Getting Preganant

Question 1

At what point in their maturation can sperm move by themselves?

Answer 1

At the tail of the epididymis. They also have the potential to fertilise here.

Question 2

What is maturation of sperm dependant on?

Answer 2

Support of the epididymis by androgens.

Question 3

What is the purpose of semen?

Answer 3

Transport medium for sperm
Nutrition
Buffering capacity
Role for prostaglandins in stimulating muscular activity in the female tract

Question 4

What is the composition of the seminal plasma?

Answer 4

Seminal vesicles - 60% - alkaline fluid (neutralises the acid: Male urethra and female reproductive tracts) , fuctose, prostaglandins, clotting factors (particularly semenogelin)
Prostate glands - 25% - milky, slightly acidic fluid. Contain proteolytic enzymes, citric acid, acid phosphotases
Bulbourethral / Cowper’s glands - Small volume - alkaline fluid containing a mucous that lubricates the end of the penis and urethral lining.

Question 5

What are the four stages of the human sexual response?

Answer 5

Excitement phase (psychogenic / somatogenic stimuli)

Plateau phase

Orgasm phase

Resolution phase - males have a refractory period

Question 6

How does errection occur?

Answer 6

Stimulants - Psychogenic or tactile (sensory afferents of the penis and perineum)

Spinal reflex

Efferents - Somatic and autonomic efferents, pelvic nerve (PNS), pudential nerve (somatic).

Causes heemodynamic changes

Question 7

What happens in the penis to cause an errection?

Answer 7

Sinusoidal relaxation
Arterial dilation
Venous compression

The tunica albuginea encases the penis and creates the venous compression.

Question 8

What are the nerves for the parasympathetic innervation of penis?

Answer 8

Fibres come from the lumbar and sacral spinal levels.

Pelvic nerve and pelvic plexus

Cavernous nerve to corpora and vasculature.

Question 9

How does NO get released during an erection?

Answer 9

Inhibition of sympathetic vasoconstrictor nerves activate the PNS.

Activation of non-adrenergic, non cholinergenic, autonomic nerves to arteries releasing nitric oxide.

Question 10

What is the role of NO in an erection?

Answer 10

Post-ganglionic release ACh
ACh bonds to M3 receptors on endothelial cells.
A rise in intracellular [Ca2+], activation of NOS and formation of NO
NO diffuses into vascular smooth muscle and causes relaxation (vasodilation)
NO also released directly from nerves

Question 11

What can cause erectile dysfunction?

Answer 11

Psychological (descending inhibition of spinal reflexes)
Tears in fibrous tissue of corpora cavernosa
Vascular (arterial and venous)
Drugs

Question 12

How does viagra work?

Answer 12

Slows rate at which cGMP is degraded

Question 13

What happens in emission?

Answer 13

• Movement of semen into prostatic urethra

- Contraction of smooth muscle in prostate, vas deferens and Seminal vesicles.

Question 14

How does ejaculation occur?

Answer 14

• Contraction of glands and ducts (smooth muscle)
• Bladder internal sphincter contracts To prevent retrograde ejaculation
• Rhythmic striatal muscle contractions (pelvic floor ad perineal muscle ischiocavernosus, bulbospongiosus)

Question 15

How does the cervical mucus change over the menstrual cycle?

Answer 15

Oestrogen - think and stretchy (when fertile)

Oestrogen and progesterone - Thick, sticky, forms a plug. (Mechanical barrier to fertilisation)

Question 16

What is capacitation?

Answer 16

This is further maturation of sperm in female reproductive tract - sperm cell membrane changes to allow fusion with oocyte cell surface and the tail movement changes from beat to whip like action.

The sperm can now undergo the acrosome reaction.

Question 17

What is the fertile window? Why?

Answer 17

Sperm deposition up to 3 days prior to ovulation or day of ovulation.

This is because sperm live 48-72hrs whereas oocytes only live 6-24hrs.

Question 18

Give an overview of the events of fertilisation.

Answer 18

Fertilisation normally occurs in the ampulla of the uterine tubes. It requires the loss of sperm outer shell (acrosome) then penetration of ovum membrane, fusion of ova and sperm membrane and eventual formation an fusion of pronuclei.

Question 19

What is the acrosome?

Answer 19

It is derived form Golgi region of the developing spermatid. It contains enzymes and is necessary for fertilisation.

Question 20

What is the acrosome reaction?

Answer 20

• Sperm pushes through corona radiata.
• Binding of sperm surface receptor to ZP3 glycoproteins of zone pellucida.
• Triggers acrosome reaction
• Digestion of zona pellucida.

Question 21

How does the body make sure that only one sperm penetrates?

Answer 21

Cortical reaction - ca2+ released to make sure only one sperm can reach the oocyte nucleus

Question 22

What is the morula?

Answer 22

A collection of totipotent cells produced just after fertilisation.

Question 23

What happens in assisted reproductive technology?

Answer 23

Oocytes are fertilised in vitro and allowed to divide to the 4 or 8 cell stage.

The morula is then transferred to the uterus.

This can also be used for Pre-implantation Genetic Diaagnosis (PGD). This is when a cell is safely removed from the morula and tested for serious heritable conditions prior to transfer of the embryo into the mother.

Question 24

How does implantation occur?

Answer 24

Outer cell mass (trophoblast) interacts with endometrium.

Endometrium controls degree of invasion.

But, ectopic can be dangerous…

No endometrium = invasion not controlled

Lower uterine = placenta previa