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REPRODUCTION
6.6, 11.4, D5
Reproduction
You must name and know the function of these organs
The Y-chromosome
In human embryos, the SRY gene (sex determining region Y)
encodes a unique transcription factor that activates a testisforming pathway around Week 7 of development
SRY gene
• Cytogenetic Location: Yp11.2
• Codes for a transcription factor which ‘turns on’ genes to
code for primary male characteristics – testes –
(testosterone production)
• Gene is switched on at w6 – 8 of embryo development and
STOPS default development of a female embryo while
promoting male development
Testosterone
• Essential for prenatal development into male
• Stimulates interstitial cells of the testes to
make sperm
• Stimulates the prostate gland to make seminal
fluid
Romantic relationships and
testosterone…
According to wikipedia…
• Falling in love lowers
testosterone production in
men but increases it in
women
• Testosterone ‘returns to
normal’ after the
honeymoon period
• Fatherhood decreases
testosterone production
• ‘competition’ affects
testosterone levels
Spermatogenesis – let’s make
some babymakers….
..involves mitosis, meiosis and
differentiation…
Single sperm
Digital artwork of a sperm, showing the head, midpiece and tail. The head of the sperm is surrounded by an acrosome ‘cap’ (blue), which contains enzymes that help the sperm penetrate the outer
membrane of the egg to permit fertilisation. The midpiece contains large coiled a mitochondrion (gold) to provide energy to the tail, and two centrioloes (green), which are required for a viable
embryo.
Credit: Anna Tanczos, Wellcome Images
BIGPICTUREEDUCATION.COM
• The testes are composed of seminiferous tubules which produce
sperm
• Each tubule is surrounded by a basement membrane lined by
germline epithelium cells
• The germline epithelium will divide by mitosis to make
spermatogonia (which divide by meiosis to make spermatozoa)
• The developing spermatozoa are nourished by Sertoli cells
• Outside of the tubules are blood capillaries and interstitial cells
(Leydig cells), which produce the male sex hormone, testosterone
Spermatogenesis is influenced by
three hormones: LH, FSH, testosterone
Section of a testis
Light microscopy image of a transverse cross-section through a testis. Staining of the tissue reveals the numerous seminiferous tubules - the location of sperm production. Between them are
interstitial cells that support sperm production.
Credit: Spike Walker, Wellcome Images.
BIGPICTUREEDUCATION.COM
Seminiferous tubule
Confocal microscopy image of a cross-section through a seminiferous tubule showing the developing sperm; they can be seen as a row of cells with their tails pointing into the lumen (opening) of the
tubule. The nuclei are stained blue, and the mitochondria red. Sperm have a large number of mitochondria for energy to allow them to swim towards the egg.
Credit: MRC NIMR, Wellcome Images
BIGPICTUREEDUCATION.COM
Making babymakers…
• Germ cells (spermatagonia) divide by
mitosis
• Then there are two meiotic divisions
(primary and secondary
spermatocytes) to make spermatids
• Spermatids differentiate into mature
spermatazoa (nursed by Sertoli cells)
Spermatogenesis