LAB 8 NOTES

Female Reproductive Anatomy: Internal Organs

• Ovaries: Primary sex organs that produce oocytes and hormones.
• Structures of the reproductive tract:
  • Uterine tubes (fallopian tubes): Extend from ovaries to the uterus.
  • Uterus: Site of embryo implantation and development.
  • Cervix: Narrow, inferior end of the uterus that connects to the vagina.
  • Vagina: Copulatory organ and birth canal.

Internal Structures: Ovaries

• Carry out oogenesis: Production of female gametes (ova or eggs) and sex steroid hormones (estrogens and progesterone).
• Ovarian follicle: Contains an immature egg surrounded by follicle cells.

Internal Structures: Uterine Tubes

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Internal Structures: Uterus

• Situated between the bladder and the rectum.
• Three regions of the uterus:
  • Fundus: Superior rounded region above the entrance of the uterine tubes.
  • Body: Major portion of the uterus.
  • Cervix: Narrow inferior portion.
• Wall of the uterus:
  • Endometrium: Innermost layer, a thick mucosal lining where a developing embryo will implant and develop.
    • The superficial stratum functionalis is sloughed off every 28 days in response to ovarian hormone cycles.
  • Myometrium: Composed of bands of smooth muscle.
  • Perimetrium: Outermost, serous layer.

Female Reproductive Anatomy: External Genitalia

• Mons pubis: Fatty pad overlying the pubic symphysis.
• Labia majora (sing. labium magus): Larger, pigmented skin fold (homologous to the scrotum).
• Labia minora (sing. Labium minus): Smaller skin fold enclosed by labia majora.
• Vestibule: Area enclosed by labia minora, containing the clitoris, urethral orifice, and vaginal orifice.
• Clitoris: Composed of sensitive erectile tissue (homologous to the penis).
• Urethral orifice: Outlet for urine.
• Vaginal orifice: Opening into the vaginal canal.
• Hymen: Thin mucous membrane that partially or completely closes the vaginal opening.
• Greater vestibular glands: Secrete lubricant (homologous to bulbourethral glands).

Mammary Glands

• Primary function: Produce milk for infants.
• Estrogens and progesterone stimulate breast growth during puberty and pregnancy by increasing alveoli and lactiferous ducts.
• Structures:
  • Alveoli: Mammary glands that produce milk during lactation.
  • Nipple: Structure designed to allow infant to feed.
  • Areola: Pigmented region around each nipple.
  • Lactiferous ducts: Transport milk from alveoli.
  • Lactiferous sinus: Stores milk.

Oogenesis

• Occurs in the ovary.
• Before birth, oogonia (primitive stem cells) undergo mitosis to produce primary oocytes.
  • Primordial follicle: Primary oocyte surrounded by pre-granulosa cells.
  • Primary oocytes have started meiosis I and are arrested in prophase I.
• At puberty, monthly cycles begin where one primary oocyte will mature and continue meiosis.
• Completion of meiosis I gives rise to a secondary oocyte.
  • The secondary oocyte is ovulated; called an ovum once it is fertilized.
  • Secondary oocyte is arrested in metaphase II; will only complete meiosis if fertilized.

The Female Cycles

Ovarian Cycle

• Monthly fluctuation in estrogens and progesterone (hormones produced by the ovaries).
• Monthly maturation of a primary oocyte into a secondary oocyte.
• One secondary oocyte, arrested in metaphase II, will be ovulated.
  • Will complete meiosis II if fertilization occurs.
• Induced by LH and FSH.

Uterine (Menstrual) Cycle

• Monthly build-up of the stratum functionalis of the endometrium.
  • Will be sloughed off if no embryo implants into the endometrium.
• Induced by the ovarian hormones (estrogens and progesterone).

Reproductive Hormones: Females

• Estrogens and progesterone are produced by the ovaries (and by the corpus luteum when fertilization occurs).
• Estrogen:
  • Promotes the development of female secondary sex characteristics.
  • Regulates changes in the uterine lining during the menstrual cycle.
  • Helps prepare mammary glands for lactation.
• Progesterone:
  • Regulates changes in the uterine lining during the menstrual cycle.
  • Maintains uterine musculature in a quiescent state during pregnancy.
  • Helps to prepare the breast tissue for lactation.
• Prolactin is produced by the anterior pituitary.
  • Stimulates breast development.
  • Maintains lactation by the mammary glands after childbirth.
• Gonadotropins are produced by the anterior pituitary.
  • Follicle Stimulating Hormone (FSH)
    • Stimulates ovarian follicle maturation and production of estrogens.
  • Luteinizing Hormone (LH)
    • Triggers ovulation.
    • Stimulates ovarian production of estrogen and progesterone.
• Human Chorionic Gonadotropin (hCG) is produced by the placenta.
  • Maintains the corpus luteum and promotes the secretion of estrogen and progesterone by the corpus luteum.

