Renal & Urogenital Development Flashcards
renal embryology & reproductive embryology - overview
*the intermediate mesoderm gives rise to the urinary and genital systems
*intermediate mesoderm → pronephros → mesonephros (gives rise to the gonads) → metanephros (gives rise to the kidneys)
3 kidneys during development
-
pronephros:
-transient, nonfunctional structures
-generate the mesonephric duct -
mesonephros:
-functional from about 6-10 weeks of gestation
-form the trigone of the bladder & give rise to ureteric bud
-induces formation of paramesonephric (Mullerian) duct
-form male duct structures in presence of testosterone; largely degenerates without testosterone -
metanephros:
-ureteric bud forms renal pelvis and ureters; branches many times and induces mesenchyme to develop into nephrons
bladder development
*urorectal septum formation separates cloaca into urogenital sinus and rectum
*urogenital sinus forms the bladder
*connected to umbilicus by allantois, which condenses into urachus → median umbilical ligament
congenital malformation of the kidney: Wilm’s Tumor
*affects children less than 5 years old
*mutation in WT1 gene on chromosome 11
*unilateral abdominal mass that does not cross midline
*may be associated with other abnormalities:
-WAGR syndrome
-Denys-Drash Syndrome
-Beckwith-Wiedmann Syndrome
-Horseshoe kidney
congenital malformation of the kidney: renal agenesis
*may be unilateral or bilateral
*bilateral renal agenesis results in renal failure and associated with Potter sequence (anuria, oligohydramnios, hypoplastic lungs)
*may have other severe defects like absence or abnormalities of the vagina and uterus, vas deferens, and seminal vesicles
*common associated defects in other systems: cardiac anomalies, tracheal and duodenal atresias, cleft lip and palate, brain abnormalities
congenital malformation of the bladder: failure of urachus to close
*allantois is a transient connection between the cloaca and umbilicus, which should close off to become the urachus and eventually seal off and become the median umbilic ligament
*failure to close off can result in:
-urachal fistula
-urachal cyst
-urachal sinus
ascent of the kidneys
*kidneys normally “ascend” from the pelvic region to the lumbar region as the embryo grows
*the kidneys blood supply changes levels as they ascend, and previous renal arteries degenerate rather than ascending with the kidneys
failure of the kidneys to ascend: pelvic kidney
*as growing embryo lengthens, one or both kidneys may not ascend and therefore remain in the pelvis
*pelvic kidneys maintain their fetal blood supply
failure of the kidneys to ascend: horseshoe kidney
*kidneys fuse together
*as the embryo lengthens, the fused kidney gets caught on the inferior mesenteric artery
*the IMA “hooks” on to the kidney and drags it down into the pelvis
*can be associated with:
-increased risk of obstruction and stones
-infection
-poor perfusion
-Wilm’s tumor
genital ducts - undifferentiated
*early in development, the ducts and gonads are undifferentiated (could give rise to male or female)
*based on the presence or absence of the SRY gene on the Y chromosome, could give rise to male or female structures
SRY and genital development
*SRY gene is on the short arm of chromosome Y
*SRY gene makes testis-determining factors, initiating male gonadal differentiation
*TDF induces development of:
1. Sertoli cells - produce anti-Mullerian hormone, inhibiting female ducts
2. Leydig cells - produce testosterone, which supports male ducts (mesonephric / Wolffian) and masculinizes external genitalia
genital ridge: male vs. female derivatives
*male: testis
*female: ovary
primordial germ cell: male vs. female derivatives
*male: spermatozoa
*female: ova
mesonephric (Wolffian) duct: male vs. female derivatives
*male: ductus (vas) deferens, ejaculatory duct, epididymis, trigone bladder
*female: trigone bladder
paramesonephric (Mullerian) duct: male vs. female derivatives
*male: utricle of prostatic urethra
*female: uterine tubes, uterus, upper vagina
urogenital sinus (lower): male vs. female derivatives
*male: penile urethra
*female: lower vagina, vestibule/labia minora
urogenital sinus (upper): male vs. female derivatives
*male: bladder, prostatic urethra, membranous urethra
*female: bladder, urethra
genital tubercle: male vs. female derivatives
*male: penis
*female: clitoris
genital swellings: male vs. female derivatives
*male: scrotum
*female: labia majora
female reproductive structures - clinical correlates
*septate uterus (incomplete resorption)
*bicomuate uterus (incomplete fusion)
*didelphys uterus (incomplete fusion)
male reproductive structures - clinical correlates
*hypospadias (urethral opening on ventral surface of penis)
*epispadias (urethral opening on dorsal surface of penis)
*communicating hydrocele
*abdominal, inguinal, and suprascrotal hernias
ambiguous genitalia: congenital adrenal hyerplasia
*decreased steroid hormone and increased adrenocorticotropic hormones
*females are masculinized - virilization of female external genitalia
*males can be missed in the early newborn period, but then present with salt-wasting
*21-hydroxylase deficiency is the most common cause
ambiguous genitalia: androgen insensitivity syndrome
*normal production of testosterone & dihydrotestosterone
*abnormal receptor activity
*androgens unable to induce differentiation of male genitalia
*may be partial or complete
ambiguous genitalia: 5-alpha reductase deficiency
*inability to convert testosterone to dihydrotestosterone
*virilization at puberty
