11. Production of seminal fluid Flashcards
Evolution of male gametes?
Spermatocyte
- -> Spermatid
- -> Speratozoon
What is the process of sperm transfer to epidydmis?
Sperm in seminiferous tubules in a large volume of fluid. Washes sperm into rete testis, vasa efferentia and epididymis
If vasa efferential blocked, seminiferous tubules and testis swells
6-12 days to travel through vasa efferntia and epididymis
Various products secreted into the seminal fluid in the epididymis
Changes to spermatozoa in epididymis in Concentration?
Concentration: 100-fold (5 x 10^7/ml entering, 5 x 10^9/mol leaving)
Changes to spermatozoa in epididymis in Sperm modelling?
- Nuclear condensation and acrosome shaping completed
2. Cytoplasmic droplet shed
Changes to spermatozoa in epididymis in motility?
- ↑ disulphide bridges between proteins in outer dense fibres of tail
- [cAMP] rises in the tail
- Acquires the capacity for forward movement
Changes to spermatozoa in epididymis in metabolism?
- ↑ dependence on external fructose for glycoly c energy 2. Little oxidative metabolism
↑ Intracellular pH (due to 3. NA+/H+ exchange)
Changes to spermatozoa in epididymis in Membrane?
Composition of various components change makes them more resilient to changes in temp
Where is seminal fluid formed
Accessory glands
role of seminal fluid?
Provides nutrients etc to protect spermatozoa.
Produces an alkaline and gelatinous fluid
Which infectious agents exploit seminal fluid?
Hep B
HIV
what are the 6 main constituents of ejaculate?
Spermatozoa Fructose Inositol Citric acid Glycerlyphosphoryl-choline Acid phosphatase
Source and function of fructose in ejaculate?
From seminal vesicle and ampulla
For anaerobic energy metabolism
Source and function of inositol in ejaculate?
Source: Testes and epididymis
Function: Osmotic ballast to keep fluid in semen and not move into sperm (swelling)
Source and function of citric acid in ejaculate?
Source: Prostate
Function: Ca2+ chelator which depresses semen coagulation
Source and function of glyceryphosphoryl-choline in ejaculate?
Source: Epididymis
Function: Used as a source of choline in phospholipid metabolism
Source and function of acid phosphatase in ejaculate?
Source: Prostate
Function: Cleaves choline from glycerophosphorylcholine
What is the process by which the penis is made turgid?
Haemodynamic changes involving the corpora cavernosa. These are sinuses along most of the length of the penis
3 sources of arousal?
– erotic psychological stimuli (e.g. visual, olfactory)
– tactile stimuli at the level of the brain
– tactile stimuli can also mediate local spinal reflexes
Sympathetic control of erection?
– lower thoracic and lumbar spinal segments
– maintains flaccidity
Innervates prostate gland and seminal vesicle
Sympathetic leads to constriction of bv everywhere apart from…
skeletal muscles
Parasympathetic control of erection?
Control centre in sacral spinal segments
Increased activity produces turgidity
Innervates erectile tissue
What is the tumescence of the penis?
Erection centre in the sacral spinal cord which mediates the erection reflex
Action of the tumescence of the penis?
- Dilatation of arterioles to c. cavernosa and c. spongiosum
- Closing of arteriovenous shunts that normally bypass the c. cavernosa
- Occlusion of vein draining penis
Parasympathetic action on vascular smooth muscle during erection?
Relaxation of vasculature by release of ACh acting on the vascular endothelial cells.
Indirectly triggers release of NO which causes relaxation of the vascular smooth muscle
Failure to obtain an erection can result from?
– mechanical damage to the c. cavernosa
– obstruction of the arteries to the penis
– drugs that block parasympathetic actions
– psychological factors
-Stress associated with high symp activity. NA causes vasoconstriction of penile arterioles and so inhibits erection.
Sympathetic role in ejaculation?
– ejaculatory centre in lower thoracic and lumbar spinal cord
– signals to ducts of genital tract and to bulbocavernosus muscle at the base of penis
What are the two phases of ejaculation?
Emission
– smooth muscle contraction in walls of the genital tract
– expels semen into urethral bulb
Expulsion
– rhythmic contractions of penis and bulbocavernosus muscle
– ejects semen in spurts
ejaculation normally followed by a refractory phase of 10 mins to an hour
Order of ejaculate composition?
First component: Prostate
Rich in acid phosphatase and citric acid
Second component: Vas deferens
Rich in spermatozoa
Third component: Seminal vesicle
Rich in fructose
Coagulation followed by liquefaction
How does sildenafil/viagra work to produce erections?
Inhibitors of PDE V.
In NO pathways to produce vasodilation the cGMP can be inactivated by PDE V. If inactivation is inhibed then the cGMP and continue it’s reaction to…
cGMP–> PKG –> Vasodilation and erection
