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37 Cards in this Set

  • Front
  • Back
What are the important functions of the Epididymis?
1. Sperm Storage
2. Sperm Maturation (motility)
3. Fluid Absorption
4. Protein secretion
What is the effect of castration on the prostate?
Decreases prostate size/ weight
What is the effect of Testosterone administration on prostate?
Increases prostate size/ weight
What are the components of the final volume of ejaculate?
Testis/epididymis: 10%
Prostate: 30%
Seminal vesicles: 60%
What is the functional importance of Leydig cells in the testis?
They produce testosterone (from cholesterol --> pregnenolone --> androstenediol --> T; under stimulation by LH)
What happens to testosterone in the sertoli cell?
1. Testosterone can be transported to the lumen via Androgen Binding Protein (ABP)
2. Testosterone can be converted to oestradiol via aromatase enzyme
3. Testosterone can be converted to Dihydro-testosterone via 5-alpha reductase enzyme
Where are androgens/oestrogens produced in the female?
- Androgens are produced by thecal cells in the ovary
- androgens are converted to oestrogens by granulosa cells in the ovary
What are the feedback effects of Progesterone?
Progesterone exerts negative feedback on the anterior pituitary gland and the hypothalamus, to decrease synthesis and secretion of GnRH, LH and FSH
What are the feedback effects of inhibin?
Inhibin exerts negative feedback only at the level of the anterior pituitary to inhibit the secretion of FSH
What are the feedback effects of Oestrdiol?
Acute high levels of oestrogen (during the follicular phase, prior to LH surge and ovulation) produce positive feedback on GnRH, LH and FSH production at the hypothalamus and anterior pituitary
During the luteal phase oestrogen exerts strong negative feedback at the SP and hypothalamus to reduce gonadotrophin secretion
Where is oestrogen produced in the female?
- Oestrogen is converted from androgen to oestrogen in granulose calls of the ovary (during the follicular phase)
- Oestrogen is also produced by the corpus luteum during the luteal phase
What is the main site of production of progesterone in the female?
The corpus luteum (during the luteal phase)
What processes determine the development of the ovaries throughout the life of a female?
1. Meiosis starts before birth but is arrested at prophase 1 (primordial follicle)
2. Meiosis (of 1 ovary) resumes at puberty through the stimulus of the LH surge
3. Follicular development is completes at ovulation (ovum)
What is the structure of a Primordial follicle?
Oocyte surrounded by granulosa cells
What is the structure of a Primary Follicle?
Fully grown oocyte surrounded by granulosa cells that start to proliferate and thecal cells start to develop
What is the structure of an antral follicle?
Antral (secondary) follicle – Antrum (fluid filled sac within granulose cells) begins to form
What is the structure of a Graafian follicle?
Oocyte is surrounded by zona pellucida, granulosa cells and antrum which dominates follicle, thecal cells surround follicle
Explain he two cell hypothesis of steroid production in females
Thecal cells (stimulated by LH) synthesise androgens
in Granulosa cells FSH stimulates aromatase production which converts androgens to oestrogen
How does the LH surge induce ovulation?
- Reduces steroid metabolism (increased local E and P, increased prostaglandins which are important for inflammation)
- Increased vasoaction and vasodilation (increased blood into follicle)
- Increased collagenases which allow follicle to burst
What is the effect of oestrogen on the endometrium during the female reproductive cycle?
Oestrogen is responsible for the proliferation of the endometrium during the follicular phase, and its maintenance (with progesterone) during the luteal phase
What is the function of progesterone on the uterus
During the luteal phase progesterone is involved in maintenance and stimulation of secretions of the endometrium
Where is GnIH produced and secreted?
GnIH is produced by the dorsomedial nucleus of the hypothalamus and released into the hypophyseal portal blood system. It also acts directly on GnRH neurones.
What is the main action of kisspeptin?
Kisspeptin stimulates GnRH and thus LH secretion
Where does kisspeptin act (and can it be blocked)?
It acts via Kiss1 receptors on GnRH neurones in the hypothalamus (can be blocked by receptor antagonist)
How is kisspeptin production regulated?
Kiss1 mRNA is regulated by Oestrogen, which exerts negative feedback on its production
Where are kisspeptin cells located?
In the Preoptic area and the Arcuate Nucleus
Where are positive and negative feedback of kisspeptin regulated?
Kisspeptin cells in the ARC (and POA) mediate the positive feedback control of GnRH
Negative feedback control of GnRH is mediated only by kisspeptin cells in the ARC
What is the relationship between kisspeptin and puberty?
Treatment with Kisspeptin can cause the inset of puberty.
What is the function of GnIH and where is it produced?
GnIH is produced in the dorsomedial nucleus in the hypothalamus, and acts both directly on GnRH neurones and the anterior pituitary (via the HPBS) to prevent the secretion of LH.
What changes in hormone production occur at the onset of puberty?
Puberty is characterised by the re-activation of pulsatile GnRH pulsatile secretion, which in turn stimulates LH, FSH and sex steroid production. These pulses occur initially irregularly at night.
What are the possible mechanisms that activate GnRH secretion across puberty?
o Gonadostat Theory: During juvenile pause the brain is highly susceptible to negative feedback from steroids (ie very little steroids are required to produce a negative feedback effect)
o Reduced inhibitory input to GnRH neurones: inhibitory neurones and neurotransmitter such as GABA have a strong influence during the pre-pubertal period, but levels decrease at puberty
o Increased excitatory input to GnRN neurones (eg kisspeptin)
What are the external cues for puberty in sheep?
o Season – ewes that are short day breeders become reproductively active when day length starts to shorten, puberty onset more likely at this stage
o Presence of the opposite sex: introduction of a male or male pheromones can advance the onset of puberty in sheep (dependant on age)
What are the internal cues for puberty in sheep?
o Adiposity: insufficient fat content can inhibit pubertal development, and excessive adiposity can cause early pubertal development.
o Breed of sheep: depending on their time of birth, lambs may or may not be ready for puberty during the breeding season. If they are too young, puberty is delayed until the next year
Why are levels of fat important in reproduction?
Until a critical fat mass is reached, there is not enough energy to support reproduction. During pregnancy and particularly lactation, energy demands are extremely high.
What is the function of Leptin?
Leptin acts at the hypothalamus to signal that sufficient energy is present for reproductive activity, and thus increases GnRH and therefore gonadotrophin production. Leptin deficiency results in the lack of a functional hypothalamo pituitary gonadal axis, the failure to undergo puberty and thus infertility (obesity also a result).
What does leptin replacement therapy achieve?
Leptin replacement therapy restores LH and FSH secretion to normal levels, reduces food intake and thus restores reproductive function.
What is the relationship between leptin and puberty?
Leptin is permissive in the onset of puberty, and is required for pubertal development, but is not the trigger of puberty.