Session 7 - Coitus and Conception Flashcards
Define sexual reproduction:
Formation of a unique individual from the gametes of two other individuals.
What is the rate of sperm production?
1000 spermatozoa per second
How long does it take spermatogonia to mature?
74 days
What are the 4 phases of coitus?
Excitement Phase
Plateau Phase
Orgasmic Phase
Resolution Phase (+/- Refractory Period)
What are the features of the female sexual response?
Blood engorgement and erection of: Clitoris, Vaginal Mucosa, Breast and Nipples Glandular Activity Sexual excitement \+/- orgasm No physiological refractory period
What are the features of the female sexual response?
Blood engorgement and erection of: Clitoris, Vaginal Mucosa, Breast and Nipples Glandular Activity Sexual excitement \+/- orgasm No physiological refractory period
Describe the steps involved in penile erection:
Stimulants can be psychogenic or tactile.
This causes efferents via the Pelvic nerve (PNS) and Pudendal nerve (somatic) to cause hameodynamic changes.
What is the overall mechanism of erection?
Smooth muscle in the arteries of the corpus cavernous dilate allowing more blood in. The bulbospongiosus and ischiocavernous muscles compress the veins restricting the drainage of blood.
What is the overall mechanism of erection?
Smooth muscle in the arteries of the corpus cavernous dilate allowing more blood in. The bulbospongiosus and ischiocavernous muscles compress the veins restricting the drainage of blood.
What specific changes occur which produce haemodynamic changes or tumescence?
Inhibition of sympathetic arterial vasoconstrictor nerves
Activation of the PNS
Activation of non-adrenergic, non-cholinergic nerves to arteries releasing NO
What is the action of NO on smooth muscle?
Post ganglionic PNS releases ACh
ACh binds to M3 on endothelial cells
This increases Calcium levels intracellular and activates NOS and NO is formed.
NO diffuses into smooth muscle and causes relaxation of vasodilation.
(NO can also be released directly from the non-adrenergic, non cholinergic nerves)
What is the action of NO on smooth muscle?
Post ganglionic PNS releases ACh
ACh binds to M3 on endothelial cells
This increases Calcium levels intracellular and activates NOS and NO is formed.
NO diffuses into smooth muscle and causes relaxation of vasodilation.
(NO can also be released directly from the non-adrenergic, non cholinergic nerves)
What are some of the causes of erectile dysfunction?
Psychological - descending inhibition of spinal reflexes
Tears in fibrous tissue of corpora cavernosa
Vascular - arterial and venous
Drugs
Factors that block NO - alcohol, anti-hypertensives, diabetes
How does viagra work?
Viagra blocks an enzyme that causes cGMP breakdown.
cGMP is needed to cause a reduction in intracellular calcium which is needed to cause vasodilation.
How does viagra work?
Viagra blocks an enzyme that causes cGMP breakdown.
cGMP is needed to cause a reduction in intracellular calcium which is needed to cause vasodilation.
What is emission?
Otherwise known as pre-ejaculate
Movement of ejaculate into prostatic urethra - caused by Vas deferens peristalsis
Accessory glands secretions (bulbourethral glands) may be involved
What is mechanism of ejaculation?
Under sympathetic nervous system control L1,L2
- Contraction of glands and ducts (smooth muscle)
- Bladder internal sphincter contracts
- Rhythmic striatal muscle contractions (pelvic floor, ischiocavernous, bulbospongiosus, hip and anal muscles)
What is mechanism of ejaculation?
Under sympathetic nervous system control L1,L2
- Contraction of glands and ducts (smooth muscle)
- Bladder internal sphincter contracts
- Rhythmic striatal muscle contractions (pelvic floor, ischiocavernous, bulbospongiosus, hip and anal muscles)
What is the volume of a normal ejaculate?
2-4ml
What is the sperm content of a normal ejaculate?
> 40 x 10(6) or 20-200ml per ml
What is the criteria for abnormal oligospermia?
What is the criteria for abnormal oligozoospermia?
What do seminal vesicles contribute to ejaculate and what volume does it constitute?
Alkaline fluid (neutralises the acid of the male urethra and female reproductive tract) Fructose Prostaglandins Clotting factors (semenogelin) 60% volume
What does the prostate contribute to ejaculate and what volume does it constitute?
Milky, slightly acidic fluid
Proteolytic enzymes - breakdown of clotting proteins - reliqueyfies semen in 10-20 minutes
Citric acid and acid phosphatase
25% volume
What do bulbourethral glands contribute to ejaculate and what volume does it constitute?
Alkaline fluid
Very small volume
Also produces a mucous that lubricates the end of the penis and urethral lining.
What do bulbourethral glands contribute to ejaculate and what volume does it constitute?
Alkaline fluid
Very small volume
Also produces a mucous that lubricates the end of the penis and urethral lining.
