Lecture 38 - Coitus, fertilisation, and contraception Flashcards
Definitions of monarch
The onset of menstrual cycles
Definition of menopause
The cessation of menstrual cycles (usually in a woman’s 50s)
GnRH from the hypothalamus directly regulates the secretion of …
LH and FSH
During oogenesis, at what point in meiosis II is the secondary oocyte suspend and what event causes the cell cycle to resume?
Metaphase II
Dertilisation causes the cell cycle to resume (fertilisation can also be called sperm penetration)
What happens to the oocyte if fertilisation does not occur?
Atresia (degeneration)
Coitus
From the latin ‘a meeting together, sexual union’
Sexual intercourse/copulation
Erect penis introduced into vagina (intromission)
Semen released into upper part of vagina (insemination) so that sperm can travel to appropriate site for fertilisation (ampulla of uterine tube)
It is all about ensuring that the male gamete can be transported up into the female reproductive tract
Intromission
Erect penis introduced into vagina
Stages of the male sexual act
Erection of penis - parasympathetic (allows for intromission)
Mucus secretion into urethra - an erection is associated with secretion of fluid from the bulbourethral glands (in the pelvic diaphragm) which provides lubrication for the urethra and also cleans out any residual urine that might be present and this is then followed by ejaculation
Ejaculation
Two phases (both sympathetic)
Emission
Expulsion
Resolution - penis becomes flaccid
And then there is a refectory period where another erection can not occur
Two phases of ejaculation
Ejaculation
Two phases (both sympathetic)
Emission
Expulsion
The erection of the penis is a ________ response
Parasympathetic
The ejaculation is a __________ response
Sympathetic (both phases are)
Corpus spongiosum
Structure through which the urethra runs
Runs the entire length of the penis and widens to form the glans penis
Corpus cavernosum
Runs from the root of the penis to just below the glans penis - there is two of them
Bulbocavernosus muscle (bulbospongiosus)
very important in the ejaculatory process
Covers the bulb of the penis
Fascia of the penis
The erectile tissues are surrounded by different layers of fascia
Fascia are important in restraining the erection
Superficial fascia
Outermost fascia
Tunica albuginea
Two of these - one around the spongiosum and one around cavernosum
The tunica albuginea around the corpus spongiosum (and therefore surround the urethra as it is inside this) is not as dense as the other tunica albuginea
Deep (Buck’s) fascia
Buck’s fascia, which covers the corpora cavernosa and corpus spongiosum and attaches posteriorly to the suspensory ligaments of the penis, allowing the erect penis to achieve a horizontal or greater angle.
Trabeculae
Connective tissue containing smooth muscle which is important for the constraining and allowing of the vasculature to the erectile tissues
Lacunae
Blood filled spaces that are part of the process of expanding and causing an erection
Comparative structure of the clitoris and the penis
Structure of the clitoris and penis are homologous
Tissues of the clitoris are erectile as in the penis
It is thought that the glans, the body and the cura of the clitoris are homologous to the corpra cavernosa of the male
Branches of the abdominal artery
Abdominal aorta to common iliac artery to internal iliac artery to internal pudendal artery
Gonadal artery
Branch off the abdominal aorta
Gonadal artery - in females this is the ovarian artery and in males it is the testicular artery, quite a high branch point off the abdominal aorta which reflects the devleopmental orgin of the testes as the testes originally develop up within the abdominal cavity and then migrate downwards into the scrotum and as they develop down they bring their vasculature with them hence the length of the testicular arteries
What does the internal pudendal artery feed?
