3. Urinary System Development

Question 1

From what embryological tissue do the kidneys form?

Answer 1

Intermediate mesoderm.

Question 2

What are the 3 kidney systems that form in a developing embryo?

Answer 2

Pronephros.
Mesonephros.
Metanephros.

Question 3

What is the purpose of the development of the pronephros?

Answer 3

Formation of the pronephric duct that extends from the cervical region to the cloaca and drives development of the mesonephros.

Question 4

What is the urogenital ridge?

Answer 4

Region of intermediate mesoderm that gives rise to both the embryonic kidney and the gonad.

Question 5

What structures form the embryonic kidney?

Answer 5

Mesonephric tubules and the mesonephric duct.

Question 6

What is the purpose of the mesonephric duct?

Answer 6

Role in the development of the male reproductive system (vas deferens).
Sprouts the ureteric bud which induces development of the definitive kidney.

Question 7

Describe the development of the definitive kidney.

Answer 7

Ureteric bud forms caudal to the mesonephros, coming into contact with metanephric blastema. Bud expands and branches to form the major and minor calyx.

Question 8

How does the position of the metanephros (definitive kidney) change?

Answer 8

First appears in the pelvic region and undergoes a caudal to cranial shift, crossing the arterial form formed by vessels returning blood from the fetus to the placenta. Gets new branches of blood supply from the abdominal aorta as ascend, with old branches disappearing.

Question 9

What causes renal agenesis?

Answer 9

Ureteric bud fails to interact with intermediate mesoderm.

Question 10

What causes the development of a horseshoe kidney?

Answer 10

As kidney ascends through abdomen, inferior poles touch each other, creating a horseshoe kidney hooked on the midline branch of the aorta.

Question 11

What is a pelvic kidney?

Answer 11

One kidney fails to ascend to the lumbar region and so stays in the pelvis. Adrenal gland forms in normal region.

Question 12

What is the symptomatic consequence of splitting of the ureteric bud?

Answer 12

Ectopic urethral opening.

Question 13

What is the urogenital sinus formed from?

Answer 13

The hindgut by the urogenital septum.

Question 14

During development of the fetal bladder, what does the allantois (connecting the urogenital sinus to the umbilicus) become?

Answer 14

The urachus, which then closes to become the median umbilical ligament.

Question 15

What does the lower part of the urogenital sinus develop into?

Answer 15

Urethra (sex differences in structural development of the urethra).

Question 16

Describe urinary system formation in the female, including what happens to the mesonephric ducts.

Answer 16

Reach urogenital sinus, and ureteric bud sprouts (for definitive kidney formation). Urogenital sinus expands to form the bladder. 2 ureteric buds becomes ureters and the mesonephric ducts regress (no testosterone producing testis).

Question 17

Describe urinary system formation in the male, including what happens to the mesonephric ducts.

Answer 17

Reach urogenital sinus, and ureteric bud sprouts (for definitive kidney formation). Urogenital sinus expands to form the bladder. 2 ureteric buds becomes ureters and the mesonephric ducts remain (under influence of testosterone produced by testis), making 2 separate openings in the urogenital sinus. Mesonephric ducts form the prostate, prostatic urethra, and hook over the ureters, to form the vas deferens.

Question 18

What are the 4 anatomical divisions of the male urethra?

Answer 18

Pre-prostatic.
Prostatic.
Membranous.
Spongy.

Question 19

What structures form the spongy urethra in the male?

Answer 19

Genital tubercle elongates and genital folds fuse to form the spongy urethra.

Question 20

What is a hypospadia?

Answer 20

Defect in fusion of the urethral folds, resulting in the urethra opening onto the ventral surface of the penis, rather than at the end of the glans.