Embryology EXAM II

Question 1

What 3 kidneys arise from the nephrogenic cord?

Answer 1

1. Pronephric system (segmented intermediate mesoderm)
2. Mesonephric system (unsegmented intermediate mesoderm; 4th week) - functional glomeruli
3. Metenephric system (unsegmented mesoderm)

Question 2

Describe the steps of renogenesis, what factor is required for this to occur? What does the metenephric blastema give rise to? What does the ureteric bud give rise to?

Answer 2

RA dependent

1. Metanephric blastema forms by the cranial-caudal patterning that establishes a region within intermediate mesoderm
2. MB secretes growth factors = ureteric bud via caudal portion of mesonephric duct
3. Ureteric bud proliferates & stimulates differentiation of metanephric blastema into glomeruli and kidney tubules

Question 3

What is the function of the metanephros

Answer 3

Filters blood plasma from glomerular capillaries by 10th week

Urine is produced which assist in amniotic fluid production

Question 4

What is a potential problem due to insufficient amniotic fluid due by bilateral renal agenesis or urethral obstruction?

Answer 4

Oligohydramnios

Question 5

List the 5 congenital defects associated with renogenesis

Answer 5

1. Accessory renal vessels
2. Renal agenesis
3. Renal fusion
4. Renal ectopic
5. Wilma tumor

Question 6

Define accessory renal vessels

Answer 6

Aberrant renal arteries that enter upper or lower poles of kidney

Those that enter inferior pole can cause obstruction of ureter, and urinary drainage from the renal pelvis

Question 7

Define renal agenesis

Answer 7

The failure of one or both kidneys developing

Can accrue Potter’s syndrome or club foot

Question 8

Define renal fusion, what does it prevent

Answer 8

Prevents normal rotation

Abnormal blood supply - usually via middle sacral or common iliac arteries

Horseshoe kidney (90% fused at lower pole)

Question 9

Define Wilms tumor; caused by which gene mutation?

Answer 9

Cancer of the kidney

Caused by WT1 gene mutations

Question 10

Define urachal fistula/cyst

Answer 10

Bladder defect

When the bladder is continuous superiorly with allantois which is normally supposed to collapse and become the urachus

Remnants of urachal lumen may give rise to urachal cysts

Question 11

What can occur from paramesonephric duct anomalies?

Answer 11

Vagina anomalies

1. Uterus didelphys w/ double vagina
2. Uterus arcuatus (indentation)
3. Uterus bicornis
4. Uterus bicornis unicolliis 1 rudimentary horn
5. Atresia of cervix (tiny passage)
6. Atresia of vagina

Question 12

What causes mullerian agenesis? What does it result in?

Answer 12

Failure of the paramesonephric ducts to develop

Results in missing uterine tubes, uterus, and variable malformations of the upper portions of the vagina

Question 13

In the future bladder, the cloaca is divided by the urorectal septum. What forms from the dorsal/inferior portion and the ventral/superior portion?

Answer 13

Dorsal - rectum and anal canal

Ventral - bladder and lower urogenital tracts I.e. Prostatic & penile urethrae, urethra & lower vagina

Question 14

During 4-6 weeks, which kidney portion(s) incorporate into the posterior wall of urinary bladder?

Answer 14

Mesonephric duct and ureteric bud

Ureteric bud = opens into bladder wall

Mesonephric ducts = opens more inferiority into pelvic urethra

**DO NOT want ductus deferens to open into the bladder

Question 15

At what stage of development is the embryo genotype established?

Answer 15

Fertilization

Question 16

During what week(s) is the embryo in an undifferentiated state in terms of sex?

Answer 16

Weeks 1-6

Question 17

At what week(s) does phenotypic sexual differentiation begin during development of the genital system?

Answer 17

Week 7

Question 18

At what week(s) can male and female external genitalia be recognized and when does phenotypic differentiation complete?

Answer 18

Week 12

Phenotypic diff complete = Week 20

Question 19

What does the SRY gene determine?

Answer 19

The formation of XY chromosomes; testis-determining factor

When no SRY is present, no sertoli and leydig cells are formed = female XX

Question 20

Define Mullerian Agenesis, what fails to develop?

Answer 20

Internal genitalia problem

Failure of the paramesonephric ducts to develop

Question 21

Define Hypospadias

Answer 21

External genitalia problem

Incomplete fusion of the urethral folds

Urethra opens into the ventral aspect of the penis

Can result from inadequate androgen production or inadequate receptor sites for DHT

Question 22

Classic virillizing adrenal hyperplasia

Answer 22

External genitalia problem

46, XX

Female intersex

Females w/ ambiguous genitalia at birth due to excess adrenal androgen production in utero

Clitoral hypertrophy and labioscrotal folds

No ovary abnormalities

Question 23

Androgen Insensitivity Syndrome

Answer 23

External genitalia problem

47, XY; male with feminized genitalia

X-linked disorder where receptors are unresponsive to androgens

Feminine external genitalia with internal non-functional nudes ended testes

Possible female secondary characteristics at puberty

Question 24

Describe 5-alpha reductase deficiency (5-ARD)

Answer 24

Inability to convert testosterone into DHT, which is required for normal masculinization of external genitalia in utero

As a result, males are born with ambiguous genitalia

Often misdiagnosed with AIS