E - Development of The Urinary System Flashcards
Main functions (4) of the urinary system include:
Removal of metabolic waste products such as urea; maintain electrolyte, water and pH balance; regulation of blood pressure, blood volume and erythropoietin; vitamin D synthesis
Development of the urniary system is tightly linked to…
Development of the reproductive system in early stages, until the urinary system eventually develops ahead
The urinary system consists of…
The kidneys, ureters, bladder and urethra
What tissue gives rise to the structures of the urinary system?
The urogenital ridge of the intermediate mesoderm
The kidneys develop from…
The overlapping sequential systems - pronephros, mesonephros and metanephros.
Pronephro development begins in…
The fourth week of gestation in the cervical region
First stage of pronephro development
6-10 pairs of segmented tubules deriving from the intermediate mesoderm called nephrotomes are formed.
Second stage of pronephros development
Nephrotomes join with a pronephric duct - a duct which extends from the cervical region to the cloaca - this system regressed by the end of week 4
Cloaca
Distal end of the embryo
The mesonephros develops
Caudally/inferiority to the pronephros
First stage of mesonephros development
Presence of the pronephric duct stimulates the thoracolumbar region of the intermediate mesoderm to form mesonephric tubules
Second stage of mesonephros development
Mesonephric tubules receive a tuft of capillaries from the dorsal aorta - empty into the mesonephric duct (continuation of the pronephric duct) which acts as the primitive blood filtration system for the growing embryo - most of these tubules regress by the second month
The mesonephric duct…
Sprouts the ureteric bud caudally which induces development of the definitive kidney
Metanephros development forms… and occurs…
The definitive kidney - occurs between the 5th and 12th weeks
First stage of metanephros development
The ureteric bud from the mesonephric duct makes contact with the caudal region of intermediate mesoderm = forms the metanephric blastema which is the metanephric system
Metanephric system has two components
Collecting system and excretory system
The metanephric collecting system is derived from…
The ureteric bud
The metanephric collecting component gives rise to..
The ureter, renal pelvis, major/minor calyces and collecting tubules. Terminates at the distal convoluted tubule.
If the ureteric bud splits too early…
Can give rise to two ureters or two renal pelvices connected to one ureter
The metanephric excretory component is derived from…
Metanephric blastema
First stage of metanephric excretory component
Each collecting tubule from the collecting component is capped with a metanephric tissue cap - gives rise to excretory tubules
Excretory tubules in the metanephric excretory component give rise to
The nephrons
The proximal end of the metanephric excretory tubule forms
The bowman’s capsule around a glomerulus
The distal end of the metanephric excretory tubule forms
The proximal convoluted tubule, loop of henle and distal convoluted tubule
The definitive kidney develops…
In the pelvic region but eventually ascends into the abdomen
In the pelvis, the kidney…
Receives its blood supply from a pelvic branch of the abdominal aorta
As the kidney ascends during development…
It receives new arteries from the abdominal aorta
The pelvic renal arteries…
Usually regress, but can continue as accessory renal arteries
Horseshoe kidney/cake kidney/fused kidney
Where the two developing kidneys fuse into one horseshoe-shaped kidney
Development of horseshoe kidney
Occurs when kidneys become to close in abdominal ascent - become fused and stuck underneath the inferior mesenteric artery
Horseshoe kidneys are…
Still drained by two ureters and asymptomatic but prone to obstruction
What are the bladder and urethra derived from?
The cloaca
What happens to the cloaca in weeks 4-7 of urinary development
Divided into two parts by the uro-rectal sinus
The anterior section of the uro-rectal septum
The urogenital sinus
Upper section of urogenital sinus
Forms the bladder
Pelvic section of uro-genital sinus
Forms The entire urethra and some of reproductive tract jn females. Forms membranous and prostatic urethra in males
Phallic section of uro-genital sinus
Forms part of the female reproductive tract. Forms the spongy urethra in males
Posterior section of uro-rectal septum
Anal canal
What is the urinary bladder initially drained by during gestation?
The allantois
What happens to the allantois?
Gets obliterated into the urachus (a fibrous chord). The remnant of the urachus can be seen as the median umbilical ligament within adults. (Connects apex of bladder to umbilicus)
What happens to bladder as it develops from urogenital sinus
It absorbs the caudal parts of the mesonephric ducts (Woffian ducts) - forms the trigone of the bladder.
Ureter/bladder connection
Ureters sprout from the mesonephric ducts and connect to the base of the trigone bladder
What happens in both males and females as kidneys ascend in abdomen?
The ureteric openings move cranially
What happens to mesonephric ducts in males and females?
(Males) Move caudally and closer together, enter prostatic urethra to become ejaculatory ducts. (Females) degenerate due to a lack of testicular androgens.
What is the urethra formed by in males?
Prostatic and membranous urethra is formed by the pelvic uro-genital sinus. The spongy urethra is formed by the phallic uro-genital sinus
What is the urethra formed by in females?
The pelvic part of the urogenital sinus
