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Amazing women! | the art of menstruation | artists (non-menstrual) | asbestos | belts | bidets | founder bio | Bly, Nellie | MUM board | books: menstruation and menopause (and reviews) | cats | company booklets directory | contraception and religion | costumes | menstrual cups | cup usage | dispensers | douches, pain, sprays | essay directory | extraction | famous women in menstrual hygiene ads | FAQ | founder/director biography | gynecological topics by Dr. Soucasaux | humor | huts | links | masturbation | media coverage of MUM | miscellaneous | museum future | Norwegian menstruation exhibit | odor (olor)| pad directory | patent medicine | poetry directory | products, current | religion | your remedies for menstrual discomfort | menstrual products safety | science | shame | slapping, menstrual | sponges | synchrony | tampon directory | early tampons | teen ads directory | tour of the former museum (video) | underpants directory | videos, films directory | Words and expressions about menstruation | Would you stop menstruating if you could? | What did women do about menstruation in the past? | washable pads
More articles by Dr. Soucasaux: Anatomical drawings - Anovulatory cycles - Archetypal aspects of the female genitals - The breasts: some morphological aspects - Colposcopy - Comments on the corpus luteum and related aspects - Comments on some anatomical and symbolic aspects of the female pelvis - The curious relations between androgens and estrogens in women - Drospirenone Oral Contraceptives - Due to prohibition, Brazilian women don't have access to modern medicinal abortion - Endocrinology of menstruation - The Fallopian tubes - Female sexual response - The Gräfenberg Spot (G-Spot) - The Gynecologic Palpation (descendant of "The Touch") - Gynecological assistance: the three basic areas - Gynecology and Gynecologic Surgery - Gynecologist versus obstetrician: what lies behind the combination? - "Gyneco-obstetric-surgical" stubborness and the perpetuation of one of the greatest mistakes of women's medicine - Hypermenorrhea and/or Menorrhagia (Prolonged and/or Excessive Menstrual Bleedings) - Hypertrichosis, Hirsutism and Androgenic Manifestations in Women - Mayer-Rokitansky-Kuster-Hauser (MRKHauser) Syndrome - Menstrual toxin: An old name for a real thing? - Nature and the ovaries - On the Intimate, or Small-Scale, Mechanisms of Menstruation - On the Strange Nature of the Ovaries - Oral hormonal contraceptives (the "Pill") - The Ovaries: Some Functional and Archetypal Considerations - Peculiarities of the Female Genitals' Sensory Innervation - Physiology of menstruation - Polycystic ovaries syndrome - The Possibility of Becoming Pregnant, Its Implications for Women, and Abortion - Premenstrual congestion of the breasts - Premenstrual syndrome (PMS) - The Psychology of Gynecology part 1 (part 2) - Psychosomatic and symbolic aspects of menstruation - Psychosomatic gynecology - Some Details on the Function of the Hypothalamus-Pituitary-Ovaries Axis - Stanislav Grof's Perinatal Matrixes of the Unconscious and Women's Medicine - Symmetric Patterns in the Female Genitals - Thoughts on Female Sexual Psychology - Uninterrupted use of hormonal contraceptives for menstrual suppression: why I do not recommend it - The uterine cervix - Uterine contractility - The Uterus and the Female "Passive-Active" - Women's corporeal consciousness and experience - Women's Experience of the Breasts - Women's Undesired Pregnancies and Women's Right to Abortion and see his Art of Menstruation


Uterine Contractility

Dr. Nelson Soucasaux, Brazilian gynecologist

In my article "The Physiology of Menstruation" [here] I have analyzed the hormonal actions upon the endometrium - the mucosa that lines the interior of the cavity of the uterine corpus -, as well as the main endometrial histological structures and, finally, menstruation. Now, let us proceed to a brief analysis of some topics on the physiology of the myometrium - the thick and potent uterine muscular layer.

Since the uterus is endowed with this potent muscular structure (whose development and trophicity depends on the estrogens), this organ is capable not only of modifying its basal tonus, but also of contracting and relaxing through systoles and diastoles that vary greatly in intensity and duration. The variations in the uterine contractile intensity are so wide that they include: 1) weak and moderate contractions that occur in the periods in which the organ is predominantly relaxed, as during the greatest part of the menstrual cycle and pregnancy; 2) stronger contractions that characterize menstruation and the orgasmic response, as well as those resulting from pathological conditions; 3) the extremely powerful contractions of parturition.

