Male Infertility Flashcards
how is infertility defined?
failure to achieve a clinical pregnancy after 12 months of regular unprotected sex in a couple who have never conceived a child
how common is subfertility?
1 in 6 couples
only half of these need assisted conception
primary vs secondary infertility?
primary = couple have never conceived secondary = have had previous pregnancy (including miscarriage, ectopics and terminations)
chances of conception within 1 year in a healthy couple with no known infertility problems?
80%
where are sertoli cells found?
cells within the seminiferous tubules in the testes
role of sertoli cells?
creates blood-testes barrier (protects spermatozoa from antibodies)
provide nutrients for developing sperm cells
destroy defective sperm cells
remove excess cytoplasm from seminiferous tubules
secrete seminiferous tubule fluid, androgen binding globulin, inhibin and activin
what does seminiferous tubule fluid do?
helps carry spermatozoa to epididymis
what does androgen binding globulin do?
essential for sperm production (binds to testosterone)
what do activin and inhibin do?
regulate FSH secretion and control of spermatogenesis
where does spermatogenesis occur?
inside seminiferous tubules
describe the path developing sperm take within male genital tract?
spermatogenesis occurs in seminiferous tubules
developing sperm are collected in rete testes and transported to epididymis for storage and maturation
spermatozoa pass from epididymis to urethra via vas deferens
what is the vas deferens?
muscular tube continuous with tail of epididymis which travels with the spermatic cord through inguinal canal, passes the bladder and joins the seminal vesicle and forms the ejaculatory duct which joins into the urethra
what is the bulbourethral gland (cowpers gland)?
gland which produces and releases fluid which lubricates urethra and neutralises any acidity prior to ejaculation
what does seminal vesicle do?
Produces and releases majority of seminal fluid, containing: • Fructose (nourishes sperm cells) • Prostaglandins (Triggers contraction of vaginal muscles for sperm motility) • Fibrinogens (Clot precursors)
what does prostate do?
Produces and releases: • Acid phosphatase • Citric acid • Inositol • Calcium, zinc and magnesium
describe hormonal control of spermatogenesis?
GnRH released in pulsatile manner every 2-3 hrs from hypothalamus > GnRH stimulates anterior pituitary to release FSH and LH > LH stimulates testosterone secretion from leydig cells > FHS and testosterone together stimulate spermatogenesis in seminiferous tubules
inhibin released by sertoli cells reduced FSH and testosterone decreases GnRH secretion which decreases LH (Negative feedback) which inhibits spermatogenesis again
describe development of sperm (spermatogenesis)?
diploid primordial germ cell > diploid spermatogonia > diploid spermatocytes > meiosis 1 > haploid secondary spermatocytes > meiosis 2 > haploid spermatids > tails and acrosomes are formed > fully formed spermatozoa
role of acrosome?
around head of sperm
contains enzymes for penetrating the ovum
how are sperm attracted to oocyte?
chemoattraction (Sperm follows conc gradient of chemoattractant secreted by oocyte)
what is capacitation?
the series of biochemical and electrical events that take place to allow the
sperm cell to penetrate the cell layer that surrounds the oocyte, by giving the sperm cell the
ability to bind to the zona pellucida via the acrosome reaction
describe the changes that occur during capacitation?
sperms tail movement increases in speed and strength
changes in sperm cell membrane to allow acrosomal reaction
what happens in acrosomal reaction? (3 steps)
- specific cell surface glycoproteins (ZP3) of the zona
pellucida interact with the sperm cell, allowing calcium to enter the spermatozoa, increasing
the intracellular cAMP. - Acrosome then swell and allows enzymes from the acrosome to
be released. - Another glycoprotein in the zona pellucida (ZP2) holds the sperm in place while
these enzymes are released from the acrosome, allowing the tail to propel the sperm into the oocyte and the enzymes to create the fusion of the sperm to the zona pellucida.
3 categories of male factor infertility?
idiopathic (most common)
obstructive
non-obstructive
obstructive causes of male infertility?
cystic fibrosis (often have bilateral obstruction or absence of vas deferens) vasectomy (vas deferens is cut and sealed shut) both will have normal sperm production etc
how are hormones affected in obstructive male infertility?
normal LH, FSH and testosterone
non-obstructive causes of male infertility?
cryptorchidism chromosomal abnormalities infections endocrine disorders pathological causes such as testicular tumour specific sperm abnormalities
what is cryptorchidism?
one or both testes being undescended into the dependant part of scrotal sac
(usually descend by 6-9 months)
testes arent ideal environment for sperm production ( too warm)
ideal temp for spermatogenesis?
2-4 degrees
where may undescended testes be found?
upper scrotum
inguinal canal
intra-abdominal
can have no testes at all (anorchia)
who is cryptorchidism more common in?
premature babies
low birth weight
small for gestational age
what chromosomal abnormalities can cause non-obstructive male infertility?
klinefelters (47 XXY) microdeletions of Y chromosome (missing genes on Y chromosome) robertsonian translocation (extra or missing chromosomes)
features of klinefelters?
47 XXY genetic male tall slight developmental delays including motor control, learning and socialising as a child redued facial hair poor muscle tone gynaecomastia in puberty small penis and testicles
how can infection cause non-obstructive infertility?
mumps can cause obstructive or non-obstructive
can have testicular swelling which can block pathways
swelling can also damage seminiferous tubules and affect sperm production (short term, only lasts a few months)
some STIs can cause epididymitis and orchitis which can effect morphology, motility and quantity of sperm produced
endocrine causes of non-obstructive infertility?
pituitary tumours and hypothalamus disorders (decreased FSH, LH, testosterone)
thyroid disorders (hyper = decreased sexual function, hypo = increased prolactin production)
diabetes (decreased sexual function and testosterone)
CAH (increased testosterone)
how can steroid abuse affect fertility?
can result in decreased FSH, LH and testosterone
how can testicular cancer affect fertility?
tumour itself and its treatment
the cancer can change levels of testosterone and cause genetic damage to sperm cells
tumour can also damage tubules or cause obstruction
chemo/radiotherapy can affect spermatogenesis (short term)
give an example of a specific sperm abnormality which can cause non-obstructive infertility?
globozoospermia
sperm have rounded heads instead of oval and no acrosome so cant undergo capacitation
general hormone changes in non-obstructive infertility?
high FSH and LH
low testosterone
(not always)
