1. Reproductive Physiology Flashcards
(34 cards)
What two systems are connected in males? What impact does this have?
The testes is connected with the urinary system which also deals with the provision of sperm.
This means that if one of these systems malfunctions it is likely to impact the other one
What are the two main functions of the male reproductive tract?
The provision of androgens (mainly testosterone) to initiate and sustain the male sexual features
The production of mature sperm.
How do testosterone levels change in a male as he ages?
Testosterone has an important function before birth but this is reduced in the first 12 years of life where testosterone is greatly reduced. Kicks in again during puberty
Outline the structure of the male reproductive tract and sperm secretion
The male reproductive tract can be seen as the epididymis, going through the vas deferens which loops around the bladder and joins the ureter in the penis where the sperm will come out
There is one epididymis within each scrotal sac. Sperm are released from the testis and stored here prior to ejaculation. At ejaculation sperm pass through the two Vas Deferens (which are contractile), and is mixed with fluid from the seminal vesicles. The fluid then leaves the ejaculatory duct, and passes into the urethra where it mixes with secretions from the prostate gland.
What are the main hormones that control male reproduction and where are they released from?
Gonadotrophin releasing hormone (GnRH) – from the hypothalamus (acts on the pituitary)
Luteinising hormone (LH) and Follicle stimulating hormone (FSH) – from the anterior pituitary
Testosterone (T) – Testis
What is the initial hormone that is released which causes the secretion of other male hormones?
GnRH produced in hypothalamus, and acts on the anterior pituitary to give rise to FSH and LH (enter the bloodstream, but only have effects on the testes).
How are LH and FSH released from the anterior pituitary?
LH release is pulsatile and FSH also has some pulsality
Where does LH act? What does it give rise to?
Leydig cells: lie outside of the seminiferous tubules in the interstitial compartment of the testes. They are the primary source of androgens in ALL male mammals. This gives rise to testosterone, which is released into the testes. LH acts here.
How is testosterone production regulated?
The testosterone produced by the leydig cells negatively feedbacks to the hypothalamus to suppress the production of GnRH and LH causing a fall in testosterone production
Where does the FSH produced by the anterior pituitary act? What is its function?
FSH acts on sertoli cells in the seminiferous tubules which support the process of spermatogenesis as they convert precursors of sperm into mature sperm. FSH is critical for all reproductive processes in males. Function of Sertoli cells is driven by FSH and testosterone together.
How is FSH production controlled?
Sertoli cells produce inhibin, an inhibitory peptide that acts on the HPA and inhibits the production of FSH
What are the two general parts of the testes?
The testes is made up of two compartments – the interstitial compartment where the Leydig cells are and the seminiferous tubules where sperm are produced
Why are there more primary spermatocytes than mature sperm?
In the initial stages of sperm division, we start of with normal mitotic division so the cells remain diploid but in the latter stages there is a switch to miotic division so haploid sperm are produced
As mitosis produces four cells, there are many more cells that are developed through mitotic division that the later miotic division. This means there is a very large pool of primary spermatocytes which then converge into mature sperm
What happens to sperm with increasing age?
Sperm quantity and quality generally decreases with increasing age
What happens to egg cells with increasing age?
Egg quality generally decreases with increasing maternal age – at around 35 years is the point where this is most noticeable
What are the functions of LH and FSH in women?
FSH stimulates (some) development of ovarian follicles and 17beta-oestradiol synthesis LH stimulates progesterone production and also has a role in sustaining oestradiol The steroids regulate uterine endometrium during the menstrual cycle
What are the hormones involved in the female reproductive tract? Where are they released from and where do they act?
LHRH released from the hypothalamus, going to the pituitary to release LH
LHRH also drives FSH production from the pituitary gland.
LH and FSH act on the ovaries. The ovaries give rise to progesterone and oestrogen (which themselves feedback on the hypothalamus and pituitary gland). These then act on the uterus rather than the LH and FSH itself.
What are the different phases of the ovarian cycle?
Follicular phase - first 10 days
Mid-cycle/Ovulation
Luteal phase - last 10-15 days
How do the hormone levels and their actions change throughout the ovarian cycle?
In the follicular phase the main follicle is being matured in the ovaries. GnRH is produced causing LH and FHS production. The ovaries are stimulated with estradiol which negatively feedbacks to the hypothalamus.
In the mid-cycle, the system changes. Oestradiol begins to exert a positive feedback effect, to enhance the activity of the hypothalamus and pituitary to release GnRH instead of suppressing it leading to LH/FSH being produced. There is the LH SURGE at this point in the cycle which causes the switch in mechanism to a positive feedback one. The ovary is still making oestradiol at this point.
The hormones continue to increase - this is the buildup to ovulation
In the luteal phase (occurs once ovulation has taken place), the feedback mechanism goes back to negative. However, progesterone is mainly being produced instead of oestrogen from the ovary - previously both hormones were being produced from the ovaries but oestrogen was dominant. There is still negative feedback.
What happens to hormones during pregnancy?
Progesterone levels RISE, and continues to do so for the whole length of pregnancy
This switches off the whole hypothalamic-pituitary axis
The menstrual cycle completely comes to a halt during pregnancy (due to progesterone –ve feedback)
How does the thickness of the endometrium vary?
At minimum, the endometrium is between 2-4 mm thick and at maximum it can be 2-16mm thick
What causes the thickness of the endometrium to change?
The proliferation of the endometrium is driven by the steroids produced in the developing follicle
The high levels of oestrogen produced by the follicle in the first part of the ovarian cycle feed into the early part of the development of the endometrium whereas the combination of progesterone and oestrogen feeds into the second part of the endometrial cycle and further increases the thickness of the lining
Why is a thick endometrium lining needed?
This peak thickness of the endometrium is when implantation would be expected
What are the two parts of the endometrial cycle and which hormones control them?
The first part of the endometrial cycle is the proliferative phase, led by oestrogen, and the second part is the secretory phase, led by progesterone
