Physiology of Menstruation
Menstruation – is the periodic discharge of blood, mucus and epithelial cells from the uterus.
Menstrual Cycle – periodic uterine bleeding in response to cyclic hormonal changes. A process that allows for conception and implantation of new life.
It is usually determined by counting as day 1 the 1st day of a menstrual period until the last day before the next menstrual period.
Purpose:
- To bring an ovum to maturity
- To renew a uterine tissue bed that will be responsive to fetal growth
- To prepare the uterus for pregnancy
Characteristics of Normal Menstrual Cycles
|
TERM |
DESCRIPTION |
| Beginning (Menarche) | average age of onset: 12 or 13 years; average range of age: 9-17 years |
| Interval between cycles | average 28 days; cycles of 23 to 35 days not usual |
| Duration of Menstrual flow | average flow: 2-7 days; ranges 1-9 days not normal |
| Amount of menstrual flow | difficult to estimate; average 30 to 80 ml. per menstrual period; saturating a pad in less than an hour is considered heavy bleeding. |
| Color of menstrual flow | dark red; a combination of blood, mucus, and endometrial cells |
| Odor of menstrual flow | marigold |
Discomforts of Menstruation
- Breast tenderness and feeling of fullness
- Tendency towards fatigue
- Temperament and mood changes – because of hormonal influence and decreased levels of estrogen and progesterone
- Discomfort in pelvic area, lower back and legs
- Retained fluids and weight gain
Abnormalities of Menstruation
- Amenorrhea – absence of menstrual flow
- Dysmenorrhea – painful menstruation
- Oligomenorrhea – scanty menstruation
- Polymenorrhea – too frequent menstruation
- Menorrhagia -excessive menstrual bleeding
- Metrorrhagia – bleeding between periods of less than 2 weeks
- Hypomenorrhea – abnormally short menstruation
- Hypermenorrhea – abnormally long menstruation
Four body structure involved in the physiology of the menstrual cycle:
- Hypothalamus
- Pituitary gland
- Ovaries
- Uterus
Reproductive Hormones:
- Gonodotropin-Releasing Hormone (GnRH)
- Stimulates release of FSH and LH initiating puberty and sustaining menstrual cycle.
- Follicle-stimulating Hormone (FSH)
- secreted by anterior pituitary gland during the 1st half of menstrual cycle
- stimulate growth and maturation of graafian follicle before ovulation
- thins the endometrium
- Luteinizing Hormone (LH)
- secreted by the anterior pituitary gland
- stimulates final maturation of graafian follicle
- surge of LH about 14 days before next menstrual period causes ovulation
- stimulates transformation of graafian follicle into corpus luteum
- thickens the endometrium
- Estrogen
- secreted primarily by the ovaries, corpus luteum, adrenal cortex and placenta in pregnancy
- considered the Hormone of Women
- stimulates thickening of the endometrium; causes suppression of FSH secretion
- responsible for the development of secondary sex characteristics
- stimulates uterine contractions
- increases water content of uterus
- high estrogen concentration inhibits secretion of FSH and Prolactin but stimulates secretion of LH7.
- low estrogen concentration after pregnancy stimulates secretion of Prolactin
- Progesterone
- secreted by the ovary, corpus luteum and placenta during pregnancy
- inhibits secretion of LH
- has thermogenic effect (increases body temperature)
- relaxes smooth muscles thereby decreases contractions of uterus
- causes cervical secretion of thick mucus
- maintain thickness of endometrium
- allows pregnancy to be maintained = Hormone of Pregnancy
- prepares breasts for lactation
- Prolactin
- secreted by the anterior pituitary gland
- stimulates secretion of milk
- Oxytocin
- secreted by the posterior pituitary gland
- stimulates uterine contractions during birth and compress uterine blood vessels and control bleeding
- stimulates let-down or milk-ejection reflex during breastfeeding
- Prostaglandins
- fatty acids’ categorized as hormones
- produced by many organs of the body, including the endometrium
- affects menstrual cycle
- influences the onset and maintenance of labor
Daisy Jane Antipuesto RN MN
Currently a Nursing Local Board Examination Reviewer. Subjects handled are Pediatric, Obstetric and Psychiatric Nursing. Previous work experiences include: Clinical instructor/lecturer, clinical coordinator (Level II), caregiver instructor/lecturer, NC2 examination reviewer and staff/clinic nurse. Areas of specialization: Emergency room, Orthopedic Ward and Delivery Room. Also an IELTS passer.
