Female Reproductive System Anatomy

Female Reproductive Anatomy

Ligaments of the Female Reproductive System

• Broad ligament: A large ligament divided into sub-portions that hold the uterus, fallopian tubes, and ovaries in place.
• Suspensory ligament: Holds the fallopian tube and ovary to the back body wall, primarily supporting the fallopian tube as the ovary is not directly attached.
• Ovarian ligament: Attaches the ovary to the uterus, specifically between the fallopian tube and the uterus.
• Round ligament: Attaches the uterus to the front body wall, preventing it from falling too far forward or backward.
• Uterosacral ligament: Attaches the uterus to the sacrum, preventing it from falling too far forward or backward.

Vagina and Perineum

• Cervix: The round, distal portion of the uterus that projects into the vagina.
• Vagina (or vaginal canal):
  • The site for penis insertion during copulation.
  • The pathway for childbirth.
  • The route for menstrual flow to exit the uterus.
  • Slightly acidic environment to protect against bacteria and viruses.
• Perineal region: The area between the legs.
  • Mons pubis: The anterior portion of the perineal region.
  • Prepuce: Foreskin covering the clitoris.
  • Vestibule: A depression area containing the clitoris, the opening to the urethra, and the opening to the vagina.
  • The vagina is posterior to the clitoris and anterior to the rectum.

External Genitalia (Vulva)

• Vulva: The entire external genitalia, including the mons pubis and labia majora, but not the anus (which is part of the perineal area).
  • Includes the vagina, urethra, and clitoris.
  • It is important to differentiate between the perineum, vulva, and vestibule.
• Mons pubis: The most anterior part of the female genitalia, a bump where pubic hair is located.
• Clitoris:
  • Erectile tissue, similar to the corpus cavernosum in the male penis.
    • Glans clitoris: Enlarged distal portion of the clitoris.
    • Body of the clitoris: Contains corpus cavernosum erectile tissue, located internally.
    • Crus of the clitoris: Lateral flared portions continuous with the corpus cavernosum tissue.
  • Prepuce: A foreskin that covers the body of the clitoris.
• Urethra: The opening to the urethra is posterior to the clitoris.
• Vagina: The opening to the vagina is posterior to the urethra.
• During female development:
  • The clitoris elongates similarly to the penis in males but is then pulled back into the body.
  • Structures that would become the scrotum in males become the labia majora in females.
    • Labia majora: Outer bumps that are skin and contain pubic hair.
    • Labia minora: More internal folds that do not have skin covering or pubic hair; they form the edges of the vestibule.
    • Vestibule: Internal portion of the female external genitalia, including the glands clitoris, urethra, and vaginal opening.
    • Bulb of the vestibule: Erectile tissue equivalent to the corpus spongiosum in males, located underneath the labia minora and around the urethra for sensation/stimulation.
    • Greater vestibular glands: Secrete lubricating fluid during arousal; openings surround the vaginal opening, equivalent to the bulbourethral glands in men.
    • Perirethral gland: The female equivalent to the prostate gland, it encircles the urethra, sometimes referred to as the G-spot, stimulating it through the vagina might induce ejaculation because it produces fluid for some women, but serves no real physiological function.

Muscles of the Perineal Space

• Three layers: transverse aphasia, pelvic diaphragm, and urogenital diaphragm.
• Muscles superficial to the urogenital and pelvic diaphragms are involved in reproductive physiology and sexual response.
  • Ischiocavernosus: Runs along the ischium to the clitoris (cavernosum tissue); equivalent in men and women, goes from the ischial tuberosity up to the pubic symphysis.
  • Bulbospongiosus: Surrounds the vagina; in men, the bulb of the penis elongates into the corpus spongiosum tissue, gripping onto the penis.
  • These muscles contract to grip the penis, assisting with semen expulsion during copulation.