The degree of contractility/relaxation of the uterus depends on the excitability level of the smooth muscle cells of the myometrium.

The increase in the excitability of the myometrial cells stimulates the uterine contractility, while its reduction induces to a relaxation of the organ. These phenomena depend on an interaction of hormonal, biochemical and neurovegetative factors, the most important of which are the first two ones.

By reducing the excitability of the myometrial cells, progesterone is the hormonal factor that promotes uterine relaxation, keeping the uterus quiescent (in "repose"). Conversely, the estrogens have the opposite effect - by increasing the myometrial excitability, they promote a moderate stimulation of the uterine contractility. Due to the estrogenic action, the uterus also becomes highly sensitive to the action of oxytocin - the most important hormone in the causation of uterine contractions. Oxytocin has a powerful contractile action upon the myometrium, being the hormonal factor responsible for the very strong uterine contractions of parturition. Oxytocin production takes place in the hypothalamus and its release is triggered by a reflex neurogenic pathway that starts in nerve endings especially sensitive to pressure located inside the cervical canal and in the nipples. During parturition, it is the strong mechanical stimulation of the endocervix that causes the hypothalamic liberation of a great quantity of oxytocin, giving rise to increasingly potent uterine contractions.

As non-hormonal factors that also cause strong myometrial contractions, we must mention several prostaglandins. The formation of these prostaglandins in the endometrium during the menstrual necrosis of this tissue generates the increase in the uterine contractility typical of this phase of the cycle, giving rise to the menstrual cramps. Together with several other factors, these substances also play a role in the triggering of parturition labour.

In spite of the fact that the uterine contractility is predominantly commanded by the hormonal and biochemical factors mentioned here, there are indications that the sympathetic and parasympathetic innervation of the uterus may also have a considerable influence upon it. Independently of the majority of the uterine contractions being endocrinally and biochemically triggered, the myometrial contractile activity exhibits a very peculiar characteristic that seems to demonstrate the existence of a precise and subtle nervous coordination: it is the "triple descending gradient." This gradient gives the uterine contractility its typical expulsive pattern.

According to Caldeyro-Barcia, the uterine contractile waves originate in "pacemakers" situated around the uterine insertion of the Fallopian tubes, one on the right and the other on the left. This author describes the "triple descending gradient" with the following characteristics: 1) the propagation of the contractile wave along the uterus has a descending direction. That happens because, after starting in one of the "pacemakers," the contractile wave spreads throughout the uterine fundus and propagates downwards; 2) the systolic phase of the contraction lasts more at the uterine fundus and less at the inferior parts of the organ; 3) the contractions are stronger in the upper parts of the uterus than in the lower ones (Caldeyro-Barcia, R.- "Fenômenos ativos do parto: Contratilidade uterina" - in: Rezende, J.- "Obstetrícia, Vol 1" - Guanabara Koogan, Rio de Janeiro, 1962).

In my opinion, it seems somewhat difficult to explain this so precise and symmetric coordination of the myometrium contractile waves exclusively by means of the hormonal mechanisms that trigger them. Even the double spiral arrangement of most myometrial fibers throughout the uterus does not seem to be, only by itself, capable of entirely explaining the "triple descending gradient" - regardless of being an essential condition for its occurrence. Several facts suggest that the neurovegetative system may have some coordinating activity upon the uterine contractions. For details on this subject, see my article "Fundamentos para o Estudo das Influências Neurovegetativas em Ginecologia" ("Basis for the Study of the Neurovegetative Influences in Gynecology"), published in Jornal Brasileiro de Medicina, Vol. 57, Nº 4, October 1989, Rio de Janeiro.

Specifically about the orgasmic contractions of the uterus, everything indicates that they are fundamentally triggered and commanded by the vegetative innervation of this organ. These uterine contractions are the acme of the neurogenic myotonic reaction that occur in the female genitals during sexual excitement, and happen simultaneously with the widely known contractions of the muscles that surround the vaginal entrance. Still regarding the neurovegetative influences upon the myometrial contractile activity, it is pertinent to remind that neurogenic uterine contractions are well-known in gynecologic practice.

