Describe the composition of semen
- Spermatozoa +
- Seminal plasma
Identify 3 functions of the semen
- Transport medium
- Buffering capacity
Where is seminal plasma derived from?
Accessory glands of the male reproductive tract:
- Prostate gland
- Seminal vesicles
- Bulbourethral gland
What is the usual site for fertilisation?
Ampulla of uterine tube
Identify the 4 phases in the sexual response
- Excitement phase
- Plateau phase
- Orgasm phase
- Resolution phase
What sort of stimuli trigger the excitement phase?
Psychogenic and / or somatogenic stimuli
What happens after the resolution phase in the sexual response?
Return to haemodynamic norm followed by a refractory period (males)
Identify the 2 stimulants of the male sexual response – erection
- Tactile (sensory afferents of penis and perineum)
Identify the 2 efferent nerves in the male sexual response – erection
Somatic and autonomic efferents:
- Pelvic nerve (PNS)
- Pudendal nerve (Somatic)
Which three processes are required for an erection to occur?
- Sinusoidal relaxation
- Arterial dilation
- Venous compression
Identify the nerves involved in the parasympathetic innervation of the penis
- Pelvic nerve and pelvic plexus
- Cavernous nerve
Describe 3 neurophysiological events which produce an erection
- Inhibition of sympathetic arterial vasoconstrictor nerves
- Activation of non-adrenergic, non-cholinergic, autonomic nerves to arteries
- Release of Nitric Oxide (NO)
In five steps, describe the events leading to the release of NO in an erection
⇒ Post-ganglionic fibres release ACh
⇒ ACh bonds to M3 receptor on endothelial cells
⇒ Rise in [Ca2+]i activates NO synthase and formation of NO
⇒ NO diffuses into vascular smooth muscle and causes vasodilation
⇒ NO is also directly released from nerves
Identify 4 causes of erectile dysfunction
- Tears in fibrous tissue of corpus cavernosa
Describe the psychological cause for erectile dysfunction
Psychological – descending inhibition of spinal reflexes
What sort of neural control governs emission and ejaculation?
Sympathetic Nervous System
Which 2 events occur in the male sexual response – emission?
- Movement of semen into prostatic urethra
- Contraction of smooth muscle in prostate, vas deferens and seminal vesicles
What occurs in the male sexual response – ejaculation?
Expulsion of semen:
- Contraction of smooth muscle in glands and ducts
- Bladder internal sphincter contracts
- Rhythmic striatal muscle contractions
Why does the bladder internal sphincter contract in ejaculation?
To prevent retrograde ejaculation
Which structures are involved when the striatal muscles contract in ejaculation?
- Pelvic floor
- Perineal muscles
- Ischiocavernosus muscle
- Bulbospongiosus muscle
Describe the hormonal influence over the changes of the character of cervical mucus in the menstrual cycle
- Oestrogen: thin, stretchy cervical mucus
- Oestrogen & progesterone: thick, sticky cervical mucus (forms a plug)
What is the site of sperm deposition?
Describe the process which occur as part of capacitation in the female reproductive tract?
- Further maturation of sperm (6-8 hours)
- Sperm cell membrane changes to fuse with oocyte
- Sperm tail movement changes to a whip-like action
- Acrosome reaction can now occur
State the fertility windows for the sperm and oocyte respectively
- Spermatozoa: 48 - 72hr
- Oocytes: 6 - 24 hr
What is the fertile period?
Fertile period: sperm deposition up to 3 days prior to ovulation or day of ovulation
Distinguish between the transport of the gametes
- Oocyte: beating cilia & peristalsis of uterine tube
- Sperm: own propulsion
Describe the origin, structure and function of the acrosome
- Origin: derived from golgi region of developing spermatid
- Structure: contains enzymes
- Function: necessary for fertilisation
Which 2 events trigger the acrosome reaction?
- Sperm pushes through corona radiata
- Binding of sperm surface receptor to ZP3 glycoprotein of zona pellucida
What is the result of the acrosome reaction?
Which 2 processes lead to fertilisation?
- One sperm penetrates leading to fusion of plasma membranes
- Cortical reaction occurs (blocks polyspermy)