What are the affects of hormones of the cervix?
Progesterone and oestrogen produce a thick, sticky mucous plug that blocks the cervix.
Oestrogen only - abundant clear, non-viscous mucous
What happens to sperm when it enters the vagina?
It first coagulates due to clotting factors - fibrinogen and vesiculae - this is to prevent sperm being physically lost from the vagina.
It then liquefies by action of enzymes - fibrinolysis
Where and what distance do the sperm have to travel from the cervix?
They travel from the cervix to the uterine tube. This is approximately 15 to 20cm. This may take several hours.
How do the sperm move from the cervix to the fallopian tube?
Own propulsive capacity
Fluid currents generated by ciliated cells in the uterine tubes.
How do the sperm move from the cervix to the fallopian tube?
Own propulsive capacity
Fluid currents generated by ciliated cells in the uterine tubes.
What is capacitance?
Further maturation of sperm within the female reproductive tract.
Sperm cell membrane changes to allow fusion with oocyte cell surface
Tail movement changes from beat to whip like action. 3mm/hour
How many sperm but reach the occyte and why?
Approx 300
1 needed for fertilisation
299 needed to disperse the zona pellucida
What is the average survival of spermatozoa and oocytes in the female reproductive tract?
Spermatozoa 48-72hr
Oocytes 6-24hr
When is the fertile period?
Sperm depositive up to 3 days prior to ovulation or day of ovulation.
How is the oocyte transported?
Via beating cilia
Peristalsis of the fallopian tube
Describe fertilisation:
Occurs in the ampulla of the fallopian tube.
What is capacitance?
Further maturation of sperm within the female reproductive tract.
Sperm cell membrane changes to allow fusion with oocyte cell surface - removal of glycoprotein coat
Tail movement changes from beat to whip like action. 3mm/hour
Describe fertilisation:
Occurs in the ampulla of the fallopian tube.
Sperm pushes through granulosa cells
Proteins on sperm head bind to ZP3 proteins of zona pellucida. Binding triggers acrosome reaction.
Acrosomal enzymes exposed to zona pellucida.
Hydrolysing enzymes digest path through ZP.
One sperm pentrates - there is a fusion of plasma membranes (egg and sperm)
Sperm moves into cytoplasm - zygote
Polyspermy blocked - corticol reaction
Egg completes meiosis II
Pronuclei (2 sets of chromosomes)
Fusion of Pronuclei - to form diploid zygote
Mitosis
What is the process of cleavage?
Series of rapid mitotic division. There is an increased number of cells with no increase in size. All the cells are totipotent and it is at this point that monozygotic twins can form.
What is the process of cleavage?
Series of rapid mitotic division. There is an increased number of cells with no increase in size. All the cells are totipotent and it is at this point that monozygotic twins can form.
What happens to the zygote after formation?
It waits in the fallopian tube for 3 days awaiting a rise in progesterone. This period of cell division is called the blastocyst.
Progesterone primes the endometrium.
Conceptus in nourished in intrauterine fluid - 3 days of floating
Sticky trophoblasts adhere to endometrium hCG
Implantation commences - 6 days after ovulation
Describe a blastocyst:
Has lost totipotency
Has an outer layer of trophoblast cells
Inner cell mass (which becomes the embryo)
And a fluid filled cavity
Describe a blastocyst:
Has lost totipotency
Has an outer layer of trophoblast cells
Inner cell mass (which becomes the embryo)
And a fluid filled cavity
Describe methods of ‘natural conception’:
Abstinence
Coitus interruptus - however there can be sperm in the pre-ejaculate
Rhythm method - need a regular cycle - avoid having sex during fertile period days 7-16 of the menstrual cycle.
What methods of contraception prevent the sperm from entering the ejaculate?
Vasectomy - divide the vas deferens bilaterally - have to ensure duct past the point of division is free of sperm before you can use it as a method of contraception. e.g. first couple of months
What methods of contraception prevent the sperm from reaching the cervix?
Condons - also protect against STIs
Diaphragm - however needs correct fitting - does not completely occlude passage of sperm - holds sperm in acid environment of vagina therefore reducing their survival time.
Cap - fits across cervix - physical barrier
Spermicide - not often used solely - most effective with barrier methods.
What are some of the hormonal methods of contraception?
Combined OCP - oestrogen and progesterone - Negative feedback to hypothalamus and pituitary inhibits follicular development. Oestrogen - loss of positive feedback mid cycle so no LH surge.
Progesterone Injection - 3 monthly injections - negative feedback effect to inhibit ovulation
Progesterone-only pill - low dose progesterone only - may inhibit ovulation (mini-pill)
Progesterone implants - may inhibition ovulation
What are some of the hormonal methods of contraception?
Combined OCP - oestrogen and progesterone - Negative feedback to hypothalamus and pituitary inhibits follicular development. Oestrogen - loss of positive feedback mid cycle )as progesterone present also) so no LH surge.
