Obstetrics & Gynecology

Week 1Female anatomy, normal menstrual cycle

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

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

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

Female Anatomy

Female Anatomy

Female Anatomy

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

Puberty

Tanner Stages I-V pubic hair and breast development

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

Hypothalamus-Pituitary-Ovaries

Hypothalamus- pituitary-ovary

Hypothalamus and pituitary glands

Anterior Pituitary

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

Cyclic changes in hormones, ovarian folliles,

and endometrium

Ovarian cycle