Lets take a look at Doe's Reproductive Physiology....

The primary messengers, which allow all of the organs involved in reproduction to communicate and coordinate, are "hormones". Hormones are protein molecules that are produced by many organs and structures in the body, usually in response to an external stimulus (such as light or smell). Reproductive hormones rise and fall at appropriate times (cycles) to ensure the female behaviorally accepts the male (is standing heat) when ovulation is about to occur, and to ensure the uterus is ready to accept and nourish the fertilized egg. Hormones also "feedback" and decrease some reproductive functions when it is appropriate, so that the ovaries do not produce and ovulate eggs needlessly when an animal is pregnant. In animals which breed only during certain seasons of the year, these hormal reproductive cycles are turned on and off accordingly.

The hypothalamus is a gland located on the ventral (bottom) surface of the brain. The hypothalamus produces several hormones that are important in regulation of various body functions, including reproduction. The primary reproductive hormone produced by the hypothalamus is "Gonadotropin-Releasing Hormone (GNRH). GNRH is produced in response to daylight length (photoperiod) in animals that have a seasonal reproductive pattern. In deer, as the days get shorter and the length of daylight per day decreases, GNRH production in the hypothalamus increases, and levels of GNRH rise in the bloodstream.

The anterior pituitary gland is located in close proximity to the hypothalamus. Rising levels of GNRH stimulate the anterior pituitary gland to produce and release two hormones: Follicle Stimulating Hormone (FSH) and Leutinizing Hormone (LH). FSH stimulates the development of egg containing follicles on the ovary. LH promotes ovulation of these follicles and initiates the development of the corpus luteum after ovulation. Stimulation of the follicle by FSH is required before LH can be effective and cause a follicle to ovulate.

The ovary produces two reproductive hormones: Estrogen and Progesterone. As a follicle develops in the ovary, it secretes Estrogen. The primary function of Estrogen is to cause the behavioral signs of heat (estrus) or receptivity to the male. Once a follicle ovulates, the remains of the follicle wall develop into a Corpus Luteum, which then secretes Progesterone. The primary function of progesterone is to prepare the uterus for implantation of the fertilized egg. The Corpus Luteum must be stimulated by Estrogen before it can produce Progesterone. Because it would be wasteful for an animal, which has already ovulated and bred, to continue to produce follicles or to ovulate, rising estrogen levels inhibit the production of follicle stimulating hormone (FSH) and luetinizing hormone (LH), preventing both. Progesterone, produced by the corpus luteum during pregnancy, also inhibits follicle stimulating hormone (FSH) and the development of follicles.

The uterus also produces a reproductive hormone from its lining: Prostaglandin F2 Alpha. If an animal does not become pregnant, prostaglandin F2 alpha is produced, which destroys the corpus luteum and thus progesterone production, and allows a new estrous cycle to begin.

The cycle of follicle development, ovulation, corpus luteum formation, prostaglandin destruction of the corpus luteum, and its repetition until pregnancy occurs is known as the Estrous Cycle. In humans, the estrous cycle is called the Menstrual Cycle. The length of the estrous cycle varies, but is approximately 21 days in most deer. Breeding occurs during “standing heat” or “estrus”, which lasts only 18-24 hours in deer. If the animal is bred or semen introduced at the proper time, the ovulated egg is fertilized in the fallopian tube. After fertilization, the embryo implants in wall of the uterus. Implantation of the fertilized egg into the uterine wall prevents prostaglandin production and the corpus luteum continues to produce progesterone, the hormone which maintains pregnancy. The uterine wall then forms a Placenta to nourish and develop the fetus.

Temperate deer species only breed and have estrous cycles seasonally. This ensures babies are born at the time of the year when food is plentiful and the environmental conditions are more amenable to survival. Nature thus required a consistent, unquestionable cue which would signal the proper time to initiate the estrous cycle and breeding. The primary stimulus initiating the estrous cycle in white-tailed deer is shortened day length, which occurs in the fall.

In Review: It is an interaction of all the reproductive organs, glands and hormones, which results in the estrous cycle. The sequence of events of the estrous cycle starts with the production of GNRH. The production of GNRH stimulates the secretion of FSH and LH. The increased level of FSH stimulates the development of follicles with subsequent increased estrogen secretion. The increased estrogen level causes a decrease in FSH and an increase in LH. The increased LH comes in a pulse and causes the follicle to ovulate and release the ovum. This causes the female to enter “estrus” or “standing heat”. The remains of the follicular wall develop into a corpus luteum, which produces progesterone. If the female is not pregnant, the uterine wall produces prostaglandin F2 alpha which causes destruction (lysis) of the corpus luteum. The corpus luteum regresses and ceases the production of progesterone. The resulting decreased progesterone level stimulates increased secretion of FSH and LH, which starts the cycle all over again.


Can anybody explain why this is importantfor proper scent collection or does anybody want to know why this is important to know as a scent user?