Menstrual Cycle and Oral Contraceptives
Study guide:
Definition:
Menstruation (menses, or menstrual flow): periodic discharge of sloughed endometrium and blood from the uterine cavity through the vaginal canal, which happens due to different hormonal changes in the absence of pregnancy.
Basics:
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The normal menstrual cycle ranges from 21 to 35 days.
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Day 1 of the cycle is the first day of bleeding (14 days post-ovulation).
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The menstrual flow normally lasts from 2 to 7 days (average is 4 days).
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The amount of blood loss is usually between 30-50 ml and should NOT form clots; >80 ml in an abnormally high amount of blood loss.
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A normal menstrual cycle consists of a menstrual, proliferative, and secretory phases.
→ Also can be divided into follicular, ovulatory, & luteal phases.
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If fertilization does not occur, the corpus luteum involutes.
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Progesterone and estradiol levels fall, and subsequently endometrial sloughing occurs (menses).
→ Due to the functional endometrium ischemia & necrosis.
Menstrual Cycle
Estrogen which causes:
1- Endometrial Proliferation
2- Thinning of cervical mucus to allow easier passage of sperm
FSH causing follicle maturation
Follicular Phase
Ovulatory Phase
LH Surge
Follicular phase length varies; however, the length of the luteal phase is fixed.
Luteal Phase
Corpus luteum
Progesterone which causes:
1- Endometrium maturation and preparation for implantation of the Blastocyst.
2- Increased production of estrogen by the adrenal glands.
3- Increase the basal body temprature.
Organ:
Endometrium
Cervix
Changes:
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Intermediate spongiosa layer and the epithelial layer form the transient functionalis layer, which is sloughed during menses.
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Estrogen causes thickening and proliferation of the basal layer.
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Glands will become coiled and torturous in response to estrogen.
Changes:
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In the follicular phase, high levels of estrogen will increase the cervical vascularity causing edema.
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With high estrogen levels, mucus will increase in quantity, elasticity, and salt concentration (ferning), which will aid in the sperm transport.
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In the luteal phase, progesterone will cause the cervical mucus to be thicker and less elastic inhibiting the access of sperm.
Notes:
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The endometrium normally consists of glands and stroma.
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The stroma consists of:
1. Basal layer.
2. Intermediate spongiosa layer.
3. Epithelial layer
Notes:
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Ferning indicates high levels of salt in the cervical mucus, which becomes maximally prominent just before ovulation when estrogen levels are in their maximum.
Vagina
Changes:
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In the late follicular phase, high estrogen will cause squamous cells to mature and be cornified.
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In the luteal phase, progesterone will cause number of cornified squamous cells will increase as well as the number of leukocytes and cellular debris.
Reffrences:
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Potter L, Hempenstall L, Mahmood H, İşler E, Potter L, Shahid S et al. The Menstrual Cycle | Geeky Medics [Internet]. Geeky Medics. 2011 [cited 9 January 2016]. Available from: http://geekymedics.com/the-menstrual-cycle/
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Merck Manuals Professional Edition. Female Reproductive Endocrinology - Gynecology and Obstetrics [Internet]. 2016 [cited 9 January 2016]. Available from: http://www.merckmanuals.com/professional/gynecology-and-obstetrics/female- reproductive-endocrinology/female-reproductive-endocrinology
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Dunn, Robert B et al. USMLE Step 1 Physiology Lecture Notes. [New York, N.Y.]: Kaplan Medical, 2011. Print.
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Merck Manuals Professional Edition. Female Reproductive Endocrinology - Gynecology and Obstetrics [Internet]. 2016
[cited 9 January 2016]. Available from: http://www.merckmanuals.com/professional/gynecology-and-obstetrics/female-
reproductive-endocrinology/female-reproductive-endocrinology (Figure 1).
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Le T, Bhushan V, Sochat M, Sylvester P, Mehlman M, Kallianos K. First aid for the® USMLE.
Written by: Samaher AlHarbi
Reviewed by: Ghadah Al-Qahtani
Dana Alturaifi
Roaa Amer
Format editor: Roaa Amer
Web Publisher: Adel Yasky