Pelvic Floor Prolapse

• Occurs when pelvic organs push out of the body, more common in women.
• Due to weakened pelvic floor and urogenital diaphragm muscles, resulting in organs shifting downward and potentially exiting the vaginal canal.
• Examples:
  • Bladder, rectum, or uterus (cervix) projecting out of the vagina, which cause issues like bladder not emptying completely, urine getting stuck leading to UTIs, brain telling you to pee more frequently, rectum feeling the need to defecate but not fully emptying, stool retention issues and more.
• Risk factors include childbirth, weight gain, and hormonal changes (especially in older women).
• Prevention: Kegel exercises (contracting pelvic floor muscles) to strengthen these muscles.

Female Sexual Response

• Includes erection and orgasm/climax but no ejaculation.

• Erection Process:

  • Requires stimulation, thoughts and reflexes along with rest and digest state to allow vasodilation, which sends messages to arteries in the clitoris which inturn vasodilate.

• Arousal phase: Arteries in clitoris vasodilate, veins compress, increasing blood flow and dilation of the vagina.

• Plateau phase: Lasts until orgasm.

• Orgasm: Vagina and bulbospongiosus/ischiocavernosus muscles contract, and physiological changes such as increased heart rate, blood pressure, and breathing rate occur.

• Resolution: End of climax.

• Women do not have a refractory period (unlike men), allowing for multiple orgasms because they do not have to go through the resolution phase.

Female Reproductive Physiology

Overview

• Women have two cycles and multiple hormones.
• Ovaries create ova (mature eggs), but the egg does not mature until fertilization; oocytes (immature eggs) are produced in the ovary.
• Two options: no pregnancy or pregnancy, each with different outcomes.

Oogenesis

• Oogenesis is the creation of oocytes (eggs).
• Oogonia: Stem cells (like spermatogonia in males) with 46 chromosomes that undergo mitosis (before birth).
  • Mitosis duplicates oogonia creating lots for the lifetime.
  • Daughter cells are identical to the original and have 46 chromosomes.
• During fetal development (before birth):
  • Oogonia undergo mitosis to create primordial follicles (primary oocyte with 46 chromosomes + one layer of follicle cells).
  • About 2,000,000 primordial follicles are made in each ovary.
• Around the time of creation, many, maybe up to 4,000,000 primordial follicles, the oocyte starts meiosis division.
• The oocyte gets the DNA doubled in preparation to meiosis.
• The primordial follicles essentially don't have 46 chromosomes, it has those chromosomes times two.
• By puberty, many have been reabsorbed, leaving possibly 500,000.
• Each menstrual cycle pulls more than one egg and usually ovulates only one.

Mitosis vs. Meiosis

• Mitosis: Parent cell divides into two identical daughter cells (maintains chromosome number).
• Meiosis:
  • Two rounds of division: meiosis I and meiosis II.
  • A parent cell with 4 chromosomes will double DNA and at conclusion of the first phase (prophase one) can have crossover events.
  • Two daughter cells result from meiosis I, each with half the DNA (but chromosomes still doubled/X-shaped).
  • Meiosis II breaks those chromosomes apart to produce four daughter cells, each with half the DNA and single chromosomes that are arranged depending on the phase.

Oogenesis Before Birth

• As primordial follicles are created, oocytes enter meiosis I and stop in prophase I.
• During infancy and childhood, ovaries are inactive, and primordial follicles remain arrested in prophase I (46 chromosomes x 2).
• May have roughly 2,000,000 primordial follicles per ovary, potentially losing some to reabsorption.

Oogenesis After Puberty (Ovarian Cycle)

• Postnatal cycles occur from menarche to menopause when cycles begin in females.

• After puberty, hormones stimulate primary oocytes to become secondary oocytes that are ovulated.

• Uterine cycle also prepares uterus for embryo implantation.

• Two Cycles working in sync:

  • Ovarian cycle: events in the ovaries (oocyte development).
  • Uterine cycle: changes in the endometrial layer of the uterus.

• Average cycle is 28 days, but length varies.

• Shorter cycles have shortened luteal phases; longer cycles have elongated luteal phases.

