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Jess Repro > 5.1: Coitus and Fertilisation > Flashcards

5.1: Coitus and Fertilisation Flashcards

1
Q

How many days does it take for spermatogonia to mature into spermatozoa?

A

74 days

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2
Q

What is an additional role of the epididymis other than transport?

A

Aids in maturation of the sperm; sperm become motile and gain the ability to recognize and fertilize an oocyte

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3
Q

What are the three regions of the epididymis? What are three areas where they can differ?

A

Caput, cordus and Cauda

Can differ in luminal fluid contents, epithelial cell type/size, receptors/transporters

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4
Q

What are the four phases of coitus in males?

A
  1. Excitement phase (erection)
  2. Plateau phase
  3. Orgasmic phase (emission and ejaculation)
  4. Resolution phase (+/- refractory period)
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5
Q

What happens during the phases of the female sexual response?

A
  1. Sexual excitement: blood engorgement and erection of clit, vaginal mucosa, breast and nipples
  2. Plateau: glandular activity
  3. +/- orgasm

**No physiological refractory period

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6
Q

What are two stimulants and two efferent pathways that lead to hemodynamic changes in a penile erection?

A

Psychogenic and tactile stimulants can lead to the pelvic nerve (PNS) and the pudendal nerve (somatic) efferent nerve stimulation

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7
Q

What signalling molecule is required for an erection? What releases it and why is it so important?

A

NO is released by nerves and endothelial cells and causes decreased intracellular calcium leading to smooth muscle relaxation; allowing an erection to occur

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8
Q

List four potential causes for erectile dysfunction

A
  1. Psychological: descending inhibition of spinal reflexes
  2. Tears in fibrous tissue of corpora cavernosa
  3. Vascular (arterial and venous)
  4. Drugs
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9
Q

List 3 factors that can block NO

A

Alcohol, anti-hypertensives, diabetes

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10
Q

What is the mechanism of action in viagra?

A

Inhibits the PDE-5 enzyme which breaks down cGMP - inevitably promoting a further decrease in intracellular calcium to allow for more vasodilation

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11
Q

Name three accessory glands that produce secretions to help transport sperm

A
  1. Prostate
  2. Seminal vesicle
  3. Bulbourethral
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12
Q

Which accessory glands contribute the most and the least to the sperm’s volume?

A

Seminal vesicles contribute 60% of the volume, Bulbourethral produce a very small volume of secretions

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13
Q

Which accessory glands produce alkaline fluid and what is it’s purpose?

A

The seminal vesicles and bulbourethral glands both produce alkaline fluid to help neutralize the acid and protect the male urethra and female reproductive tract

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14
Q

Which accessory gland produces milky, slightly acidic fluid and why?

A

The prostate as it produces citric acid and acid phosphatase

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15
Q

Which accessory gland produces proteolytic enzymes and what do they do?

A

The prostate; these enzymes assist in breaking down clotting proteins to re-liquify semen (in 10-20 minutes)

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16
Q

Which accessory gland produces mucous and why?

A

The Bulbourethral gland to lubricate the end of the penis and the urethral lining

17
Q

Which muscles and structures must contract in order for an ejaculation to occur?

A
  1. Glands and ducts (smooth muscle)
  2. Bladder internal sphincter (to prevent backflow into the bladder)
  3. Rythmic striatal muscle; pelvic floor, ischiocavernosus, bulbospongiosus, hip and anal muscles
18
Q

What is a normal volume of sperm per ejaculation?

A

1.5-4mL

19
Q

What defines oligozoospermia?

A

Not enough sperm per ejaculation; less than 15 million sperm/mL

20
Q

How does having an estrogen rich vs estrogen and progesterone rich system impact the likelihood of fertilization?

A

An estrogen rich system: clear, nonviscous mucous around the cervix

Estrogen and progesterone rich system: thick sticky mucous plug around the cervix that makes it harder for sperm to swim through

21
Q

What is sperm capacitation? Describe the two main events during the capacitation of sperm and where it takes place

A

Sperm capacitation refers to the physiological changes spermatozoa must undergo to be able to fertilize an oocyte. (Although sperm is technically able to fertilize by the time it reaches the female repro tract (i.e in a lab) there are two main maturations that occur in the 6-8 hours that the sperm moves towards the egg within the female repro tract)

  1. Sperm cell membrane changes to permit an acrosome reaction (losing the sperm’s outer shell); this also allows for exposure of certain receptors that are important for the fusion between the sperm and the oocyte’s surface
  2. Tail movement changes from beating to a whip-like action
22
Q

Why is it important for fertilization that more than one sperm finds the oocyte?