This article is an excerpt from my book "Os Órgãos Sexuais Femininos: Forma, Função, Símbolo e Arquétipo" ("The Female Sexual Organs: Shape, Function, Symbol and Archetype"), published by Imago Editora, Rio de Janeiro, 1993. For information on the book, see page http://www.nelsonginecologia.med.br/orgaos.htm , from my Website www.nelsonginecologia.med.br

Copyright Nelson Soucasaux 1993, 2001

__________________________________________________________

Nelson Soucasaux is a gynecologist especially dedicated to clinical, preventive and psychosomatic gynecology. Graduated in 1974 by Faculdade de Medicina da Universidade Federal do Rio de Janeiro, Brazil, he is the author of several articles published in medical journals and of the books "Novas Perspectivas em Ginecologia" ("New Perspectives in Gynecology") and "Os Órgãos Sexuais Femininos: Forma, Função, Símbolo e Arquétipo" ("The Female Sexual Organs: Shape, Function, Symbol and Archetype"), published by Imago Editora, Rio de Janeiro, 1990, 1993.

Web site (Portuguese-English): www.nelsonginecologia.med.br

E-mail: nelsons@nelsonginecologia.med.br


NEWS | homepage | LIST OF ALL TOPICS | MUM address & What does MUM mean? | e-mail the museum | privacy on this site | who runs this museum?? |
Amazing women! | the art of menstruation | artists (non-menstrual) | asbestos | belts | bidets | founder bio | Bly, Nellie | MUM board | books: menstruation and menopause (and reviews) | cats | company booklets directory | contraception and religion | costumes | menstrual cups | cup usage | dispensers | douches, pain, sprays | essay directory | extraction | famous women in menstrual hygiene ads | FAQ | founder/director biography | gynecological topics by Dr. Soucasaux | humor | huts | links | masturbation | media coverage of MUM | miscellaneous | museum future | Norwegian menstruation exhibit | odor (olor)| pad directory | patent medicine | poetry directory | products, current | religion | your remedies for menstrual discomfort | menstrual products safety | science | shame | slapping, menstrual | sponges | synchrony | tampon directory | early tampons | teen ads directory | tour of the former museum (video) | underpants directory | videos, films directory | Words and expressions about menstruation | Would you stop menstruating if you could? | What did women do about menstruation in the past? | washable pads
More articles by Dr. Soucasaux: Anatomical drawings - Anovulatory cycles - Archetypal aspects of the female genitals - The breasts: some morphological aspects - Colposcopy - Comments on the corpus luteum and related aspects - Comments on some anatomical and symbolic aspects of the female pelvis - The curious relations between androgens and estrogens in women - Drospirenone Oral Contraceptives - Due to prohibition, Brazilian women don't have access to modern medicinal abortion - Endocrinology of menstruation - The Fallopian tubes - Female sexual response - The Gräfenberg Spot (G-Spot) - The Gynecologic Palpation (descendant of "The Touch") - Gynecological assistance: the three basic areas - Gynecology and Gynecologic Surgery - Gynecologist versus obstetrician: what lies behind the combination? - "Gyneco-obstetric-surgical" stubborness and the perpetuation of one of the greatest mistakes of women's medicine - Hypermenorrhea and/or Menorrhagia (Prolonged and/or Excessive Menstrual Bleedings) - Hypertrichosis, Hirsutism and Androgenic Manifestations in Women - Mayer-Rokitansky-Kuster-Hauser (MRKHauser) Syndrome - Menstrual toxin: An old name for a real thing? - Nature and the ovaries - On the Intimate, or Small-Scale, Mechanisms of Menstruation - On the Strange Nature of the Ovaries - Oral hormonal contraceptives (the "Pill") - The Ovaries: Some Functional and Archetypal Considerations - Peculiarities of the Female Genitals' Sensory Innervation - Physiology of menstruation - Polycystic ovaries syndrome - The Possibility of Becoming Pregnant, Its Implications for Women, and Abortion - Premenstrual congestion of the breasts - Premenstrual syndrome (PMS) - The Psychology of Gynecology part 1 (part 2) - Psychosomatic and symbolic aspects of menstruation - Psychosomatic gynecology - Some Details on the Function of the Hypothalamus-Pituitary-Ovaries Axis - Stanislav Grof's Perinatal Matrixes of the Unconscious and Women's Medicine - Symmetric Patterns in the Female Genitals - Thoughts on Female Sexual Psychology - Uninterrupted use of hormonal contraceptives for menstrual suppression: why I do not recommend it - The uterine cervix - Uterine contractility - The Uterus and the Female "Passive-Active" - Women's corporeal consciousness and experience - Women's Experience of the Breasts - Women's Undesired Pregnancies and Women's Right to Abortion and see his Art of Menstruation

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