Embryology of urogenital system Flashcards
From what tissue layer does the urinary and genital tracts arise?
- intermediate mesoderm
True/ False
The intermediate mesoderm separates the lateral and paraxial mesoderm, and will form to give rise to the urogenital ridge.
true
What are the three phases of kidney development?
- pronephros
- mesonephros
- metanephros
What features best characterize the pronephros time frame?
- regress at 5 weeks
- begins development in cervical region of embryo
- fully contained in embryo; essentially useless for secretion of waste out of embryo
Which features characterize the mesonephros development from 6-10 weeks?
- time functional glomeruli form
- mesonephric tubes form off the mesonephric duct
- mesonephric duct opens into cloaca
- ureteric bud begins formation
What structures are derived from the ureteric bud?
- collecting ducts
- major/minor calyces
- major calyces
- renal pelvis
- ureters
What structures does the mesonephric duct system give rise to?
- ductus deferens
2. vestigial female structures
What features characterize the metanephros phase of development?
- ureteric bud forms the metanephric duct which developems into ureter
- metanephrogenic blastema forms the renal tubules
- glomerulus forms
What is the primary purpose of the metanephros (in utero)?
- provides supplementation to amniotic fluid
2. no filtering; performed by placenta
What is one way that oligohydramnios can occur?
- obstruction to emrbyo urethra
2. kidney agenesis
Renal agenesis can result in both oligohydramnios and fetal compression, what are further effects of both of these symptoms?
- pulmonary hypoplasia
- altered face (deformity)
- club foot, from compression; lack of space
- breech presentation
What is an accessory renal vessel and is it problematic?
- extra vessel that supplies the kidney.
2. only problematic if it enters at upper/lower pole of kidney. Entrance at hilum has no negative effects
What is an aberrant accessory renal vessel?
- vessel that enters kidney at upper/lower poles
What negative side effects can an aberrant renal vessel have?
- obstruct portions of the ureters
- reduce glomerular pressures–> systemic effects
- all vessels arise from abd aorta
What is renal fusion?
- when the kidneys develop, they fuse together preventing their rotation of hilum to midline.
- generally unnoticed
Horseshoe kidneys are best described as what?
- kidneys that fuse into shape of horsehoe.
- generally catch on IMA while rising from the pelvic caivty
- then can receive blood supply from iliac or middle sacral artery
What are commone types of ectopic kidneys?
- horseshoe
2. pelvic kidney
Where will most ectopic kidneys receive blood supply?
- potentially abd aorta, unless trapped in the pelvis.. Then from common iliac artery or middle sacral artery
What is a Wilmer’s Tumor? (this does not refer to the pig in Charlotte’s web; that’s Wilber)
- benign kidney cancer in newborn
2. caused by mutation to WT1 gene
The cloaca separates to form what during urinary bladder development?
- anteriorly: forms bladder and urogenital sinus
2. posteriorly: forms rectum and anal canal
The anterior section of the cloaca further develops to form what structures?
- lower urogenital tract
- prostate and penile urethra
- lower vaginal urethra
What are the borders of the trigone?
- ureters entrance mark the top border
- mesonephric ducts (form ductus deferens in males) mark the inferior most point
- mesonephric migration inferiorly expands the bladder and moves the vas deferens out of the bladder into the urethra for ejaculation
How does the body correct the small size of the bladder, and prevent semen from entering into the urinary bladder?
- the mesonephric ducts migrate inferiorly to the ureters causing the bladder to expand
- mesonephric ducts then insert into the urethra just inferior to the internal urethral sphincter
What must the bladder be continuous with in order to remove urine into the umbilical cord?
- continuous with the allantois which becomes the urachus
What is a urachal fistula?
- malformation where the urachus does not close and urine is able to leak from the bladder out of umbilicus
What is a urachal sinus?
- urachus is patent to the umbilicus, but has closed some portion that reaches to the bladder. Small amount of urine able to leak, but will not continue to leak
What is a urachal cyst?
- small pockets of urine that are trapped, when the urachus began to close.
- these become infectious and painful.
- Present as hard “pockets” from umbilicus inferiorly
How much of the genital system has developed at week 1-6?
- none, still undifferentiated embryo
What genital features are present at week 7?
- phenotypic genital differentiation begins to take place
What genital features are occurring during week 12?
- external genitalia can begin to become recognized
At what time is sex determined for the fetus?
