1.1 Development of the reproductive tract Flashcards
Describe the components of the male internal genitalia
Testis Duct system (epididymis, ductus deferens, urethra)
Seminal vesicles
Prostate
Bulbourethral glands
What is the purpose of the male internal and external genitalia
Internal: collect and mature sperm
External: deliver ejaculate semen into the vagina during coitus
Describe the components of the female internal genitalia
Ovaries
Duct system (Fallopian tube, uterus, cervix, vagina)
What is the purpose of the female internal and external genitalia
Internal: produce ovum and provide optimal environment for sperm
External: allow the introduction of sperm into the female reproductive tract and allow formation of a birth canal
Compare the male vs female EXTERNAL genitalia
Male:
- Penis
- Scrotum
Female:
- Vagina
- Vestibule
- Labia minora
- Labia majora
- Clitoris
What is meant by the indifferent stage of of reproductive development?
Initial stage in both male and female begins the same
Depending on the expression of genes has the potential to become either male or female
What is the difference between structural and functional development?
Structural: occurs in utero
Functional: continues after birth
List 3 things that will develop/not develop if the primordial germ cells express XY on an indifferent gonad
Develpment into testis (male)
- Medullary cords develop
- No cortical cords
- Thick tunica albuginia
List 3 things that will develop/not develop if the primordial germ cells express XX on an indifferent gonad
Development into ovaries (female)
- Medullary cords degenerate
- Cortical cords develop
- No tunica albuginea
The primordial germ cells are formed in which layer of the trilaminar disc and during which week?
epiblast, 2nd week
What region/gene is specific to only the Y chromosome?
What does expression of this do?
SRY region (Sex determining region) / TDF (Testis determining factor)
Directs testicular formation
Absence of a Y chromosome (ie. XX) means what gene will be absent and what will occur as a result?
Absence of the SRY region
Directs development of a female (ovaries, tubes, uterus + external female genitalia)
At what week do we get migration of the PGC’s (primary germ cells)
week 3
Where do the PGC’s originate and how do they migrate?
Originate in the wall of the yolk sac
Migrate along the wall of the hindgut and dorsal mesentery into the genital ridge
Where is the urogenital ridge found?
What is found either side of this ridge and what is the fate of these?
Found on the dorsal body wall
Laterally: mesonephric ridge ➞ kidneys
Medially: genital ridge ➞ ovaries/testis
The genital ridge consists of two components, what are these?
Mesenchyme
Coelomic epithelium
What are the 3 sources of gonadal development?
1) condensed mesenchyme of gonadal ridges (plica genitalis)
2) coelomic epithelium (mesodermal origin)
3) gonocytes (primordial cells)
Male internal genitalia develop from what duct?
Wolfian/ Mesonephric duct
Female internal genitalia develop from what duct?
Mullarian/ Paramesonephric duct
Explain gonadal development in the presence of SRY (TDF)
1) Gonadal cords develop ➞ expression of TDF leads to the growth of sex chords into the medullary region of the gonad
* primordial germ cells enter these cords and give rise to seminiferous tubules in an adult
2) No cortical cords develop
3) A Thick Tunica Albuginea forms
Explain gonadal development in the absence of SRY (TDF)
1) Gonadal cords degenerate (leaves space for oogonia to develop)
2) Cortical cords develop
3) The germ cells become surrounded by mesenchymal cells to form primordial follicles
*** No Tunica Albugina
What is the gubernaculum and what is its purpose?
Undifferentiated band of mesenchyme that guides the decent of the gonads
After atrophy of the mesonephros, what happens to the proximal (upper) portion of the gubernaculum in males vs females?
Males: disappears
Females: forms the ovarian ligament (connecting ovary to uterus)
After atrophy of the mesonephros what happens to the distil (lower) portion of the gubernaculum in males vs females?
In both, it inserts at a lower pole of gonad and extends to the inguinal region
Males: becomes the scrotal ligament
Females: becomes the round ligament of the uterus (connecting the uterus to the labia)
What is the only ligament in females to pass through the inguinal canal?
The Round ligament
What happens to the paramesonephric duct and mesonephric duct in females?
Paramesonephric duct at the top forms uterine tubes and at the bottom each side fuses ➞ uterus and part of the vagina
Majority of the Mesonephric duct degenerates EXCEPT
1) a small portion on outer vagina wall ➞ “Gartners cyst”
2) some tubules that persist as Paroophoron (distil) and Epoophron (proximal)
(these are remenants of the Mesonephric ducts in females)
Before the decent of the testis what forms in order to protrude through the abdominal wall?
