Lecure 10 - Pregnancy Flashcards
Normal site of fertilisation
Ampulla of Fallopian tube
Human sexual response stages
Excitement phase - erection
Plateau phase - emission
Orgasm phase - ejaculation
Resolution phase
Excitement phase
Psychogenic or somatic stimuli
Parasympathetic efferent via pelvic nerve and somatic efferents via pudendal nerve causes erection
Arteries secrete nitrous oxide which vasodilates arteries
Inhibition of sympathetic arterial vasoconstriction nerves
Erection
Sinusoids within the corpus cavernosum relax and arterioles dilate
Venous compression due to increased blood flow against the tunica albuginea surrounding the corpus cavernosa
Corpus spongiform during erection
Not completely compressed as would block semen pathway
Vasodilation of arteries
- Post ganglionic fibres release Ach
- Ach binds to M3 receptors on endothelial cells
- M3 receptors stimulate an increase in intracellular calcium
- Nitric oxide synthase activated, producing nitric oxide
- Nitric oxide diffuses into the vascular smooth muscle and causes vasodilation
NO is also released directly from the cavernous nerve
Causes of erectile dysfunction
Psychological- inhibition of spinal reflexes
Tears in corpora cavernosum
Vascular defect
Drugs
Sidenofil
Slows rate at which cGMP is degraded
Therefore more NO can be released
Maintains NO release
Emission
Sympathetic control
- movement of semen into the prostatic urethra
- contraction of smooth muscle in the prostate, vas deferens and seminal vesicles
Ejaculation
Contraction smooth muscle in the glands and ducts
Internal ureteric sphincter contracts to prevent retrograde ejaculation into the bladder
EUS also contracts
Rhythmic striated muscle contractions of the pelvic floor and perineal muscles
Expulsion of semen
Spinnbarkeit test
Stretchyness of cervical mucous
Fern test
Cervical mucus dries on glass and looks like fern under a microscope
Site of sperm deposition
External OS
Capacitation
Maturation of sperm in the female genital tract (6-8 hours)
Tail moves from beat like to whip like motions so it can penetrate the zone pellucida
Enzymes are released from the acrosome which removes the outer granulosa cells of the ovum - corona radiata
Now sperm can fuse with the oocyte cell surface
Corona radiata
Granulosa cells lining the ovum before capacitation
Acrosome reaction
Sperm pushed through the corona radiata
Sperm interacts with the zone pellucida - sperm surface receptors bind to ZP3 glycoproteins of the zona pellucida
The outer layer of the sperm head is lost and the zona pellucida is digested
The sperm penetrates the ovum and fused with the membrane
Cortical reaction of ovum
Prevents further sperm from entering the oocyte - polyspermy
Triggers meiosis II to finish
Morula
Multiple mitotic divisions of the zygote (8 cell stage) to form morula
Totipotent cells - can differentiate into anything
Fertile window
Spermatozoa - 2 - 3 days
Oocytes - 6 - 24 hours
Fertile period
Sperm deposition up to 3 days before ovulation to 1 day after
Gamete transport
Oocyte - beating of cilia and peristalsis of the uterine tube
Sperm - own propulsion and tail movements
Acrosome
Derived from Golgi region of developing spermatid
Contains enzymes
Fertilisation
Sperm and ovum plasma membranes fuse
Meiosis II
Series of calcium waves are activated after ovum fusion to sperm
Meiosis II resumes and the pronuclei fuse together
