Lecture 11– Getting pregnant: sex and fertilisation Flashcards
1
Q
Maturation of sperm in the epididymis – the sperms journey (continues!)
- *
A
- On entry, spermatozoa not capable of movement
- Once at the tail of the epididymis they are capable of movement and have the potential to fertilise
- Addition of secretory products to surface of sperm
- Maturation
- Dependent on support of the epididymis by androgens
2
Q
constituents of semen
A
- Spermatozoa
- Seminal plasma
- Seminal plasma derived from accessory glands of the male reproductive tract
3
Q
function of semen
A
- Transport medium
- Nutrition
- Buffering capacity
- Role for prostaglandins in stimulating muscular activity in the female tract
4
Q
seminal palsma contirbutions from
A
- seminal vesicles
- prostate gland
- bulbourethral glands (Cowpers glands)
5
Q
-
Seminal vesicles
*
A
- 60% of volume
- Alkaline fluid (neutralises the acid: male urethra and female repro tract)
- Fructose, prostaglandins, clotting factors (semenogelin)
6
Q
- Prostate gland
A
- 25% volume
- Milky, slightly acidic fluid
- Proteolytic enzymes (breakdown clotting proteins, re-liquefying semen in 10-20 minutes)
- Citric acid, acid phosphatase
7
Q
- Bulbourethral glands (COwpers glands)
A
- Very small volume
- Alkaline fluid
- A mucous that lubricates the end of the penis and urethral lining
8
Q
normal values of semen
A
9
Q
next step after sperm and egg mature
A
Next step….
- Male and female gametes need to meet in the female reproductive tract
- Male gamete needs to travel 100,000 times its own length
- Fertilisation site is normally ampulla of uterine tube
10
Q
Fertilisation site is normally
A
ampulla of uterine tube
11
Q
The human sexual response….
*
A
- Excitement phase
- Psychogenic and/ or somatogenic stimuli
- Plateau phase
- Orgasm phase
- Resolution phases
- Return to haemodynamic normal followed by a refractory period in males
- Before the male is ready to initiate excitement phase
- In the female no refractory phase
12
Q
male sexual stimulations
A
- psychogenic
- tactile (sensory afferents of penis and perineum)
13
Q
male sexual response after stimulation
A
spinal reflex
somatic and autonomic efferents
- pelvic nerve (PNS)
- pudendal nerve (somatic)
cause haemodynamic changes- namely vasodilayion
14
Q
tunica albiginea qualities
A
verg rigid - not much venous return
15
Q
- Erection requires
A
- Sinusoidal relaxation
- Arterial dilation- blood rushes into corpus cavernosum and spongiosum= erection
- Venous compression
16
Q
summarise erection
A
- Sympathetic- inhibition (reduction of tone at arterioles)
- Parasympathetic- activates
17
Q
which fibres are involved with parasympathetic innervation
A
- Lumbar and sacral spinal levels
- Pelvic nerve and pelvic plexus
- Cavernous nerve to corpora and vasculature
18
Q
Neurophysiology of erection
A
- Inhibition of sympathetic arterial vasoconstrictor nerves
- Activated PNS- vasodilation
- Activation of non-adrenergic, non-cholinergic, autonomic nerves to arteries, releasing Nitric oxide (NO)
19
Q
role of NO in erection
A
- Post-ganglionic fibres release ACh
- Ach binds to M3 receptor on endothelial cells
- A rise in [Ca2+]i , activation of NOS and formation of NO
- NO diffuses into vascular smooth muscle and causes relaxation (vasodilation)
- NO also released directly from nerves
20
Q
Erectile dysfunction causes
A
- Psychological (descending inhibition of spinal reflexes)
- Tears in fibrous tissue of corpora cavernosa
- Vascular (arterial and venous)
- Drugs
21
Q
emission is the
A
- Movement of semen into prostatic urethra
- Caused by contraction of SM in prostate, vas deferens and seminal vesicles
22
Q
ejaculation
A
expulsion of semen- sympathetic response
23
Q
outline ejaculation
A
- Contract of the glands and ducts (smooth muscle)
- Bladder internal sphincter contracts
- Preventing retrograde ejaculation
- Rhythmic striatal muscle contraction (pelvic floor, and perineal muscles ischiocavernosus, bulbospongiosus)
24
Q
Menstrual cycle changes in female tract
*
A
- The character of cervical mucus changes over the course of the menstrual cycle
- Oestrogen
- Thin, stretchy
- Oestrogen and progesterone
- Thick, sticky; forms a plug
25
ways to test fertility
fern test
spinnbarkeit mucus
26
sperm deposition
27
capacitation
* Further maturation of sperm in female reproductive tract (6-8h)
* Sperm cell membrane changes to allow fusion with oocyte cell surface
* Tail movement changes from beat to whip=like action (b)
* Now capable of undergoing the acrosome reaction (C)
28
uterus anteversiona dn anteflexion changes during the sexual response
29
**Fertile window- window of opportunity for fertility**
Spermatozoa will survive for 3 days in the vagina
* Spermatozoa 48 -72hr
* Oocytes 6 –24 hr (max)
* Fertile period: sperm deposition up to 3 days prior to ovulation or day of ovulation
* Gamete transport
* Oocyte: beating cilia & peristalsis of uterine tube
* Sperm: own propulsion
30
**Overview of events in fertilisation**
* Occurs normally in the ampulla of the uterine tubes
* Requires loss of sperm outer shell (acrosome)
* Penetration of ovum membrane, fusion of ova and sperm membrane
* Eventual formation and fusion of pronuclei
31
the acrosome is derived from the
* golgi region of developing spermatids
* contains enzyme necessary for fertilisation
32
**Acrosome reaction- allows the sperm to**
* Sperm pushes through corona radiate
* Binding of sperm surface receptor **ZP3 glycoprotein of zona pellucida**
* Triggers acrosome reaction digestion of zona pellucida
33
**Fertilisation**
*
* One sperm penetrates leading to fusion of plasma membranes
* Cortical reaction
* Blocks polyspermy
34
completion of meiosis II
* series of calcium waves are activated following fusion of oocyte and sperm membrane
* resumption of meiosis II occurs
* pronuclei move together
* mitotic spidlle froms leading to cleavage
35
assisted reproductive technology
* oocytes fertilised in vitro and allowd to divide to the 4 or 8 cell stage
* morula transferred into the uterus
* pre-implanation genetic diagnosis (PGD)
* a cell can be safely removed from the morula and tested for serious heritable conditions priot to transfer of the embyro into the mother
36
the blastocyst and hatching
* first differnetiation
* inner and outer cell masses
* formation of the balstocyst
* blastocyst hatches from zona pellucida
* it is no longer constrained - free to enlarge
* can now interact with uterine surface to implant
37
implantation
* outer cell mass (trophoblast) interacts sigh endometrium
* endometrium controls degree of invasion
* ectopic implantation
* at sites other than endometrium lined uterine cavity
* invasion not controlled
* implantation in lower uterine segment can cause placenta praevia
