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Flashcards in Reproductive physiology Deck (30)
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What are the 2 main functions of the male reproductive system?

The provision of androgens (primarily testosterone) to initiate and sustain the necessary male phenotype The production of mature sperm


Describe the male Hypothalamic-gonadal axis

  • Hypothalamus produces GnRH
  • Gonadotrophs in anterior pituitary release LH and FSH
  • LH acts on Leydig cells to promote testosterone production
  • Testosterone acts to inhibit gonadotroph production in the hypothalamus and anterior pituitary 
  • FSH and testosterone bind to androgen binding protein (ABP)
  • ABP activates Sertoli cells
  • Sertoli cells produce inhibin which inhibits gonadotroph production in the anterior pituitary


Where are leydig cells found?

Interstitial compartment of the testies


How is GnRH, LH and FSH released?

GnRH and LH are released in a very pulsatile fashion

FSH is released in a less pulsatile way and is more constant


What is the function of sertoli cells?

  1. Produce inhibin
  2. Support development of sperm precursors into mature sperm


Where is sperm produced?

Seminiferous tubules


What is the pathway of sperm in ejaculation?

  1. Sperm produced in seminiferous tubules
  2. Stored in epididymis
  3. Pass into 2 vas deferens (contractile)
  • Mixed with fluid from seminal vesicles
  1. Leaves via the ejaculatory duct
  2. Enters the urethra
  • Mixes with the secretions of the prostate gland


Does sperm change with age?


Sperm quantity and quality generally decreases with increasing age


When does female reproductive function generally stop?

Aprox 45 years old


Do female eggs change with age?


Egg quality generally decreases with increasing age – gradual decline


Describe the female Hypothalamic-gonadal axis

  • Hypothalamus produces GnRH

  • Gonadotrophs in anterior pituitary release LH and FSH 

  • FSH stimulates (some) development of ovarian follicles & 17b-estradiol synthesis

  • LH stimulates progesterone production

  • FSH and LH negatively feedback at the hypothalamus and anterior pituitary


How does the female Hypothalamic-gonadal axis change during mensturation?

  1. Follicular phase:
  • The dominant hormone produced by ovary is ESTRADIOL
  • Estradiol has NEGATIVE feedback on the anterior pituitary and the hypothalamus
  1. Midcyle
  • The dominant hormone produced by ovary is ESTRADIOL
  • Estradiol has POSITIVE feedback on the anterior pituitary and the hypothalamus
  1. Luteal phase
  • The dominant hormone produced by ovary is PROGESTERONE
  • Progesterone has NEGATIVE feedback on the anterior pituitary and the hypothalamus


Which phase in menstruation can change length?

Luteal phase


What is a common cause of change in menstruation length and how does it change it?

Stress - prolongs it


What causes endometrial remodelling?

Oestrogen begins the process of endometrial hyperplasia in the proliferative phase

Combination of progesterone and oestrogen is more effective at promoting endometrial hyperplasia


What are the phases of endometrial remodelling?

Give a time course

Day 1-5: Menstrual phase (5 days)

Day 5-14: Proliferative phase (9 days)

Day 14-27: Secretory phase (13 days)

Day 27-28: Ischemic phase (1 day)


What is the pathway for maturation of an ovarian follicle?

  1. Primordial follicle containing primary oocyte
  2. Primary follicle
  3. Antral follicle
  4. Ruptured follicle
  5. Corpus luteum
  6. Degenerating corpus luteum


How does body temperature change during the menstrual cycle?

Raises aprox 0.5oc after ovulation (day 14)


When does the maturation of ovarian follices take place?

  1. Primordial follicle -produced during intrauterine life
  2. Meiosis 1 is paused at prophase until puberty
  3. Meiosis 2 is paused at metaphase until fertilisation


How long does folliculogenesis take?

Aprox 3 months from Primary follicle to graffian follicle


How long does the oocyte last once it is released from the ovary?

24 hours


Which ovary releases an oocyte each month?

Usually alternates

Sometimes can release one from each (non-identical twins)


How does fertilisation occur?

  1. Passage of sperm through uterus

  2. Passage of sperm into Fallopian tube

  3. Swim from there to Fallopian tube ampulla

  4. Survival of the fittest (a few days)

  5. Capacitation – takes time within uterus

  • Capacitation is essential preparation before the sperm meet the oocyte

  1. When reach fallopian tubes are chemo-attracted to egg
  2. Sperm produce enzymes to degrade outer layers of egg
  • Acrosome reaction: penetration of Zona Pellucida (& Coronal cells)


What happens when a sperm enters an egg?

  1. Calcium flux

  2. Meosis of maternal chromosomes resumes, forming female pronucleus (23 chromatids), and 2nd polar body.

  3. Change in Zona Pellucida to prevent additional sperm fusing with zygote.

  4. Sperm chromosomes decondense to form male pronucleus (23 chromatids).

  5. Chromatids in both pronuclei are duplicated

  6. They align on the mitotic spindle, and are separated into 2 identical ‘daughter’ cells (1st cleavage division of the embryo).


How is the brain linked to sex?

  1. Mesolimbic dopaminergic system - Pathway for reward and pleasure
  • Encourages intercourse and thus the continuation of our race
  1. Nigrostriatal tract - control of movement
  2. Hypothalamus and pituitary - neuroendocrine pathways regulating fertility and pregnancy


What is the mechanism of an erection?

  • Spinal cord initiates increased parasympathetic activity of efferent pudendal nerve fibres to pudendal artery
  • Increases the activity of Nitric Oxide Synthase (NOS), and hence nitric oxide (NO)

  • NO increases production of cyclic GMP which induces dilatation of arterial smooth muscle.

  • counteracts sympathetic-maintained myogenic tone

  • increases blood flow in corpus cavernosum

  • which compresses the dorsal vein, restricting the outflow of blood


How is the urethra protected from increased pressure during an erection?

The urethra is protected from increased pressure by surrounding corpus spongiosum (less turgid)


How does viagra prevent loss of an erection?

  • Cyclic GMP is normally de-activated by a phosphodiesterase enzyme, and this will reverse the changes leading to penile erection.
  • Viagra inhibits the phosphodiesterase, thus potentiating the effects of cyclic GMP.


What can cause an erection?

  1. 'Sexy thoughts' activate the limbic system which in turn stimulates the spinal cord
  2. Tactile stimulus on the penis stimulates afferent pudendal nerve fibres to the spinal cord


What happens mid-cycle to allow sperm to enter the uterus?

  • Cervical mucus is normally hostile to sperm
  • This forms a physical barrier to sperm
  • Cervical mucus changes at mid-cycle
  • This change permits sperm to enter uterus