3.7.4. Urinary Tract Development Flashcards
urachus
distal portion of the allantois; it becomes a fibrous cord and forms the medial umbilical ligament
urachal cysts
result of a patent urachus (accumulation of fluid within the medial umbilical ligament)
urogenital ridge
covered elevation of intermediate mesoderm that lies in the lower thoracic and lumbar regions and forms the mesonephric kidneys
apoptosis
programmed cell death
intermediate mesoderm
mesoderm-derived layer lying between the paraxial and lateral plate layers and responsible for forming much of the urogenital system
WTI gene product
Wilms’ tumor gene: stimulates the induction of growth via the ureteric bud
pronephros
rudimentary, nonfunctional kidney precursor; forms vestigial excretory units called nephrotomes
Wilms’ tumor
kidney cancer that typically occurs in children
pronephric duct
predecessor of the Wolffian duct
Renal agenesis
condition in which one or both kidneys fail to develop
mesonephros
intermediate kidney with short span of function (5-10 weeks of embryological life); formation of the glomerulus and bowman’s capsule. Site of the urogenital ridge
dysplastic kidney
condition that results from malformation of the kidney during fetal development. consists of irregular cysts of varying sizes and has no function
mesonephric duct
the longitudinal collecting duct
potter sequence
atypical physical appearance of a fetus or neonate due to oligohydramnios
mesonephric tubules
genital ridges that are next to the mesonephros
trigone
smooth triangular region of the internal urinary bladder formed by the two urethral orifices and the internal urethral orifice
metanephros
definitive kidney developed from the mesonephros; formation of the collecting ducts
cloacal membrane
portion of the cloaca that septates to give rise to the urogenital sinus and the anorectal canal
nephron
functional unit of kidney consisting of the proximal and distal convoluted tubes, loop of henle, bowman’s capsule, and a glomerulus
allantois
vestigial structure that serves as a respiratory and waste storage organ for embryos
ureteric bud
gives rise to the ureter, the renal pelvis, the major and minor calyces, and 1-3 million nephrons; an outgrowth of the mesonephric duct close to the cloaca that induces differentiation of the metanephric system
urogenital sinus
anterior portion of the cloacal division; gives rise to the urinary tract
metanephric tissue cap (blastema)
mass of intermediate mesodermal cells around the distal end of the metanephric diverticulum that give rise to nephrons in the permanent kidneys.
perineal body
pyramidal fibromuscular mass in the middle of the perineum.
exstrophy of the bladder
a ventral body defect in which the bladder mucosa is exposed; results in an open urinary tract that extends along the dorsal aspect of the penis through the bladder to the umbilicus
median umbilical ligament
adult remnant of the urachus
epithelial/mesenchymal interactin
when signals pass back and forth between these two cell types to regulate organ differentiation
characteristics of pronephros
- first kidney to form
- intermediate mesoderm condenses to form epithelial buds
- pronephri in humans do not differentiate into functional excretory units
- disappear by 24 days
- functional excretory units within 6-10 weeks
- Remnants of tubules differentiate into structures of male and female reproductive systems
mesonephros characteristics
- Middle kidney which contains simple nephrons and is functional
- early in the 4th week, mesonephric ducts develop, extend caudally and fuse with the walls of the cloaca on day 26
- early in the 4th week, mesonephric ducts induce the intermediate mesoderm to form about 40 mesonephric tubules. Induced by pronephros
- remnants of tubules differentiate into reproductive system structures
metanephros characteristics
- definitive kidney derived from the metanephric diverticulum which induces formation of metanephric blastema
- Composed of excretory and collecting system
where is excretory system formed?
metanephric mesoderm
where is collecting system formed?
mesonephric duct (ureteric buds). The ureteric buds sprout from the mesonephric duct and penetrate the metanephric blastema
synthesis of BMP7 and FGF2 allow for what?
maintenance of WTI which allows for differentiation of nephrons
What forms the minor calyces?
tubules of the 2nd, 3rd, and 4th subdivisions fuse to form the minor calyces of the renal pelvis
What forms the renal pyramid?
tubules of the 5th and later divisions that have elongated.
portions of the cloaca?
urogenital and rectal portions. Furthermore, the urorectal septum divides the cloaca and yields the formation of the urinary bladder and the urogenital sinus
What is a horseshoe kidney?
abnormal ascent of a single kidney that gets caught under the inferior mesenteric artery. More common in males.
What are bifid ureters?
Two ureters that share a common opening into the bladder.
What is an ectopic ureter?
It is an extra ureter that does not open into the urinary bladder. The original upper ureter opens into the abdomen and causes incontinence.
Describe potter syndrome
Presented by a baby with bilateral renal agenesis. Associated with:
Pulmonary hypoplasia, Oligohydramnios (the trigger event), Twisted face, Twisted skin, Extremity defects, Renal failure.
Describe the multicystic dysplastic kidney
Caused by an abnormal interaction between a ureteric bud and metanephric mesenchyme. This leads to a nonfunctional kidney consisting of cysts and connective tissue. If unilateral, is generally asymptomatic. Diagnosed prenatally via ultrasound
vas deferens arises from where?
mesonephric (wolffian) duct
What are the embryological sources for the suprarenal glands?
intermediate mesoderm for the cortex and neural crest for the medulla. Differentiation occurs during the 5th week of development.
