What causes erection?
Psychogenic stimuli include visual cues & olfactory cues.
Visual: Mating in others, lordosis
Olfactory: Sniffing of vulva, female urination, pheromones (Androgens)
Neurologically, the pelvic nerve is stimulated, causing arterial dilation and increased blood flow into corpus cavernosa of males with musculocutaneous penises such as dogs, cats & stallions.
For males with fibroelastic penises such as the boar, bull & ram, the retractor penis muscle relaxes upon stimulation of the pelvic nerve, straightening the sigmoid flexure.
Once the sperm is inside the female tract, it must breach the vagina, cervix, uterus and oviducts to fertilise the ovum. The sperm must become "primed" to fertilise the egg as it travels through the female tract. What is this process called?
What happens to the sperm during capacitation & where does it happen?
Capacitation starts in the uterine horn and ends by the time it reaches the uterotubal junction between the uterine horn and the oviducts.
Capacitation is the undoing of what occurred with the sperm structure, plasma membrane, metabolism and motility in the epididymis.
As the sperm progresses through the female tract, its plasma membrane becomes progressively DESTABILIZED.
Glycoproteins that formed the cap over the head are stripped off the plasma membrane.
Exposure of ZP3 binding proteins for binding with the oocyte.
Surface charge altered, possibly drawing sperm to oocyte
Membrane fluidity increased to aid breakdown of acrosome - further destabilises membrane; less cholesterol & more fatty acids to destabilise
What happens when the sperm is capacitated and it reaches the uterotubal junction, or the Isthmus of the Oviduct?
Hyperactive motility - the sperm goes into action overdrive
How would you evaluate a sperm for morphological abnormalitites?
How does it work?
ASMA (Automated Sperm Morphology Analysis)
ASMA evaluates the number of morphologically normal sperm in an ejaculate by measuring how much a sperm feature deviates from a "perfect mathematical circle".
What type of abnormalities should one look for with an ASMA evaluation?
Sperm-head abnormalities usually due to acrosome being breached or plasma membrane problem:
- Nuclear vacuoles
- sperm that would fail Comet assay test
- Tapered Heads
- Ruffled Acrosome
- Knobbed Acrosome
Tail abnornalities usually due to change in temperatures during collection of sperm; causes breach of plasma membrane:
- Coiled Tail
- Double Midpiece
- Folded Tail
- Detached Head
What are the benefits & disadvantages of doing an ASMA evaluation?
Such tests of normality important because many fertililty treatments remove "biological selection" from process
"Abnormal" defined by laboratory (subjective)
Wide variation in fertility of sperm we classify morphologically as "normal"
How is motility of sperm assessed? How does it work?
Computer Assisted Semen Analysis (CASA)
Assesses how many sperm are progressively motile vs hyperactivated. Typically do not want sperm that are manically swimming under microscope, ie., hyperactivated for AI sample
What are the parameters of assessing a progressively motile sperm vs a hyperactivated sperm using CASA?
Not hyperactivated: swimming in straight line
Hyperactivated: erratic movement, even though generally in straight line;
- more head movement (high ALH)
- less linearity (high VCL/low LIN)
ALH - amplitude of lateral head displacement
VCL - curve of linear velocity
VAP - velocity of average path
What are the two phases of sperm transport? Why are they both important?
Rapid transport phase - reaches oviducts very quickly upon entry into vagina; rapidly transported sperm hasn't been capacitated to fertilise oocyte.
Sustained transport phase - sperm undergoes capacitation & hyperactivation in oviducts, enabling it to fertilise oocyte; sperm also held in "storage reservoirs" in cervical crypts & oviducts.