Erection and Ejaculation (repro)

Question 1

Nerve control of erection and ejaculation

Answer 1

• vasodilation of the corpus cavernosum
• partial constriction of the venous return
• autonomic nervous system causes coordinated smooth muscle contractions of vas deferens, glands and urethra
• parasympathetic control causes erection
• sympathetic nervous system control causes movement of sperm into epididymis, vas defers, penile urethra (emission)
• somatic nervous system (perineal branch of the pudendal nerve from nerve roots S2-S4) causes expulsion of the glandular secretion and evacuation of urethra

Question 2

Ejaculate

Answer 2

• 300 million sperm produced per day on average
• 3500 per second, approx 120 million in average ejaculate
• normal ejaculate volume is 1.5ml-6ml (approx 1/3 to just over a teaspoon full)
• initial portion of the ejaculate is most sperm rich
• 99.9% lost before reaching ampulla of the uterine tube
• around 120,000 sperm get near to the egg, only one enters
• seminal fluid consists of secretions from seminal vesicles, prostate, bulbo-urethral gland combined with epididymal fluid

Question 3

Seminal fluid

Answer 3

Bulbo-urethral fluid:
- produces a clear viscous secretion, high in salt, known as pre-ejaculate
- this helps to lubricate the urethra for spermatozoa to pass through, neutralising traces of acidic urine
Seminal vesicles:
- secretions comprise 50-70% of the ejaculate
- contains proteins enzymes, fructose, mucus, vitamin C and prostaglandins
- high fructose concentrations provide energy source
- high pH protects against acidic environment in vagina
Prostate:
- secretes milky or white fluid roughly 30% of seminal fluid
- protein content is less than 1% and includes proteolytic enzymes, prostate acid, prostate-specific antigen which are involved in liquefaction
- high zinc concentration 500-1000 times that in blood is antibacterial

Question 4

Semen analysis

Answer 4

• volume: 1.5-6.0ml
• sperm concentration: >15million/ml
• liquefaction: <30 mins
• motility: >40%
• progressive motility: >32%
• vitality (live): >58%
• morphology (normal forms): >4%
• pH: >7.2
• leucocytes: <1 million/ml

Question 5

Spermatozoon

Answer 5

(tail to head)
- plasma mebrane all around 
End piece:
- sperm tail (back half)
Principal piece:
- sperm tail (front half) 
Midpiece:
- Mitochondrial sheath
- Connecting piece
Head:
- nucleus 
- acrosome