Lecture_15_Comparative Anatomy_The Urogenital System

O the mesonephros often becomes functional in the

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: in the nephric ridge, eventually reaching and opening into the cloaca. o Fluid filters from glomeruli that may protrude into the coelom or make direct contact with the pronephric tubules. Pronephric tubules then take up this coelomic fluid through the ciliated peritoneal funnels, act on it, and eventually excrete the fluid as urine. o Pronephric tubules are functional in the embryos of most vertebrates, but as they regress during development that are replaced by the mesonephros. • Mesonephros o Tubules of the mesonephric kidney (mesonephric tubules) arise in the middle of the nephric ridge and tap into the preexisting pronephric duct. To be consistent, the pronephric duct is then renamed to be the mesonephric duct. o The mesonephros often becomes functional in the embryo, but if it persists into the adult, it is modified by the incorporation of additional tubules arising within the posterior nephric ridge. It is then called the opisthonephros. o The opisthonephros is found in most adult fishes and amphibians, but gets replaced in amniotes by the metanephros. • Metanephros o The earliest hint of metanephros formation is the appearance of the metanephric duct, which appears as a ureteric diverticulum arising at the base o the preexisting mesonehpric duct. o The ureteric diverticulum grows dorsally into the posterior region of the nephric ridge where it enlarges and stimulates the growth of metanephric tubules that come to make up the metanephric kidney. o The metaneprhos becomes the adult kidney in amniotes and the metanephric duct is called the ureter. o Kidney Function and Structure  Tetrapod Kidney Structure • Most amphibians, sharks, and teleosts have opisthonephric kidneys whose anterior kidney segments transport s...
View Full Document

Ask a homework question - tutors are online