14-chapter 11 - Chapter 11: The Urogenital System Purpose...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 11: The Urogenital System Purpose Become familiar with the basic vertebrate urogenital system. Compare the ontogenetic and phylogenetic development of the kidney and its associated ducts in the major vertebrate groups. Appreciate how the reproductive systems of males and females are more similar than different by studying homologous structures and understanding sexual differentiation. Introduction Mammalian Anatomy: The Cat -Urogenital System Chapter Ch. 11 Supplement- Figs. 11-5, 11-6, 11-7 Urogenital System of Squalus Ch. 11 Urogenital System slide guide Filtration is a process of removing cellular waste and contaminants from the bloodstream. Uric acid, urea, and ammonia, nitrogenous waste compounds, are removed from blood by the kidney and transported for immediate removal or storage by a system of ducts. Gametes are produced by the gonads, which are homologous between males and females, and are transported for storage to the exterior by ducts. The structure of the kidney and the nature of the ducts have evolved extensively in vertebrates. Ducts that transport nitrogenous waste and ducts that transport gametes have a complex interaction and history. External genitalic structures eliminate waste and toxins as well as carry out gamete transfer ( copulation ). These external sexual structures are also homologous between male and female. Evolution of the kidney and its associated ducts The vertebrate kidney is an inherently segmented structure, although in living forms the details of the segmentation change with development. Current evidence suggests the original vertebrate kidney, called the holonephric kidney, was composed of functional segmented tubules running the length of the organ. A modified version of this original form is now found only in the larval stage of hagfishes and some caecilians (legless amphibians). This hypothesized holonephric kidney can be divided into three parts from anterior to posterior: the pronephros , the mesonephros , and the metanephros . While most adult craniates have lost the pronephros portion of the kidney, it is retained in adult hagfishes and some teleosts (this portion is then called the “head kidney” as it is more anterior than the major functional unit of the kidney). These organisms represent the primitive opisthonephric (“back kidney”) condition. The middle (mesonephros) and posterior (metanephros) portions of the kidney are retained in all craniates. In most fishes and amphibians both the mesonephros and the metanephros are retained as functional units of the kidney, though the metanephros appears to play the primary role. This is an example of the advanced opisthonephric condition. Among amniotes, the metanephros portion plays the major role in filtration of the blood and water/ion homeostasis. A portion of the mesonephros is retained, but it functions as a kidney only in the embryonic stage.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Figure 11-1. Evolution of the craniate kidney. A. Theoretical holonephros; B. Primitive opisthonephros; C. Advanced opisthonephros; and D.
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This document was uploaded on 02/13/2010.

Page1 / 7

14-chapter 11 - Chapter 11: The Urogenital System Purpose...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online