Embryology - Development of Cloaca Flashcards
What is an allantois?
Diverticulum form the endoderm of the yolk sac.
What occurs at the caudal end of the embryo?
The hindgut and allantoid meet in a common cavity - cloaca.
How is the cloaca bound?
Dismally by the cloacal membrane.
What grows from the dorsal wall of the allantois?
Urorectal septum - grows downwards to meet the cloacal membrane.
What happens when the urorectal septum meets the cloacal membrane?
It divides the cloaca and membrane into two.
What are the two areas that the cloaca and membrane are divided into?
- Front:
- Urogenital sinus.
- Urogenital membrane. - Back:
- Anorectal canal.
- Anal membrane.
Where does the anorectum and anal membrane lie?
Small ectodermal depression - proctodeum.
What does the dorsal part of the sinus become?
- Rectum.
- Anal canal.
How many parts does the Urogenital sinus (endoderm) have?
Three parts.
What is the uppermost part of the Urogenital sinus?
Vesicular (veiscourethral) part - largest part.
What does the vesicourethral part form?
- Most of the bladder epithelium.
- Female urethra.
What does surrounding mesoderm in the vesicourethral part form?
Muscle and connective tissue of the bladder.
How is the urethra formed in males?
The lower part of the urogenital sinus becomes the proximal prostatic urethra as far as the openings of the ejaculatory ducts and prostatic utricle.
Where does the mesopnephric duct open up?
Into the lower part of the vesicourethral part.
Where/how does the ureter form?
As a bud form the mesonephric duct. THe duct and the ureter grow apart and open separately into the sinus, the ureter opens at a higher level than the duct.
