Production of seminal fluid Flashcards
What is the structure of the tail of the sperm called?
9 + 2 axonemal structure
What is thought to be the overall length of the seminiferous tubules?
~ 250m
How many sperms cells are released per ejaculate?
~ 20 million
What is the epididymis is comprised of what?
Head, body and tail
How much sperm can the tail of the epididymis contain?
100 million
What happens when the sperm travels from the end of the body to the tail?
They become fully active ready for capacitation (journey can last 6 - 12 days)
How long after a vasectomy are men still advised to use protection?
3 - 4 months
What are the changes that hapeen to the spermatozoa in the epididymis?
- 100 fold increase in concentration
- Sperm are remodelled: nuclear condensation and acrosome shaping, cytoplasmic droplet shed
- Increased dependance on external fructose for glycolytic energy, little oxidative metabolism
- Increased intracellular pH (due to Na+/H+ exchange)
- Increased motility dueto increased disulphide bridges between proteins in outer dense fibres of tail, cAMP rises in tail, able to move forward
- Composition of membrane changes
By how much does the sperm concentration change in the epididymis?
100-fold (5x10^7/ml to 5x10^9/ml leaving)
How long is the epididymis if spread out?
~ 4m
How many parts of the vas deferens are there?
5
What is the proportion of muscle to lumen in the vas deferens
10:1 (most muscle abundant tube in human body, used to propel sperm)
What are the functions of the vas deferens?
- Propels sperm
- Gives sperm glycoproteins
- Absorption features which get rid of dead sperm
What is the volume produced by each gland?
- Testes: 0.1-0.2 ml
- Seminal vesicle: 1-3ml
- Prostate 0.5-1ml
- Bulbourethral glands 0.1-0.2ml
What does the bulbourethral glands produce?
Viscous, clear, alkaline fluid, lubricates urethra
What are the constitutes of the seminal vesicle?
alkaline, gelatinous
What does the prostate secretion contain?
acidic, watery
What are the major constituents of ejaculate?
- Spermatozoa (50 - 150)
- Fructose (8-37)
- Inositol (1-3)
- Citric acid (5-73)
- Glycerylyphosphorylcholine (2-3)
- Acid phosphatase
Where is fructose produced?
Seminal vesicle and ampulla
Where is citric acid produced?
Prostate
Where is glycerylphosphoryl-choline produced?
Epididymis
Where is acid phosphatase produced?
Prostate
How does the penis become turgid?
- Haemodynamic changes
- Involves corpus cavernosa (sinuses along length of penis)
What is fructose used for?
Anaerobic energy metabolism
What does inositol do?
Osmotic ballast
What does citric acid do?
Ca2+ chelator - Depresses semen coagulation
What does glycerlyphosphorylcholine do?
Used as a source of choline in phospholipid metabolism
What does acid phosphatase do?
Cleaves choline from glycerophosphorylcholine
What is the main veins of the penis?
- Subcutaneous dorsal vein
- Deep dorsal vein
What are the arteries in the penis?
Dorsal artery, profunda artery, circumflex artery, cavernous artery, hecline arteries
What is the main nerve of the penis?
Dorsal nerve
What can arousal be produced by?
- Erotic psychological stimuli (eg visual, olfactory)
- Tactile stimuli at the level of the brain
- Tactile stimuli can also mediate local spinal reflexes
What maintains flaccidity?
Lower thoracic and lumbar spinal segments
What increases turgidity?
- Increased activity of parasympathetic control centre in sacral spinal segments
- Shunts between arteries and veins close
- Dilation of arterioles to c. cavernosa and c. spongiosum
What are the 3 main components of ejaculate?
1st component: Prostate - Rich in acid phosphatase and citric acid 2nd component: Vas deferens - Rich in spermatozoa 3rd component: Seminal vesicle - Rich in fructose
What follows coagulation?
Liquefaction
How long is the refractory phase
10 minutes to an hour
How does parasympathetic stimulation relax vascular smooth muscle?
- Para action involves ACh acting on vascular endothelial cells
- Indirectly triggers release of nitric oxide
- NO causes relaxation of vascular smooth muscle
What enzyme is activated after ejaculation?
PDE V (PDE V catalyses cGMP to an acive product0
What type of compound is Viagra or Sildenafil?
PDE V inhibitor (also used to treat pulmonary hypertension)
WHat can failure to obtain an erection be due to?
- Mechanical damage to c cavernosa
- Obstruction to arteries of the penis
- Drugs that block parasympathetic actions
- Psychological
- Stress associated with high sympathetic activity, NA causes vasoconstriction of penile arterioles and so inhibits erection
What are the 2 phases of ejaculation?
Emission phase
- SM contraction in walls of genital tract
- Expels semen into urethra; bulb
Expulsion phase
- Rhythmic contractions of penis and bulbocavernous muscle
- Ejects semen in spurts
