Embryology: Urinary

Question 1

After gastrulation what are the 2 areas of the mesoderm that do not separate the ecto and endoderm?

Answer 1

The buccopharyngeal membrane cranially

The cloacal membrane caudally

Question 2

What is the embryological derivative of the kidneys?

Answer 2

Intermediate mesoderm

Question 3

What are the 3 kidney systems that form?

Answer 3

1. Pronephros - makes a duct which the mesonephros can use (purely structural, never functional)
2. Mesonephros (has tubules and duct)
3. Metonephros - the permanent kidney
   (disappearance of 1 system marks the onset of development of the next system)

Question 4

What is the urogenital ridge?

Answer 4

A region of intermediate mesoderm that gives risk to the embryonic kidney and gonad

Question 5

What is the function of the mesonephros?

Answer 5

The mesonephric duct sprouts the ureteric bud which indices development on the definitive kidney
The mesonephric duct has an important role in the development of the male repro system

Question 6

What is the role of the ureteric bud?

Answer 6

The ureteric bud drives development of the definitive kidney

The collecting system is derived from the ureteric bud itself

Question 7

Outline the ascent of the kidney

Answer 7

The metanephric kidney first appears in the pelvic region
It undergoes a caudal to cranial shift - partially upward movement, partially elongation of the abdomen
As it descends it sprouts new vessels off the abdo aorta and the old vessels regress

Question 8

What defects occur if there is splitting of the ureteric bud?

Answer 8

There can be accessory ureters (generally dont cause a problem)
The problem occurs if one of the ureters drains into the wrong place eg into the vagina, this causes incontinence

Question 9

What is the urogenital sinus?

Answer 9

It is created from the urorectal sinus (mesoderm that grows downwards to separate the GI and urinary tracts)
It is continuous with the umbilicus
Has 3 parts - large upper part forms the bladder, then has pelvic and phallic parts

Question 10

What happens to the mesonephric ducts in males and females?

Answer 10

Both sexes: The mesonephric ducts reach the urogenital sinus and the ureteric bud sprouts from the mesonephric ducts. The uorgenital sinus expands due to smooth muscle appearing and the ureteric bud makes a separate opening into the urogenital sinus.

• *Males: the mesonephric duct becomes the vas deferens
• *Females: The mesonephric duct regresses

Question 11

What happens to the genital folds in males and females?

Answer 11

In males the genital folds fuse (driven by androgens) to form the spongey urethra
There is no fusion in females and the urethra opens into the vestible

Question 12

What is hypospadias?

Answer 12

Occurs in males
A defect in fusion of the urethral folds resulting in the urethra opening onto the ventral surface of the penis instead of the end of the glans

Question 13

How does horseshoe kidney occur?

Answer 13

The kidneys fuse during development to form a large horseshoe shaped kidney

Question 14

What happens to the urachus?

Answer 14

The urachus usually regresses in the 12th week leaving behind a fibrous chord called the median umbilical ligament

Question 15

What is a patent urachus?

Answer 15

The urachus fails to close off therefore there is a connection between the bladder and the umbilicus - there is leakage of urine out the umbilicus

Question 16

What is a diverticulum?

Answer 16

The urachus does not seal close to the bladder and leads to a blind ending tract from the bladder into the urachus called a diverticulum. These also can be asymptomatic or present with a urinary tract infection.