S5) Sexual Function and Fertilisation Flashcards

1
Q

Describe the composition of semen

A
  • Spermatozoa +
  • Seminal plasma
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2
Q

Identify 3 functions of the semen

A
  • Transport medium
  • Nutrition
  • Buffering capacity
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3
Q

Where is seminal plasma derived from?

A

Accessory glands of the male reproductive tract:

  • Prostate gland
  • Seminal vesicles
  • Bulbourethral gland
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4
Q

What is the usual site for fertilisation?

A

Ampulla of uterine tube

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5
Q

Identify the 4 phases in the sexual response

A
  • Excitement phase
  • Plateau phase
  • Orgasm phase
  • Resolution phase
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6
Q

What sort of stimuli trigger the excitement phase?

A

Psychogenic and / or somatogenic stimuli

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7
Q

What happens after the resolution phase in the sexual response?

A

Return to haemodynamic norm followed by a refractory period (males)

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8
Q

Identify the 2 stimulants of the male sexual response – erection

A
  • Psychogenic
  • Tactile (sensory afferents of penis and perineum)
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9
Q

Identify the 2 efferent nerves in the male sexual response – erection

A

Somatic and autonomic efferents:

  • Pelvic nerve (PNS)
  • Pudendal nerve (Somatic)
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10
Q

Which three processes are required for an erection to occur?

A
  • Sinusoidal relaxation
  • Arterial dilation
  • Venous compression
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11
Q

Identify the nerves involved in the parasympathetic innervation of the penis

A
  • Pelvic nerve and pelvic plexus
  • Cavernous nerve
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12
Q

Describe 3 neurophysiological events which produce an erection

A
  • Inhibition of sympathetic arterial vasoconstrictor nerves
  • Activation of non-adrenergic, non-cholinergic, autonomic nerves to arteries
  • Release of Nitric Oxide (NO)
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13
Q

In five steps, describe the events leading to the release of NO in an erection

A

⇒ Post-ganglionic fibres release ACh

⇒ ACh bonds to M3 receptor on endothelial cells

⇒ Rise in [Ca2+]i activates NO synthase and formation of NO

⇒ NO diffuses into vascular smooth muscle and causes vasodilation

⇒ NO is also directly released from nerves

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14
Q

Identify 4 causes of erectile dysfunction

A
  • Psychological
  • Tears in fibrous tissue of corpus cavernosa
  • Vascular
  • Drugs
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15
Q

Describe the psychological cause for erectile dysfunction

A

Psychological – descending inhibition of spinal reflexes

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16
Q

What sort of neural control governs emission and ejaculation?

A

Sympathetic Nervous System

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17
Q

Which 2 events occur in the male sexual response – emission?

A
  • Movement of semen into prostatic urethra
  • Contraction of smooth muscle in prostate, vas deferens and seminal vesicles
18
Q

What occurs in the male sexual response – ejaculation?

A

Expulsion of semen:

  • Contraction of smooth muscle in glands and ducts
  • Bladder internal sphincter contracts
  • Rhythmic striatal muscle contractions
19
Q

Why does the bladder internal sphincter contract in ejaculation?

A

To prevent retrograde ejaculation

20
Q

Which structures are involved when the striatal muscles contract in ejaculation?

A
  • Pelvic floor
  • Perineal muscles
  • Ischiocavernosus muscle
  • Bulbospongiosus muscle
21
Q

Describe the hormonal influence over the changes of the character of cervical mucus in the menstrual cycle

A
  • Oestrogen: thin, stretchy cervical mucus
  • Oestrogen & progesterone: thick, sticky cervical mucus (forms a plug)
22
Q

What is the site of sperm deposition?

23
Q

Describe the process which occur as part of capacitation in the female reproductive tract?

A
  • Further maturation of sperm (6-8 hours)
  • Sperm cell membrane changes to fuse with oocyte
  • Sperm tail movement changes to a whip-like action
  • Acrosome reaction can now occur
24
Q

State the fertility windows for the sperm and oocyte respectively

A
  • Spermatozoa: 48 - 72hr
  • Oocytes: 6 - 24 hr
25
What is the fertile period?
**Fertile period:** sperm deposition up to 3 days prior to ovulation or day of ovulation
26
Distinguish between the transport of the gametes
- **Oocyte**: beating cilia & peristalsis of uterine tube - **Sperm**: own propulsion
27
Describe the origin, structure and function of the acrosome
- **Origin**: derived from golgi region of developing spermatid - **Structure**: contains enzymes - **Function**: necessary for fertilisation
28
Which 2 events trigger the acrosome reaction?
- Sperm pushes through corona radiata - Binding of sperm surface receptor to ZP3 glycoprotein of zona pellucida
29
What is the result of the acrosome reaction?
30
Which 2 processes lead to fertilisation?
- One sperm penetrates leading to fusion of plasma membranes - Cortical reaction occurs (blocks polyspermy)
31
Explain how fertilisation leads to the completion of meiosis II in the oocyte
- Series of **calcium waves** are activated - Resumption of **meiosis II** occurs: I. Pronuclei move together II. Mitotic spindle forms leading to cleavage
32
What is unique about the cells of the morula?
Each cell at this stage of development is **totipotent**
33
Define the term totipotent
A **totipotent** cell has the potential to give rise to any type of cell
34
Explain the process of assisted reproductive technology
- Oocytes are fertilised in vitro and allowed to divide to the 4- or 8- cell stage - The morula is then transferred into the uterus
35
What is the benefit of Pre-implantation Genetic Diagnosis in assisted reproductive technology?
A cell can be safely removed from the morula and tested for serious heritable conditions before transferring the embryo into the mother
36
Describe the structure of a blastocyst
- It has an inner cell mass which eventually forms the embryo - It has an outer cell layer called the **trophoblast**
37
What is the significance of the blastocyst hatching from the zona pellucida?
- Blastocyst can enlarge freely - Blastocyts interact with uterine surface & implants
38
How does implantation occur?
- Outer cell mass (trophoblast) interacts with endometrium - Endometrium controls degree of invasion
39
What is ectopic implantation and how does it occur?
- Blastocyst implants at sites other than endometrium - Invasion is not controlled
40
How is placenta praevia caused?
Implantation of blastocyst in lower uterine segment can cause **placenta praevia**