Embryo - Reproductive Flashcards
Describe the development of the reproductive system from three germ layer stage.
3 sources of Gonads:
- intermediate mesoderm
- primordial germ cells
- mesothelium lining of posterior abdomenal wall
Describe the formation of gonadal ridges.
Gonadal ridge
- Mesoderm origin
- forms primary sex cords
Primordial germ cells
- Endoderm
Note:
-
Gonadal ridge appears in the THORACOLUMBAR AREA
- forms testes/ovaries
- Develops on medial side of mesonephros
Describe the embryology of the indifferent stage of the gonadal development & development thereafter into male and female gonads.
Basics:
- Primordial germ cells migrate from the yolk sac –> gonadal ridges
- Gonadal ridges –> Primary Sex Cords
- outter cortex = finger like projections
- inner medulla = underlying mesenchyme
Sex determination & gonads:
- Genetic sex (XX or XY) is est. during fertilization
- Indifferent gonad = shows cortex & medulla
- identical for males/females before 7th week
Gonadal sex:
-
Testis Determining Factor (TDF) on the Y chromosome
- induces the indifferent gonad to differentiate into testes
- Happens in 7th week!
- Ovaries develop in the absense of Y chromosome
Briefly describe in descent of Testes and Ovaries during the development.
Dev of Gonads
- Testes & ovaries dev on the POSTERIOR ABDOMINAL WALL
- high up in the lumbar region
Descent of Testes
- into Scrotum
- Gubernaculum = scrotal ligament
- Leaves behind tunica vaginalis
Descent of Ovaries
- into Pelvis
- Gubernaculum = divided into 2 parts:
- upper part = ovarian ligament
- lower part = round ligament of uterus
Describe the embryological basis of conditions; Cryptorchidism, ectopic testes, Hydrocele, Congenital inguinal hernia, varicocele.
Cryptorchidism:
-
Hidden testes
- akaundescended testis
- Due to:
- defective gubernaculum or
- hormonal failure (descent is arrested)
Ectopic testes:
-
Testis in abnormal position
- thigh, abd wall, perineum, pubis
- Due to:
- abnormal tails of gubernaculum
Hydrocele:
- Encysted
- fluid collects in middle of unclosed part of processus vaginalis
- Congenital
- fluid collects in the tunica vaginalis thru unclosed processus vaginalis
Congenital inguinal hernia:
- Persistent processus vaginalis
- loop of intestine my herniate thru into scrotum
- Due to:
- communication btw tunica vaginalis + peritoneal cavity fail to close
Varicocele:
- twisted spermatic cord (pampiniform plexus, vas deferens, testicular a + n)
- commonly seen on the left side
Describe the formation of mesonephric & paramesonephric ducts and list their derivatives.
First 7th weeks:
- Both mesonephric duct + paramesonephric duct are present
Males:
- Androgens secreted by interstitial cells –>
- dev of male genital tract from MESONEPHRIC (WOLFFIAN) duct
- MIS secreted by sertoli cells –>
- degeneration of Paramesonephric (Mullerian) duct
-
Forms the:
- ureter
- epididymis
- ductus deferens
- seminal vesicles
- ejeculatory duct
- efferent ductules (persisting mesonephric tubules)
Females
- Presence of ovarian hormones + absence of testosterone & MIS –>
- dev female genital tract from the PARAMESONEPHRIC (MULLERIAN) duct
- Mesonephric (Wolffian) duct system –> degenerates (mostly)
- forms the ureter & ovary
-
Forms the:
- Uterus
- Uterine tubes
- fusion w/ urogential sinus (form vagina)
- sinovaginal bulb –> vaginal plate
Describe the embryological formation of external genitalia.
Development of External Genitalia
-
Genital (phallic) tubercle
- body of clitoris
- cranial to oriface
- body of clitoris
-
Genital (urethral) folds
- surrounded by UG folds
- lateral margins of oriface
- surrounded by UG folds
-
Genital (labio-scrotal) swellings
- forms labia = females
- forms scrotum = males (folds fuse)
- lateral to folds
Timeline of Differentiation:
- Week 4 = Dev starts
- Week 7 = Still indifferent gonads
- Week 9 = Distinguishing characteristics appear
- Week 12 = Full differentiation
Describe the embryological basis of hermaphroditism.
Female Hermaphroditism
- exposure of female fetus to EXCESSIVE androgens
- ie: congenital adrenal hyperplasia (CAH)
- tumor can cause excess androgens
- ie: congenital adrenal hyperplasia (CAH)
Male Hermaphroditism
-
Androgen insensitivity syndrome
- lack of androgen receptors
- androgens = ineffective in inducing growth of male genitalia
- MIS = present (Mullerian duct degenerates)
- Usually 46XY (external appearance of female)
- X linked disorder
Note:
- Pseudohermaphrodites
- Female fetus w/ XX but w/ CAH
- observe the varying degrees of masulinization in children
- clitoral hypertrophy
- labioscrotal fusion
Describe the embryological basis of epispasdias and hypospadias.
Epispasdias
- urethra opens on DORSAL surface of penis
- exposed bladder to outside
Hypospadias
- abnormal urethral orifice on the VENTRAL surface of penis (glands or body)
- most common anomaly of penis
- Caused by:
- failure of URETHRAL FOLDS to unite
What does the mesonephric duct form in fe/males?
Females:
- Collecting parts of kidney
- Ureter
- rest degenerates
Males:
- Collecting parts of kidney
- Ureter
- Epididymis
- Vas deferens
- Ejaculatory duct
- Seminal vesicle
What does the mesonephric tubules form in fe/males?
Females:
- Degenerates
Males:
- Efferent ductules of the testis
What does the Paramesonephric duct form in fe/males?
Females:
- Uterine tube
- Uterus
Males:
- Degenerates
What does the UGS form in fe/males?
Females:
- Urinary bladder
- Urethra
- Phallic part –> vagina
Males:
- Urinary bladder
- Urethra (except in the glans penis)
What does the Genital tubercle form in fe/males?
Female:
- Clitoris
Males:
- Penis
What do the Urethral folds form in fe/males?
Females:
- Labia minora
Males:
- Ventral aspect of penis
What do the Labioscrotal swellings form in fe/males?
Females:
- Labia majora
Males:
- Scrotum
