male reproductive system Flashcards
purpose of male reproductive system
gametogenesis (spermatogenesis)
delivery of sperm to female tract
secretion of sex hormones (androgens esp. testosterone)
what are the parts of the male reproductive system
Gonads:
Testes
Reproductive tract:
Epididymis
Ductus (Vas) Deferens
Urethra
External genitalia
External Genitalia:
Penis
Corpora cavernosa
Corpus spongiosum
Accessory Glands:
Prostate
Seminal Vesicles
Bulbourethral Glands
what is the function of the testes
Key roles:
Sperm production
Hormone production
what are the 3 types of cells in the testes
3 cell-types
Leydig cells
outside tubules
Sertoli cells
within tubules
Germ cells @different stages
within tubules & lumen
where is LH and FSH produced and which hormone stimulates it
LH and FSH produced by gonadotroph cells in Anterior Pituitary
Secretion of LH and FSH is stimulated by the hypothalamic peptide Gonadotrophin Releasing Hormone (GnRH)
LH and FSH act on cell-types in testis:
LH => Leydig cells => Testosterone
FSH => Sertoli cells => Inhibin
what are the effects of Effects of Androgens
(principally TESTOSTERONE; T)
Before birth T is synthesized by foetal Leydig cells in response to maternal hCG
T masculinizes the external genitalia (requires T conversion to DHT by 5-alpha reductase enzyme)
T promotes descent of testes into scrotum
After birth
T production very low until puberty
Around puberty LH production by the pituitary is initiated and this stimulates T output by testis
At PUBERTY promotes growth & maturation of reproductive system
- penis & scrotum enlargement
- scrotum darkening
- enlargement of epididymis, prostate, seminal vesicles
essential for spermatogenesis
maintains reproductive tract throughout adulthood
Other reproductive effects of T
development of sex drive (Libido) at puberty
control of gonadotrophin secretion (via negative feedback)
Effects of Androgens on
Secondary Sex Characteristics
Promotes muscle growth responsible for male body conformation
increases protein synthesis
decreases protein degradation
increases lean:fat ratio
Promotes bone growth at puberty and then closure of epiphyses
Induces male pattern of hair growth (i.e. beard)
Causes deepening of voice
Skin thickens & sebaceous glands thicken (acne)
what is Andropause
Decreased Testosterone Production
Reduced testicular androgen response to LH
Age, 48 -70
Physical Changes
Loss of muscle mass
Shrinking reproductive organs - penis, testis, accessory glands
Loss of libido, increased stimulus needed for erection, longer refractory period
Osteoporosis
Mental Changes
Depression, reduced ‘energy’
what is the 3 different regions of erectile tissue
- pair of parallel spongy columns called corpus cavernosum
- central corpus spongiosum enclosing urethra.
Erectile tissue rich in tiny pool-shaped blood vessels called cavernous sinuses - that fill with blood during an erection.
Penis: anatomy & physiology
Sympathetic and parasympathetic nerves innervate BVs and sinusoids in erectile tissues of penis.
Psychogenic and/or tactile stimulation triggers increased acetylcholine (parasympathetic) and decreased noradrenaline (sympathetic) release => increased eNOS => increased NO
NO leads to dilation of smooth muscle of arterioles and sinusoids within erectile tissue =>
Increase in blood flow into the corpus cavernosum and corpus spongiosum => erection
nos- nitric oxide synthase
no-nitric oxide
In flaccid state the cavernous sinuses contract, less blood present.
In erect state the smooth-muscle surrounding the sinuses relaxes, causing sinusoidal dilation.
Tissue engorgement flattens the surrounding veins ‘trapping’ blood => erection
Biochemical process of erection
Neurotransmitters (Ach) and neuronal nNOS released from the cavernous nerve, stimulate production of eNOS within the vascular endothelial cells
NO diffuses into surrounding vascular smooth muscle
NO binds to and activates guanylyl cyclase which converts GTP into the second messenger cGMP
‘Free’ cytosolic calcium levels play essential role in relaxation of smooth muscle cells within erectile tissue
‘Free’ intracellular calcium can bind to and activate calmodulin
Calmodulin aids the phosphorylation of myosin light chains (MLC)
MLCs are subunits found on myosin heads - when phosphorylated they cross-bridge the myosin heads and actin filaments causing cellular contraction.
Thus, decrease in cytosolic calcium initiated by PKG results in vascular SM relaxation.
causes of ED
nervousness - especially about ‘performing’
* guilt - adultery etc.. * relationship problems * depression * exhaustion.
- deterioration of arteries – common in older men, including those with high BP
- diabetes
- being obese and out-of-condition
- smoking
- excessive alcohol
- side-effects of certain drugs (e.g. anti-hypertensives, anti- depressants)
moa of viagra and side effects
Sildenafil competitively inhibits the enzyme responsible for the degradation of cGMP to GMP, phosphodiesterase type 5 (PDE5).
stabilization of cGMP => prolonged action of second messenger
Greater, more sustained dilation of sinusoidal smooth muscle via PKG-dependent reduction in free cytosolic calcium ion concentration
Engorgement of erectile tissue with blood
Common
Flushing*
Headache*
Nasal* congestion
stomach discomfort following meals
Less common
blurred vision , loss of hearing
bladder pain
dizziness
pain on urination
what is PRIAPISM
what are the classifies into
treatment
Persistent, painful erection lasting longer than 4 hours – in absence of sexual stimulation/desire
Classified into two types —
ischemic (no-flow) – obstruction in venous drainage
non-ischemic (high-flow) – excess arterial supply
Medical attention should be sought immediately as ….
Delayed treatment (esp. of ischemic type) can cause damage to the erectile tissue in the penis and irreversible erectile dysfunction
Treatment may involve intracavernosal injection of alpha- adrenoceptor agonist (e.g. phenylephrine)
