Sex and fertilisation

Question 1

What is in semen?

Answer 1

Spermatozoa and seminal plasma derived from accessory glands of the male reproductive tract

Question 2

What is the function of the seminal plasma?

Answer 2

• transport medium
• nutrition for the sperm
• buffering capacity (neutralise acidic vagina)

Question 3

What is released from the seminal vesicles?

Answer 3

alkaline fluid that neutralises the make and female urethra ) - needed to ensure correct environment fro spermatozoa - and fructose

Question 4

What is released from prostate gland?

Answer 4

proteolytic enzymes that breakdown the clotting proteins- milky slightly acidic fluid

Question 5

What is released from the bulbourethral glands?

Answer 5

very small volume of alkaline fluid that lubricates the end of the penis and urethral lining

Question 6

Where is the sit of fertilisation?

Answer 6

the ampulla of the uterine tube

Question 7

What phases are in the human sexual response?

Answer 7

excitement phase, plateau phase, orgasm phase and resolution phase (and refractory period for men only)

Question 8

What is the male excitement phase?

Answer 8

occurs due to psychogenic stimuli as well as tactile sensory afferents as part of the spinal reflex

Question 9

What efferent fibres are involved in the excitement phase?

Answer 9

somatic (via pudendal nerve) and parasympathetic (via pelvic nerve) efferents

Question 10

What is the end result of the excitement phase?

Answer 10

Erection

Question 11

How do erections come about physiologically?

Answer 11

• sinusoids must relax and arteries dilate (all due to neuronal stimulation)
• venous dilation required (due to increased blood flow against the tough tunica albuginea surrounding the corpus cavernous)

Question 12

What does venous dilation do?

Answer 12

compresses the venous drainage within the tunica albuginea

Question 13

Which innervation needs to be activated?

Answer 13

the parasympathetic

Question 14

How is this done?

Answer 14

the parasympathetic is stimulated via the pelvic and cavernous nerve

Question 15

What is the important neurotransmitter and why is it released?

Answer 15

NO - released as;
post-ganglionic fibra release ACh which bonds to M3 receptor on endothelial cells. This causes a rise in the intracellular Ca2+ conc activating formation of NO. NO diffuses into vascular smooth muscle and causes vasodilation - NO also released directly from nerves

Question 16

What is a key mediator in the process of NO formation?

Answer 16

cGMP

Question 17

What causes erectile dysfunction?

Answer 17

• psychological input
• vascular disorders
• anti-hypertensives
• neurological disorders
• trauma of the tissue of the corpus cavernousum

Question 18

How does viagra work?

Answer 18

slows the rate at which cGMP is degraded to produce more NO

Question 19

What happens in emission?

Answer 19

semen is moved into the prostatic urethra - this requires smooth muscle contraction from the prostate, VD and seminal vesicles

Question 20

What happens in ejaculation?

Answer 20

expulsion of semen - requires contraction of the glands and ducts and internal sphincter to prevent retrograde ejaculation

Question 21

What innervation is this under?

Answer 21

sympathetic (point and shoot)

Question 22

What is the acrosome?

Answer 22

surrounds the head of the sperm - contains enzymes necessary for fertilisation

Question 23

what occurs in the acrosome reaction?

Answer 23

sperm pushes through the corona radiata and binds to the zone pellucida which allows the head of the sperm to penetrate and degrade the zone pellucid to penetrate the ovum and fuse with the membrane

Question 24

What is the cortical reaction?

Answer 24

it happens in the oocyte and prevents further sperm entering (polyspermy)

Question 25

What happens at the end of fertilisation?

Answer 25

a number of calcium waves are activated following fusion of oocyte and sperm membranes which completes meiosis 2, moves the pronuclei together and forms mitotic spindles

Question 26

What is a morello?

Answer 26

collection of 16 cells that are totipotent so have the capacity to become any cell type

Question 27

What needs to happen to the blastocyst now?

Answer 27

needs to get rid of the zone pellucida as its constraining the size- this process is called hatching

Question 28

What can the blastocyst do after hatching?

Answer 28

implant into the endometrial lining

Question 29

What happens in implantation?

Answer 29

the trophoblast layer interacts with the endometrium and the endometrium controls how deep it invades into - best to implant into stroma as that is where the secretory glands and increased vasculature has formed

Question 30

What is ectopic implantation?

Answer 30

where implantation occurs at sites other than endometrium lined uterine cavity

Question 31

What is the fertile window?

Answer 31

sperm can survive up to 72 hrs but the ovum will only last 24 hrs therefore sperm can be deposited 3 days before ovulation for fertilisation to be successful!!