Embryology Flashcards
What two embryological structures does the urinary system develop from?
The intermediate mesoderm and the cloaca
What parts of the urinary system arise from the intermediate mesoderm?
The kidneys and ureters
What parts of the urinary system arise from the cloaca?
The bladder and urethra
How do the kidneys and ureters form?
The urogenital system arises from the intermediate mesoderm which forms a urogenital ridge on either side of the aorta. The ridge develops into three sets of tubular nephric structures known as the pronephros, the mesonephros and the metanephros
What happens to the pronephros?
They regress
What happens to the mesonephros?
They develop into the mesonephric tubules and the mesonephric duct. The tubules carry out some kidney function to start with but then regress. The duct persists and opens to the cloaca
What happens to the metanephros?
Gives rise to the definitive adult kidney
How do the collecting tubules of the kidney develop?
The excretory portion develops from derivatives of the metanephric blasterna
The collecting portion develops from derivatives of the ureteric bud
What are the two parts of the cloaca and what separates them?
Urogenital sinus and rectum divided by urorectal septum
How does the trigone of the bladder develop?
Derived from absorption of the caudal ends of the mesonephric ducts, which are of mesodermal origin. Over time the mesodermal lining is replaced with endodermal epithelium
What parts of the urinary system does the urogenital sinus give rise to?
Cranial part- forms bladder
Middle part- Forms prostatic and membranous urethra in males and entire urethra in females
Caudal part- forms penile urethra in males
From which part of the embryo does the alantois develop?
The endoderm
At what stage does the intermediate mesoderm become the pronephros?
During week 4
How does the ureteric bud develop?
The ureteric bud undergoes repeated branching at its distal end. The stalk becomes the ureter and the cranial end becomes the renal pelvis
How are the nephrons produced?
Through the ureteric bud and the metanephric mesoderm reciprocally inducing each other
What are the component parts of the nephrons and the uriniferous tubule?
Nephron- Renal corpuscle + proximal convoluted tubule + Loop of Henle + distal convoluted tubule
Uriniferous tubule- Nephron + collecting duct
Where do the kidneys ascend from and why do they ascend?
Kidneys initially lie on either side of the bladder and in the developing pelvis. Ascends into the abdominal cavity due to differential growth of lower body away from kidneys
When does the ascent of the kidneys stop?
When they come in contact with the adrenal glands
