics in males
AMH (anti-Mullerian hormone); DHT (dihydrotestosterone); testosterone
These hormones are important in development of the male genital system (3)
DHT (dihydrotestosterone)
This hormone is responsible for development of external male genitalia, prostate, and other structures; derived from testosterone
7
If SRY is present, the male genital system starts to develop at week __
Leydig cells; sertoli cells; spermatogonia
The cells found in the testes (3)
Specific germ cells
Once indifferent gonad starts to differentiate, PGC become these
Efferent ducts (efferent ductuli); vas deferens
Sperm travel through seminiferous tubules to rete testes to ____ to epididymis to ____
Granulosa cells
These cells differentiate from cortical sex cord cells; these form follicles
10
If SRY is not present, the female genital system starts to develop at week __; medulla regresses
Urethra (all of female, most of male; caudal); urinary bladder (medial)
These develop from the urogenital sinus; lined by endoderm
Testosterone
(AMH/DHT/Testosterone) production leads to formation of male genital duct system: epididymis, ejaculatory duct, and ductus deferens
Efferent ducts (efferent ductuli)
These are derived from the few persistent tubules from the mesonephric duct; part of testes
Paramesonephric
Without SRY and AMH, the (mesonephric/paramesonephric) ducts persist while the other degenerates
Uterus
The fusion of part of the paramesonephric ducts produce this adult structure
Uterine tubes
The unfused part of the paramesonephric ducts produce this adult structure
Uterus; uterine tubes
The paramesonephric ducts give rise to these adult derivatives
Urogenital sinus (urinary bladder)
The vagina is derived from this
Vagina
The septum/diverticulum outgrowth which forms when the uterus makes contact with dorsal wall of bladder becomes this; elongates and communicates with uterus
Hymen
This closes the vagina; from bladder; ruptures before birth leaving ring of CT around orifice of vagina
Abdomen (must descend to pelvis/scrotum; descent begins in week 7 for testes)
The gonads begin development here
Testosterone
Descent of the testes (to outside of the body) is at least partially controlled by this hormone (control not well understood)
7; 28
The first part of the descent of the testes begins in week (7/8/9) and ends in week (26/28/30)
Gubernaculum ligament
This structure aids in first part of descent of testes
Most caudal part of abdomen
The testes descend to here in first part of descent, aided by gubernaculum ligament
Scrotum (outside of body)
The testes descend to here in second part of descent, aided by processus vaginalis
Processus vaginalis (peritoneal fold)
This structure aids in second part of descent of testes
Processus vaginalis
Peritoneal fold; forms inguinal canal; pulls abdominal wall with it as it descends; testes pass posterior to this into scrotum (still attached to gubernaculum)
Inguinal canal
The testes pass through this into scrotum; after testes pass, it closes (in humans)
95
(35/60/95)% of full term male babies' testes are in their scrotum
Scrotal ligament
Adult derivative of gubernaculum ligament; keeps testis invested in scrotum
Anterior
The tunica vaginalis is (anterior/posterior) to the testes
Tunica vaginalis
This is the remnant of the processus vaginalis, after connecting stalk (to abdomen) degenerates
Ovarian ligament (connects ovary to lateral surface of uterus); round ligament (connects uterus to labia majora, for anteversion)
Adult derivatives of gubernaculum ligament in females (2)
3
The ovaries descend from the abdomen to the pelvis in month (3/4)
Gubernaculum ligament
This structure aids descent of ovaries
Processus vaginalis
A very small inguinal canal formed by this usually degenerates in females
Canal of Nuck
A persistent remnant of the processus vaginalis (inguinal canal) in females; usually asymptomatic
12
Development of external genitalia occurs between week 7 and week (12/14/16)
Labioscrotal swellings; urogenital folds
The two pairs of folds which form during indifferent stage; form around cloacal membrane in weeks 4-7
Urogenital folds
These are the inner, smaller folds of the indifferent external genitalia
Labioscrotal swellings
These are the outer, larger folds of the indifferent external genitalia
Phallus
This diverticulum develops cranial to cloacal membrane in weeks 4-7
Anal membrane; urogenital membrane
These are formed after complete division of cloacal membrane (by urorectal septum)
Phallus
This elongates, pulling (both pairs of) folds cranially, starts to close urethra (occurs in males and females)
Phallus
In males, this elongates, pulling folds cranially until entire urethra is closed; forms glans penis
Glans penis
Ectodermal ingrowth communicates with urethra here; tip of the penis
Phallus (pulls urogenital folds and labioscrotal swellings cranially; closes urethra)
In males, all external genitalia seems to depend on elongation of this
