St A - Production of Seminal Fluid Flashcards
Describe the development from a spermatocyte
It develops into a spermatid then to a mature spermatozoon.
Describe the sperm axonemal structure
Has a central pair of tubules with 9 pairs arranged in a ring surrounding it. There is a Dynein regulatory complex which allows the tail to move.
Describe the structure of the testies
- Coiled seminiferous tubule converge onto rete testes which branch into efferent ductules which then enter the head of the epididymis. The tail of the epididymis becomes the vas deferens.
Explain the transfer of sperm into the epididymis
It takes 6-12 days to travel through the vasa efferentia to the epididymis. If the vasa efferentia is blocked then the seminiferous tubules and testis swell
Describe the changes to spermatozoa in epididymis
- Concentration increases 100-fold.
- Sperm modelling results in nuclear condensation and acrosome shaping completed.
- Metabolism changes so there is increased dependency on external fructose and there is an increase in intracellular pH.
- Motility changes results in increased . disulphide bridges between proteins in outer dense fibres of tail. cAMP rises in tail.
- Membrane component changes
Describe where seminal fluid is made
- Testies produce 0.1-0.2mls containing spermatoza,
- Seminal vesicle produce 1-3mls of alkaline, gelatinous syndrome.
- Prostate produces 0.5-1mls of acidic, watery fluid.
- Bulbourethral glands produce 0.1-0.2mls of clear, viscous fluid
What are the major constituents of ejaculate, where they are made and their function?
Spermatazoa (made in testies),
- Fructose (made in seminal vesicles and ampulla, anaerobic energy metabolism),
- Inositol (testies and epidiymis - osmotic balance.
- Citric Acid (prostate - depresses semen coagulation)
- Glycerlyphosphorylcholine (epididymis and used in phospholipid metabolism)
- Acid Phosphatase (prostate - cleaves choline from above)
Describe the structure of the penis
Corpora cavernosum (two sinuses side by side) and corpus spongiosum (surrounds the urethra)
- Subcutaneous and deep dorsal veins, dorsal artery and nerve.
- Profunda artery
How can arousal be produced?
- Erotic psychological stimuli,
- Tactile stimuli at the level of the brain,
- Tactile stimuli can also mediate local spinal reflexes
What is the role of the SNS?
It maintains flaccidity and originates from thoracic and lumbar spinal segments
What is the role of the PSNS?
- Increased activity produces turgidity. Control centre is found in sacral spinal segments
Describe the tumescence of the penis
Stimulated by erection centre in sacral spinal cord resulting in dilation of arterioles to c.cavernosa and c.spongiosum. Closing of aterovenous shunts that normally bypass the c.cavernosa
Describe the PSNS relaxation of vascular smooth muscle
- PSNS action involves ACh acting on vascular endothelial cells which indirectly triggers release nitric oxide.
What is Viagra?
PDE V inhibitors (promotes penile erection)
Failure to obtain an erection can result from what?
- Mechanical damage to c.cavernosa,
- Obstruction of the arteries to the penis,
- Drugs that block the PSNS action,
- Psychological factors (stress associated with high SNS activity causes vasoconstriction of penile arteries so inhibits erection)
