Uterus Anatomy and Function

Study Notes

The uterus, or womb, weighs 40 to 70 grams and is pear-shaped, measuring approximately the size of a fist.
Its length is around 6 to 8 cm and is divided into three regions: cervix, isthmus, and corpus (endometrial cavity).

The cervix is the lowest portion, approximately 2.5 cm in length, connecting the uterus to the vagina.
Contains two openings: internal os (junction with isthmus) and external os (opens during menstruation and active labor).
Functions include effacement (thinning) and dilatation (enlargement) during labor.
Dilation measurement is significant, with 1 inch indicating active labor and a 10 cm diameter signaling imminent delivery.
Comprises one-third of uterine size and maintains an alkaline environment for sperm survival.
Houses mucus-secreting glands that provide lubrication and have bacteriostatic properties.

The isthmus connects the cervix to the corpus, measures about 6 mm, and is a site for low segment cesarean sections during pregnancy.

Male and female reproductive systems share similar structures, functions, and embryonic origins.
Development of reproductive organs is the last among body systems and occurs without fertilization until sexual maturity.

Genotypic sex is established (XX for females, XY for males) and leads to phenotypic sex differentiation.
Physical characteristics develop between 5 to 24 weeks into pregnancy, including the formation of undifferentiated ducts: wolffian (male) and mullerian (female).
Hormonal influences dictate the presence or regression of these ducts; testosterone promotes male traits, while its absence allows female traits to emerge.

The endometrium is the mucosal layer lining the uterus, undergoing monthly regeneration controlled by hormones.
Prepares the uterine environment for fertilization and sustains the embryo before implantation, referred to as decidua during pregnancy.

Multiple ligaments support uterine position including:
- Broad ligament: Stabilizes the uterus and maintains its central position within the pelvic cavity.
- Round ligament: Maintains the position of the uterus, especially during labor.
Additional ligaments in the middle and lower segments include cardinal, uterosacral, and pubocervical ligaments, which prevent uterine prolapse and provide structural integrity.

The primordial follicle matures into a graafian follicle around the 14th day of the menstrual cycle, releasing the mature egg during ovulation influenced by hormonal peaks.
The corpus luteum forms post-ovulation, producing progesterone and degenerating into corpus albicans if fertilization does not occur.

Comprised of pre-ovulatory (menses, proliferative) and post-ovulatory (secretory) stages.
The ischemic phase occurs on days 26 to 28, characterized by constricted arteries and subsequent shedding of the endometrial lining, restarting the menstrual cycle.

Occurs approximately 14 days before the next menstrual period; peak fertility corresponds to this timing.
The lifespan of an egg is 24 to 48 hours, while sperm remains viable for 48 to 72 hours.
Female libido peaks around ovulation, enhancing sexual responsiveness.

Fern test: Observing cervical mucus under a microscope reveals a fern-like pattern due to high estrogen levels, indicating optimal time for conception.