Reproductive Hormones: How the Birth Control Pill Works

• The pill is usually a combination of estrogen and progestin.
  • Some pills are progestin only.
• The pill mimics pregnancy to suppress FSH and LH.
  • Estrogen stimulates the production of prolactin.
  • Prolactin suppresses gonadotropin-releasing hormone (GnRH).
  • Without FSH and LH, ovarian follicles don't mature, and ovulation does not occur.
• Progestin is a synthetic form of progesterone.
  • Thickens mucus in the cervix, making it difficult for sperm to enter the uterus.
  • Also suppresses ovulation, but not as consistently as estrogen.
  • Thins the lining of the uterus, discouraging implantation of a zygote.

Male Reproductive Anatomy: Testes

• Located inside the scrotum, hanging outside the body attached to the perineum.
• Function:
  • Spermatogenesis.
  • Production of the male sex hormones: testosterone and other androgens.
• Intra-scrotal temperature must be at 34-36ºC for optimal sperm production.
• Seminiferous tubules: Highly coiled tubules inside testes are sites for sperm production.
  • Produce 100-400 million sperm per day.
• Interstitial cells: Produce the androgens.

Male Reproductive Anatomy: Sperm Ducts

• Epididymides (sing. Epididymis)
  • Connect testes to the vasa deferentia.
  • Sites of spermatogenesis: sperm mature and gain the ability to swim.
  • Sperm storage.
• Vasa deferentia = ducti deferentia (sing. Vas or ductus deferens)
  • Transports sperm from epididymis to ejaculatory ducts.
  • Enclosed in the spermatic cord (with deferential and nerves).
  • Vasectomy = cutting of both vasa deferentia.
• Ejaculatory ducts
  • During ejaculation, receive sperm from vasa deferentia and secretions from the seminal vesicles and the prostate gland.
• Urethra has three sections
  • Prostatic, membranous (intermediate), and penile (spongy) urethra.

Male Reproductive Anatomy: Glands

• Seminal vesicles (seminal glands)
  • Secrete 70% of seminal fluid.
  • Secretion is viscous, alkaline, and contains fructose used by sperm to produce energy.
  • Alkaline fluid also neutralizes acids in the female reproductive tract.
• Prostate gland
  • Secretes 30% of seminal fluid.
  • Secretion is a milky fluid that activates sperm.
• Bulbourethral glands
  • Secrete a thick, clear, alkaline fluid which neutralizes acidic urine residue in the urethra.

Male Reproductive Anatomy: Penis

• Composed of three cylindrical erectile tissues with large vascular spaces.
  • 2 dorsal corpora cavernosa.
  • 1 ventral corpus spongiosum.
• Function: copulatory organ that delivers sperm to the female reproductive tract.
  • Penile erection: penis becomes engorged with blood as the vascular spaces in the erectile tissues fill with blood.
• Shaft: terminates at the glans, the expanded tip of the penis.
• Prepuce (foreskin): a cuff of loose skin surrounding the glans.
  • Can be removed in a surgical procedure known as circumcision.

Spermatogenesis

• Spermatogonia (sing. Spermatogonium) undergo mitosis.
• Primary spermatocyte: undergoes the first meiotic division to give two secondary spermatocytes.
• 2 secondary spermatocytes: undergo a secondary meiotic division to give 4 spermatids.
• Spermatids: undergo spermiogenesis to develop into spermatozoa (sing. Spermatozoon; the functional sperm).

Reproductive Hormones: Males

• Gonadotropins are produced by the anterior pituitary.
  • Follicle Stimulating Hormone (FSH)
    • Stimulates sperm production.
  • Luteinizing Hormone (LH)
    • Promotes testosterone production.
• Testosterone is produced by the testes.
  • Promotes maturation of the reproductive system accessory structures.
  • Promotes the development of male secondary sex characteristics.
  • Responsible for libido.
• Prolactin is produced by the anterior pituitary, but is primarily active in females.
  • Can stimulate testosterone in males.