ZOO 2090 Lecture Notes - Lecture 14: Oogenesis, Seminiferous Tubule, Ontogeny
13 Sep 2017
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Document Summary
The reproductive and excretory systems are intimately associated with each other and it is easier to combine them in order to understand how they evolved. In vertebrates, mesomeres of the mesoderm give rise to urogenital organs. In other fish, pronephros degenerates into (cid:862)head kid(cid:374)ey(cid:863), a(cid:374)d orga(cid:374) li(cid:373)ited to he(cid:373)opoietic, lymphoid and endocrine functions: opisthonephros mesonephros, reduced segmentation. In late larval and adults anamniotes, all or most of the mesomere posterior to pronephros forms one kidney, it is called opisthonephros: among amniotes, the middle part of the nephrogenic cord develop first, is called. Functional unit: nephron: nephron = nephric (renal) tubule + renal corpuscle, basic design is paired and segmented nephric tubules opening on one end, facing glomeruli, then each connecting to nephric duct. This helps establish the strong concentration gradient needed to produce highly concentrated urine: aquatic mammals like the beaver, who have no need to produce highly concentrated urine show the opposite.
