GU embryology Flashcards
From what region does the kidneys, ureters, bladder and urethra develop from? 3 overlapping sequential systems?
The intermediate mesoderm= urogenital ridge
Pronephros, mesonephros and metanephros
The pronephros develops in what week? From what region? Segmented divisions of intermediate mesoderm form tubules known as what?
4th week
Cervical region of the embryo
Nephrotomes= 6-10 pairs
Pronephric duct- from cervical region to cloaca of embryo- completely non-functional and regresses by end of week 4
Where does the mesonephros develop from? Propnephric duct induces nearby intermediate mesoderm in thoracolumbar region to form what? They drain into what? The duct sprouts what caudally?
Caudally to pronephros
Mesonephric tubules
The mesonephric duct
Ureteric bud
The metanephros forms what? It appears in what week and becomes functional during what week? The ureteric bud makes contact with what caudal region of intermediate mesoderm?
The definitive kidney
5th and 12th weeks
Metanephric blastema
What is the collecting system derived from? This includes what? What is the excretory system derived from?
The ureteric bud
Ureter, renal pelvis, major and minor calyces and collecting tubules
The metanephric blastema
Each collecting tubule from the collecting system is covered by what which gives rise to what? These tubules with the developing glomeruli form what? The proximal end forms what? The distal end elongates to form what?
A metanephric tissue cap which gives rise to excretory tubules
The nephron
The Bowman’s capsule around a glomerulus
The proximal convoluted tubule, loop of Henle and distal convoluted tubule
The definitive kidney develops in what before ascending into what? How is urine passed throughout amniotic cavity? During fetal and embryonic life, what is responsible for excretion of waste products?
The pelvic region before ascending into the abdomen
Urine is passed into cavity and mixes with amniotic fluid, is swallowed by the foetus and is recycled through the kidneys
Not the kidneys but the placenta
The bladder and urethra are derived from what? What is the allantois? Obliterated to form what? During what week is the cloaca divided by the urorectal septum into the urogenital sinus and anorectal canal?
The cloaca
An anterior outgrowth of the cloaca into the bladder
The urachus
4-7th week
What is the remnant of the urachus? How does the trigone of the bladder develop?
Median umbilical ligament- connects apex of the bladder to the umbilicus
The urogenital sinus absorbs the caudal parts of the mesonephric ducts
Upper part of the urogenital sinus develops into what? Pelvic (middle) part? Phalic part? How does the ejaculatory ducts form in the male?
Urinary bladder
Prostatic and membranous parts of the urethra
Penile urethra
The mesonephric ducts move caudally and closer together, entering prostatic urethra to become ducts
How does the bladder form in males and females?
The kidneys ascend into the abdomen and the ureteric openings move cranially
What is the indifferent stage in relation to reproductive embryology? They appear as what instead? Pairs of ducts that form?
Where the gonads have no male/ female characteristics.
Pair of longitudinal genital ridges on medial side of mesonephric ridge.
Paramesonephric(Müllerian) and mesonephric (Wolffian duct)
During what week do germ cells migrate from yolk sac endoderm to genital ridges via dorsal mesentery of hindgut? They reach the ridge in what week? The epithelium of the genital ridges proliferates and penetrates the intermediate mesoderm to form what?
4th week
6th week
The primitive sex cords
The Y chromosome containing the SRY gene stimulates the primitive sex cords to form what? What forms around these cords? A portion of the rests cords breaks off to form what?
Testis(medullary cords)
Tunica albuginea
The future rete testis
Remaining cords contain what 2 cell types? In puberty, these cords acquire a lumen to become what? Between the testis cords are what cells? In what week do they begin to produce testosterone? Drives what process?
Germ and Sertoli cells The seminiferous tubules Leydig cells 8th week Differentiation of internal and external genitalia
What happens to the primitive sex cords in females? In what month do these cords break up into clusters to surround each oogonium with layer of follicular cells?
They degenerate- the gonad epithelium proliferate to produce cortical cords
3rd month–> primordial follicle
The mesonephric ducts in males give rise to what? The Mullerian ducts degenerate why? In females, Wolffian ducts degenerate to leave what behind?
Efferent ductules, epididymis, vas deferens and seminal vesicles
Due to presence of anti-Mullerian hormone produced by Sertoli cells in testes
Gartner’s duct
Cranial and horizontal parts of Mullerian ducts form what? Caudal part fuses to form what? The urogenital sinus forms what?
Fallopian tubes
The uterus, cervix and upper 1/3 of vagina
Lower 2/3 vagina, labia majora, labia minora and clitoris
Development of external genitalia begins in what week? Mesenchymal cells from primitive streak migrate–> cloacal membrane to form what? Cranially these fuse to form what? Caudally divide into what? What develops either side of urethral folds?
3rd week Pair of cloacal folds Genital tubercle Urethral folds and anal folds Genital swellings
Development of indifferent genitalia driven by presence of what? The urethral folds form what? The genital swellings form what?
DHT
Penile urethra
Scrotal swellings
Hormone responsible for female external genitalia development? The genital tubercle forms what? Urethral folds form what? Swellings form what? Urogenital groove form what?
Oestrogens Clitoris Labia minora Labia majora Vestibule
Gonads tethered to scrotum/ labia by what?Adult remnants in males and females? Testes pass through inguinal canal and reach scrotum during what weeks? Ovaries reach their final position where?
Gubernaculum- from mesenchyme
Scrotal, ovarian and round ligaments of uterus
Pass through around 28th week and reach scrotum by 33rd week
Just within true pelvis
