Urinary Embryology Flashcards
How do the kidneys shift from the pelvic region to the abdomen
Migration and expansion of the caudal region of the foetus causes an apparent ascension of the kidneys
As the kidneys move up, they are vascularised by new vessels from the aorta at higher levels with old vessels degenerating as kidneys move up the abdomen
If vessels do not degenerate, they become accessory renal arteries
What are the three kidneys that appear during embryological development
Pronephros
Mesonephros
Metanephros
Describe the pronephros
First kidney system to develop and is found in cervical region
Has no function but is a useful duct that extends and grows form the cervical region to the cloaca and drives the development of the mesonephros
Describe the mesonephros
Second kidney system to develop
Is derived from intermediate mesoderm
Plays an important role in development of the male reproductive tract and sprouts the ureteric bud which causes the development of the metanephros
Mesonephric tubules and mesonephric duct form the embryonic kidney
Describe the metanephros
Becomes the functional kidney
Is functional from the end of 1st trimester
Produces urine that is excreted into the amniotic sac to become a major component of amniotic fluid
Briefly describe the development of excretory units in the metanephros
Excretory tubules appear which rapidly lengthen to form S-shaped loops and these then acquire a tuft of capillaries to form the glomerulus
Tubules along with the glomeruli form nephrons:
- Proximal ends of nephrons form Bowman’s capsule
- Distal ends of nephrons form a connection with the collecting tubules
Excretory tubules lengthen to form the other structure of the nephron
What is the function of the ureteric bud
Ureteric bud induces the development of the definitive kidney and becomes the true ureter
Ureteric bud induces undifferentiated, intermediate mesoderm caudal to mesonephros to develop into metanephros
After bud penetrates metanephric tissue, it dilates and forms the primitive renal pelvis which splits into cranial and caudal portions which later form the calyces
What does the allantois become after its lumen is obliterated and what does this structure become after birth
Allantois becomes urachus once lumen obliterated
Urachus becomes median umbilical ligament after birth
What do the parts of the urogenital sinus become
Upper part - connects to umbilicus and majority of it forms the bladder
Pelvic part - in males it gives rise to prostatic and membranous parts of the urethera
Phallic part - develops into urethra as GT grows
What forms the female urethra
The pelvic part of the UGS
What does the prostatic urethra form in males and females
In males the prostatic urethra forms the prostate gland
In females the cranial part of the urethra forms the urethral and paraurethral glands
What is renal agenesis
Where the ureteric bud fails to interact with the mesoderm and can be unilateral or bilateral
Unilateral - defect is in the ureteric duct. Will have normal levels of amniotic fluid as body can function with one kidney
Bilateral - defect is in the intermediate mesoderm. Results in low levels of amniotic fluid
What is a pelvic kidney
Where one or both kidneys don’t ascend -> remain in starting position, close to common iliac artery
Still functions normally
What is a horseshoe kidney
Where the caudal poles of the kidneys fuse as they move up, causing the kidneys to stop moving due to a physical barrier - usually blocked by inferior mesenteric artery
Occurs if caudal poles become close to each other as the kidneys ascend
What happens if the ureteric bud splits
Can have either:
- Partial splitting where there is an additional ureter but no additional pelvis. Additional ureter can attach to bladder or another structure which may result in incontinence
- Full splitting where there is an additional ureter and an additional pelvis. This results in a less well functioning kidney
