S2) Development of Urinary System Flashcards
What is the name of the first kidney system and where does it form?
- Pronephros is the first kidney system
- Forms in the cervical region
What is the purpose of the pronephros?
- No function in adult humans
- Pronephric duct drives the development of the next developmental stage
What is the urogenital ridge?
Urogenital ridge is a region of intermediate mesoderm giving rise to both the embryonic kidney and the gonad
Outline the development of the mesonephros
Mesonephric tubules develop caudally to the pronephric region and have no water conserving function
Identify the components of the embryonic kidney
- Mesonephric tubules
- Mesonephric duct
What are the 2 functions of the mesonephric duct?
- Role in development of the male reproductive system
- Sprouts the ureteric bud which induces development of the definitive kidney
Describe the structure and function of the ureteric bud
- Structure: undifferentiated intermediate mesoderm, caudal to the mesonephros
- Function: induces development of the true kidney, metanephros in this tissue
Explain how the ureteric bud drives the development of the definitive kidney
- The collecting system is derived from the ureteric bud
- The excretory component is derived from the intermediate mesoderm under the influence of the ureteric bud
Identify the steps involved in the ‘ascent’ of the kidney
- The metanephric kidney first appears in the pelvic region
- It undergoes a caudal to cranial shift
- It crosses the arterial fork formed by vessels returning blood from the foetus to the placenta
What is different about the movement of the gonads and the kidneys during embryonic development?
Unlike the gonads which take their blood vessels with them, the kidney forms new branches as it ascends
Identify all the things that can go wrong during the development of the urinary system
- Renal agenesis
- Errors in migration
- Ectopic ureter
- Cystic disease
Identify two structural anomalies related to migration of the kidneys
- Horseshoe kidney
- Pelvic kidney
Renal agenesis is a congenital disorder of the urinary system.
What happens?
- Renal agenesis is when the ureteric bud fails to interact with intermediate mesoderm
- Presentation:
I. Absence of one (unilateral) or both (bilateral) kidneys
II. Reduced amniotic fluid volume
Describe the structure and formation of the urogenital sinus
- Structure: continuous with umbilicus (urachus)
- Formation: created from the hindgut by the urorectal septum
Describe the differentiation of the urogenital sinus
- Superior part connects to umbilicus
- Majority differentiates into urinary bladder
- Inferior part develops into the urethra
Outline the 4 steps involved in the development of the urinary system in females
⇒ Mesonephric duct reach urogenital sinus
⇒ Ureteric bud sprouts from urogenital sinus
⇒ Urogenital sinus expands and mesonephric duct regresses (lack of exogenous androgen)
⇒ Ureteric bud opens into urogenital sinus
Outline the 5 steps involved in the development of the urinary system in males
⇒ Mesonephric duct reach urogenital sinus
⇒ Ureteric bud sprouts from urogenital sinus
⇒ Smooth musculature appears; urogenital sinus expands
⇒ Ureteric bud & mesonephric duct make independent openings in urogenital sinus
⇒ Prostate and prostatic urethra are formed
Describe the formation of the female urethra
Female urethra is formed by the pelvic part of the urogenital sinus
Describe the development of the male urethra
- Genital tubercle elongates
- Genital folds fuse to form the spongy urethra
Describe the structure of the male urethra
Male urethra is divided into 4 parts:
- Pre-prostatic
- Prostatic
- Membranous
- Spongy
What is hypospadias?
- Hypospadias is a defect in fusion of urethral folds
- Urethra opens onto the ventral surface rather than at the end of the glans
Label the following structures on the diagram below:
- Pronephros
- Mesonephros
- Mesonephric duct
- Uteric bud
- Metanephros
What foetal abnormality would you suspect if you examined a pregnant patient with an abnormally low amniotic fluid volume?
Amniotic fluid is foetal urine, thus renal agenesis would cause low amniotic fluid volume
- Partial decrease = unilateral renal agenesis
- Abnormal decrease = bilateral renal agenesis
On the diagram below, indicate the following:
- Collecting system (and its origins)
- Excretory system (and its origins)
Based on your knowledge of the development of the kidney, provide a likely explanation of the anomalous anatomy below:
Pelvic kidney:
- Kidneys develop in the pelvis then ascend to the abdomen
- On occasion, one of the kidneys fail to ascend and remains at the pelvis at the level of the common iliac artery
Based on your knowledge of the development of the kidney, provide a likely explanation of the anomalous anatomy below:
Horseshoe kidney:
- Two developing kidneys come too close during ascent and fuse into a single horshoe-shaped structure
- Consequently become stuck underneath the inferior mesenteric artery
The presence of accessory/supernumerary renal arteries is relatively common.
Explain the embryological basis for this variation
- Supernumerary renal arteries are blood vessels that aren’t required but fail to regress
- As the kidney ascends, it forms new arteries
Label the following structures on the diagram below:
A = Cloaca
B = Cloacal membrane
C = Hind gut
D = Urorectal septum
E = Urachus (/allantois)
Label the following structures on the diagram below:
- Urogenital sinus
- Anorectal canal
- Urorectal septum
Identify the following sections of the urogenital sinus:
- Pelvic part
- Phallic part
Identify the derivative of the phallic part of the urogenital sinus in the male
Spongy urethra
Identify the derivative of the pelvic part of the urogenital sinus in the male
- Pre-prostatic urethra
- Prostatic urethra
- Membranous urethra
Suggest the likely embryological basis for the duplication of the ureter
- Uteric bud splits and ureter is duplicated
- Can lead to duplication of renal pelvis or complete renal duplication
Why might a patient with a duplicated ureter complain of bladder incontinence?
- The sphincter is at the level of the bladder
- There is an ectopic ureteral opening inferior to the bladder
- No sphincter control of urine
What is the normal adult derivative of the urachus?
Median umbilicus ligament
Label the following structures in the diagram:
- Bladder
- Anal canal
- Urorectal fistula
What is the embryological basis for a urorectal fistula?
The urorectal septum hasn’t pushed all the way through the hindgut