Phallus
In females, this elongates then stops, becomes smaller; forms clitoris
Clitoris; glans penis
Adult derivatives of phallus (in males and females)
Labia minor; (most of) penis
Adult derivatives of urogenital folds (in males and females)
Labia majora; scrotum
Adult derivatives of labioscrotal swellings (in males and females)
Hermaphroditism (intersexuality)
Malformation; a discrepancy between the gonads, genital ducts and external genitalia; general term
Female pseudohermaphroditism; male pseudohermaphroditism; true hermaphroditism
Three types of hermaphroditism
True hermaphroditism
Rare malformation; may occur in genetic males with SRY mutation, genetic females with SRY translocation, or mosaics; has testicular and ovarian tissue; ambiguous external genitalia
Ovotestis
A true hermaphrodite may have this; a single organ with both testicular and ovarian tissue
Male pseudohermaphroditism
Malformation; genetic males with female external genitalia; results from inadequate testosterone or DHT production, or abnormal androgen receptors
Male pseudohermaphroditism
This condition is generally discovered at puberty; abnormal testes removed; individual is considered psychologically female; no uterus due to AMH
Testicular feminization syndrome (androgen insensitivity syndrome)
A form of male pseudohermaphroditism; caused by abnormal androgen receptors
Male pseudohermaphroditism
5α-reductase deficiency can cause this malformation in genetic males
Female pseudohermaphroditism
Malformation; genetic females with male external genitalia; results high level of androgens; may be caused by CAH or agents for spontaneous abortion treatments
Congenital adrenal hyperplasia
CAH
Congenital adrenal hyperplasia (CAH)
Excessive androgen production by the fetal adrenal glands; results in (a possible cause of) female pseudohermaphroditism
Female pseudohermaphroditism
Malformation; might get menses; connection between uterus and urethra; enlarged clitoris; results from high levels of androgens
Cryptorchid testes; ectopic testes
Undescended testicle anomalies (infertile; 2)
Cryptorchid testes
Anomaly; undescended testicles; along the usual path of descent; might result from deficient androgen production; treat with testosterone if descent does not occur
Cryptorchid testes
Anomaly; undescended testicles; testes attached to gubernaculum ligament; failure of second process of descent
Ectopic testes
Anomaly; undescended testicles; deviate from usual path of descent, lodge in various abnormal locations
Ectopic testes
Anomaly; undescended testicles; testes not attached to gubernaculum ligament or error of gubernaculum ligament
Incomplete congenital inguinal hernia (herniated intestine can become necrotic)
Anomaly; may result from abnormal closure of inguinal canal; most cranial portion of processus vaginalis not obliterated
Hydrocele; complete congenital inguinal hernia; incomplete congenital inguinal hernia
These result from abnormal closure of processus vaginalis (3)
Hydrocele
Anomaly; accumulation of fluid in abnormally closed (or unclosed) processus vaginalis
Complete congenital inguinal hernia (herniated intestine can become necrotic)
Anomaly; may result from complete failure of processus vaginalis to obliterate
Hypospadias (common, esp in hermaphrodites)
Urethra opens on ventral (lower) surface of penis; ectodermal part is not canalized (no orifice at tip); results from inadequate testosterone and/or abnormal receptors
Epispadias (very rare; don't know mech)
Urethra opens on dorsal (upper) surface of penis; results from inadequate ectodermal-mesenchymal interaction; often associated with exstrophy of bladder
Agenesis of external genitalia (very very rare)
Anomaly; orifice for urethra but no male or female genitalia; results from inadequate ectodermal-mesenchymal interaction
Double uterus and vagina
Anomaly; abnormal fusion of paramesonephric ducts (very low)
Uterus; vagina (double uterus results in two vaginas)
In females, the ____ induces development of a ____
Bicornuate uterus
Anomaly; incompletely fused uterus; some fusion (and degradation of septum) complete caudally
Septate uterus
Anomaly; abnormal fusion of paramesonephric ducts; fusion complete, but has septum
Double uterus and single vagina
Anomaly; abnormal fusion of paramesonephric ducts, some fusion caudally
Bicornuate uterus with rudimentary horn
Anomaly; not fully fused uterus; one half is somewhat degenerated
Unicornuate uterus
Anomaly; half of uterus does not develop; only one paramesonephric duct develops
Hymen anomalies (incomplete perforation of hymen, septate h., cribriform h., stenotic h., imperforate h.)
This group of anomalies results from abnormal perforation of inferior end of vagina
Imperforate (completely closed)
The (cribriform/imperforate/septate/stenotic) hymen is the most severe anomaly caused by abnormal perforation of inferior end of vagina
Vaginal atresia
Anomaly; failure of canalization of vaginal plate