Ovaries Follicles Ovaries Note: Ovum=singular Ova=plural The ovaries serve two functions Produce ova (female germ cells) Secrete the hormones called: Estradiol Progesterone These ovaries have blister-like structures called follicles which secrete increased amounts of estradiol between days 18 and 21 of the 21-day reproductive cycle. Estradiol stimulates increased blood flow to the reproductive tract and acts with the brain to cause the behavioral signs of estrus(heat) Each follicle contains one developing ovum and estradiol stimulates LH release which causes ovulation and releases each ovum. Ovulation occurs over a period of about 2 hours Follicles Ovaries Note: Ovum=singular Ova=plural

Ovaries Days 4 to 18 of the cycle Corpora Lutea Ovaries The structures on these ovaries are called corpora lutea or “yellow bodies”. The number of CL’s reflects the number of ova shed during the previous estrus cycle. They form in the spaces left by the follicle after ovulation occurs. They become functional about 3 to 4 days post ovulation and secrete the hormone called progesterone. Progesterone is involved in the preparation of the uterus for the in coming zygotes and in the maintenance of pregnancy. If the female does not become pregnant, another hormone, prostaglandin is released from the uterus on about day 15 of the cycle, which lyses( regresses) the CL’s and the the female will return to estrus a few days later. Days 4 to 18 of the cycle Corpora Lutea Ovaries Note: Corpus luteum = singular Corpora lutea = plural