Feeds perineum and external genitalia including the penis and also the rectum
Branches of the internal pudendal artery to the penis includes…
Artery to bulb
Urethras artery
Dorsal artery
Deep (cavernosal) artery
Blood supply to the penis _______ during erection
Increases
Have the lacunae , the spaces, which are surrounded by the smooth muscle layers or the tissues of the trabeculae and then the little venules form a venous plexus that surrounds the circumference of the column of erectile tissue and when you have an erection taking place then the lacunae fill with blood, the trabeculae relax and the engorgement puts pressure on the venous plexus and it is being restrained by the fascia which allows for the erection and also reduces the venous return to the body
Genital sexual reflexes
Coordination of sympathetic, parasympathetic and somatic divisions of the nervous system
Reminder of the different divisions of the nervous system
CNS = Brain and spinal cord
PNS = communication between the CNS and the rest of the body
Sensory (afferent) division as well as the motor (efferent) division
From the motor division have the somatic nervous system (it is voluntary) and autonomic nervous system (involuntary)
From the ANS we have the sympathetic nervous system (mobilises body systems during activity) and parasympathetic division (promotes house keeping functions during rest)
Nerve supply to the penis
Penis richly innervated by sensory and motor nerves
Includes sensory fibres responsive to touch, pressure, temperature
Richly innervate by sensory nerves in the glans of the penis which are sensitive to touch, pressure and temperature and the afferent signals from these sensory nerve fibres are sent via the dorsal nerve of the penis via the pudunoal nerve up to the sacral region of the spinal cord
Pudendal nerve supplies sensory and somatic motor innervation to perineum and external genitalia, including penis (dorsal nerve)
Autonomic innervation to penis derived from pelvic plexus (parasympathetic and sympathetic)
All of the autonomic nerves converge at the pelvic plexus so the sympathetic innervation derives up from in the thoracic lumbar region via the hypogastric nerves converging one the pelvic plexus whereas the parasympathetic innervation comes from the sacral region converging via the pelvic plexus and then providing einnervation into the arteries of the penis and other regions of the external genitalia, providing innervation to the accessory glands and also innervation to ducts that make up the reproductive tract
Parasympathetic (erection)
Stimulates production of nitric oxide/NO (vasodilator) by deep arteries of penis
Deep arteries dilate and fill lacunae in corpora cavernosa
Simulates vasodilation in the deep arteries of the penis which all’s blood flow into the lacunae (erectile tissues) which helps fill them up and allows the engorgement of an erection to take place
Sympathetic (ejaculation)
Stimulates contraction of smooth muscle
Reproductive ducts
Accessory glands
In the ductus deferens and also the smooth muscle around the accessory glands, all about the movement of the spermatozoa and also secretion of the dmseminal fluid so that they can be combined in the urethra to form semen
Somatic motor (ejaculation)
Stimulates contraction of skeletal muscles around the bulb of the penis
Erection
Parasympathetic response to stimuli….
Might be visual stimuli, tactile stimuli particular;y of the perineum and penis specifically the glans part of the penis, thoughts, memory and this results in efferent parasympathetic signals to the penis and the bulbourethral glands
Arteries in erectile tissues dilate
Erectile tissue becomes engorged with blood
Erect penis can be inserted into vagina (intromission)
Efferent parasympathetic signals cause …
Penis =
Deep artery dilates in response to nitrous oxide
Trabecular muscle of erectile tissue relaxes
Erectile tissues fill with blood
Engorgement of erectile tissues
Penis becomes erect
Bulbourthral gland =
Secretes bulbourethral fluid for lubrication and the clean up of residual urine
Emission
Sympathetic response
Smooth muscle of ductus defers contracts to move sperm into the ampulla (peristaltic contractions)
Smooth muscle of ampulla, seminal vesicles and prostate gland contract moving sperm and seminal fluid into urethra
Assuming you have continuation of the afferent signals you will then have a process where you have peristalsis of the ductus deferns which moves sperm up the ductus and into the dilated region that is known as the ampulla which is then followed by the contraction of the smooth muscle of the ampulla but also the smooth muscle surrounding the seminal vesicles and prostate which allows the movement of the spermatozoa and seminal fluid into the prostatic urethra
Efferent sympathetic signals cause… Ductus deferens= Peristalsis Sperm move into ampulla Ampulla contracts Sperm moves into urethra Seminal vesicles = Secretes components of seminal fluid Prostate gland = Secretes components of seminal fluid
Expulsion
Semen in the urethra activates somatic and sympathetic reflexes (semen in urethra sends afferent signals)
Contractions of urethral smooth miclse
Pelvis floor muscles contract
Semen is ejected
Efferent sympathetic signals cause…
Accessory glands=
Additional secretion from prostate gland and seminal vesicles
Internal urethral sphincter contracts (urine remains in bladder) - prevents retrograde ejaculation
Efferent somatic signals cause…
Bulbospongiosus muscle=
Contracts and rhythmically compresses bulb/root of penis which compresses the urethra. Semen is expelled (if this occurs during intromission then the semen will be deposited into the upper regions of the vagina)
Resolution
Sympathetic response
