SM179 Development

Question 1

What are the two major urogenital primordia in the embryo?

Answer 1

Intermediate mesoderm and hindgut splanchnopleure

Question 2

What develops from the medial urogenital ridge? Lateral urogenital ridge?

Answer 2

Medial: gonadal ridge
Lateral: nephrogenic cord

Question 3

What is the first step in formation of the gonad?

Answer 3

Primary germ cells migrate from the gut tube into the gonadal ridge. Then the primary sex cords grow into the underlying mesenchyme to form the medulla and surround the germ cells.

Question 4

List the series of embryonic kidneys from cranial to caudal

Answer 4

Pronephros, mesonephros, metanephros

Question 5

What is the first functioning kidney?

Answer 5

Mesonephros

Question 6

What does the mesonephric/Wolffian duct connect?

Answer 6

This is the embryonic ureter: connects the mesonephric tubules to the hind gut cloaca

Question 7

Where do the permanent kidneys develop from?

Answer 7

Ureteric buds (also called the metanephric diverticulum) off the mesospheric ducts near the cloaca. Invade the nephrogenic cord.

Question 8

What does the cloaca divide into?

Answer 8

Rectum and urogenital sinus

Question 9

How do the paramesonephric (Mullerian) ducts develop?

Answer 9

Invaginate on the lateral surface of each UG ridge, then fuse in the midline to form the uterovaginal primoridum that is connected to the UG sinus

Question 10

What structures are formed from the paramesonephric (Mullerian) ducts?

Answer 10

Uterus and uterine tubes

Question 11

What structures are present during the indifferent stage? (8 weeks)

Answer 11

Metanephros, mesonephros, gonads, mesonephric/Wolffian ducts, paramesonephric/Mullerian ducts, UG sinus, genital tubercle (phallus), labioscrotal folds

Question 12

What forms from the genital tubercle?

Answer 12

Primitive phallus

Question 13

What forms from the metanephric mesoderm?

Answer 13

Nephrons

Question 14

What forms from the ureteric buds?

Answer 14

Ureters, renal pelvis, calyces, and collecting tubules

Question 15

How does the kidney get to its final position? Blood supply considerations?

Answer 15

Has to ascend up to the level of the adrenal glands. Sequential arteries hook up to it while it does this, can persist as multiple renal arteries.

Question 16

How does a horseshoe kidney form?

Answer 16

Ureteric buds fuse around the IMA as they ascend

Question 17

What develops into the testis?

Answer 17

Medulla of the primitive gonad

Question 18

What develops into the seminiferous tubules?

Answer 18

Primary sex cords

Question 19

What develops into the ovary?

Answer 19

Cortex of the primitive gonad

Question 20

What develops into the ovarian follicles?

Answer 20

Secondary sex cords

Question 21

What results from improper division of the cloaca?

Answer 21

Rectal fistulas

Question 22

What develops from the allantois?

Answer 22

Urachus: a fibrous cord (can persist as a cyst, sinus, or fistula)

Question 23

What sex retains the mesonephric duct, and what does it develop into?

Answer 23

Males

Becomes the ductus/vas deferens and epididymis

Question 24

What sex retains the paramesonphric duct, and what does it develop into?

Answer 24

Females

Becomes the uterine tubes, uterus, and upper vagina

Question 25

What happens when the paramesonpheric ducts fail to fuse?

Answer 25

Vertical septae in the uterus/vagina or double uterus (bicornuate - partially fused or Didelphys - no fusion)

Question 26

What are the two primordial of the male urethra? What happens when they don’t fuse?

Answer 26

Urogenital sinus and ectodermal invagination (forms the navicular fossa)
Hypospadius

Question 27

What does the lower UG sinus form in males? Females?

Answer 27

Males: prostate gland, prostatic urethra, most of the penile urethra
Females: urethra, vestibule, greater vestibular glands

Question 28

What guides the descent of the testes?

Answer 28

Gubernaculum (through the inguinal canal)