Progesterone Injection - 3 monthly injections - negative feedback effect to inhibit ovulation
Progesterone-only pill - low dose progesterone only - may inhibit ovulation (mini-pill)
Progesterone implants - may inhibition ovulation.
What are some of the hormonal methods of contraception?
Combined OCP - oestrogen and progesterone - Negative feedback to hypothalamus and pituitary inhibits follicular development. Oestrogen - loss of positive feedback mid cycle )as progesterone present also) so no LH surge.
Progesterone Injection - 3 monthly injections - negative feedback effect to inhibit ovulation
Progesterone-only pill - low dose progesterone only - may inhibit ovulation (mini-pill)
Progesterone implants - may inhibition ovulation.
What methods of contraception prevent transport along the fallopian tube?
Clips, rings, ligation of the fallopian tube - in order to occlude the tubes. Can rarely 1:300-500 reconciles.
What methods of contraception prevent transport along the fallopian tube?
Clips, rings, ligation of the fallopian tube - in order to occlude the tubes. Can rarely 1:300-500 recanalise.
What methods of contraception prevent the sperm from passing through the cervix and how?
Combined OCP
Progesterone injection, Implant, Pill
Makes cervical mucous thick and sticky - hostile so that sperm cannot travel through
This is the main role of the progesterone only pill and implant.
What methods of contraception prevent the sperm from passing through the cervix and how?
Combined OCP
Progesterone injection, Implant, Pill
Makes cervical mucous thick and sticky - hostile so that sperm cannot travel through
This is the main role of the progesterone only pill and implant.
What methods of contraception prevent implantation?
Hormonal - affect receptivity of the endometrium - plus absence of corpus luteum prevents preparation of endometrium for implantation. OCP, POP, Depot progesterone and progesterone implant.
Post-coital contraception - emergency contraception - high dose oestrogen and progesterone or progesterone only - can be given up to 72hrs after intercourse.
Intra-uterine device - can be used post-coital contraception of up to 5 days after ovulation. Inert or copper containing or progesterone implanted (marina coil) Copper interferes with endometrial enzymes - may also interfere with sperm transport into fallopian tubes.
What methods of contraception prevent implantation?
Hormonal - affect receptivity of the endometrium - plus absence of corpus luteum prevents preparation of endometrium for implantation. OCP, POP, Depot progesterone and progesterone implant.
Post-coital contraception - emergency contraception - high dose oestrogen and progesterone or progesterone only - can be given up to 72hrs after intercourse.
Intra-uterine device - can be used post-coital contraception of up to 5 days after ovulation. Inert or copper containing or progesterone implanted (marina coil) Copper interferes with endometrial enzymes - may also interfere with sperm transport into fallopian tubes.
Define infertility:
Failure to conceive within 1 year
Can be primary if there has been no previous pregnancy or secondary if there has (successful or not)
Affects approximately 15% of couples
What are some of the causes of infertility?
Coital problems
Anovulation 15-20% of cases
Tubal Occlusion 15-40% of cases
Abnormal/absent sperm production 20-25% of cases
What can cause anovulation?
Hypothalamic problems - Hyperprolactinaemia, weight loss, exercise and stress
Pituitary problems - Pituitary tumours and necrosis
Ovarian problems - ovarian failure, menopause, radiotherapy, chemotherapy
What can cause anovulation?
Hypothalamic problems - Hyperprolactinaemia, weight loss, exercise and stress
Pituitary problems - Pituitary tumours and necrosis
Ovarian problems - ovarian failure, menopause, radiotherapy, chemotherapy
Polycystic ovarian syndrome - increased androgen secretion and a raised LH/FSH ratio. Some insulin resistance, multiple small ovarian cysts - anovulation, amenorrhoea or oligomenorrhea.
How do you diagnose anovulation?
Measure 21 day progesterone e.g in the mid luteal phase
How can you induce ovulation?
Anti-oestrogen - reduce negative feedback to hypothalamus/pituitary - increase GnRH and increase FSH
Gonadotrophins - FSH administration
GnRH agonists - pulsatile to mimic normal secretion.
What can cause tubular occlusion?
Sterilisation
Scarring from infection - STI’s especially chalymydia - PID
Endometriosis
How would you diagnose tubular occlusion?
Use a HSO - Hysterosalpinogram - X ray with contrast to view any occlusions.
What is the treatment for tubular occlusion?
Surgery
Or assisted contraception.
What are causes of abnormal/absent sperm production?
Abnormal production - testicular disease
Obstruction of ducts - infection, vasectomy
Hypothalmic/pituitary dysfunction
What are causes of abnormal/absent sperm production?
Abnormal production - testicular disease
Obstruction of ducts - infection, vasectomy
Hypothalamic/pituitary dysfunction
