Question Answer
Give the two functions of the testes secrete testosterone and produce sperm by process called spermatogenesis
what's spermatogenesis? process by which immature stem cells (spermatogonia) proliferate and differentiate into mature sperm
outline the three basic stages of spermatogenesis proliferation (spermatogonia divide several times), meiosis (produces haploid cells), spermiogenesis (differentiation process)
what has to happen in spermatogenesis as well as proliferation? cell differentiation also has to occur to generate a motile 'DNA package'
how long does spermatogenesis take, when does it start and where does it end? takes about 64 days and starts at puberty, ends at death
what three types of spermatogonia are there? A dark, Apale and B
what are Adark spermatogonia? a backup if there is severe damage to spermatogenesis (e.g. irradiation, cytotoxic drugs)
where do all proliferative stages take place? on basement membrane
Give the 9 stages of meiosis of sperm B spermatogonium -> resting primary spermatocyte -> leptotene spermatocyte -> zygotene spermatocyte -> pachytene spermatocyte -> diplotene spermatocyte -> secondary spermatocyte -> round spermatid -> spermiogenesis
whens the first meiotic division when the diplotene spermatocyte gets turned into the secondary spermatocyte
when's the 2nd meiotic division when the secondary spermatocyte gets turned into the round spermatid
what happens at leptotene cells move off the basement membrane, through the blood-testis barrier. This means spermatocytes and spermatid s are 'sealed off' inside the lumen of the tubule by the blood-testis barrier between Sertoli cells
why is it important that spermatocytes and spermatids are 'sealed off' inside the lumen of the tubule by the blood-testis barrier between Sertoli cells important as haploid cells are protected from the immune system in the lumen of the seminiferous tubule
what sort of process is spermiogenesis a cell differentiation process
briefly outline the stages of spermiogenesis nuclear condensation, acrosome forms from Golgi, tail develops from centriole, cytoplasm re-distributes – residual body lost, mitochondria re-arrange in middle piece
what is a spermatozoon/spermatozoa essentially? a nucleus with a tail
what is the head of the spermatozoa like? nucleus with compacted and inactive DNA. Surrounded by the acrosome – enzymes for penetrating the egg
what does the midpiece of the spermatozoa contain? many mitochondria which generate power
what does the tail of the spermatozoa do? generates movement
what sort of process is spermatogenesis? a continuous one
what happens as a B spermatogonium develops into a spermatocyte and passes blood testis barrier? another B spermatogonium forms behind it in a continuous production line
what are testes controlled primarily by? endocrine regulation
what does the hypothalamus secrete? gonadotrophin-releasing hormone (GnRH)
what does gonadotrophin-releasing hormone do? causes release of LH and FSH
what do the LH and FSH do in the male? stimulate testis growth and function – system controlled by negative feedback
what is testosterone and what is this it's an androgen – androgens are a class of steroids
what cell function does FSH stimulate? Sertoli cell function (and thereby spermatogenesis)
what does LH stimulate? Leydig cells to secrete testosterone
what does testosterone stimulate? Sertoli cells (and peritubular myoid cells)
what does testosterone secreted into the blood act to do? maintain androgen-dependent structures (e.g. prostate, SV), and stimulates sex-drive in the male
what does hormonal control of spermatogenesis come largely through? the Sertoli cells
Hormonal control of spermatogenesis: what does FSH do? stimulates spermatogonial proliferatopm
what do FSH and testosterone stimulate? spermatogonial differentiation to spermatocytes
what is testosterone essential for? passage of spermatocytes through meiosis
what does testosterone stimulate ? spermiogenesis
what does the epididymis function to do? induce sperm maturation
what sort of sperm enter at the head of the epididymis? what happens to them? non-motile, non-fertile sperm enter at the head and then become fertile and motile as they travel down the epididymis
what does the tail of the epididymis act as? a sperm storage area
what are endocrine disruptors? exogenous (natural or man-made) chemicals which disrupt normal endocrine function – have similar structure to endogenous hormones
how do endocrine disruptors work? (agonistic) mimic hormone biological activity by binding to receptor and activating it (agnostic)
what two things can agonistic endocrine disruptors do? cause too much hormone activity, activity at inappropriate time
how do antagonistic endocrine disruptors work? bind to receptor so preventing binding of the natural hormone (antagonistic)
what do antagonistic endocrine disruptors do? prevents normal hormone action
what is the third way that endocrine disruptors can fuck things up? interfere with metabolic processes in body – affects synthesis or breakdown of natural hormones
what reproductive problems do endocrine disruptors cause? reduced fertility, developmental abnormalities, menstrual problems, early puberty, brain/behaviour problems, cancers – but they don't just affect the reproductive system
what are phthalates ? man-made chemicals
what might some phthalates pose a risk to? human development, especially for male infants
what does Cryptorchid increase risk of? low sperm count and cancer
what's IUGR a risk factor for? TDS
what is associated with all TDS disorders? reduced androgen action – not surprising given importance of androgens in reproductive development
can you cure symptoms of TDS? can treat symptoms but not cure TDS
hypospadias? forms a penis that doesn't work well and doesn't look normal – something to do with leydig cells
cryptorchidism absence of one or both testes from the scrotum – something to do with leydig cells
testicular germ cell cancer? something to do with sertoli cells
what's diethylstillbestrol (DES)? synthetic oestrogen
why is DES prescribed to about 5 million pregnant women? blocks spontaneous abortion and promotes foetal growth – banned in early 70s because caused vaginal cancer and affected reproductive development – not noticed until exposed children pubertal
what do cigarettes contain? a complex mixture of chemicals and EDCs – largest preventable cause of adverse fetal outcomes
what percentage of women still smoke during pregnancy? 20%
Spermatogenesis Spermatogenesis and Endocrine Disruptors week 5 x

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