Lecture 38 - Coitus, fertilisation, and contraception

Question 1

Definitions of monarch

Answer 1

The onset of menstrual cycles

Question 2

Definition of menopause

Answer 2

The cessation of menstrual cycles (usually in a woman’s 50s)

Question 3

GnRH from the hypothalamus directly regulates the secretion of …

Answer 3

LH and FSH

Question 4

During oogenesis, at what point in meiosis II is the secondary oocyte suspend and what event causes the cell cycle to resume?

Answer 4

Metaphase II

Dertilisation causes the cell cycle to resume (fertilisation can also be called sperm penetration)

Question 5

What happens to the oocyte if fertilisation does not occur?

Answer 5

Atresia (degeneration)

Question 6

Coitus

Answer 6

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

Question 7

Intromission

Answer 7

Erect penis introduced into vagina

Question 8

Stages of the male sexual act

Answer 8

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

Question 9

Two phases of ejaculation

Answer 9

Ejaculation
Two phases (both sympathetic)
Emission
Expulsion

Question 10

The erection of the penis is a ________ response

Answer 10

Parasympathetic

Question 11

The ejaculation is a __________ response

Answer 11

Sympathetic (both phases are)

Question 12

Corpus spongiosum

Answer 12

Structure through which the urethra runs

Runs the entire length of the penis and widens to form the glans penis

Question 13

Corpus cavernosum

Answer 13

Runs from the root of the penis to just below the glans penis - there is two of them

Question 14

Bulbocavernosus muscle (bulbospongiosus)

Answer 14

very important in the ejaculatory process

Covers the bulb of the penis

Question 15

Fascia of the penis

Answer 15

The erectile tissues are surrounded by different layers of fascia
Fascia are important in restraining the erection

Question 16

Superficial fascia

Answer 16

Outermost fascia

Question 17

Tunica albuginea

Answer 17

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

Question 18

Deep (Buck’s) fascia

Answer 18

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.

Question 19

Trabeculae

Answer 19

Connective tissue containing smooth muscle which is important for the constraining and allowing of the vasculature to the erectile tissues

Question 20

Lacunae

Answer 20

Blood filled spaces that are part of the process of expanding and causing an erection

Question 21

Comparative structure of the clitoris and the penis

Answer 21

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

Question 22

Branches of the abdominal artery

Answer 22

Abdominal aorta to common iliac artery to internal iliac artery to internal pudendal artery

Question 23

Gonadal artery

Answer 23

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

Question 24

What does the internal pudendal artery feed?

Answer 24

Feeds perineum and external genitalia including the penis and also the rectum

Question 25

Branches of the internal pudendal artery to the penis includes…

Answer 25

Artery to bulb Urethras artery Dorsal artery Deep (cavernosal) artery

Question 26

Blood supply to the penis _______ during erection

Answer 26

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

Question 27

Genital sexual reflexes

Answer 27

Coordination of sympathetic, parasympathetic and somatic divisions of the nervous system

Question 28

Reminder of the different divisions of the nervous system

Answer 28

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)

Question 29

Nerve supply to the penis

Answer 29

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

Question 30

Parasympathetic (erection)

Answer 30

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

Question 31

Sympathetic (ejaculation)

Answer 31

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

Question 32

Somatic motor (ejaculation)

Answer 32

Stimulates contraction of skeletal muscles around the bulb of the penis

Question 33

Erection

Answer 33

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

Question 34

Emission

Answer 34

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 ```

Question 35

Expulsion

Answer 35

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)

Question 36

Resolution

Answer 36

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)

Question 37

Refractory period

Answer 37

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

Question 38

Stages of the female sexual response

Answer 38

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)

Question 39

Insemination and what happens from there...

Answer 39

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

Question 40

What is contraception?

Answer 40

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)

Question 41

Natural methods

Answer 41

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

Question 42

Barrier methods - caps, diaphragms

Answer 42

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

Question 43

Barrier methods - condoms

Answer 43

``` Cheap Readily available Male and female versions Easy to use Reduce risk of STI ```

Question 44

Steroidal contraceptives for females - Combined oral contraceptive pills

Answer 44

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)

Question 45

Steroidal contraceptives for females - Progestin-only contraception

Answer 45

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

Question 46

Intrauterine device (IUD)

Answer 46

``` 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 ```

Question 47

Sterilisation in females

Answer 47

Tubal ligation - cut uterine tubes

Question 48

Sterilisation in males

Answer 48

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

Question 49

Why is sterilisation technically not a type of contraception?

Answer 49

Because a good contraception allows you to regulate if and when you want pregnancy to occur

Question 50

Technical term for no longer being able to achieve an erection

Answer 50

Erectile dysfunction

Question 51

Does the clitoris contain erectile tissue?

Answer 51

Yes

Question 52

Combined oral contraceptive pills

Answer 52

Give someone oestrogen, negative feedback, less FH therefore less follicle growth Progesterone taken, reduces LH surge, decrease pregnancy chance