Reproductive System - V Flashcards
define 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 the sperm can travel to appropriate site for fertilisation (ampulla of uterine tube)
what are the stages of the male sexual act?
- erection of penis (parasympathetic)
- mucus secretion into urethra
- ejaculation: two phases, both sympathetic
- emission
- expulsion - resolution
describe the fascia of the penis
the executive tissues are surrounded by different layers of fascia
From inner to outer:
- tunica albuginea surrounds both the corpus cavernosa in one loop and the corpus spongiosum in a separate loop
- deep (bucks) fascia
- superficial fascia
- lacunae: gaps that fill with blood
- trabeculae: smooth muscle fibres
describe the comparative structure of the clitoris and penis
- structure of the clitoris and penis share developmental origins
- tissues of clitoris are erectile as in the penis
- the only structure that is unclear is the corpus spongiosum
describe the branches off the abdominal aorta for blood supply to penis
- Abdominal aorta
- Common iliac artery
- Internal iliac artery
- Internal pudendal artery
Internal pudendal artery feeds perineum and external genitalia, including penis
Branches to the penis include: - artery to bulb
- urethral artery
- dorsal artery
- deep (cavernosal) artery
Note: gonadal artery braces off the abdominal aorta quite high up because the development of the gonads occurs up in the abdomen and then the gonads descend, bringing their vasculature down with them
describe how the blood supply to the penis changes during an erection
Blood supply increases during an erection
- get dilation of deep arteries and blood fills up the lacunae, which puts pressure against the veins (and helps keep the erection bc less venous return). makes engorged cavernous spaces
describe the nerve supply to the penis
- penis richly innervated by sensory and motor nerves
- includes sensory fibres responsive to touch, pressure, temperature
- 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)
- parasympathetic: sacral region of spinal columns
- sympathetic: thoracic region of spina columns
describe what the parasympathetic, sympathetic and somatic motor innervation do
Parasympathetic (erection):
- stimulates production of nitric oxide (NO, vasodilator) by deep arteries of penis
- deep arteries dilate and fill lacunae in corpora cavernosa
Sympathetic (ejaculation):
- stimulates contraction of smooth muscle
- reproductive ducts
- accessory glands
Somatic motor (ejaculation:
- stimulates contraction of skeletal muscles around bulb of penis
describe what occurs in the first phase of the male sexual act, erection
- parasympathetic response to stimuli
- arteries in erectile tissue dilate
- erectile tissue becomes engorged with blood
- erect penis can be inserted into vagina (intromission)
Penis:
- deep artery dilates,
- trabecular muscle of erectile tissue relaxes
- erectile tissue fills with blood
- engorgement of erectile tissues
- penis becomes erect
Bulbourethral gland:
- secretes bulbourethral fluid
describe what occurs in the second phase of the male sexual act, emission
- sympathetic response
- smooth muscle of ductus deferens contacts to move sperm into ampulla (peristaltic contractions)
- smooth muscle of ampulla, seminal vesicles and prostate gland contract moving sperm and seminal fluid into urethra
Ductus deferens:
- peristalsis
- sperm moved into ampulla
- ampulla contracts
- sperm move into urethra
Seminal vesicles:
- secretes components of seminal fluid
Prostate Gland:
- secretes components of seminal fluid
describe what occurs in the third phase of the male sexual act, expulsion
- semen in urethra activates somatic and sympathetic reflexes
- contractions of urethral smooth muscles
- pelvic flood muscles contract
- semen ejected
Semen in urethra sends afferent signals to the spinal cord which make you get efferent sympathetic signals that make the following occur
Accessory glands:
- additional secretion from prostate gland and seminal vesicles
- internal urethral sphyncter contracts (urine remains in bladder)
Bulbospongiosus muscle:
- contracts and rhythmically compresses bulb/root of penis, which compresses urethra
- semen is expelled
describe what occurs in the fourth phase of the male sexual act, resolution
- blood flow to penis is reduced
- penis becomes flaccid
Internal pudendal artery:
- contracts
- reduces blood flow to penis
Trabecular muscles:
- contract
- squeeze blood from erectile tissues
Penis:
- becomes flaccid (detumescent)
describe the stages of the female sexual response
- similar sequence of reflex responses as in the male
- engorgement of the clitoris, labia and vagina in response to autonomic stimulation
- lubricating fluid secreted through vaginal wall; secretion of mucus into vestibule (greater vestibular glands)
- increases width and length of vagina. uterus elevates upwards
- rhythmic contraction of vaginal uterine and perineal (pelvic flood) muscles
- semen released into upper part of vagina (insemination). sperm travel to uterine tube for fertilisation (ampulla)
- sperm fuses with secondary oocyte
- oocyte completes meiosis II
- fertilised oocyte/ovum known as zygote
- zygote initiate cleavage (takes about 7 days) and travels towards the uterus for implantation
What is contraception?
Any method used to prevent pregnancy (or to regulate when and how many pregnancies)
- natural methods
- artificial methods (barrier methods, intrauterine devices, hormonal contraceptives, sterilisation)
describe the natural methods of contraception
- rely on timing of coitus or behaviour during coitus
- high failure rate
- rhythm method (periodic abstinence when the female is ovulating, not great because can’t really be precise on when she is ovulating)
- withdrawal method (coitus interruptus, not great because could be residual spermatozoa in urethra or if the male doesn’t withdraw in time)
- lactational infertility (when female is breastfeeding there is reduced release of GnRH and therefore less FSH and LH (so can prevent ovulation sometimes), problem is you don’t know when this will stop and when she will ovulate again)
Describe the barrier methods of contraception
Caps, diaphragms
* Imperfect barrier so should be used
in conjunction with spermicidal
foams / jellies / creams / sponges.
* Needs to remain at least 6 hours
after intercourse.
* Not commonly used anymore;
preference for more effective and
convenient methods.
Condoms
* Cheap
* Readily available
* Easy to use
* Reduce risk of sexually
transmitted infections
(STIs) - the only type of contraception that does this!!!
Describe the Non-hormonal intrauterine device (IUD)
Copper IUD
* Causes low grade inflammation
* Reduces sperm transport
* Toxic - oocyte and zygote
* Impairs implantation
What are the mechanisms of action for steroidal contraceptives for females?
- Variable depending on type, concentration and mode of
delivery of hormones - Deliver a progestin with/without an estrogen
- Suppress ovulation (affect feedback loops to hypothalamus
and pituitary, by use of exogenous hormones) - Affect mucus produced by cervix (prevent sperm
penetration)
Describe the steroidal contraceptives for females
Combined oral contraceptive pills
* Contain estrogen and progestin
* Suppress ovulation (affect feedback loops to hypothalamus
and pituitary by using estrogen and progestin which do negative feedback)
* Affect mucus produced by cervix (prevent sperm
penetration, progestin does this)
Progestin-only contraception
* Progesterone-only pill
* Low doses of progestin
* Effects on cervical mucus
* Subdermal implant / Injectable progestins
* Long acting (over years)
* Act primarily by disrupting follicular growth and ovulation
* Hormonal Intrauterine devices (see next slide)
describe the hormonal intrauterine device (IUD), which is also a steroidal contraceptive
Hormonal IUD (e.g. Mirena)
* Contains progestins
* Affects cervical mucus, reducing sperm
transport
* Local affects on endometrium (can cause it to become very thin)
* May prevent ovulation
describe the sterilisation method in both males and females that can act as a contraceptive
- Tubal ligation or
salpingectomy –
cut/cauterise or
remove uterine tubes - Vasectomy – cut
ductus (vas) deferens
