Development of the Urinary System Flashcards
Also referred to as nephrogenic plate
intermediate mesoderm
Early proliferation of this portion of the mesoderm causes a longitudinal swelling– termed the ____
urogenital plate
urogenital plate consists of
nephrogenic cord
gonadal ridge
Laterally-positioned ____ (which forms kidneys & ureter)
nephrogenic cord
Medially-positioned ____ (for ovary/testis & female/male genital tract formation).
gonadal ridge
THREE GENERATIONS OF KIDNEY PRIMORDIA
- Pronephros
- Mesonephros
- Metanephros
- Consists of seven or eight pairs of pronephric tubules that appear briefly at the level of somites seven to 14.
- In the sheep, pronephric tubules become quite well developed and connect to the pronephric duct.
- The tubules soon degenerate, but the pronephric duct persists as the mesonephric duct.
Pronephros
- In domestic animals, 70–80 pairs of mesonephric tubules appear approximately between the levels of somites nine through 26.
- The functional kidney for fish and amphibians.
- Largest in species with a six-layered placental barrier such as the pig and sheep, and smallest in carnivores with a four-layered barrier
Mesonephros
- The mesonephric tubules lengthen rapidly, form an S-shaped loop, and acquire a tuft of capillaries that later form the ____ at their medial extremity..
- Around each glomerulus, the tubulus forms a ____
- Together these structures constitute a ____
glomerulus
Bowman’s capsule
renal corpuscle
The third generation of urinary organs that matures to form the permanent kidney of reptiles, birds, & mammals.
Metanephros
metanephros Originates from two sources:
- Ureteric bud
- Metanephric blastema
- Grows out of the mesonephric duct in the region of the cloaca
- Eventually develops into the ureter, renal pelvis, and numerous collecting ducts
URETERIC BUD
- Metanephrogenic mass
- The caudal region of the nephrogenic cord.
METANEPHRIC BLASTEMA
*Nephron Formation
Mesodermal cells proliferate to form ____.
The cords canalize and elongate, becoming S-shaped ____ and eventually nephrons
One end of each metanephric tubule establishes communication with a collecting tubule; the other end of the
tubule expands to surround a capillary ____.
Between the two ends, each metanephric tubule differentiates into the regions characteristic of a nephron (_____)
cell cords
metanephric tubules
glomerulus
proximal segment, thin loop, & distal segment
*Species differences
- The kidney develops 12– 25 separate lobes, each retaining its distinct pyramid forming papillae, therefore often referred to as a multipyramidal kidney.
- With distinct gross lobulationas
- No renal pelvis
Cattle
- The cortex is not lobated but the medulla is subdivided into renal pyramids forming papillae and so multipyramidal.
- No distinct gross lobulations
Pig, Man
The cortex undergoes a complete fusion resulting in a nonlobated, smooth surface of the kidney.
- No calyces are formed
- Fusion of the apical regions of the medullary pyramids results in the formation of a ridge-like common papilla, the renal crest.
HORSE, SMALL RUMINANTS, AND CARNIVORES
Develops from expansion of the cranial end of the urogenital sinus, including the adjacent portion of the urachus.
Urinary bladder
The primitive urogenital sinus divides into the ____, the primordium of the bladder, and a ____.
cranial vesico‐urethral canal
caudal urogenital sinus proper
The ____ in the dorsal wall of the bladder is lined by epithelium of mesodermal origin whereas the rest of the bladder epithelium is derived from the endoderm
trigone
urethra Develops from the _____.
urogenital sinus
*Gender specific
- In females, the mid region of the urogenital sinus becomes ____.
- The caudal region of the urogenital sinus become _____.
- The _____ arises as an outgrowth of the vestibule.
urethra
vestibule
vagina
*Gender specific
In males, the _____ develops from the mid region of the urogenital sinus and the ____ develops from elongation of the caudal end of the urogenital sinus.
pelvic urethra
penile urethra
Derived from neural crest (ectoderm).
ADRENAL MEDULLA
Arises from cells of mesonephric nephrons
that dissociate from the nephron when the
mesonephros degenerates.
ADRENAL CORTEX
- Condition in which one or both kidneys fail to develop
- Unilateral or bilateral
RENAL AGENESIS
- An intermediate condition between a normal kidney and renal agenesis
- Hereditary condition in Cocker Spaniels, Norwegian Elkhounds, Samoyeds, Keeshonds, Bedlington Terriers
RENAL HYPOPLASIA
Duplication of the renal pelvis to the production of a complete supernumerary organ.
RENAL DUPLICATIONS
The metanephros gives rise to a kidney which remains in the sacral region.
ECTOPIC KIDNEY
Abnormal renal structure formed by the fusion of the caudal poles of bilateral pelvic kidneys
HORSESHOE KIDNEY
- Arises from the accumulation of urine within nephrons which fail to connect to their collecting duct system
- Autosomal dominant pattern in Persian cats
CONGENITAL CYSTIC KIDNEY
- Entry of the ureters into the vagina or urethra instead of the bladder
- High risk exists in Siberian Huskies, West Highland Terriers and small Poodles
ECTOPIC URETER
Results from a failure of the allantoic stalk to close at birth.
PATENT URACHUS (URACHAL FISTULA)
