10 - Sexual Function and Fertilisation

Question 1

What are the reactions that occur in the sperm just before/during fertilisation?

Answer 1

• Capacitation
• Acrosome reaction

Question 2

Where does the sperm start to mature and how?

Answer 2

• In the epididymis not capable of movement but by the end near vas def it is
• Addition of secretory products to surface of sperm
• All this dependent on androgens

Question 3

What is the function of semen?

Answer 3

Seminal plasma + Spermatozoa

• Transport medium
• Nutrition
• Buffering capacity against acidic vagina

Question 4

What is seminal plasma made up of?

Answer 4

Semen clots due to clotting factors from the seminal vesicles but then prostate has enzymes that break the clotting factors down. Can cause issues with fertility

Question 5

What are some parameters of the male you need to look at when they are having issues with fertility?

Answer 5

• Morphology
• Motility
• Coagulation

Question 6

What are the phases of the human sexual response?

Answer 6

- Excitement: psychogenic and somatic stimuli

• Plateau: if stimuli maintained

- Orgasm: if stimuli maintained and threshold reached

- Resolution: return to haemodynamic norm

Same in males and females but males have refractory period after resolution phase

Question 7

What is the neural response of the excitement phase in males to gain an erection?

Answer 7

• Parasympathetic efferents dominate the pelvic nerve and the sympathetics have to be inhibited
• Somatic efferents from pudendal nerve

Question 8

What is the physiology of getting an erection?

Answer 8

• Sinusoid relaxtion in CC
• Arterial dilation
• Venous compression by tough tunica albugenia around CC

Question 9

What parasympathetic nerve innervates the corpus cavernosum?

Answer 9

Cavernous nerve from the pelvic nerve (S2-S4) and pelvic plexus

Question 10

What neurotransmitter is involved in getting an erection and how does it work on a cellular level?

Answer 10

• Sympathetics inhibited and NO released in response to rise in Ca
• NO causes smooth muscle relaxation
• cGMP is key regulator

Question 11

What are some causes of erectile dysfunction?

Answer 11

• Psychological (poor spinal reflexes)
• Vascular disorders like diabetes
• Tear in fibrous tissue of corpus cavernosum
• Anti hypertensives and other drugs
• Neurological disorders

Question 12

How can erectile dysfunction be managed?

Answer 12

• Increase amount of NO and cGMP with drugs

Question 13

What is emission and how is it controlled?

Answer 13

• Semen is moved into prostatic urethra by smooth muscle contraction of the prostate, vas def and seminal vesicles
• Sympathetic innervation

Question 14

What happens during ejaculation and what nervous control is it under?

Answer 14

• Sympathetic
• Expulsion of semen that requires contraction of IUS to prevent retrograde ejaculation and rhymic striated muscle contraction of pelvic floor
• Glands also contract but these are smooth muscle

Question 15

How does cervical mucus change over the menstrual cycle?

Answer 15

- Oestrogen only: thin and stretchy to faciltate sperm entry

- Oestrogen and progesterone: thick and sticky to form a plug to prevent outside world getting in if fertilised and prevent further sperm entry

Question 16

Where in the female reproductive tract does fertilisation occur?

Answer 16

Ampulla

Question 17

What needs to happen in the female reproductive tract to the sperm to make it fully mature?

Answer 17

Question 18

When is the fertile period in a woman?

Answer 18

Question 19

What events happen during fertilisation?

Answer 19

• Enzymes in acrosome released to remove outer granulosa cells (corona radiata)

- Acrosome reaction when sperm interacts with zona pellucida. Sperm loses outer membrane so it can penetrate ovum and fuse with ova membrane

- Cortical reaction in the oocyte to stop more sperm entering and then this triggers meiosis II to finish via calcium wave

- Fusion of pronuclei and formation of morula by mitotic spindle and cleavage

Question 20

When can you say fertilisation has been successful?

Answer 20

When cleavage occurs

Question 21

What is assisted reproductive technology?

Answer 21

• Medical procedures that are used to tackle infertility
• Can do pre-implantation genetic diagnosis by taking one cell from morula before implanted in uterus
• Implanted at 4-8 cell morula

Question 22

What has to happen to the blastocyst for implantation to occur?

Answer 22

Hatching from zona pellucida so outer cell mass (trophoblasts) can interact with endometrium where secretory glands and increased vasculature are