obstetrics & gynecology week 1 female anatomy, normal menstrual cycle
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Female Anatomy
Terms to know:
Vulva: external genital organs Consists of: mons pubis, labia majora, labia minora,
hymen, clitoris, vestibule, urethra, Skene’s glands, Bartholin’s glands, vestibular bulbs
Female Anatomy
Labia majora: cutaneous folds of adipose and fibrous tissue
Outer surface covered in hair follicles
Inner surface has sebaceous glands
Both have sweat glands
Homologous to scrotum in male
Size related to fat content; atrophy after menopause
Female Anatomy
• Labia minora are cutaneous folds located between labia majora
• Dense connective tissue with erectile tissue and elastic fibers
• Sebaceous glands but no hair follicles (as are the breasts)
• Homologous to penile urethra
• Relatively more prominent in children and postmenopausal women
Female Anatomy
Clitoris is a short, cylindrical erectile organ at superior portion of vestibule (area within labia minora)
Distal 1/3rd is glans, contains many nerve endings
Homologous to penis in male
Female anatomy
Urethra is a conduit for urine from the urinary bladder to the vestibule
Approximately 3.5 to 5 cm in length (male urethra is 17.5 cm in length
Length is one of the factors in frequency of UTIs in females vs. males
Female Anatomy
Skene’s glands: branched, tubular glands adjacent to distal urethra
Secrete lubrication
Highly variable anatomy
Homologous to prostate in males
Female Anatomy
Bartholin’s glands are vulvovaginal glands located beneath fascia, 4 and 8 o’clock
Ducts open into a groove between labia minora and hymen
Secrete mucus for vaginal lubrication
Homologous to Cowper’s glands in men
Both Bartholin’s and Skene’s glands may become infected
Female Anatomy
Introitus: vaginal opening (technically any opening into a cavity or canal)
Anus: rectal outlet or opening
Female Anatomy
Internal anatomy terms to know: Vagina, cervix, uterus, broad ligament, ovaries,
fallopian tubes, bladder, rectum Broad ligament is a thin, double layer of peritoneum
that envelopes Fallopian tubes, ovarian and round ligaments, uterus, ovarian and uterine arteries and veins
Normal Stages of Development
Pre-pubertal changes Adrenarche: maturation of adrenal cortex
Ages 6-10 average Development of pubic and axillary hair Sweat composition changes (body odor) Skin oiliness and acne
Normal stages of Development
Pre- pubertal changes: Gonadarche: gradual maturation of interactions
between GnRH (gonadotropin- releasing hormone), pituitary hormones, and ovaries
Earliest gonadal changes in puberty Growth of gonads (ovaries and testes), increase in
sex steroid hormones in response to pituitary hormones
Normal stages of development
Puberty: sequence of events by which a child reaches sexual maturity
Early puberty: decreased sensitivity of hypothalamus to sex hormones Development of secondary sex characteristics
without ovulation May also be independent of HPO axis
Normal Stages of Development
Thelarchy: postnatal breast development 60% of the time this is the first stage of puberty Breast bud development occurs on average 2 years
prior to menarche
Normal Stages of Development
Menarche: onset of menstruation, which is a bloody vaginal discharge that occurs as a result of endometrial shedding after ovulation, when fertilization has not occurred
In US, average age 12.5 years
Time influenced by environment, genetics, nutritional status
Normal Stages of Development
Menarche: Critical weight, body fat % needed
Obesity- earlier menarche Malnourishment or athletes- delayed menarche
During adolescence/ menarche, more common to have annovulatory cycles, leading to irregular or heavy bleeding
It is possible for ovulation to occur prior to or after menarche
Normal Stages of Development
Menarche: Ovaries secrete estrogen in response to pituitary
hormones Pituitary hormones released by stimulation from
GnRH from hypothalamus Effects: growth in stature, breast growth, increase in
adipose tissue, pelvic widening
Menstruation
Hormones involved:• GnRH: gonadotropin- releasing hormone
Released by hypothalamus in pulsatile manner Acts upon pituitary
• LH: Leutinizing hormone Released by anterior pituitary Acts upon ovary:
• Tells theca cells to make steroid hormones• Induces “leutinization” of granulosa cells– make
progesterone
Menstruation
Hormones involved (cont.) FSH: Follicle stimulating hormone
Secreted by anterior pituitary Acts on granulosa cells of ovary to stimulate follicular
growth Estrogen (E1/E2/E3)
Secreted by ovarian follicle Progesterone
Secreted by ovarian corpus luteum
Menstruation
Hypothalamic-pituitary- ovarian axis: Refers to interactions between hormones secreted
by hypothalamus, pituitary, and ovaries Positive and negative feedback interactions Separate from HPA (adrenal) and HPT (thyroid) axes,
although entire endocrine system interconnected
Menstruation
Cyclic vaginal discharge of sloughed endometrium (lining of uterus)
Normal cycle considered between 25-36 days
Only 10-15% of women have exact 28 day cycle (moon cycle)
Average of 130mL of blood loss
Pads/tampons absorb approx. 20-30mL
Menstrual Cycle
Follicular/ pre-ovulatory phase
Variable in duration (average 14 days)
First few days: slight increase in FSH, stimulates follicular growth
One growing follicle recruited for ovulation, starts producing estrogen
LH slowly rising
Menstrual Cycle
Follicular phase (cont.) Estrogen levels peak, produces positive feedback on
LH LH levels surge, resulting in ovulation (the release of
ovum from the follicle) Rising estrogen levels inhibit FSH Progesterone levels rise Endometrium thickens with rising E levels Increase in cervical mucus
Menstrual Cycle
Ovulatory phase Begins with LH surge LH released in pulses for about 36-48 h Ovum released from follicle 16-32 h after LH surge External cervical os opens from 1 to 3mm in
diameter Elastic cervical mucus forms “superhighway” for
sperm
Menstrual Cycle
Luteal/ post-ovulatory phase Follicle reorganizes, becomes corpus luteum Functional life of corpus luteum is 14 days, less
variation in duration of this phase Corpus luteum secretes progesterone, which
supports process of implantation of fertilized ovum FSH and LH levels are low
Menstrual Cycle
Luteal phase Effects of progesterone:
Rise in basal body temperature Thickening, loss of elasticity of cervical mucus