Embryology of the urinary system Flashcards
How many kidney systems form during development?
- 3 separate systems develop sequentially
- Disappearance of one system marks onset of development of next stage
- Develop from intermediate mesoderm
Where does the pronephros develop?
- 1st appears in the cervical region
- Pronephros is 1st kidney system
Which part of the embryo forms the bladder?
- Endoderm
What are the names of the different kidney systems that form during embryonic development?
- 1st attempt called pronephros
- Then mesonephros
- Then metanephros - gives rise to functioning kidney
What is the pronephros?
- First kidney system, never functions in humans
- Forms pronephric duct - important for next stage of kidney system
Where does the pronephric duct extend from?
- Cervical region to cloaca
What is the mesonephros?
- Mesonephric tubules develop caudal to pronephric region
- Mesonephric duct = embryonic kidney
- No water conserving function
Why do we need to know about the mesonephros?
- Mesonephric duct has important role in development of reproductive system in male
- Sprouts ureteric bud which induces development of definitive kidney
What is the metanephros?
- Undifferentiated intermediate mesoderm, caudal to mesonephros
- Ureteric bud induces development of true kidney, metanephros in this tissue
How is the definitive kidney formed?
- Ureteric bud contacts metanephric blastema
- Sends out growth factors
- Bud expands and branches, becomes differentiated to form kidney as we know it
- Ureteric bud becomes collecting system
- Undifferentiated tissue of metanephric blastema becomes nephrons
How does the renal functional unit develop?
- Ureteric bud drives development of definitive kidney
- Collecting system is derived from ureteric bud
- Excretory component is derived from intermediate mesoderm under influence of ureteric bud
Outline the ascent of the kidney
- Metanephric kidney first appears in pelvic region
- Undergoes an apparent caudal to cranial shift, crossing arterial fork formed by vessels returning blood from foetus to placenta
- Kidney swaps positions with gonads
What happens to blood supply of the kidneys as they ascend?
- They pick up blood supply from aorta
- These vessels degenerate as kidneys continue their ascent and move higher up in the body
- By week 9 only supplemental arteries should remain
What can go wrong with the development of the kidneys?
- Ureteric bud fails to interact with intermediate mesoderm - causes renal agenesis
- Migration goes awry
- Duplication defects
- Ectopic ureter
- Cystic disease
What structural abnormalities can occur in the kidneys that are related to migration?
- Pelvic kidney - kidney never ascends to underneath adrenal glands
- Horseshoe kidney - poles of kidney fuse together so kidneys get caught on inferior mesenteric artery and can’t ascend
What duplication defects and ectopic urethral orifices can occur during development of the kidneys?
- Splitting of ureteric bud
- Partial or complete
- Symptomatic consequence is ectopic ureteral opening
