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Vagusstoff (literally translated from German as "Vagus Substance") refers to the substance released by stimulation of the vagus nerve which causes a reduction in the heart rate. Discovered in 1921 by physiologist Otto Loewi , vagusstoff was the first confirmation of chemical synaptic transmission and the first neurotransmitter ever discovered.
As with most things related to the reproductive system, folliculogenesis is controlled by the endocrine system. Five hormones participate in an intricate process of positive and negative feedback to regulate folliculogenesis. They are: gonadotropin-releasing hormone (GnRH) secreted by the hypothalamus; two gonadotropins:
The anterior pituitary complex and hypophyseal portal system, where FSH and LH are released. Theca cells are responsible for synthesizing androgens, providing signal transduction between granulosa cells and oocytes during development by the establishment of a vascular system, providing nutrients, and providing structure and support to the follicle as it matures.
Birds have only one functional ovary (the left), while the other remains vestigial. In mammals including humans, the female ovary is homologous to the male testicle, in that they are both gonads and endocrine glands. Ovaries of some kind are found in the female reproductive system of many invertebrates that employ sexual reproduction. However ...
The female reproductive system likewise contains two main divisions: the external genitalia (the vulva) and the internal genitalia. The ovum meets with the sperm cell: a sperm may penetrate and merge with the egg, fertilizing it with the help of certain hydrolytic enzymes present in the acrosome.
The follicular phase, also known as the preovulatory phase or proliferative phase, [1] is the phase of the estrous cycle (or, in primates [2] for example, the menstrual cycle) during which follicles in the ovary mature from primary follicle to a fully mature graafian follicle.
The development of the gonads is part of the prenatal development of the reproductive system and ultimately forms the testicles in males and the ovaries in females. The immature ova originate from cells from the dorsal endoderm of the yolk sac. Once they have reached the gonadal ridge they are called oogonia.
Fertilization was not understood in antiquity. Hippocrates believed that the embryo was the product of male semen and a female factor. Aristotle held that only male semen gave rise to an embryo, while the female only provided a place for the embryo to develop, [5] a concept he acquired from the preformationist Pythagoras.