A

The remaining sperm are needed to disperse the granulosa cumulus cells that surround the oocyte in layers (they also have junctions containing mucus-like fluid that helps them stick together) so that one sperm is able to penetrate through

23
Q

What is the fertile period? How long do spermatozoa and oocytes live after being released?

A

The fertile period is sperm must be deposited up to 3 days prior to ovulation; since spermatozoa can live up to 3 days but oocytes only live 6-24 hours after being released

24
Q

What three features that surround the oocyte must be penetrated to allow for the formation of pronuclei?

A
  1. Granulosa cell layers
  2. Zona pellucida
  3. Ovum membrane
25
Q

What triggers the acrosome reaction and which two enzymes are involved?

A

The acrosome reaction is triggered by signals released from the cumulus cells (surrounding the oocyte):

Two enzymes are released:

  1. Hyaluronidase: breaks down the bonds between the cumulus cells (more spaces for sperm to swim through)
  2. Acrosin: breaks down the ZP proteins
26
Q

What mechanism is in place to prevent polyspermy?

A

Once the gamete membranes have fused the oocyte releases a wave of calcium from the SER, this triggers the cortical reaction: underneath the egg’s surface you have many cortical granules which are released once one sperm has entered, the granules change the structure of the ZP3 protein making it unavailable for more sperm to bind

27
Q

What happens in the oocyte following and around the cortical reaction?

A

The oocyte completes meiosis II and forms the pronuclei, both pronuclei then fuse to form the diploid zygote.

28
Q

What process immediately follows the formation of the diploid zygote?

A

‘Cleavage’; when cells rapidly divide but there is no cytoplasmic growth between divisions. They divide symmetrically and are totipotent

29
Q

What are the daughter cells that are formed from cleavage called? What do they eventually form?

A

Daughter cells are called blastomeres, they eventually form a solid ball called a morula

30
Q

How are monozygotic twins formed?

A

The blastomeres eventually form a solid ball of cells (morula), if it splits monozygotic twins are formed

31
Q

Where does the zygote travel following fertilization (and how is it receiving nutrients)? What processes are happening simultaneously to ensure a successful implantation?

A

The zygote transports down the fallopian tubes to the uterus, it is floating for 3 days and nourished by intrauterine fluid

In order for implantation to occur…
1. A rise in progesterone (since the corpus luteum has been around a few days) which ‘primes’ the endometrium

  1. The embryo is developing and reaches the blastocyst stage; (fluid-filled cavity/blastocoele appears) *important it doesn’t develop further than this before implantation as it won’t be able to survive on its own
  2. The Trophoblast cells secrete enzymes that degrade themselves and digest the ZP
32
Q

What cellular division follows the formation of the blastocyst?

A

Loss of totipotency: The outer layer differentiates into the trophoblasts which surround the embryo and the inner cell mass/embryoblast becomes the embryo

33
Q

Define an ectopic pregnancy, what are two likely consequences?

A

When the egg implants in a location other than the uterus, (i.e failure of transport of egg) will likely result in embryo death and maternal hemorrhage

34
Q

Other than alkaline fluid, what else does the seminal vesicle secrete?

A

Fructose, prostaglandins and clotting factors

35
Q

What hormone is essential in making sure the ‘hatched’ embryo adheres to the endometrium?

A

hCG

36
Q

What days of the uterine cycle does the zygote transform into a blastocyst? How many days after ovulation does implantation tend to commence?

A

Uterine cycle days 14-21

Implantation commences 6 days after ovulation

37
Q

What is the difference between primary and secondary amenorrhea?

What are the two commonest causes of secondary amenorrhea and what hormone tests will you use to distinguish them?

A

Primary: never had periods
Secondary: 3-month cessation of menses (after they’ve begun)

The two commonest causes are:

  1. pregnancy: Hcg
  2. Fall in body weight: gonadotrophin levels

Jess Repro (18 decks)

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