Lecture 3 - Development

Question 1

Kidney systems

Answer 1

Organisation of intermediate mesoderm
3 systems develop sequentially
Disappearance of one system markers the next delevopmental stage

1. Pronephros
2. Mesonephros
3. Metanephros

Question 2

Pronephros

Answer 2

Develops in the cervical region as a duct

Extends from the cervical region to the cloaca

Question 3

Urogenital ridge

Answer 3

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

Question 4

Mesonephros

Answer 4

Caudal to the pronephros
Embryonic kidney = mesonephric tubules and mesonephric duct
No water conserving function

Question 5

Ureteric bud

Answer 5

Undifferentiated intermediate mesoderm
Caudal to the mesonephros
The mesonephric duct sprouts the ureteric bud which induces the development of the definitive kidney (metanephros)

Question 6

Metanephric blastema

Answer 6

The ureteric bud contacts the metanephric blastema which causes expansion and branching to form minor and major calyxes and the renal pelvis

Question 7

Renal collecting system and excretory system development

Answer 7

Collecting system derived from the ureteric bud itself

Excretory system derived from intermediate mesoderm under the influence of the ureteric bud

Question 8

Ascent of the kidney

Answer 8

Metanephric kidney first appears in the pelvis

Undergoes caudal to cranial shift crossing the umbilical artery

Question 9

Defects in the development of the kidney

Answer 9

Renal agenesis - ureteric bud fails to interact with the intermediate mesoderm

Defective migration

Duplication

Ectopic ureter

Cystic disease

Question 10

Defective migration

Answer 10

• pelvic kidney

- Horseshoe kidney - 2 kidneys merge into 1

Question 11

Duplication

Answer 11

Caused by splitting of the ureteric bud
Partially or completely
Causes ectopic ureteral opening e.g. in vagina - symptomatic

Question 12

Urogenital sinus

Answer 12

Created from the hindgut by urorectal septum
Continuous with the umbilicus via the urachus (initially allantois)
The urachus closes to form the median umbilical ligament

Forms the bladder and inferior part develops into the urethra
Superior aspect connects to the umbilicus

Question 13

Urorectal septum

Answer 13

Separates the hindgut into a GI tract and the bladder and urethra

Question 14

Development of urinary system in females

Answer 14

1. Mesonephric ducts reach the urogenital sinus
2. Ureteric buds sprout from the mesonephric ducts
3. The urogenital sinus expands therefore the ureteric buds opens out into the urogenital sinus
4. The mesonephric ducts regress as no testosterone present

Question 15

Development of urinary system in males

Answer 15

1. The mesonephric ducts reach the urogenital sinus
2. The ureteric bud sprouts from the mesonephric duct
3. The urogenital sinus expands therefore the ureteric buds opens out into the UGS
4. Presence of androgens allow the mesonephric duct to remain
5. The mesonephric duct becomes the vas deferens
6. The prostate and practice urethra is formed from the ureteric bud, bladder and mesonephric duct

Question 16

Female urethra

Answer 16

Formed from the pelvic part of the urogenital sinus

Question 17

Male urethra parts

Answer 17

Preprostatic
Prostatic
Membranous
Spongy

Question 18

Hypospadias

Answer 18

Defect in the fusion of the urethra folds

Urethra opens into the ventral surface rather than at the end of the glans