Embryology EXAM II Flashcards
What 3 kidneys arise from the nephrogenic cord?
- Pronephric system (segmented intermediate mesoderm)
- Mesonephric system (unsegmented intermediate mesoderm; 4th week) - functional glomeruli
- Metenephric system (unsegmented mesoderm)
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?
RA dependent
- Metanephric blastema forms by the cranial-caudal patterning that establishes a region within intermediate mesoderm
- MB secretes growth factors = ureteric bud via caudal portion of mesonephric duct
- Ureteric bud proliferates & stimulates differentiation of metanephric blastema into glomeruli and kidney tubules
What is the function of the metanephros
Filters blood plasma from glomerular capillaries by 10th week
Urine is produced which assist in amniotic fluid production
What is a potential problem due to insufficient amniotic fluid due by bilateral renal agenesis or urethral obstruction?
Oligohydramnios
List the 5 congenital defects associated with renogenesis
- Accessory renal vessels
- Renal agenesis
- Renal fusion
- Renal ectopic
- Wilma tumor
Define accessory renal vessels
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
Define renal agenesis
The failure of one or both kidneys developing
Can accrue Potter’s syndrome or club foot
Define renal fusion, what does it prevent
Prevents normal rotation
Abnormal blood supply - usually via middle sacral or common iliac arteries
Horseshoe kidney (90% fused at lower pole)
Define Wilms tumor; caused by which gene mutation?
Cancer of the kidney
Caused by WT1 gene mutations
Define urachal fistula/cyst
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
What can occur from paramesonephric duct anomalies?
Vagina anomalies
- Uterus didelphys w/ double vagina
- Uterus arcuatus (indentation)
- Uterus bicornis
- Uterus bicornis unicolliis 1 rudimentary horn
- Atresia of cervix (tiny passage)
- Atresia of vagina
What causes mullerian agenesis? What does it result in?
Failure of the paramesonephric ducts to develop
Results in missing uterine tubes, uterus, and variable malformations of the upper portions of the vagina
In the future bladder, the cloaca is divided by the urorectal septum. What forms from the dorsal/inferior portion and the ventral/superior portion?
Dorsal - rectum and anal canal
Ventral - bladder and lower urogenital tracts I.e. Prostatic & penile urethrae, urethra & lower vagina
During 4-6 weeks, which kidney portion(s) incorporate into the posterior wall of urinary bladder?
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
At what stage of development is the embryo genotype established?
Fertilization
During what week(s) is the embryo in an undifferentiated state in terms of sex?
Weeks 1-6
At what week(s) does phenotypic sexual differentiation begin during development of the genital system?
Week 7
At what week(s) can male and female external genitalia be recognized and when does phenotypic differentiation complete?
Week 12
Phenotypic diff complete = Week 20
What does the SRY gene determine?
The formation of XY chromosomes; testis-determining factor
When no SRY is present, no sertoli and leydig cells are formed = female XX
Define Mullerian Agenesis, what fails to develop?
Internal genitalia problem
Failure of the paramesonephric ducts to develop
Define Hypospadias
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
Classic virillizing adrenal hyperplasia
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
Androgen Insensitivity Syndrome
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
Describe 5-alpha reductase deficiency (5-ARD)
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
