Development Flashcards
Urogential Ridge
intermediate mesoderm –> urogenital ridge
nephrogenic ridge -> urinary system
gonadal/genital ridge -> gential system
Pronephric phase
pronephros arise in cervical region and give rise to pronephric duct –> grows caudally and opens into cloaca
- eventually degenerates
Mesonephric phase
pronephric duct becomes mesonephric duct
Metanephric phase
definitive kidney
Mesonephros
gives rise to the mesonephric tubules that become efferent ductules of male testis
Ureteric Buds
mesonephric duct in male gives rise to ductus deferens in male
- also gives rise to ureteric buds in both male/female
Ureteric buds -> grow into intermediate mesoderm and initiate formation of definitive kidney
- gives rise to ureter, renal pelvis, calyces, collecting ducts
Nephrons
Bowman’s capsule, proximal tubule, loop of Henle, distal tubule
- arise from intermediate mesoderm through induction by arched collecting tubules
Glomerulus
formed by endothelial cells growing into renal capsule
Uriniferous tubules
consist of nephron and collecting ducts
Metanephric kidneys
definitive kidneys
- located deep in pelvis but ascend into abdomen later in development
Renal Agenesis
failure of ureteric bud and metanephric mesoderm to interact
- more common on L and in males
- if bilateral –> death
- suspect in single umbilical artery patients*
Duplicated/branched ureter
bifurcation of ureteric bud
Ectopic ureter
ureter enters urogential sinus derivative at some site other than dorsolateral wall of urinary bladder
Supernumerary kidney
due to divison of ureteric buds and interaction with areas of metanephric mesoderm
Pelvic kidneys
failure of kidney to migrate from pelvis
Crossed kidney
kidney migrates to opposite side and kidneys fuse
Horseshoe kidney
2 kidneys fuse at inferior poles and migration is blocked by inferior mesenteric artery
Multiple renal arteries
due to segmental blood supply during development
Urorectal septum
mesoderm origin –> divides cloaca into rectum and urogenital sinus
Urogential sinus
continuous with allantois –> extends to body stalk
- vesicle part -> forms urinary bladder (continuous with allantois which becomes urachus)
- pelvic part -> becomes bladder neck and prostatic urethra in male, full urethra in female
- phallic/spongy part -> grows toward genital tubercle
Perineal Body
forms where urorectal septum comes in close contact with cloacal membrane
Mesonephric ducts and ureteric bud
incorporated into posterior wall of developing urinary bladder
- results in trigone of bladder formed by mesonephric duct
Epithelium of entire bladder
ENDODERM of urogential sinus
Urethra
Proximal male -> urogential sinus
Distal male -> ectoderm
Female -> urogenital sinus
CT and smooth muscle of bladder
splanchnic mesoderm
Urachal sinus and fistula
Sinus –> secretion of fluid (not urine)
Fistula –> need to see if it is urine or fecal material
Exstrophy of bladder
bladder that opens onto anterior abdominal wall
- lack of anterior wall mesoderm to close during 4th week
Megacyst
ONLY in MALE
- posterior urethral valves don’t undergo apoptosis during development and block outflow of urine
- leads to renal failure and pulmonary hypoplasia
Adrenal Medulla
neural crest cells –> chromaffin cells
Adrenocortical primordia
cranial part of urogenital ridge
- cortex develops from mesoderm located on posterior ad wall
Fetal cortex –> large size
Permanent cortex -> develops later and replaces fetal cortex
Congenital Adrenal Hyperplasia
many clinical forms, due to enzyme deficiencies
- 21-beta hydroxylase gene is most common
Genetic sex determination
at time of fertilization, but phenotypic sex is determined at 7th week of development
Phenotypic maleness
presence of Y chromosome –> SRY protein –> testicular determining factor –> development of testes
Phenotypic female
2 X chromosomes -> absence of Y chromosome
Klinefelter syndrome
47 XXY -> nondysjunction of XX homologues
- infertility, gynecomastia, and impaired sex maturation
Turner syndrome
46 XO -> failure of gonads to develop and infantile genitalia -> lack of paternal sex chromosome
- short stature, high palate, webbed neck, broad-shield chest, widespaced-inverted nipples, absence of sexual maturation
Ovotesticular disorder
hermaphrodites (disorder of sexual development)
- possess both testicular and ovarian tissue
Migration of gametes from umbilical vesicle
into genital ridge during sex development
- primordial germ cells enter genital ridge during 5th week
- caudal end = gonads
- developing gonads consist of mesothelium, mesenchyme, and primordial germ cells
Cortical cords
Male - germ cells migrate to cortical cords and form seminiferous tubules –> precursors of sertoli cells
Female - cortical cords break apart and form follicular cells
Efferent ductules
form from mesonephric ducts and become epididymis
Interstitial cells of Leydig
develop from mesenchyme and synthesize androgens
Sertoli Cells
don’t mature during fetal period but under influence of hCG -> produce anti-Mullerian hormone –> suppress paramesonephric ducts
Oogonia
formed from primordial germ cells –> meiosis stimulating factor –> enter meiosis I –> primary oocyte
Differentiation of Male Sexual Duct System
- anti-Mullerian hormone from Sertoli Cells -> paramesonephric ducts degenerate -> leaving prostatic utricle
- testosterone causes mesonephric ducts to become epididymis, ductus deferens, ejac duct
Differentiation of Female Sexual Duct System
If ovaries present or gonads absent, ducts differentiate into female phenotype
- absence of anti-Mullerian hormone allows paramesonephric ducts to develop (uterine tubes and uterus) –> travel caudally and fuse to form uterovaginal primordium –> makes sinus tubercle
Upper 1/3 of vagina
develops from paramesonephric ducts
Lower 2/3 of vagina
develops from vaginal plate derived from urogential sinus
Greater vestibular glands
bulbourethral glands
Paramesonephric duct agenesis
complete/partial absence of uterine tubes, uterus, cervix, and vagina –> shallow vagina
- normal ovarian cycle but no menstruation
Double uterus and double vagina
paramesonephric ducts fail to fuse
Double uterus and single vagina
only distal end of paramesonephric ducts fuse
Bicornuate uterus
defective fusion of paramesonephric ducts
Uterine septum
incomplete resorption of tissue of developing uterus
Unicornuate uterus
only 1 paramesonephric duct develops
Absence of uterus and vagina
failure of uterovaginal primordium to form and induce formation of sinus tubercle
Migration of gonads
Male - gubernaculum guides testis down through deep inguinal ring and under influence of androgens
Female - gubernaculum becomes ligament of ovary and round ligament of uterus
Cryptorchidism
undescended testes - results in sterility and increased risk of cancer
Ectopic testis
due to migration of testis to some other site because of abnormal location of gubernaculum
Congential inguinal hernia
indirect hernia
- peritoneal cavity fails to close
Hydrocele
accumulation of fluid in remains of process vaginalis
Male external development
testosterone –> DHT
- produces masculinization by stimulating phallus to enlarge and elongate - penis
- urogential folds fuse to form spongy urethra
- ectodermal cord grows to form glans
- labioscrotal swellings form the scrotum
Female external development
lack of testosterone -> estrogens induce feminization
- phallus becomes clitoris
- urogenital folds become labia minora (space is vagina)
- labioscrotal swellings form labia majora
