embryology of UG tract Flashcards
What is the relationship between the ureteric bud and the metonephros?
• Uteric bud forms from metanephric duct as it approaches the cloaca
Describe the processes by which congenital anomalies associated with the ureter can occur
- Early splitting of uteric bud (splitting normally begins WITHIN the metanephric tissue)
- Problem based on location of split
- Bifid ureter, double ureter
- If have 2 separate uteric buds (rare): one empties to bladder, and the other one is ectopic (empties somewhere diff like urethra, vagina)
- What is the relationship between the cloaca, urogenital sinus, and anorectal canal? What is the role of the urorectal septum?
- The cloaca is a cavity associated with the hindgut and developing UG tract
- The cloaca divides into the UG sinus anteriorly and the anorectal canal posteriorly (at ~4-7 wks)
- The tip of the urorectal septum goes on to form the perineal body
- What normally happens to the allantois? If this doesn’t happen, what congenital anomalies can occur?
- The allantois usually degenerates and forms the urachus which then becomes the median umbilical ligament
- If the lumen of the allantoids persists: can get urachal fistula, urachal cyst, or urachal sinus
- T/F- the anterior (ventral) body wall is formed by ectoderm and parietal mesoderm.
- True
- The lateral body wall folds (made of parietal mesoderm and ectoderm) close off to form the ventral aspect of the body walls
- Explain how the cloacal membrane is thought to be involved in the exstrophy-epispadias complex. (be sure to put this in the context of structures involved with body wall closure)
- Normally the ventral aspect of the cloaca is composed of a layer of endoderm and ectoderm called the cloacal membrane
- Cloacal membrane ruptures and provides an opening for the division of the cloaca into the UG sinus and the anorectal canal
- Extrophy is when the cloacal membrane is overdeveloped and prevents tissue from migrating medially during closure of ventral body wall
- So when cloacal membrane ruptures: the contents of the lower abdominal region are let outside
- Describe the path that germ cells take to reach the genital ridges.
• Wk 4: germ cells located in yolk sac begin to migrate upwards to genital ridges and begin penetrating them at wk 6
o If the germ cells do not reach the genital ridge, the gonads do not develop
o These cells induce either the formation of testes or ovaries
- What happens to the primitive sex cords in males? How does this differ from females?
In males
• If Y chromosome present : SRY gene produces testis determining factor –> causes proliferating primitive sex cords to develop and break into networks of testis (medullary) cords
• Near the hilum of the gonad, the cords separate and give rise to the cords in the rete testis
In females
• Primitive sex cords become disorganized and form irregular clusters of cells which are eventually replaced by cells associated with ovarian medulla
- What tissue gives rise to the cortical cords in females? What do these go on to form?
- Surface epithelium continues to proliferate and gives rise to second set of sex cords –> cortical cords –> these enter the mesenchyme tissue and remain near the surface
- ~3rd mo –> cortical cords split into cell clusters surrounding the primordial oocyte and form a layer of follicular cells
Together the collicular cells and oocyte make up the primordial follicle
- T/F- paramesonephric ducts are never present in males.
- False
* Paramesonephric ducts are present in males but they degenerate with the help of anti-Mullerian factor
- A remnant of what system goes on to form the efferent ductules in males?
• Small portion of the regressing mesonephros makes contact with the cors in the rete testis to form the efferent ducts
- Compare development of the upper vs. lower parts of the vagina.
- Upper vagina (including fornices) : formed from the uterine canal (paramesonephric ducts)
- Lower part of vagina : formed by UG sinus
- Describe the development and anatomical (i.e., location of defect) differences between hypospadias and epispadias
- Hypospadias: incomplete fusion of the urethral folds leads to exposure of urethra on ventral aspect of penis
- Epispadias: abnormal opening on dorsal aspect of penis; defects in closure of ventral body wall (part of extrophy-epispadias complex
- Describe the relationship between the testis, gubernaculum, processus vaginalis, and inguinal canal
- Gubernaculum anchors testis within the scrotum
* Processus vaginalis forms the tunica vaginalis
- What is a patent processus vaginalis and what anomalies are associated with this condition?
o Connection b/w processus vaginalis and abdominal cavity persists
o So have partial or complete communication b/w scrotum and abdominal cavity
o With a completely open pathway: intestines easily pass through opening –> indirect inguinal hernia
o With partially closed pathway: cyst may develop leading to a hydrocele of testis or spermatic cord
