8.0 Coition, Fertilisation and Blastocyst Development Flashcards Preview

MedST IB: Human Reproduction (HR) > 8.0 Coition, Fertilisation and Blastocyst Development > Flashcards

Flashcards in 8.0 Coition, Fertilisation and Blastocyst Development Deck (78)
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1

What are the stages of human sexual responses:

EPOR model of sexual responses

Excitement → Plateau → Orgasm → Resolution

2

During erection what occurs to the pressure of the:
1) Corpora cavernosa
2) Corpus spongiosum

1) Corpora cavernosa
Pressure ↑ → erection
It is surrounded by thick fibrous capsule

2) Corpus spongiosum
Pressure must remain low to maintain patency of urethra

3

What are the hemodynamic events that occur in:
1) Flaccidity
2) Tumescence
3) Erection
4) Detumescence

1) Flaccidity
- Arterial input blocked by smooth muscle mounds
- Pressure in corpus cavernosum < pressure of artery

2) Tumescence
- PSNS stimulation (S2, S3, S4)
- ↑ blood flow (nNOS → NO → GC → ↑ cGMP)
- Within 30 seconds: ↑ pressure in cavernosum + engorgement

3) Erection
- Full arterial input (relaxation of smooth muscle at arterial input)
- Reduced blood flow
- ↓ venous drainage → ↑↑↑ pressure

4) Detumescence
- SNS → adrenergic tone → smooth muscle constriction
- Causes ↓ arterial flow and ↑ venous flow → ↓ pressure

4

How does viagra work?

Inhibits PDE5 → maintains levels of cGMP → smooth muscle relaxation

5

What muscle contracts to further increase the rigidity of the penis?

Ischiocavernosus

6

What is the bulbospongiosus reflex?
What nerve mediates it?

Pressure on glans → contraction of ischiocavernosus

Mediated by pudendal nerve (S2,3,4)

7

What are causes of erectile dysfunction?

1) Psychogenic 30-50%
2) Organic 50-70%
- Neurogenic (MS, DM, trauma, disc lesions)
- Arteriogenic (HTN, DM, hyperlipidaemia)
- Drugs (Anti-HTN, Antidepressants)
- Endocrine (Low testosterone, high prolactin)

8

How does sperm get from testis to the epididymis

Via vasa efferentia
Passive
Bulk flow
Sperm at this stage is non-motile and non-fertile

9

How does sperm move from epididymis to vas deferens?

Via muscular contractions

90% of fluid is absorbed → ↑ spermatocrit

10

Where do sperm mature?

Epididymis

11

What occurs in sperm maturation?

They become potentially fertile and motile
Cytoplasmic droplet is lost
Membrane lipid = more fluid
↑ surface glycoproteins + sialic acid

12

How do sperm gain the ability to move?

↑ cAMP content in tail/flagellum

↑ rigidity of these structures due to disulphide bonds

13

What hormone is needed for male accessory sex gland activity?

Androgens (5-DHT)

14

What is the function of seminal plasma/fluid?

1) Provides vehicle for sperm function
2) Nutritional factors

Not essential for sperm function

15

Regarding seminal plasma/fluid, comment on the following:

Amount
Nutrition
pH
Other characteristics

Amount: 3-5ml
Nutrition: Fructose
pH: Alkaline (7-8)
Other characteristics:
- Antioxidants
- Prostaglandins (muscle stimulant)
- Leukocytes

16

What structures contract to cause ejaculation?

1) Urethra
2) Bulbospongiosus
3) Ischiocavernosus

Controlled by pudendal nerve

17

What percentage of the total ejaculate is early, mid or late?

Where does the ejaculate come from at each stage?

Early = 30% from prostate
Mid = 10% from vas deferens
Late = 60% from seminal vesicle

18

What are the contents of semen? Where do they come from?

1) Spermatozoa (vas deferens)
2) Seminal fluid (prostate and seminal vesicle)
3) Lubricant (Cowper's glands)

19

During female arousal, what do the following cause:
1) Corpora cavernosa
2) Corpus spongiosum

1) Corpora cavernosa
- Enlargement of clitoris

2) Corpus spongiosa
- Enlargement and eversion of labia minora

20

What provides lubrication to the female?

Vestibular glands (Bartholin's duct + cervix)

21

What are the three aspects to the female sexual response?

1) Transudation
- Lubrication of vagina + vestibule via vascular engorgement

2) Tenting effect
- Dilation of upper part of vagina caused by ↑ stimulation

3) Uterine elevation

22

Comment on the cervical secretions and os during:
1) Oestrogen dominance
2) Progesterone dominance

1) Oestrogen dominance
- Watery secretions (Spinnbarkeit)
- Os = open
- Good for sperm

2) Progesterone dominance
- Thick secretions (Ferning)
- Os = closed

23

How many sperm are inseminated?

350,000,000

24

Semen initially coagulates but then liquefies 20-60mins later. What causes this?

Activation of pro-enzymes

25

Where does capacitation occur?

In the uterus

26

What does capacitation involve?

1) Loss of membrane cholesterol
2) Loss of glycoproteins
3) Influx of Ca²⁺ → ↑cAMP + activation of PKA
4) Mitochondrial changes

27

What can reverse capacitation?

Semen

28

An ovulated oocyte + cumulus is picked up by _________. Cilia beat in the direction from ovary to uterus. These cilia are stimulated by __________. Muscle contractions also help move the oocyte along

An ovulated oocyte + cumulus is picked up by fimbriae. Cilia beat in the direction from ovary to uterus. These cilia are stimulated by oestrogen. Muscle contractions also help move the oocyte along

29

What is Mittelschermz pain?

Pain caused by bleeding into peritoneal cavity from ovulation

30

Where does fertilisation take place?

In the ampulla region of the fallopian tube