Lecture 10 - Getting Pregnant Flashcards
How many male and female gametes do we produce?
Male - 100 million per day
Female - Approx 40 in lifetime
Epididymal Maturation of Sperm
When spermatozoa enter epididymis from semineferous tubules, they are not capable of movement.
At Epididymal Tail, they can move and have potential to fertilise
Secreted products are added to surface of sperm
All depends on support by androgens
Functions of seminal plasma?
- Transport medium for sperm
- Nutrition for sperm
- Buffering capacity
What 3 glands secrete the main constituents of seminal plasma?
- Seminal vesicles
- Prostate Gland
- Bulbourethral Gland (Cowper’s)
What are the function of the Seminal Vesicles?
- First secretion added to sperm
- Creates 60% of seminal plasma
- Contain:
- Fructose - Sperm energy source
- Prostaglandins - Make cervix more receptive to sperm during fertilisation
- Clotting Factors - Stop sperm loss in female tract
- Alkaline to neutralise acidity of vagina
What are the functions of the prostate gland?
- 25% seminal plasma
- Milky, acidic fluid
- Secrete proteolytic enzymes, citric acid and zinc
- Muscle wall of prostate propels seminal plasma along urethra during ejaculation
What are the functions of the bulbourethral glands?
- Approx 1% of seminal plasma
- Secretes an alkaline fluid that lubricates tip of penis and urethra when aroused
- Neutralises acidic urine residue in urethra
How does the structure of the Tunica Albuginea of the penis allow erection?
The Tunica Albuginea is taught and rigid, so allows growth of the tissue within it
What 3 things have to occur for an erection to take place?
- Sinusoidal relaxation in Corpus Cavernosum
- Arterial Dilatation to allow more blood into the penis
- Venous compression to limit venous return
What is the role of Nitric Oxide in erection?
- Autonomic nerves to arteries in the penis are activated by the PNS
- These nerves release Ach from postganglionic fibres
- Ach binds to M3 receptors on endothelial cells
- This causes a rise in intracellular Calcium, which leads to an increase in Nitric Oxide Synthase, creating more Nitric Oxide
- Nitric Oxide diffuses into SM and causes vasodilatation of arteries by lowering intracellular calcium levels in SM
- (Note: Some NO diffuses straight into SM from nerves)
Causes of erectile dysfunction
Psychological
Tear in fibrous tissue of Corpus Cavernosum
Vascular
Drugs that lower NO for example
Which drug treats erectile dysfunction and how does it work?
Viagra
Stops degrading of cyclic GMP into other products, thus allowing more cGMP to act on a cGMP-protein kinase.
This in turn decreases SM Calcium levels
Which nervous system innverates the erection and ejaculation periods (point and shoot)?
Parasympathetic (point) innervates erection
Sympathetic NS is inhibited
Sympathetic (shoot) innervates emission and ejaculation
How do glands and muscles aid emission and ejcaulation?
Emission
- Movement of semen into prostatic urethra via contraction of prostate, vas deferens and seminal vesicles SM
- Propels seminal plasma
Ejaculation
- Glands and ducts contract
- Rhythmic striatal contraction of muscles (pelvic floor, ischiocavernous and bulbospongiosus)
Why does the bladders internal sphincter contract during erection?
To prevent retrograde ejaculate (ejaculate going back up into bladder)