Blood flow to the penis is reduced
Penis becomes flaccid
Efferent sympathetic signals cause…
Internal pudendal artery =
Constricts, reduces blood flow into the penis (into the deep arteries of the penis located in the corpus cavernosum)
Trabecular muscles = (surrounding the lacunae, smooth muscle)
Contract, squeeze blood from the erectile tissues
Penis =
Becomes flaccid (detumescent)
Refractory period
Once resolution takes place there is a refectory period in males and this is a period of time for which the individual male will not be able to have another erection and the timing of this varies greatly between individuals
Stages of the female sexual response
Similar sequence of reflex response as in the male Again we have afferent stimuli can be psychogenic, thoughts, memories, of tactile response specifically around the perineum and clitoris
Engorgement of clitoris, labia and vagina in response to autonomic stimulation
Lubricating fluid secreted through vaginal wall; secretion of mucus into vestibule (greater vestibular glands)
There is two sites of secretion, there is transidate which comes from across the walls of the vagina which helps to lubricator the vagina and then there is also secretions by the greater vestibular glands which open just around the vestibule/opening of the vagina and they help to lubricate the vestibule and the more inferior part of the vagina
Increased width and length of vagina. Uterus elevates upwards
Particularly at the upper regions of the vagina
The uterus moves from its anteverted position (sitting over the bladder) to being more upright in position
Rhythmic contraction of vaginal, uterine and perineal (pelvic floor) muscles)
Insemination and what happens from there…
Sperm is released into the upper part of the vagina (insemination). The sperm travels to the uterine tube for fertilisation (ampulla)
Sperm fuses with secondary oocyte
Oocyte completes meiosis II
Fertilised oocyte/ovum known as zygote
Zygote initiates cleavage (takes about 7 days) and travels towards the uterus for implantation
Depending on the stage of the menstural cycle therefore depending on the natura of the secretions in the cervix (what you need for sperm to travel is the thin watery mucus that is associated with higher circulating estradiol concentrations) and the sperm can then travel through the cervix via the uterus* and then up by the isthmus and to the ampulla of the uterine tube which is the regular site of fertilisation in humans
Fertilisation might take place if you have the movement of sperm up the pulls at the right time up to the ampulla and you also have the right time in terms of ovulation and the transport of the oocyte into the ampulla
What is contraception?
Any method used to prevent pregnancy - regulate when and how many pregnancies
Natural methods
Artificial methods - barrier methods, hormone contraceptives, intrauterine devices, sterilisation (need a device/treatment or some sort of intervention to get a contraceptive effect)
Natural methods
Rely on timing of coitus or behaviour during coitus
High failure rate (because they rely on human behaviour)
Rhythm method (periodic abstinence) - dependent on the female knowing her cycle and ovulation and cervical mucus and temperature Withdrawl method (coitus interruptus) - not very successful because sometimes semen can be released before ejaculation takes place
Lactation infertility - After birth and if the women is lactating it usually takes several months for cycles to kick back in and for her to start ovulating again, this is usually used to space out pregnancies
Barrier methods - caps, diaphragms
Designed to fit over the cervix
Imperfect barrier so should be used in conjunction with spermicidal foams, jellies, creams or sponges
Needs to remain at least 6 hours after intercourse and has to be inserted before coitus
Not commonly used anymore - preference for more ejective and convenient methods
Barrier methods - condoms
Cheap Readily available Male and female versions Easy to use Reduce risk of STI
Steroidal contraceptives for females - Combined oral contraceptive pills
Contain estrogen and progestin (our natural progestin is progesterone so the on in the pill would be a synthetic one
Supress ovulation (affect feedback loops to hypothalamus and pituitary)
Affect mucus produced by cervix (prevent sperm penetration)
Steroidal contraceptives for females - Progestin-only contraception
Progesterone-only pill
Low does of progestin
Effects on cervical mucus (rather than feedback loops)
Subdermal implant/injectible progestins
Long acting (over years)
Act primarily by disrupting follicular growth and ovulation
IUDs
Intrauterine device (IUD)
Copper IUD Causes low grade inflammation Reduces sperm transport Toxic - oocyte and zygote Impairs implantation
Hormone IUDs (mirena for example) Contains progestins Affects cervical mucus, reducing sperm transport Local affects on endometrium May present ovulation
Sterilisation in females
Tubal ligation - cut uterine tubes
Sterilisation in males
Vasectomy - cut vas (ductus) deferent
Doesnt stop sperm production, Doesn’t change what going on in the testes in terms of hormone production and also has no effect on the production of the seminal fluid
Usually takes weeks to months before it is fully effective
Why is sterilisation technically not a type of contraception?
Because a good contraception allows you to regulate if and when you want pregnancy to occur
Technical term for no longer being able to achieve an erection
Erectile dysfunction
Does the clitoris contain erectile tissue?
Yes
Combined oral contraceptive pills
Give someone oestrogen, negative feedback, less FH therefore less follicle growth
Progesterone taken, reduces LH surge, decrease pregnancy chance
