Session 7 - Conception and Contraception Flashcards Preview

Semester 4 - Reproductive System > Session 7 - Conception and Contraception > Flashcards

Flashcards in Session 7 - Conception and Contraception Deck (42)
1

What is the normal volume of ejaculate in semen?

2-4ml

2

How many sperm per ejaculate

40x10^6

3

What percentage of sperm are motile?

>60%

4

What are the three contributors to semen volume?

Seminal vesicles - 60%
Prostate - 25%
Bulbourethral -?%

5

What is found in secretions of seminal vesicles

o Alkaline fluid
 Neutralises the acid in the male urethra and female reproductive tract
o Fructose
o Prostaglandins
o Clotting factors
 Fibrinogen
 Holds sperm in place after ejaculation, before liquefaction

6

What is found in secretions of prostate?

o Proteolytic enzymes
 Break down clotting factors, re-liquefying sperm in 10 – 20 minutes
o Citric acid
o Phosphotase

7

Bulbourethral glands

o Very small volume
o Alkaline fluid
o Mucous
 Lubrication of the end of the penis and urethral lining

8

Describe the physiological processes involved in emission


Emission is the movement of ejaculate into the prostatic urethra before ejaculation. This occurs due to peristalsis of the vas deferens and secretions from the seminal vesicles.

9

What are the physiological stimulants of erections

Psychogenic
Tactile (sensory afferents of penis and perineum)

10

What are the efferents of erection?

Somatic and autonomic efferents
Pelvic nerve - PNS
Pudendal nerve - Somatic

11

Outline the haemodynamic changes in erection

Inhibition of sympathetic arterial vasoconstrictor nerves

Activation of parasympathetic nervous system to stimulate vasodilation

12

How does activation of the parasympahetic nervous sytem cause vasodilation of the penis arteries

 Pelvic nerve
 Normally vasoconstriction/dilation is governed by more/less sympathetic stimulation. This is one of the few examples where an increase in parasympathetic stimulation causes vasodilation.
 Release of Ach  M3 Receptors on epithelial cells
 Rise in [Ca2+]  Activation of Nitric Oxide Synthase (NOS)  Formation of Nitric Oxide (NO)
o Activation of non-adrenergic, non-cholinergic nerves to arteries releasing NO.
o NO diffuses into and causes relaxation of vascular smooth muscle (vasodilation)
 ↑ NO  Formation of Cyclic GMP  Ca2+ taken up into intracellular stores
 ↓ [Ca2+]  Less actin-myosin cross-bridges are formed and smooth muscle relaxes

13

What happens to blood vessels and muscles in penis to maintain erection?

The central arteries in the Corpa Cavernosa (helicine arteries) straighten, enlarging their lumen and allowing blood to flow into and dilate the cavernous spaces in the corpora of the penis.

The Corpus Spongiosum also dilates, but not very much as it would compress and close off the urethra.

The Bulbospongiosus and Ischiocavernosus muscles compress veins egressing from the corpora cavernosa, impeding the return of venous blood. This combined with the dilation of the helicine arteries causes the Corpa Cavernosa to become engorged with blood near arterial pressure, causing erectile bodies to become turgid (enlarged and rigid) and erection occurs.

14

Give three main factors causing erectile dysfunction

Psychological
Tears in fibrous tissue of corpa cavernoasa
Vascular
Factors blocking NO

15

Give three factors blocking NO

Alcohol
Anti-hypertensives
Diabetes

16

How does viagra work?

