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Lecture_15_Comparative Anatomy_The Urogenital System

At this point they are ready for fertilization o if

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Unformatted text preview: , the osmotic problem results from a net tendency for an inward shift of water. Relative to fresh water, the body of the fish is hyperosmotic. In this case, fish kidneys are designed to excrete large quantities of dilute urine (~10x the amount of their marine counterparts!). • In saltwater fishes, there is a tendency for a net outward flux of water from the body tissues, dehydrating them. Relative to the salt water, the bodies of most marine fishes are hyposmotic. To aid in water conservation, the kidneys are designed to excrete very little water, thus reducing water loss. To address the problem of excess salt, the gills and sometimes special glands (e.g. salt glands) will excrete salt. The body of some animals is isosmotic and are therefore called osmoconfomers (e.g. hagfishes, chondrichtyans). •  • Reproductive System o Structure of the Mammalian Reproductive System  Ovary Overview • In mammals, each ovary consists of an outer connective tissue capsule (tunica albuginea) encloses a thick cortex and deeper medulla. • The ova (eggs) occupy the cortex and are wrapped in layers of follicle cells derived from connective tissue. An ovum plus its associated follicle cells is termed a follicle. • While some follicles remain in this rudimentary state, others pass through a series of maturation stages at the end of which the ovum and some of its clinging follicle cells are cast out of the ovary in the process of ovulation. At this point they are ready for fertilization. o If fertilization occurs, the ovum continues down the oviduct and becomes implanted in the wall of  the prepared uterus, where subsequent growth of the embryo occurs. o If fertilization does not occur, the undeveloped ovum continues down the ovi...
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