Biology of Reproduction

XIV. Estrous Cycles                          back to XIII. Reproductive Cycling

	A. estrus = restricted period of sexual receptivity
	   in female mammals

		1. changes in genital tract

			a. stimulated by ovarian steroids

	B. Estrous cycles are periodic changes in reproductive function

		1. includes estrus

		2. ovarian cycles include follicular and luteal phases

			a. separated by ovulation

		3. three types of cycle

			a. reflex or induced ovulation

				i. mating stimulates ovulation

					(1) cats, voles, rabbits

					(2) in humans the most fertile period for coitus
					    is just prior to ovulation

				ii. luteal phase only occurs following copulation

				iii. follicular phase includes follicle growth,
				     E2 priming of the brain

			b. spontaneous (+feedback driven) ovulation

				i. functional corpus luteum requires copulation
				   (rats, mice)

					(1) pseudopregnancy ensues without implantation

			c. functional CL regardless of copulation
			   (guinea pigs, humans)

		4. CL may be required to make P throughout gestation

			a. rabbit, mouse, pig and goat

		5. CL may be replaced by placenta to make P

			a. rat, guinea pig, sheep, humans
	

XV. Menstrual Cycle