Development Of Reproductive System Q1 Flashcards
Why are the male and female reproductive systems closely related?
The development of the male and female reproductive systems are closely related
– The same is true for the urinary system
• Differentiating between male and female in the early stages of
development is difficult
• This is true for both internal and external organs
• There will always be homologous structures between the two
– Organs that develop from similar progenitors, have similar structure and similar function
– E.g. Ovaries in female and testes in male
How is the urinary system relevant to urinary development?
Kidneys develop from three consecutive primordia
– Pronephros –
Mesonephros
• Mesonephric duct is important for development of the male reproductive system
– Metanephros
• Will form the definitive kidney
• Bladder and urethra develops from the urogenital sinus
–
The vagina in the female is partly formed from the urogenital sinus
What internal organs are developed in the internal organs?
• Gonads
– Ovaries – Female
– Testes – Male
• Ducts and their derivatives
– Females - Uterus, uterine tubes, vagina, greater vestibular glands (Bartholin glands)
– Male - Epididymis, ductus deferens, seminal vesicles, prostate gland, bulbourethral glands
Describe development of indifferential organs
Gonadal ridges (thickened area of mesothelium and underlying mesenchyme) appear in the 5th week on the medial aspect of the mesonephros in the thoracolumbar area (indistinguishable male/female before 7th week)
Primordial germ cells migrate from the umbilical vesicle to the gonadal ridge to initiate development
Fingerlike epithelial cords (Gonadal cords) grow into the underlying mesenchyme
• Indifferent gonads now have an outer cortex and inner medulla
• The arrival of the primordial germ cells induce formation of gonads
Describe the differentiation of gonads(Testes)
• TDF induces condensation and elongation of the gonadal cords
• This divides the medulla resulting in formation of Seminiferous (medullary)
cords
• Cords, branch and anastomose to form the rete testes
– later joins with 10-15 mesonephric tubules (efferent ductules)
• Fibrous condensation separates the testes from the surface epithelium - Tunica Albuginea
• The testes is separated from the mesonephros and is suspended by the mesorchium
• Seminiferous cords acquire a lumen at puberty to give rise to the seminiferous tubules and straight tubules which join the rete testes
– Seminiferous cords consist of primordial germ cells and Sertoli cells
– Sertoli cells produce Antimullerian hormone (AMH)
• The surrounding mesenchyme give rise to Leydig cells
– Produce testosterone
– Important for development of the
mesonephric duct
– Important for differentiation of external genitalia
Describe testicular descent
Two phases: Transabdominal & Inguinal
The developing testis is connected to the area on the anterior abdominal wall by a mesenchymal structure = gubernaculum
Transabdominal = the “descent” of the testis is a result of abdominal growth
Describe the testicular descent -inguinal phase
- Controlled by testosterone.
- Guided into the developing scrotum by the gubernaculum.
- It carries its ducts and vasculature with it.
- Spermatic cord is formed by fascial extensions from the abdominal wall.
- Processus vaginalis is a peritoneal extension into the scrotum. It forms the tunica vaginalis when the connecting stalk is obliterate
Describe the formation of the tunica vaginalis as a result of Testes descent
• Processus vaginalis
– Evagination of peritoneal
cavity and membrane
– Connecting stalk normally obliterates
• Tunica vaginalis
– Peritoneal sac
– Remnant of the processus vaginalis
What is the possibility of a hydrocele?
Hydrocele
The processes vaginalis contains a small amount
of fluid before it obliterates
Once the connecting stalk is obliterated, the fluid is reabsorbed.
If the fluid does not get reabsorbed = hydrocele May occur in adults as well but rare.
Identified by transillumination
What is Congenital inguinal hernia?
If the connecting portion of the processes vaginalis does not obliterate, it leaves a patency in the inguinal canal where intestines may herniate through
What is ectopic testis?
Testes in abnormal place
• After descending into the inguinal canal
• It may become lodged in various abnormal locations
• Very rare
What is cryptorchidism?
Undescended testes • Testes do not descend into the scrotum • May be bi- or unilateral • Testes can be anywhere along the normal descent pathway • Usually found in the inguinal canal • May be in the abdomen • Don’t mature and often sterile • Higher risk for germ cell tumors
Describe the development of the ovaries
- Starts some weeks later than testis (week 10).
- The surface epithelium continues to proliferate and gives rise to a second generation of cords - cortical cords.
- As these cords proliferate, primordial germ cells (oogonia) become incorporated into them.
- At about 16 weeks, cords dissociate into cell clusters (primordial follicles) which contains an oogonium surrounded by flattened follicular cells
Describe the indifferent Genital ducts
Development of the mesonephric ducts into the male genital ducts is stimulated by Testosterone from the Leydig cells
Development of the paramesonephric ducts into female genital ducts occurs unless suppressed by AMH from Sertoli cells of developing testes
How do male genitalia ducts develop?
Mesonephric ducts
Under the influence of testosterone and AMH
– Some of the mesonephric tubules persist and become the efferent ductules • Gives rise to the epididymis.
– The mesonephric duct thickens, acquires smooth muscle and become the ductus deferens.
Seminal vesicles
– Outgrowth from the caudal end of the mesonephric duct.
– The portion of the mesonephric duct between the duct of the gland and the urethra becomes the ejaculatory ducts
