Development of the Reproductive System Flashcards
What is the key to sexual dimorphism?
The Y chromosome contains a testes determining gene → SRY
Where is the SRY gene located?
The SRY gene is located on the short arm of the Y chromosome (Yp11).
What does the SRY gene do?
It diverts the developing fetus to become male or female.
What are the three parts of the endodermal gut tube?
Foregut, midgut, and hindgut.
What happens in the mesoderm?
Development of heart and blood vessels.
What is the cloaca?
The area of the hindgut distal to the allantoic diverticulum.
What is the cloaca membrane?
The part of the ectodermal membrane which is closer to the cloaca.
What does the cloaca need to be converted into during development?
It is converted into two regions: one for the urinary system and one for the digestive system (the rectum).
What divides the cloaca into two regions?
The urorectal septum originating from the mesoderm.
What does the primitive urogenital sinus become?
It becomes the proper urinary system.
What does the primitive rectum become?
It becomes the rectum and anus.
What can be seen in the image of the developing fetus?
The fetus is developing gonads and the urinary system, with lots of tubules seen developing.
What is another name for the developing urinary system?
Mesonephros, which means lots of tubules.
What are mesonephric ducts?
Ducts where tubules unite, opening into the cloaca.
What is medial to the mesonephric duct?
The gonadal ridge, where gonads develop.
What is gonadal development known as?
Indifferent stage of development, occurring from the 4th to the 7th week.
When do gonads acquire male or female morphological characteristics?
In the 7th week.
What does part of the mesoderm condense to form?
It condenses to form the gonadal ridge/genital ridge.
What are the three types of mesoderm?
Paraxial mesoderm, intermediate mesoderm, and lateral plate mesoderm.
What type of mesoderm is the genital ridge formed by?
It is formed by a condensation of the intermediate mesoderm.
What happens after the genital ridge is formed?
Primordial germ cells migrate from the epiblast layer to the genital ridge.
What happens once primordial germ cells reach the genital ridge?
They cause the coelomic epithelium to proliferate and fold into primitive sex cords.
What forms fingerlike projections in the genital ridge?
The coelomic epithelium of the genital ridge proliferates and penetrates the mesenchyme, forming primitive sex cords.
What happens if the embryo is genetically male?
The primordial germ cells carry an XY sex chromosome complex with the SRY gene present.
What do the primitive sex chords do if the SRY gene is present?
They migrate deeply to form medullary sex chords.
What happens to the medullary sex chords?
They disintegrate and give rise to a reticular formation known as rete testis.
What separates the rete testis from the coelomic epithelium?
A thick membrane called Tunica albuginea.
How are testicular cells derived?
From primordial germ cells, coelomic epithelium, and intermediate mesoderm.
What happens by the 7th to 8th week of gestation?
Leydig cells produce testosterone, influencing sexual differentiation of the genital ducts and external genitalia.
What happens to the primitive sex chords after the indifferent stage in females?
They migrate into the medulla and disintegrate to form the ovarian medulla.
What replaces the primitive sex cords in the ovaries?
They are replaced by stroma and blood vessels.
What happens in the 7th week regarding cortical sex cords?
The coelomic epithelium begins to proliferate a second time, forming cortical sex cords.
What happens to the cortical sex cords at 3 months?
They crumble and split into isolated cell clusters, forming primordial follicles.
What is not seen in the ovary that is seen in the testes?
Tunica albuginea.
What does the indifferent stage mean?
Both male and female ducts are present, opening into the primary urogenital sinus.
What is the mesonephric duct also known as?
Wolffian duct, which is the genital duct in males.
What is lateral to the Wolffian duct?
The paramesonephric duct (Mullerian duct), which forms the genital ducts in females.
What is the Mullerian duct?
The Mullerian duct, also known as the paramesonephric duct, forms the genital ducts in females.
What are the characteristics of the paramesonephric duct?
It has 2 vertical parts, a horizontal part, and 2 inferior vertical parts that join to form the uterovaginal primordium.
How does the mesonephric duct differ from the paramesonephric duct?
The mesonephric duct has 2 different openings because the tubes aren’t connected together.
What happens to the ducts during differentiation?
Some of the ducts disappear while others persist to form adult structures.
