AHE II 4.2 - REPRODUCTIVE SYSTEM (PART 2: FEMALES; PUBERTY)

Female Reproductive System and Puberty

• The objective is to identify anatomical structures of the male and female reproductive systems, to understand their bodily roles.

Lecture Learning Objectives

• Visually identify and recall the roles/structures/spaces/associated muscles of the female reproductive organs.
  • Focus on them in fertilization and ovulation pathways.
  • Focus on their analogous reproductive structures in males.
  • Focus on their location compared to other pelvis structures, such as the perineal membrane and pouches.
• Identify and map the vascular supply to female reproductive structures.
• List the layers of the uterus and their characteristics.
• Recall the pathway for fertilization in females.
• Compare and contrast analogous erectile structural elements in males and females.
• State the roles of prolactin and oxytocin in lactation.
• Recall the relevant nerves and their supply that contribute to somatic, parasympathetic, and sympathetic innervation in the reproductive system.
• Describe the initiation of puberty, specifically the role of the brain structures (hypothalamus, anterior pituitary) and hormones (GnRH, FSH, LH.)
• Recall the sequence of the ovarian cycle and relating phases to ovarian structures/cells/follicular development/contributing hormones.
• Describe sperm development and the composition and production of semen.

Spaces in the Female Pelvic Cavity

• Created by visceral peritoneal coverings.
• Uterovesical pouch is between the uterus and urinary bladder.
• Rectouterine pouch is between the rectum and uterus.

Female Reproductive System Components

• Mostly contained within the pelvic cavity and deep to the pelvic peritoneum; expands into the abdominal cavity during pregnancy.
• Major components: ovaries, uterine tube, uterus, vagina, clitoris.
• Associated glands: greater vestibular glands (2).

Ovaries

• Located in the lateral wall of the pelvic cavity, just inferior to the pelvic inlet on the pelvic wall.
• Attachments include:
  • Suspended by mesentery (mesovarium), an extension of the broad ligament (extension of pelvic peritoneum.)
  • Anchored to the lateral uterine wall by the ovarian ligament.
  • Anchored to the pelvic wall via the suspensory ligament.
• Primary function is oogenesis and maturation.
• Mature eggs are ovulated into the peritoneal cavity from the ovaries.
• Cilia on the ends of uterine tubes directs eggs into the uterine tube openings.
• Develop high on the posterior abdominal wall, and descend before birth, bringing vessels/lymphatics/nerves.
• They do not migrate through the inguinal canal into perineum, as in males.
• Round ligament attaches to the lateral portion of the uterus and travels through the inguinal canal; analogous to the spermatic cord in males.

The Uterine Tube

• Collects and transports the egg into the uterus; location of fertilization.
• Extends from the superior aspect of the uterus on each side.
• Enclosed within the mesosalpinx, the upper portion of the broad ligament.
  • Fimbriae: small finger-like projections bordering the infundibulum.
  • Infundibulum: funnel-shaped expansion; closest to the ovary.
  • Ampulla: expansion of the tube leading from the ovary to the uterus.
  • Isthmus: constriction of the tube leading from the ovary to the uterus; closest to the uterus.

The Uterus

• Thick-walled hollow muscular organ.
• If fertilization occurs, it hosts the implantation of the blastocyst and for embryonic/fetal development.
• Located superior to the bladder and rectum, and joins the vagina inferiorly.
• Body: largest portion.
  • Fundus: rounded superior portion.
  • Round ligament- attaches to lateral portion of uterus and travels through inguinal canal; analogous to spermatic cord in males.
• Cervix: inferior most portion that projects into the vaginal canal.
• Walls are composed of three layers: Perimetrium (thin, outer serosa), Myometrium (thick, multiple layers of smooth muscle that expand during pregnancy), and Endometrium (intricate mucosa of epithelium comprised of basal - permanent- and functional -shed after puberty without fertilization- layers).

The Cervix

• Allows the entrance of spermatozoa, and exit for the fetus.
• A dome-shaped cylinder with a narrow central channel; the central canal is continuous with the vagina.
• The inferior end projects into the upper aspect of the vagina.
• The Fornix is a circular indentation surrounding the cervix in the vaginal wall.
• External os: cervical opening into the vagina.
• Internal os: cervical opening into the uterine cavity.

The Vagina

• Functions as a copulatory organ.
• A distensible fibromuscular tube extending from the perineum through the pelvic floor into the pelvic cavity.
• Located between the urinary bladder and rectum.
• The urethra is fused to the anterior vaginal wall.
• Opens exteriorly into the vestibule of the perineum, posterior to the external opening of the urethra.
• Vaginal vault: enlarged internal end of vagina.
• Introitus: external vaginal opening.
• Fornix: a recess formed around the margin of the cervix at the superior end.
• Pathway for Fertilization:
  • Ejaculate/semen is deposited into the vaginal vault during copulation/intercourse.
  • Spermatozoa travel into the external os of the cervical canal; they pass through the cervical canal into the uterine cavity.
  • They continue through the uterine cavity into the uterine tubes.

Female Erectile Tissue

• Clitoris is made of two corpus cavernosa, and the glans clitoris.
• Vestibular bulb connects to the glans clitoris via small bands of erectile tissue (corpus spongiosum in males).
• Greater vestibular gland consists of small mucous glands that lie posterior to the bulb of the vestibule (bulbourethral glands in males); ducts open directly into the vestibule.

