INTRODUCTION 769 



C. Development of the reproductive system 



1. Early developmental features; the indifferent gonad 



2. Development of the testis 



a. Mammal 



b. Chick 



c. Frog 



3. Development of the ovary 



a. Mammal 



b. Chick 



c. Frog 



4. Development of the reproductive ducts 



a. Male reproductive duct 



b. Female reproductive duct 



5. Development of intromittent organs 



6. Accessory reproductive glands in mammals 



a. Prostate glands 



b. Seminal vesicles 



c. Bulbourethral glands 



7. Peritoneal supports for the reproductive structures 



a. Testis and ovary 



b. Reproductive ducts 



A. Introduction 



1. Developmental Relationships 



The excretory and reproductive systems often are grouped together as the 

 urogenital system. This inclusive term is appUed to these two systems because 

 they are associated anatomically in the adult form and, during development, 

 show marked interrelationships and dependencies. 



An important relationship, shared by the developing reproductive and 

 excretory systems, involves the caudal end or cloaca of the developing digestive 

 tube. It is this area of the differentiating metenteron which affords an outlet 

 to the external environment for the urogenital ducts in the majority of the 

 vertebrate species. This fact will become obvious later. 



2. Functions of the Excretory and Reproductive Systems 



The functions of the reproductive systems of the male and female are 

 discussed in Chapters 1 to 4 and 22. 



The excretory system is most important in the maintenance of life, and 

 is an important feature in the flow of fluids through the body as described 

 in the introduction to Chapter 17. Food substances and water pass into the 

 body through the walls of the digestive tract, and oxygen is admitted through 

 the respiratory surfaces. The veins convey these substances to the heart and 

 arteries (with the exception of fishes and some amphibia where oxygen passes 

 directly into the arterial system), and the heart and arteries propel them 

 to the tissues. Here the food substances and water are utilized, and excess 



