SM179 Development Flashcards
What are the two major urogenital primordia in the embryo?
Intermediate mesoderm and hindgut splanchnopleure
What develops from the medial urogenital ridge? Lateral urogenital ridge?
Medial: gonadal ridge
Lateral: nephrogenic cord
What is the first step in formation of the gonad?
Primary germ cells migrate from the gut tube into the gonadal ridge. Then the primary sex cords grow into the underlying mesenchyme to form the medulla and surround the germ cells.
List the series of embryonic kidneys from cranial to caudal
Pronephros, mesonephros, metanephros
What is the first functioning kidney?
Mesonephros
What does the mesonephric/Wolffian duct connect?
This is the embryonic ureter: connects the mesonephric tubules to the hind gut cloaca
Where do the permanent kidneys develop from?
Ureteric buds (also called the metanephric diverticulum) off the mesospheric ducts near the cloaca. Invade the nephrogenic cord.
What does the cloaca divide into?
Rectum and urogenital sinus
How do the paramesonephric (Mullerian) ducts develop?
Invaginate on the lateral surface of each UG ridge, then fuse in the midline to form the uterovaginal primoridum that is connected to the UG sinus
What structures are formed from the paramesonephric (Mullerian) ducts?
Uterus and uterine tubes
What structures are present during the indifferent stage? (8 weeks)
Metanephros, mesonephros, gonads, mesonephric/Wolffian ducts, paramesonephric/Mullerian ducts, UG sinus, genital tubercle (phallus), labioscrotal folds
What forms from the genital tubercle?
Primitive phallus
What forms from the metanephric mesoderm?
Nephrons
What forms from the ureteric buds?
Ureters, renal pelvis, calyces, and collecting tubules
How does the kidney get to its final position? Blood supply considerations?
Has to ascend up to the level of the adrenal glands. Sequential arteries hook up to it while it does this, can persist as multiple renal arteries.
How does a horseshoe kidney form?
Ureteric buds fuse around the IMA as they ascend
What develops into the testis?
Medulla of the primitive gonad
What develops into the seminiferous tubules?
Primary sex cords
What develops into the ovary?
Cortex of the primitive gonad
What develops into the ovarian follicles?
Secondary sex cords
What results from improper division of the cloaca?
Rectal fistulas
What develops from the allantois?
Urachus: a fibrous cord (can persist as a cyst, sinus, or fistula)
What sex retains the mesonephric duct, and what does it develop into?
Males
Becomes the ductus/vas deferens and epididymis
What sex retains the paramesonphric duct, and what does it develop into?
Females
Becomes the uterine tubes, uterus, and upper vagina
What happens when the paramesonpheric ducts fail to fuse?
Vertical septae in the uterus/vagina or double uterus (bicornuate - partially fused or Didelphys - no fusion)
What are the two primordial of the male urethra? What happens when they don’t fuse?
Urogenital sinus and ectodermal invagination (forms the navicular fossa)
Hypospadius
What does the lower UG sinus form in males? Females?
Males: prostate gland, prostatic urethra, most of the penile urethra
Females: urethra, vestibule, greater vestibular glands
What guides the descent of the testes?
Gubernaculum (through the inguinal canal)
