Urinary System Embryology Flashcards
What layer of mesoderm forms the urinary system?
Intermediate mesoderm
What is the area of intermediate mesoderm that forms the urinary system?
Urogenital ridge
What 3 systems do the kidneys develop from?
- Pronephros
- Mesonephros
- Metanephros
When does the pronephros appear?
4th week of development
Where does the pronephros start its development?
In the cervical region
What are the tubules of intermediate mesoderm called?
Nephrotomes
How many nephrotomes form?
6-10 pairs
Where do the tubules join?
Into the pronephric duct
What is the pronephric duct?
A duct that extends from the cervical region to the distal end of the embryo
Where does the mesonephros develop from?
Caudally (inferiorly) to the pronephros
What does the presence of the pronephric duct induce?
Nearby intermediate mesoderm in the thoracolumbar region forms mesonephric tubules
Where do the mesonephric tubules get their capillaries from? Why do they need them?
The dorsal aorta so that they can filtrate blood
Where do the mesonephric tubules drain filtered blood into?
The mesonephric duct
What is the mesonephric duct?
A continuation of the pronephric duct that drains blood from the primitive kidneys to the cloaca
What is a cloaca?
A common passageway for faeces, urine and reproduction
What sprouts from the mesonephric duct?
The ureteric bud
What does the ureteric bud induce?
The development of the definitive kidney
What forms the definitive kidney?
The metanephros
When does the metanephros appear?
5th week of development
When does the metanephros become functional?
12th week of development
What does the ureteric bud make contact with?
The metanephric blastema
What is the metanephric blastema?
A caudal region of the intermediate mesoderm
What are the 2 components of the metanephric system?
- Collecting system
2. Excretory system
What is the collecting system derived from?
The ureteric bud
What is the excretory system derived from?
The metanephric blastema
What makes up the collecting system?
- Ureter
- Renal pelvis
- Major and minor calyces
- Collecting tubules
What makes up the excretory system?
The nephron
What does the proximal end of the excretory tubule form?
The Bowman’s capsule around a glomerulus
What does the distal end of the excretory tubule form?
- Proximal convoluted tubule
- Loop of Henle
- Distal convoluted tubule
Where does the definitive kidney initially develop?
The pelvic region and then ascends into the abdomen
Where does the kidney receive blood from initially?
A pelvic branch of the abdominal aorta
Where does the kidney receive blood from when it ascends?
New arteries from the abdominal aorta supply it
Where do the bladder and urethra form from?
The cloaca
Which weeks does the cloaca divide into two?
4th-7th weeks
What does the cloaca divide into?
- Urogenital sinus
2. Anal canal
What structure divides the two sections of the cloaca?
The uro-rectal septum
What are the three parts of the urogenital sinus?
- Upper part
- Pelvic part
- Caudal/phallic part
What does the upper part of the urogenital sinus form?
The bladder
What does the pelvic part of the urogenital sinus form?
- Urethra
- Some of female reproductive tract
- Prostatic and membranous urethra in males
What does the caudal/phallic part of the urogenital sinus form?
- Part of the female reproductive tract
2. Spongy urethra in males
What is the bladder initially drained by?
The allantois
What happens to the allantois during foetal development?
It is obliterated and becomes a fibrous cord = the urachus
What is the median umbilical ligament?
Remnants of the urachus in adults, connecting the apex of the bladder to the umbilicus
What does the bladder absorb when developing?
The caudal parts of the mesonephric ducts to become the trigone of the bladder
Where do the ureters enter the bladder?
At the base of the trigone
What happens to the mesonephric ducts in females?
They degenerate due to lack of testicular androgens
What happens to the mesonephric ducts in males?
They move caudally and closer together, entering the prostatic urethra to become the ejaculatory ducts
