Urinary System Development - Veterinary Embryology PDF

Associate Professor V Department of Morphoph ysiology and Pharmacology College of Veterinar y Science and Medicine Central Luzon State University  Also referred to as nephrogenic plate Early proliferation of this portion of the mesoderm causes a longitudinal swelling–...

Associate Professor V Department of Morphoph ysiology and Pharmacology College of Veterinar y Science and Medicine Central Luzon State University  Also referred to as nephrogenic plate Early proliferation of this portion of the mesoderm causes a longitudinal swelling– termed the urogenital plate.  Consists of: Laterally-positioned nephrogenic cord (which forms kidneys & ureter) Medially-positioned gonadal ridge (for ovary/testis & female/male genital tract formation).  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.  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  The mesonephric tubules lengthen rapidly, form an S-shaped loop, and acquire a tuft of capillaries that later form the glomerulus at their medial extremity.. Around each glomerulus, the tubulus forms a Bowman’s capsule. Together these structures constitute a renal corpuscle.  The third generation of urinary organs that matures to form the permanent kidney of reptiles, birds, & mammals. Originates from two sources: Ureteric bud Metanephric blastema  URETERIC BUD Grows out of the mesonephric duct in the region of the cloaca Eventually develops into the ureter, renal pelvis, and numerous collecting ducts  METANEPHRIC BLASTEMA Metanephrogenic mass The caudal region of the nephrogenic cord.  Mesodermal cells proliferate to form cell cords. The cords canalize and elongate, becoming S-shaped metanephric tubules 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 glomerulus. Between the two ends, each metanephric tubule differentiates into the regions characteristic of a nephron (proximal segment, thin loop, & distal segment)  CATTLE 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 prominent renal pelvis  PIG, man The cortex is not lobated but the medulla is subdivided into renal pyramids forming papillae and so multipyramidal. No distinct gross lobulations  HORSE, SMALL RUMINANTS, AND CARNIVORES The cortex undergoes a complete fusion resulting in a nonlobated, smooth surface of the kidney.  HORSE, SMALL RUMINANTS, AND CARNIVORES 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.  The cloaca divides into urogenital sinus anteriorly and anal canal posteriorly via the urorectal septum  The primitive urogenital sinus divides into the cranial vesico‐urethral canal, the primordium of the bladder, and a caudal urogenital sinus proper.  The trigone 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  Develops from the urogenital sinus. Gender specific: In females, the mid region of the urogenital sinus becomes urethra. The caudal region of the urogenital sinus become vestibule. The vagina arises as an outgrowth of the vestibule.  In males, the pelvic urethra develops from the mid region of the urogenital sinus and the penile urethra develops from elongation of the caudal end of the urogenital sinus.  ADRENAL MEDULLA Derived from neural crest (ectoderm).  ADRENAL CORTEX Arises from cells of mesonephric nephrons that dissociate from the nephron when the mesonephros degenerates.  RENAL AGENESIS Condition in which one or both kidneys fail to develop Unilateral or bilateral RENAL HYPOPLASIA An intermediate condition between a normal kidney and renal agenesis Hereditary condition in Cocker Spaniels, Norwegian Elkhounds, Samoyeds, Keeshonds, Bedlington Terriers  RENAL DUPLICATIONS Duplication of the renal pelvis to the production of a complete supernumerary organ. ECTOPIC KIDNEY The metanephros gives rise to a kidney which remains in the sacral region.  HORSESHOE KIDNEY Abnormal renal structure formed by the fusion of the caudal poles of bilateral pelvic kidneys  CONGENITAL CYSTIC KIDNEY Arises from the accumulation of urine within nephrons which fail to connect to their collecting duct system Autosomal dominant pattern in Persian cats  ECTOPIC URETER 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  PATENT URACHUS (URACHAL FISTULA) Results from a failure of the allantoic stalk to close at birth. Th an k you !