bsci202 exam 3 - reproductive system

• HPG axis: production of gametes and sex hormones is regulated by a sequence of hormonal events involving the hypothalamus, anterior pituitary gland, and ovaries/testes
• how do the hormones of the HPG axis act in the female and male?

  • female and male hypothalamus produce GnRH
  • high levels of GnRH acts on the anterior pituitary to release LH and FSH for both females and males
  • FSH and LH stimulate gonads to release sex hormones
  • female: ovaries release estrogen, progesterone and inhibin
  • male: testes release testosterone and inhibin
• what other parts of the body does testosterone affect?

  growth of hair, deepening of voice, bones and muscles grow, skin thickens and becomes oily, boost basal metabolic rate
• what happens if there is a testosterone deficiency?

  atrophy of accessory organs, semen volume declines, erection/ejaculation are impaired
• what other parts of the body does estrogen affect?

  supports follicle development, affects development of female secondary sex characteristics
• what other parts of the body does progesterone affect?

  stimulates breast maturation and milk production
• what is meant by the statement that women exhibit cyclicity of reproduction, whereas men are not cyclical?

  women have reproductive cycles that are characterized by regular hormonal fluctuations:

  • variations in hormone levels such as estrogen and progesterone
  • this drives the uterine cycle and ovarian cycle

  men do not undergo cyclical hormonal changes related to production:

  • they produce sperm continuously
• what two centers does the female brain have?

  both the surge and tonic centers

  • surge center: responsible for triggering large, abrupt release of GnRH preceding ovulation
  • tonic center: maintains a baseline level of GnRH throughout the menstrual cycle
• what center does the male brain have?

  only the tonic center: maintains a relatively constant level of GnRH to support spermatogenesis
• how do the cyclical secretions in the hypothalamus relate to changes in the ovary and uterus?

  • ovarian cycle: when this surge occurs, ovulation (day 14) occurs
  • uterine cycle: end of proliferative phase (rebuilding of endometrium) at the beginning of the secretory phase (enrichment of blood supply and glandular secretion of nutrients prepare endometrium to receive an embryo)
• what happens each 28 days in a women's ovary and how does that ovarian cycle affect the hormone release from the hypothalamus and pituitary?

  1. ruptured follicle transforms into the corpus luteum, secreting progesterone and some estrogen
  2. these hormones maintain the endometrial lining for implantation of a fertilized egg
  3. if fertilization doesn't occur, the corpus luteum degenerates, dropping hormone levels, initiating menstruation
• what is the role of the hormone inhibin?

  hormone secreted by granulosa cells of developing ovarian follicles that inhibits the secretion of FSH from the pituitary glans
• describe the anatomy of the male reproductive tract from gonad to the end of the urethra:

  seminiferous tubules --> epididymis --> vas deferens (ductus deferens) --> ejaculatory duct --> urethra
• describe the anatomy of the female reproductive tract from gonad to the end of the vagina:

  ovaries --> fallopian tubes --> uterus --> cervix --> vagina
• what is the role of the dartos muscle?

  wrinkles scrotal skin; pulls scrotum close to the body
• what is the role of the cremaster muscles?

  bands of skeletal muscle that elevate testes
• what is a vasectomy?

  cutting and ligating ductus deferens; nearly 100% effective form of birth control
• what is the role of meiosis in the production of gametes?

  reduce chromosome number to 23 chromosomes and create genetic diversity
• what is the role of meiosis in men?

  1 primary spermatocyte --> 4 haploid spermatids (have 23 chromosomes)
• what is the role of meiosis in women?

  formation of one functional egg (ovum) and 3 polar bodies (eventually degenerate)
• what is the role of mitosis in spermatogenesis?

  stem cell --> 1 type A daughter cell and 1 type B daughter cell (primary spermatocyte)

  • FSH modulates spermatogonia division
• what is the difference between type A daughter cells and type B daughter cells?

  type A: remains at basement membrane as a stem cell

  type B: moves toward tubule lumen and continues to become sperm
• what is semen?

  milky-white mixture of sperm and accessory gland secretions
• what is spermatozoa?

  sperm (male gametes)
• what are all the accessory glands in the male reproductive tract and what do each of them contribute to semen?

  • seminal vesicles: 60% of semen (fructose, vitamin C, other substances that nourish and activate sperm)
  • prostate gland: milky fluids; helps activate sperm
  • bulbourethral gland: produces thick, clear mucus (pre-ejaculate); cleanses urethra of acidic urine and serves as lubricant
• how does an erection occur?

  activation of parasympathetic neurons --> nitric oxide release --> relaxation of smooth muscle walls of vessel --> arterioles dilate --> spongy tissue expands --> slow venous drainage --> engorgement of erectile tissues with blood
• what is the role of clitoris?

  highly sensitive sexual organ; can engorge with blood and becomes erect
• what is an oocyte/ovum?

  mature female gamete; large cell containing genetic material
• what is an egg?

  refers to female gamete before/after fertilization
• what is sperm?

  male gametes containing genetic material
• what is the blastocyst embryo stage?

  hollow sphere of cells formed several days after fertilization
• what is polyspermy?

  when more than 1 sperm fertilizes an egg --> lead to abnormal development
• what is fertilization?

  when a sperm penetrates an egg, resulting in the formation of a zygote

  • occurs in fallopian tube
• how does the birth control pill work?

  it contains synthetic versions of estrogen and progestin

  • maintains constant levels of these hormones, suppressing the release of FSH and LH --> ovulation does not occur
• What is mifepristone and how does it work?

  drug that blocks progesterone (needed for pregnancy), causing the uterine lining to breakdown, leading to detachment of the implanted embryo from the uterine wall

  • specifically used for terminating an existing pregnancy before 10 weeks
• what is the order of the type of cells that the zygote goes through when undergoing mitotic cell division?

  totipotent, pluripotent, multipotent, unipotent
• what is a totipotent cell?

  can form any cell in the body AND placenta cells
• what is a pluripotent cell?

  can form any cell or tissue in the body
• what is a multipotent cell?

  can form specific cell types
• what is a unipotent cell?

  only produces 1 cell type (typically used for a specific body system)