Sex and fertilisation Flashcards
(31 cards)
What is in semen?
Spermatozoa and seminal plasma derived from accessory glands of the male reproductive tract
What is the function of the seminal plasma?
- transport medium
- nutrition for the sperm
- buffering capacity (neutralise acidic vagina)
What is released from the seminal vesicles?
alkaline fluid that neutralises the make and female urethra ) - needed to ensure correct environment fro spermatozoa - and fructose
What is released from prostate gland?
proteolytic enzymes that breakdown the clotting proteins- milky slightly acidic fluid
What is released from the bulbourethral glands?
very small volume of alkaline fluid that lubricates the end of the penis and urethral lining
Where is the sit of fertilisation?
the ampulla of the uterine tube
What phases are in the human sexual response?
excitement phase, plateau phase, orgasm phase and resolution phase (and refractory period for men only)
What is the male excitement phase?
occurs due to psychogenic stimuli as well as tactile sensory afferents as part of the spinal reflex
What efferent fibres are involved in the excitement phase?
somatic (via pudendal nerve) and parasympathetic (via pelvic nerve) efferents
What is the end result of the excitement phase?
Erection
How do erections come about physiologically?
- sinusoids must relax and arteries dilate (all due to neuronal stimulation)
- venous dilation required (due to increased blood flow against the tough tunica albuginea surrounding the corpus cavernous)
What does venous dilation do?
compresses the venous drainage within the tunica albuginea
Which innervation needs to be activated?
the parasympathetic
How is this done?
the parasympathetic is stimulated via the pelvic and cavernous nerve
What is the important neurotransmitter and why is it released?
NO - released as;
post-ganglionic fibra release ACh which bonds to M3 receptor on endothelial cells. This causes a rise in the intracellular Ca2+ conc activating formation of NO. NO diffuses into vascular smooth muscle and causes vasodilation - NO also released directly from nerves
What is a key mediator in the process of NO formation?
cGMP
What causes erectile dysfunction?
- psychological input
- vascular disorders
- anti-hypertensives
- neurological disorders
- trauma of the tissue of the corpus cavernousum
How does viagra work?
slows the rate at which cGMP is degraded to produce more NO
What happens in emission?
semen is moved into the prostatic urethra - this requires smooth muscle contraction from the prostate, VD and seminal vesicles
What happens in ejaculation?
expulsion of semen - requires contraction of the glands and ducts and internal sphincter to prevent retrograde ejaculation
What innervation is this under?
sympathetic (point and shoot)
What is the acrosome?
surrounds the head of the sperm - contains enzymes necessary for fertilisation
what occurs in the acrosome reaction?
sperm pushes through the corona radiata and binds to the zone pellucida which allows the head of the sperm to penetrate and degrade the zone pellucid to penetrate the ovum and fuse with the membrane
What is the cortical reaction?
it happens in the oocyte and prevents further sperm entering (polyspermy)
