Coitus and conception Flashcards
What are the two stimulants of erection?
- Psychogenic
- Tactile
What is emission?
Movement of ejaculate into the prostatic urethra before ejaculation by peristalsis of vas deferens
What are the efferent so involved in erection?
- Pelvic nerve (PNS)
- Pudendal nerve (somatic)
What haemodynamic changes occur in erection?
- Inhibition of sympathetic arterial vasoconstrictor nerves
- Activation of PNS
- Activation of non-adrenergic, non-cholinergic nerves to arteries releasing NO
- Central arteries of corpus cavernosa straighten and dilate
- Bulbospongiosus and ischocavernosus compress veins
What does the PNS do to promote erection?
- Acts via pelvic nerve
- ACh binds to M3 receptors
- Rise in Ca concentration activates NOS
- NO increases
- NO diffuses into VSMC causing relaxation and thus vasodilation
How does NO cause vasodilation?
- Increases cGMP
- Ca moves into Intracellular stores, reducing its concentration
- Reduced actin-myosin cross bridges
- Relaxation of smooth muscle
What happens when central arteries of corpus cavernosa straighten and dilate?
Blood flows into and dilates the cavernous spaces
Why does corpus sponsiosum not dilate as much?
Do not want to compress urethra
How does the action of Bulbospongiosus and ischocavernosus help maintain erection?
- Compression of veins
- Corpra cavernosa become engorged with high blood pressure
- Erectile bodies become turgid
What are the causes of erectile dysfunction?
- Psychological
- Tears in fibrous tissue do corpus cavernosa
- Vascular pathology
- Factors blocking NO
What factors can block NO?
- Alcohol
- Anti-hypertensives
- Diabetes
How does Viagra work?
Inhibits the breakdown of cGMP
What nerve roots control ejaculation?
L1&2 SNS
What happens for ejaculation to occur?
- Contraction of glands and ducts
- Bladder and internal sphincter contract
- Rhythmic striated muscle contractions (pelvic floor, perineum, hip and anal muscles)
Why does the internal urethral sphincter contact in ejaculation?
To prevent retrograde ejaculation
What is the normal volume of ejaculate?
2-4 ml
What is the volume of sperm present in semen?
20-200 x10^6 per ml
How much do the seminal vesicles contribute to semen volume?
60%
What is present in secretion from the seminal vesicles?
- Alkaline fluid
- Fructose
- Prostaglandins
- Clotting factors
What is present in secretion from the prostate?
- Proteolytic enzymes
- Citric acid
How much does secretions from the prostate contribute to semen volume?
25%
What does the Bulbourethral gland do?
Secretes a small amount of alkaline fluid to lubricate the end of the penis and urethral lining prior to ejaculation
Why does semen coagulate immediately after ejaculation?
Prevents sperm being lost from the vagina
What causes semen to coagulate immediately after ejaculation?
Clotting factors
