12-chapter 9 - Chapter 9: The Digestive and Respiratory...

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Purpose Become familiar with the basic vertebrate digestive and respiratory systems. Learn to identify the major endocrine organs and their functions. Note modifications in the digestive systems among vertebrates. Understand the evolution of the respiratory system from aquatic to aerial respiration. Introduction Mammalian Anatomy: The Cat -Body Cavities and Mesenteries, Digestive System, Respiratory System chapters Ch. 9 Supplement- Figs. 9-1, 9-2 Digestive System of Squalus Ch. 9 Digestive System slide guide In this chapter you will learn how the body cavity is segregated and how this separation of cavities has changed in association with both the respiratory and digestive systems. You will be responsible for learning to identify the various organs of the digestive and respiratory systems. You will also be responsible for understanding the functions of these organs. You will specifically need to recognize and understand the Squalus and Felis anatomy seen in the tables at the end of this handout. Segregation of Body Cavities Just like many invertebrate animals, vertebrates possess a coelom , a body cavity bounded by mesoderm. In fishes, the coelom is divided into two cavities by the transverse septum : the pericardial cavity , containing the heart, and the pleuroperitoneal cavity , containing the visceral organs. In tetrapods, a pericardium closely surrounds the heart forming a reduced pericardial cavity. The pleuroperitoneal cavity persists in amphibians and most lepidosaurs and contains the lungs and visceral organs. This arrangement creates two main cavities within these animals. Archosaurs and mammals possess four main cavities with the lungs contained separately in two cavities. The heart remains in the pericardial cavity while the lungs are now contained separately in the paired pleural cavities . The lower viscera are contained within a peritoneal cavity . Interestingly, the pleural cavities of archosaurs and mammals are not homologous. In addition, only mammals possess a diaphragm (affixed to the transverse septum ) and mediastinum (membranous partition separating the lungs). Within the various body cavities of vertebrates are thin membranes called mesenteries . These extend from the visceral organs to the body wall and between the organs themselves to help maintain position relative to each other. Because many dissections only concern obvious, discrete organs, students typically do not perceive the mesenteries and other connective tissue structures that define the body cavities. Remember that internal body structure and function are as dependent upon these connective, cushioning, and supportive structures as on any other structures. Various mesenteries can be seen in both Squalus and Felis , the most notable of which is the greater omentum in Felis . DO NOT DESTROY THE GREATER OMENTUM! It can be easily lifted out of the way for examination of the digestive tract. (Note: In Felis , as in other mammals, the
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12-chapter 9 - Chapter 9: The Digestive and Respiratory...

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