- week 20, phenotypic differentiation is complete
If SRY is present, it will act on the gonads to produce what structures?
- sertoli cells which produce MIS which will degrade the Mullerian duct formation
If SRY is present, it will act on the testis to produce what?
- leydig cells–>testosterone**–> wolffian ducts–> epididymis, vas deferens, seminal vesicles, ejaculatory ducts
** 5 alpha reductase is required to convert testosterone into dihydrotestosterone (DHT) more active form for phenotype differentiation
No SRY present will have what effect on the gonads?
- no sertoli cells, mean no MIS secretion
- Mullerian duct will form and give rise to:
- - uterine tube (fallopian), uterus, vagina
No SRY present will have what effect on the ovary?
- no leydig cells produced
2. minimal amounts of testosterone produced “none”
What will the mesonephric duct later develop into?
- vas deferens
What will the paramesonephric duct later develop into?
- uterine tubes
- uterus
- cervix
- upper 1/3 of vagina
What tissues are required for development of gonads?
- intraembyronic coelom epithelium
- intermediate mesoderm
- primoridal germ cells
What will the intraembryonic coleom epithelium ultimately rise to form?
- cells that line the coelomic cavity and gonadal primordium.
- originate from region overlaying the ventral-medial surface of mesonephros
What does the intermediate mesoderm give rise to in terms of development?
- gives rise to pro-, meso-, metanephros development
2. develops the kidneys, gonads and associated tracts
What do the primordial germ cells give rise to?
- sex determination of the embryo
2. migrate to the genital ridge via the hindgut and dorsal mesentery
What will the phallus develop into?
- penis or clitoris
What will the urogenital fold develop into?
- labis minora, or penile shaft
What will the labioscrotal fold develop into?
- labis majora, or the scrotum
What does the presence of AMH or MIF do for development?
- cause degeneration of the paramesonephric ducts (vagina)
2. promote formation of testosterone and DHT
What does the presence of DHT lead to?
- paramesonephric ducts regress
- urogenital sinus closes–> urethra, prostate
- genital tubercle–> penis
- labioscrotal closes–> scrotum
What does lack of DHT lead to ?
- regression of mesonephric duct
- urogenital sinus remains open–> lower vagina, vestibule
- genital tubercle–> clitoris
- labioscrotal remain open–> vulva
- paramesonephric duct open–> uterus, upper vagina, oviductus
What leads to the formation of the ductus deferens and epididymis?
- expression of AMF, or MIF
2. testosterone converts the mesonephric ducts into these structures
What is Mullerian Agenesis?
- a failure of paramesonephric duct development
2. no uterus, uterine tube, upper vagina formation
What is MRKH. Mayer-Rokitansky-Kuster-Hauser Syndrome?
Mullerian Agenesis
Hypospadias?
- incomplete fusion of urethral folds
- urethra opens on ventral aspect of penis
- inadequate androgen production or inadequate recptor sites for DHT
Epispadias?
- incomplete fusion of urethral folds
2. urethra opens on dorsal aspect of penis
What are the types of hypospadias and how are they named?
- named for region that urethra opens on the penis
- names
- glandular ( most normal)
- penile
- penoscrotal
- perineal (more vaginal like)
What is female intersex?
- female (XX, 46) genotype
- has adrenal hyperplasia leading to ambiguous external genitalia formation
- contain normal ovary, uterine tubes, uterus
- clitoromegaly or labioscrotal fold fusion
What is the phenotypic presentation of female intersex (XX, 46)?
- clitoromegaly (minor)
2. labioscrotal fold fusion (major)
What is the best way to characterize Androgen Insensitivity Syndrome (AIS)
- male genotype with female external genitalia
2. testis develop but are non-functioning leading to default genitalia development
What genitalia are common to form is Androgen Insensitivity Syndrome (AIS)?
- female external
2. breasts later with estradiol production
What is the role of 5-alpha reductase?
converts testosterone to dihydrotestosterone (DHT) the more active form to promote growth or male external genitalia.
What can occur with 5-alpha reductase deficiency?
- underdeveloped male genitalia, depends on amount of reductase that was or was not formed.
Are the ductus deferens or epididymis, derivatives of the mesonephric ducts, affected with a 5-alpha reductase deficiency?
- no, mesonephric duct development is based on presence of testosterone, not DHT
