Reproductive Physiology Flashcards
The two main functions of The Human Male Reproductive System are?
- provision of androgens (primarily testosterone) to initiate and sustain the necessary male phenotype
- production of mature sperm.
Seminiferous tubules produce what?
Leydig (interstitial) cells produce what?
The Testis contains seminiferous tubules (which produce sperm) and Leydig (interstitial) cells which produce testosterone (and some other androgens).
Describe the storage and course of sperm at ejaculation.
- Sperm are released from the testis and stored in the epididymis prior to ejaculation.
- At ejaculation sperm pass through the two Vas Deferens (which are contractile), and are 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.
Function of sertoli cells in the seminiferous tubules =?
Nutritional and hormonal support for spermatogenesis
What hormones stimulate the Leydig cells and Sertoli cells?
LH stimulates testosterone production
FSH and testosterone sustain Sertoli cell function
*Note: remember that LH/FSH are stimulated by GnRH
Describe the negative feedback control within this system
Testosterone (from Leydig cells) negatively feeds back at the level of the hypothalamus and anterior pituitary
Sertoli cells also produce a small amount of inhibin which negatively feeds back at the level of the anterior pituitary
Describe the sequential steps of spermatogenesis (in the seminiferous tubule)
- Primordial germ cell/spermatogonium 44+XY (diploid), near the basement membrane, undergoes mitotic division.
=> - Primary spermatocyte 44+XY (diploid).
undergoes 1st meiotic division.
=> - Secondary spermatocyte 22+X, 22+Y (haploid) undergoes 2nd meiotic division.
=> - Spermatids 22+X, 22+Y (haploid).
=> - Further maturation to Spermatozoa 22+X, 22+Y (haploid) which are released into lumen.
The overall production of sperm from both testes is estimated to up to
200 million sperm per day.
When does the process of spermatogenesis start and for long does it normally continue for? How does the quality and quantity of sperm change with increasing age?
Once the process of spermatogenesis starts (at puberty) it normally continues for the rest of adult life. The quality and quantity of sperm produced may decline with increasing age
Differentiate between:
- Sexual reproduction
- Sexual intercourse
- Biological sex
Sexual reproduction – produce genetically different offspring.
Sexual intercourse – required for sexual reproduction, sexual activity, sexual pleasure, human bonding.
Biological sex – identifies gender, a result of chromosomes, produces different gametes.
Reward & pleasure pathways involve?
Meso-limbic DA system
Penile changes during erection
- Initiated by increased parasympathetic activity to smooth muscle of 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
- The urethra is protected from increased pressure by surrounding corpus spongiosum (less turgid)
Note:
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.
Fertilisation
- Deposition of sperm near the cervix.
a. Cervical mucous is hostile to sperm which forms a physical barrier.
b. Cervical mucous changes at mid-cycle to permit sperm to enter the uterus. - Passage of sperm through uterus and then fallopian tubes.
- Sperm moves to fallopian tube ampulla.
a. Capacitation takes place (within the uterus) which matures the spermatozoa. - Egg meets sperm fusion of egg with sperm (24 hours post ovulation).
a. Acrosome reaction – penetration of zona pellucida (& Coronal cells).
b. Calcium flux.
c. Resumption of meiosis, release of 2nd polar body.
d. Alignment of maternal and paternal chromosomes to generate zygote. - Change in Zona Pellucida to stop additional sperm fusing (cortical reaction)
- Initiation of mitotic divisions in embryo.
Fertilisation
- Deposition of sperm near the cervix.
a. Cervical mucous is hostile to sperm which forms a physical barrier.
b. Cervical mucous changes at mid-cycle to permit sperm to enter the uterus. - Passage of sperm through uterus and then fallopian tubes.
- Sperm moves to fallopian tube ampulla.
a. Capacitation takes place (within the uterus) which matures the spermatozoa. - Egg meets sperm fusion of egg with sperm (24 hours post ovulation).
a. Acrosome reaction – penetration of zona pellucida (& Coronal cells).
b. Calcium flux.
c. Resumption of meiosis, release of 2nd polar body.
d. Alignment of maternal and paternal chromosomes to generate zygote. - Hardening of the Zona Pellucida to stop additional sperm fusing (cortical reaction)
- Initiation of mitotic divisions in embryo.