Where is it located?
Processus vaginalis ➞ a peritoneal outpouching
Lies immediately anterior to the gubernaculum within the inguinal canal
Describe how the coverings of the spermatic cord are established
The processus vaginalis protrudes through the layers of the anterior abdominal wall and acquires coverings, these become the layers of the spermatic cord:
1) The transversalis fascia (deep) ➞ internal spermatic fascia
2) Musculature of the internal oblique ➞ cremaster fascia
3) Aponeurosis of the external oblique (superficial) ➞ external spermatic fascia
Describe the decent of the testis and incl what marks the completion of the spermatic cord
1) As body grows the position of the testis moves more caudal
2) this causes the processus vaginalis to become a tubular structure with multiple coverings (forms inguinal canal)
3) As testis decends, its accompanying nerves, vessels and ducts pass through the inguinal canal
4) the completion of the spermatic cord occurs when the processus vaginalis obliterates
What is Cryptorchidism?
What does this mean for male fertility and what does this increase risk of?
Failure of the testis to complete decent, causing the testis to remain in the abdominal cavity
This results in non-functioning scrotum due to the temperature of the abdominal cavity.
Iincreases risk of testicular cancer
What are the two fates of mesonephric tubules in males? In males all tubules are linked to mesonephric ducts, what occurs in females?
Epigenital tubules: these establish contact with the cords of the rete testis and persist as the ductile efferentes (connects seminiferous tubules to epididymis)
Paragenital tubules: disappear (can occasionally persist as the paradidymis) In females the mesonephric ducts disappear
Describe the development of prostate and seminal vesicles, include what week these occur
11th week: 5 independent solid cords of prostatic tissue develop lumina and acini
13th week: prostatic acini begin to develop secretory activity and mesenchyme surrounding prostate develops into muscle and connective tissue
What is the equivalent of the prostate in females?
Where do these derive from?
Skene’s glands, paraurethral glands
Derived from the urogenital sinus
What is the veramontanum and what is its importance?
Found in males ➞ midline region of the prostate, slightly raised
Important landmark for orientation of the openings of 2 ejaculatory ducts and the prostatic utricle
The formation of the EXTERNAL genitalia starts with the indifferent stage, what 3 basic components does this require?
1) genital tubercle
2) urethral folds
3) labioscrotal swellings
What happens to the following structures in males and what controls this?
1) genital tubercle
2) urethral folds
3) labioscrotal swellings
1) genital tubercle: elongates to form the glans penis
2) urethral folds: fuse to form the spongy urethra
3) labioscrotal swellings: fuse to form scrotum
Controlled by Dihydrotestosterone
What happens to the following structures in females and what controls this?
1) genital tubercle
2) urethral folds
3) labioscrotal swellings
1) genital tubercle: glans clitoris
2) urethral folds: remain open: labia minora
3) labioscrotal swellings: labia majora
+ urethra opens into the vestibule
Controlled by lack of Dihydrotestosterone (no fusion occurs)
Briefly describe how exactly fusion occurs in a male
1) phallic part of UG sinus (endoderm) grows into the phallus as the vertical urethral plate
2) the urethral plate split to form the urethral groove and urethral folds on ventral surface of penis
3) The urethral folds fuse to form the penile urethra EXCEPT in the glans
What are the two genetic disorders that result from failure of fusion in males?
Briefly describe the anatomical location where failure occurs in each
Hypospadias: incomplete fusion of urethral folds, urethra opens inferiorly (on the ventral surface)
Epispadias (rarer): urethral meatus found on dorsum of penis (urethra opens on upper aspect)
*In both cases urine can dribble out
What hormones are responsible for the outcomes of the Wollfian and the Mullarian duct in an XX embryo?
1) No androgen therefore mesonephric (wolfian) duct degenerates
2) No testis derived Mullerian inhibiting hormone (MIH) so Mullerian duct develops
What hormones are responsible for the outcomes of the Wollfian and the Mullarian duct in an XY embryo?
1) Androgen secretions supports mesonephric (wolfian) duct
2) Sertoli cells secrete Mullerian Inhibitry hormone (MIH) causing the paramesonephric (Mullarian) duct to degenerate
What does the term virilised mean?
Virilisation is the biological development of sex differences, changes that make a male body different from a female body
