Reproduction

Pituitary gland (aka hypophysis)

  • Pea sized organ located a the base of brain ; 2 lobes

    • Adenohypophysis (anterior)

    • Neurohypophysis (posterior)

    • Regulated by the hypothalamus with negative feedback by circulating hormones

    • Adenohypophysis produces 6 hormones

      • Tropic hormones: prolactin, growth hormone, ACTH, luteinizing hormone LH, FSH (follicle stimulating hormone, TSH thyroid stimulating hormone

      • Neurohypophysis produces antidiuretic hormone (ADH) and oxytocin

Growth hormone aka somatotropin

  • Produced by the anterior pituitary 

  • Affects all parts of the body promoting growth of tissues (liver, heart, kidneys) and bone

  • Stimulates growth of long bones before puberty

  • After puberty, GH promotes tissue replacement and repair

    • Diseases include:

      • Pituitary dwarfism

      • Gigantism

      • Acromegaly

Gonadotropins

  • Produced by anterior pituitary

  • Lutenizing hormone (LH) and follicle-stimulating hormone FSH

  • Regulates sexual development and function

  • Fsh stimulates egg and sperm production

  • LH stimulates overies to produce testosterone

  • LH surge signals ovulation

The reproductive system: require structural integrity, neurologic and hormonal process

  • Male reproductive tract structural integrity

    • Testess, epididymis, vas deferens, seminal vesicles,prostate , and penis

    • Also responsible for urine elimination (female system isn’t)

  • Do not follow cyclical pattern, hormone secretion remain constant throughout life

  • Androgens: male sex hormones

    • Hypothalamus stimulates GnRH, which stimulates anterior pituitary to o lease LH and FSH

    • LH acts on leydig cells in testes to produce testosterone excess testosterone triggers negative feedback with hypothalamus

  • Spermatogenesis

    • Occurs in the seminiferous tubules of the testes

    • Requires a  2-3 cooler temperature than core body temperature

    • Maturation of sperm takes place in 60 days

    • Exit body through urethra

  • Female reproductive tract structural integrity

    • Required to achieve reproduction

    • External genitalia protection and lubrication

    • Internal reproductive structures

    • Cervix offers some protection to infection

    • Uterus : lining proliferates and sloughs in preparation for absence of pregnancy, muscle contract for childbirth

    • Fallopian tubes, from uterus to overies

    • Overies

  • Ovarian produced hormones

    • Needed for reproduction

    • Stimulated by secretion from hypothalamus (GnRH) and anterior pituitary (LH, FSH)

    • Secreted in monthly cyclical pattern

    • Female sex hormones: 

      • Estrogens: estradiol, estrone, estriol

        • Primary female sex hormone

        • Secreted throughout monthly menstrual cycle by ovary

        • Major actions

          • Reproductive organ development

          • Body fat contour distribution

          • Breast development and skeletal growth during puberty

          • ovulation/support of pregnancy

          • Cervical mucus alterations

          • Axillary and pubic hair growth

          • Female skin maintenance

          • Decreased bone resorption

          • Retention of sodium and water

      • Progesterone

        • Secreted by ovary from ovulaitotn to the onset of menses

        • Functions:

          • Thickens lining of uterus to support implantation

          • Helps maintain pregnancy by relaxing smooth muscles

          • Elevated core body temperatures, can induce nausea, headaches, indigestion, etc

      • Androgens

  • Ovulation:

    • Releases multiple follicles

    • Produce of releasing a oocyte from ovarian follicle

    • Occurs once every 21-40 days for most women

    • Relies on hormone regulation, 2 phases:

      • Follicular phase (1st half)

      • LUteal phase (2nd half)

    • Follicles: epithelial capsules that hold oocytes

      • Primary (inactive) vs secondary (active) follicles 

      • During ovulation, ~ 10 primary follicles are stimulated by FSH and LH to become secondary

    • Follicular phase

      • Secondary follicles enlarge and can secrete estrogen and progesterone

      • One secondary follicles become dominant by secreting large amounts  of estrogen

      • Rest of follicles become atrophic

      • Dominant follicle secretes estrogen → triggers pituitary to decrease FSH

      • LH levels surge , causing oocyte to break from fluid filled follicle (ovulation)This process is essential for the release of the mature egg, which can then be fertilized by sperm.