Inhibits the breakdown of cGMP, maintaining erection

17

Describe the physiological changes in the female which facilitate coitus

o Vaginal lubrication
o Swelling and engorgement of the external genitalia
o Internal enlargement of the vagina
o Cervical Mucus
 Oestrogen – Abundant, clear, non-viscous mucous
 Progesterone + Oestrogen – Thick, sticky mucous plug

18

Describe the mechanism of ejaculation

o Spinal reflex
o Sympathetic Nervous System Control (L1, L2)
1. Contraction of glands and ducts
 Smooth muscle
2. Bladder internal sphincter contracts
 Prevents entry of semen into the bladder
3. Rhythmic striatal muscle contractions
 Pelvic floor
 Ischiocavernosus – Pudendal (S2-S4)
 Bulbospongiosus – Pudendal (S2-S4)
 Hip and anal muscles

19

Describe the process involved in sperm transport through the cervix and uterus

Immediately after ejaculation, the semen coagulates due to the action of clotting factors. This prevents sperm being physically lost from the vagina.
10-20 minutes later the semen re-liquefies by the action of enzymes found in prostatic secretion.

20

How far do sperm in cervix have to travel to reach the uterine tube?

15-20cm

21

How is sperm transported in the uterus?

Own propulsive capacity and fluid currents caused by the actions of ciliated cells in the uterine tract

22

What changes happen to sperm in uterus?

Capacitation and acrosomal reaciton

23

How do changes happen to sperm in uterus?

Influx of calcium and rise in cAMP

24

What is capacitation?

o Further maturation of sperm in female reproductive tract (6 – 8 hours)
o Sperm cell membrane changes to allow fusion with oocyte cell surface
 Removal of glycoprotein coat
o Tail movement changes
 Beat  Whip-like action
o Sperm become responsive to signals from the oocyte

25

What is acrosomal reaction?

o Capacitated sperm comes into contact with the oocyte zona pellucida
o Membranes fuse  Start of reaction
o Acrosome swells and liberates its contents by exocytosis
o Proteolytic enzymes and further binding facilitate penetration of the zona pellucida by the sperm (takes about 15 minutes)
o 300 sperm required before break down of ZP

26

What is produced from first meiotic division of ovum?

Secondary oocyte + First polar body

27

What is pronuclei?

2 sets of chromosomes combine, and mitosis then occurs

28

Give sequence of ectopic pregnancy

o Failure of transport of egg
o Embeds in uterine tube, ovary or abdomen
o Embryo dies
o Severe risk of maternal haemorrhage

29

Give two types of natural conception

Abstinence
Coitus interruptus
- Sperm in pre-ejaculate

30

What is vasectomyu?

o Prevent sperm from entering ejaculate
o Divide vas deferens bilaterally
o Ensure ejaculate is free of sperm before relying on it for contraception
 Check a few months later

31

Give three barrier methods of contraception

Condoms
Diaphragm
Cap

32

What is a diaphragm?

 Lies diagonally across the cervix
 Needs correct fitting
 Does not completely occlude the passage of sperm
 Holds sperm in the acid environment of vagina and reduces survival time

33

Where is a "cap" fitted

Fits across the cervix

34

Give two parts of hormonal contraceptive

Progesterone
Oestrogen

35

Give two reasons progesterone prevents conception

o Thick, ‘hostile’ cervical mucus plug
 Prevents sperm from entering uterus
 Main contraceptive action of progesterone
o Negative feedback to hypothalamus / pituitary
 Decreases frequency of GnRH pulses
 Inhibits follicular development

36

Why does oestrogen prevent conception?

o Oestrogen negatively feeds back on anterior pituitary
o Loss of positive feedback mid-cycle
o No LH surge

37

Give four types of hormonal contraceptive

o Combined OCP
 (Progesterone and Oestrogen)
o Progesterone Only Pill (POP)
o Depot Progesterone (3 monthly injections)
o Progesterone implants

38

Give two types of intrauterine contraceptive device

Inert copper
Impregnated progesterone

39

How does inert copper work?

 Interferes with endometrial enzymes
 Interferes with implantation
 May also interfere with sperm transport into fallopian tube

40

What is a main form of post-coital contraception?

Combined oestrogen/progesterone

41

When is post-coital contraception given?

o Up to 72 hours after intercourse

42

What are the three main effects of post-coital contraception?

o May disrupt ovulation
o Blocks implantation
o May also impair luteal function