Vascular Supply to the Ovaries

• Supplied by branches from the descending abdominal aorta, inferior vena cava, and left renal veins.

Vascular Supply to the Uterus and Vagina

• Extensive arterial supply to internal reproductive organs comes from the internal iliac artery anterior trunk arteries named for their destination.
  • Anterior trunk: includes the umbilical, obturator, uterine, and vaginal arteries.
• Companion veins in the area will empty into internal iliac veins.
• The perineum is supplied by branches of the anterior trunk internal pudendal artery.

Mammary Glands

• Series of ducts and secretory lobules that secrete breast milk for infants; modified sweat glands in the superficial fascia anterior on the pectoral muscles and thoracic wall.
  • Nipple: cylindrical projection at the center with openings for lactiferous sinuses.
  • Areola: pigmented skin around the nipple.
  • Suspensory ligaments: are supportive fibrous connective bands that extend from the skin to the connective tissue overlying the pectoralis major muscle.
• Lobes are subdivisions of the glands, within which are lobules - smaller compartments.
• Alveoli are milk-producing secretory units, from which lactiferous ducts carry outwards towards the lactiferous sinus.
• Lactation is stimulated by prolactin, while milk ejection is induced by oxytocin.

Innervation

• Branches of the pudendal nerve (spinal nerves S2-S4) supply somatic sensory and motor innervation.
  • Perineal nerve and dorsal nerve of clitoris or penis.
• Branches also arise from the sacral and coccygeal plexuses to innervate the levator ani and external anal sphincter muscles.
• Pudendal nerve and its branches: sensory for the skin, motor for skeletal muscles, sphincters, and levator ani.
• S4 and coccygeal branches are sensory for a patch of skin between the anus and coccyx, and motor for levator ani, coccygeus, and the external anal sphincter.
• Autonomic innervation includes the parasympathetic pelvic splanchnic nerve and the sympathetic sacral splanchnic nerve.
• Will contribute to inferior hypogastric plexus (forms rectal, urterovaginal, prostatic, and vesical plexuses)

- Parasympathetic Pelvic Splanchnic Nerve

• Visceral afferents from pelvic viscera and pain from the cervix, also responsible for stimulation of erectile tissue via vasodilation, resulting in an erection.

- Sacral Splanchnic Nerves - Sympathetic

• Visceral motor relating to smooth muscle contraction associated with ducts and accessory glands.
• Important in moving secretions from epididymis and glands to the urethra, as well as vasocontraction for relaxation of erectile tissue.
• Visceral sensory relates to sensations of pain from the cervix and other pelvic organs.

Puberty

• Initiated when the hypothalamus significantly increases GnRH (gonadotropin-releasing hormone) secretion.
• Increased levels of FSH and LH cause the gonads to produce significant levels of sex hormones to start both gamete maturation processes and sexual maturation.
  • Females: estrogen and progesterone.
  • Males: androgens.
• GnRH then acts on specific cells in the anterior pituitary gland to trigger the release of FSH (follicle-stimulating hormone) and LH (luteinizing hormone), which spurs sex hormone production from the gonads and starts gamete/sexual maturation.

Female Puberty - Uterine (Menstrual) Cycle and Menstruation

• At puberty, the hypothalamus secretes GnRH.
• This stimulates the anterior pituitary to release LH and FSH in a cyclical temporal pattern called the ovarian cycle.
• The ovarian cycle consists of the follicular phase, ovulation, and the luteal phase.
  • During the follicular phase about 20 primordial follicles are stimulated into primary follicles, granulosa releases hormones to inhibit FSH and estrogen. The primary follicles then become secondary and eventually vesicular. Antrum increases in size.
  • In ovulation, increased LH causes a secondary oocyte to release from the vesicular follicle in the Fallopian tubes.
  • In the luteal phase, LH stimulates the remaining Granulosa and forms corpus luteum. Secretes prog/estro to prepare/stabilize uterine lining for implantation.
• If fertilization does not occur
  • Corpus luteum degrades to corpus albicans
  • Progesterone/Estroges drop
  • Uterine walls shed
• If fertilization occurs, implant -Embryoblast begins to screte hCG, developing from Fall, hCG promotes for corpus luteum hormone secretion, progesterone for uterine development.

Female Puberty: Follicular Development

• Classified by ovarian structure/type of oocyte/time of appearance.
• The order of transformations goes:
  • Primordial/Primary follicle (fetal period)-->Primary Oocyte/Primary follicle (puberty)-->Primary Oocyte/Secondary Follicle (puberty)-->Secondary oocyte/Vesicular (Graffian) follicle (puberty)
• Puberty allows the formation of corpus luteum and corpus albicans.

Spermatogenesis/Male Puberty:

• Begins with spermatogenesis or Sperm Creation (puberty) to maturation in spermatogenesis (Spermatids into spermatoza), sperm then leave and are further matured in epididymis
• Semen = sperm + fluid.
• Fluids come from prostate gland, bulbo urethral, and seminal vesicles.
• Sperm created in testes and matured in epididymis.
• Ejaculate contains between 200-500 million sperms.