Male gametogenesis Flashcards
what is fecundity?
The potential for reproduction: gamete production, fertilisation and ability to carry a pregnancy to term
what is fertility?
A measure of reproductive outcome: the number of children born per person, couple or population
what is the fertiltiy rate?
The number of births per time period per person, couple or population
is fecundity afffected by age?
yes.
males - constant / then gradual decline
females = monthly / sharp drop off at menopause
peak fertility rate – _____ years
peak fertility rate – 20-24 years
menopause: ___ years old average
menopause: 51 years old average
male fertility is lost in later life due to?
many factors
Vascular disease Erectile dysfunction Diabetes
describe the HPG axis
the hypothalsmus releases what?
gonadotrophic releasing hormone
GnRH. into pituitarty portal system - stimulates release of FSH LH and prolactin from anterior pituitary
- Release controlled by hypothalamus – GnRH – release is ______ – peaks hourly – important for function
- Release controlled by hypothalamus – GnRH – release is. Pulsatile – peaks hourly – important for function
when hormones provide feedback from the gonads to the brain?
Inhibin oestrogen and testosterone
•FSH and LH are secreted by …
•FSH and LH are secreted by gonadotroph cells in the anterior lobe of the pituitary gland
•Prolactin secreted by ____
•Prolactin secreted by lactotrophs
acidophiles in the ant pituitaery produce?
what about basophils?
acidophils: Growth hormone or prolactin
basophils: TSH, ACTH, FSH or LH
Secretion of FSH and LH is regulated by ….
Secretion of FSH and LH is regulated by gonadotrophin-releasing hormone (GnRH) produced by neurons in the hypothalamus and
the
released into the pituitary portal vein
Release of GnRH is ….
Release of GnRH is pulsatile, peaking approximately hourly
role of LH
•LH stimulates thecal cells in ovary to produce oestradiol, and Leydig cells in testis to produce testosterone
are oestradiol and testosterone negative feedback mediators?
yes
expect oestrdiol is a positive feedback mediator in high concentrations. = LH surge
describe FSH
•FSH stimulates granulosa cells in ovary and Sertoli cells in testis to produce inhibin
does Inhibin exert negative feedback
•Inhibin exerts –ve feedback on FSH secretion by gonadotrophs
only FSH release.
Functions of prolactin?
- diverse unclear actions
- potentiates actions of FSH and LH through actions on receptors and enzymes e.g. 5 alpha reductase
*
•Hyperprolactinaemia is associated with ________ in both men and women
•Hyperprolactinaemia is associated with infertility in both men and women
how is prolactin regulated?
and so hwo do we treat hyperprolactinaemia?
Regulated primarily by negative action of dopamine released from TIDA neurons
•Hence, treated with bromocriptine, a dopamine D2
receptor agonist
TIDA neurones are located where?
the arcuate nucleus
when dothe testis decend>
jus tbefore birth
why are the testis located outside the body
This position, plus the countercurrent heat exchange between the testicular artery and the pampiniform plexus of veins lowers the temperature by a few degrees centigrade
wat is poor decent of the testis assocaited with
• Maldescent (cryptorchidism) associated with teratocarcinoma, reduced spermatogenesis and subfertility
testis has ___ lobes
250
how many seminiferous tubules does each lobule contain
1-4
shape of the seminiferous tubules?
hourse shoe shaped
what the seminiferous tubules connected to?
- Tubules are horse-shoe shaped and both ends connect with the rete testis and hence to the efferent ductules
- Released sperm are non-motile at this point, and so movement by bulk- fluid flow
• Maturation and storage of sperm takes place in the _____
• Maturation and storage of sperm takes place in the epididymis
•Seminiferous tubules are developed during the ……
when are they activateD?
•Seminiferous tubules are developed during the fetal period but inactive until puberty
what effect do FSH and LH have on the seminiferous tubules?
• Once FSH and LH rise at puberty the testis enlarges as the Leydig cells and seminiferous tubules expand, and spermatogenesis starts
the wall of the seminiferous tubule is how thick?
Sertoli cells make up the wall of the tubule, which appears multilayered but is only 1 cell thick
Whether sperm are present in the smeiniferous tubule lumen depends on ?
Whether sperm are present in the lumen depends on the stage of the spermatogenic cycle of that particular profile
Blood vessels and lymphatics are confined to the _________, and the tight junctions between Sertoli cells constitute the ____________
Blood vessels and lymphatics are confined to the interstices, and the tight junctions between Sertoli cells constitute the blood-testis barrier
the basal testicular compartment is high in?
testosterone
teh apical testis compartment is ?
immunologically provilages - to stop immune cells repsonding to new spermy bois
The tubules are lined by Sertoli cells attached to a ….
The tubules are lined by Sertoli cells attached to a basement membrane
Spermatogonia are also attached to the …..
Spermatogonia are also attached to the basement membrane
Tight junctions between the Sertoli cells divide the testis into …..
Tight junctions between the Sertoli cells divide the testis into basal and apical (adluminal) compartments
Basal compartment has a high _________ concentration secreted by Leydig cells in response to ___, and bound by androgen binding protein secreted by Sertoli cells in response to FSH
Basal compartment has a high testosterone concentration secreted by Leydig cells in response to LH, and bound by androgen binding protein secreted by Sertoli cells in response to FSH
problems if teh tight junctions in the basement membrane in the testis break down
If tight junctions break down can develop an autoimmune reaction, and anti- spermatozoal antibodies, leading to subfertility
3 stages of spermatogenesis
- mitotic proliferation
- Meiotic division
- Cytodifferentiation (spermiogenesis)
what is spermiation?
Spermatozoa are released luminally into testicular fluid in a process called spermiation
describe 1: mitotic proliferation
Numbers of sperm produced depend on mitotic activity of spermatogonia from stem cells in basal compartment (5-7 division rounds)
descxribe 2: meiotic division
Meiosis occurs in spermatocytes, and they move from the basal to the apical compartment as they divide
describe 3: cytodifferentiation
Post-meiotic haploid spermatids transform their phenotype from round spermatid through elongating spermatid to a spermatozoon
in sperm - histones are replaced by
protamines
high condensation = loss of transcription in late spermatids and spermatozoa
human spermatogenic cycles last for?
In the human the cycle lasts for 16 days, and spermatogenesis for 64 days
describe the Transport of spermatozoa
From testis through vasa efferentia
- passively in bulk fluid flow
- non-fertile and immotile
Through the epididymis to vas deferens
- 90% fluid absorbed so spermatocrit rises
- muscular contractions move the sperm along
Maturation and storage of spermatozoa in the epididymis;
describe
Maturation and storage of spermatozoa in the epididymis; stiffening of outer dense fibres in tail, addition of glycoproteins, change in lipid composition of membranes (lectures on fertilisation)
Epididymal function, prostate and seminal vesicles all dependent on ______
Epididymal function, prostate and seminal vesicles all dependent on androgens
Normally produce ~_- million spermatozoa per day
Normally produce ~30 million spermatozoa per day
Reduced sperm count may be associated with:
Reduced sperm count may be associated with:
- Cryptorchidism
- Overheating of the testis e.g. varicocoele
- Drugs e.g. anti-mitotic drugs, alcohol, xenobiotics, bisphenol A
- Hyperprolactinaemia
- Obstructive pathology of the epididymis or vas e.g. congenital or post-infective
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