What hormones do Leydig and Sertoli cells produce?
Leydig cells produce testosterone, while Sertoli cells produce Mullerian inhibiting substance.
What is the effect of the hormone secreted by Sertoli cells?
It suppresses the paramesonephric ducts.
What does testosterone do in males?
It stimulates the mesonephric duct (Wolffian duct) to produce dihydrotestosterone, which promotes the growth of external genitalia.
What do primitive sex cords form?
They form seminiferous tubules, which then join and disintegrate to form the rete testis.
What do the tubules of the mesonephric duct form during differentiation?
They form efferent ductules.
What occurs when a male reaches puberty?
The Wolffian duct becomes canalized.
Where does the prostatic urethra originate?
It originates from the region of the primitive urogenital sinus.
How is the prostate formed?
The primitive urogenital sinus gives rise to 5 prostatic buds that develop into the prostate.
What happens to the prostate gland at 11 weeks?
Cords develop into glandular acini.
Where are bulbourethral glands located?
They sprout from the urethra just inferior to the prostate.
What hormone influences female ducts?
The hormone influencing female ducts is estrogen.
What does the cranial part of the paramesonephric duct form?
It forms the fallopian tube.
What gives rise to the uterus?
The horizontal part and the area where the paramesonephric tubes join later form the upper part of the vagina and the uterus.
What is the uterovaginal primordial?
It is the opening of the paramesonephric duct.
What happens when the uterovaginal primordial touches the primitive urogenital sinus?
It gives rise to a bulb-like projection called the sinovaginal bulb.
What are the two sources of the vagina?
The vagina comes from the paramesonephric duct and the sinovaginal bulb.
Is the sinovaginal bulb canalized?
No, it is completely filled and is referred to as the vaginal plate.
What happens when a girl reaches puberty?
Fluid accumulates within the lower part of the cervix and the uterus, forming hematocolpos due to failure of canalization of the vaginal plate.
What are the remnants of the Wolffian duct in females?
They include the paraphoron, epophoron, and Gartner’s duct.
What anomalies can occur with improper division of the paramesonephric duct?
Anomalies of the uterus can occur.
What happens to the urethral folds in females?
Urethral folds develop into labia minora, and genital swellings form labia majora.
What happens to the urogenital membrane in females?
It disintegrates slowly, revealing the urethra and vagina.
What happens to the genital tubercle in females?
It slightly raises and forms the clitoris.
What influences males during development?
Dihydrotestosterone causes the genital tubercle to elongate and form the penis.
What happens when the urethral membrane ruptures in males?
The urethral folds approximate each other, leaving a small opening at the tip of the penis.
What is hypospadias?
It is a birth defect where the urethral opening is not at the tip of the penis.
What do the genital swellings give rise to in males?
They develop into the scrotum.
Where are the testis first found?
In the abdominal cavity at the posterior aspect.
How are the testis attached to the wall?
They hang via the cranial suspensory ligament.
What does the gubernaculum do?
It guides the testis from the thoracic position to the scrotum.
What vertebral level are the testis formed?
They are formed at the 10th vertebral level.
Where are the testis located during the 3rd to 7th month?
In the vicinity of the deep ring.
What is the process vaginalis?
It is a piece of peritoneum that descends with the scrotum for protection.
What is the clinical importance of a persistent tunica vaginalis?
It can lead to the formation of a hydrocele.
What is the process vaginalis?
A piece of peritoneum which is brought down by the scrotum for protection. It then becomes tunica vaginalis and will disappear.
What is the clinical importance if the tunica vaginalis stays persistent and does not disappear?
Hydrocele forms, swelling around the testes due to fluid from the peritoneum. Can also lead to an inguinal hernia when there is a patent process vaginalis.
Why doesn’t the ovary descend much?
Because it has to sit near the uterus.
What does the gubernaculum attach to?
Attaches the ovary to the genital swelling which then develops into the labia majora.
What gets in the way of the gubernaculum?
The Mullerian duct, preventing the ovary from descending too much, so it sits near the fallopian tube and uterus.
What does the ovarian ligament connect?
Connects the ovary to the paramesonephric duct.
What does the round ligament of the uterus connect?
It is the gubernaculum from the paramesonephric duct to the labia majora. Connects the uterus to labia majora.