  • Follicular phase (approximately 14 days): Follicle cells build around the oocyte, going through meiosis to develop toward the end of development. Primordial follicles develop into primary follicles, then secondary follicles. Only one will become a vesicular (Graafian) follicle, which is the oocyte that can potentially get ovulated.
    • Primordial follicle: a couple of layers, maybe 1 or 2 layers
    • Secondary follicle: maybe has three layers
    • Graphene Follicle: many layers, contains an antrum.

• Luteal phase: Phase after ovulation. Can last 2 weeks for best hormone development and depends on the cycle.
  * Both of these components have a common goal, build the endometrial lining to be ready for fertilization of the oocyte.

Ovarian Cycle (Follicular Phase)

• Hormones are required to continue the development of the oocyte through meiosis.
• The start of the follicular phase takes place around sexual maturity.
• Primary follicle is in prophase I.
• Secondary follicle will also have a primary oocyte but will contain more follicle layers.
• The primordial follicles will develop in this phase to create the other follicles, the endometrium, and to help them with meiosis.
• These will develop until they finally end up in a vesicular follicle (antrum filled space).
• Meiosis starts, primary follicle, follicle cells are added, and this is the process that completes the Meiosis I division. This division also injects the spindle from the oocyte.
• Select one daughter cell to become the egg and the other develops as a polar body.

Ovulation

• The process of the follicle continues until it finally get to this vesicular follicle that has the fluid filled space called the antrum and going through meiosis one.
• Meiosis will end, and when a luteinizing hormone kicks in, ovulation is stimulated.
• With the development of the Graffian follicle, or vesicular follicle you're going to end up with an LH surge, resulting in ovulation.
• Going through follicle development ends and meiosis one finishes so technically what ends up being ovulated is the secondary oocyte.

Developing Meiosis To Complete Fertilization

• Going through LH development meiosis one finishes to have Meiosis two and a create a secondary oocyte.
• During Vesicular follicle and oogenesis meiosis 1 will end creating a first polar body with all cytoplasm pulling to the creation of a secondary oocyte to begin through metaphase 2.
• Reaching the hormone surge and stimulating ovulation the secondary oocyte is ejected to start metaphase 2 and fertilizations is required at this stage.

Transport and Fertilization

• When a secondary oocyte is ejected it comes into contact with the tube and meiosis as it is now being moved.
• Both oocyte and sperm meet and meiosis two needs to have completion otherwise it is in viable and will not complete fertilization.
• Only after sperm enters does the process to get 23 pair complete and for ovum and sperm to fuse to create a Zygote.

Important Pointers of Creating an Egg

• Halting of the process can potentially give a opportunity for genetic disorder to show up later down the road.

Chromosome Errors

• Nondisjunction can create a stall that has chromosomes ending up on the wrong sides of the metaphase plate.
• These chromosomes can add to the risk of genetic disorders like down syndrome.

Luteal Phase (After ovulation)

• After the secondary oocyte is ovulated out, the follicle cells develop into the corpus luteum.
• The corpus luteum secretes hormones affecting the uterine cycle and makes the endometrium thicker.
• After 2 weeks and the oocyte has been fertilized for one week, the endometrial should get time to implant.
• If no implantation happens then menstruation occurs, the corpus luteum degrades into the corpus albicans and stops producing hormones.

Reproductive Hormones and The Endometrial Lining.

The Beginning

• Beginning with releasing hormones in the Hypothalamus which can hit the anterior pituitary gland, releasing with FSH and LH, the same with men.
• FSH and LH helps with the release of testosterone and helps during meiosis.

The Role of Hormones (Fsh, LH, Estrogen)

• Blue (FSH- Follicular): The first development hits the primordial follicles and FSH helps develop it with the production of LH while creating more estrogen releases.
• LH- is secreted during both follicular phase AND in the beginning of the luteal phase and will release the hormone to take with them to make estrogen.
• The spike in LH will help induce the ovulation process leading to development of the corpus luitum.
  *Estrogen will help with high FSH & LH that increase as each get secreted.

Endometrial Layer

• The uterus is thickening to give both time for the oocyte to fertilize and the endometrial layer is given time to implant it's self into place if the lining did not take properly leading to hormone decrease.
• The corpus luteum and the progesterone can lead to a decrease and that can lead to menstruation