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Reproductive systems > Sex and fertilisation > Flashcards

Sex and fertilisation Flashcards

1
Q

Briefly outline spermatogenesis

A
  • Occurs in seminiferous epithelium found in testis
  • Controlled by HPG axis
  • 100 million sperm produced per day
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2
Q

What is the sperm’s journey through the epididymis?

A
  • On entry, spermatozoa not capable of movement
  • Once at tail of epididymis, they are capable of movement and have potential to fertilise
  • Addition of secretory products to surface of sperm
  • Maturation dependent on support of epididymis by androgens
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3
Q

What makes up the semen?

A
  • Spermatozoa and seminal plasma
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4
Q

Where is seminal plasma derived from?

A
  • Accessory glands of male reproductive tract
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5
Q

What are the functions of seminal plasma?

A
  • Transport medium
  • Nutrition
  • Buffering capacity
  • Prostaglandins may stimulate muscular activity in female tract
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6
Q

Which glands contribute to making seminal plasma?

A
  • Seminal vesicles
  • Prostate gland
  • Bulbourethral glands (Cowper’s glands)
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7
Q

What do seminal vesicles contribute to seminal plasma?

A
  • 60% of volume
  • Alkaline fluid - neutralises acid in male urethra and female
  • Fructose, prostaglandins, clotting factors (semenogelin)
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8
Q

What do bulbourethral (Cowper’s) glands contribute to seminal plasma?

A
  • Very small volume
  • Alkaline
  • A mucous that lubricates end of penis and urethral lining
  • (pre ejaculate)
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9
Q

What does the prostate gland contribute to seminal plasma?

A
  • 25% volume
  • Milky, slightly acidic
  • Proteolytic enzymes (keep semen fluid)
  • Citric acid, acid phosphatase
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10
Q

What should the normal sperm count be?

A
  • 33-46 million
  • Normally around 40 million
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11
Q

How far does the sperm have to travel to meet the female gamete?

A
  • 100 000 times its own length
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12
Q

What is the normal site of fertilisation?

A
  • Ampulla of uterine tube
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13
Q

What are the phases of the human sexual response?

A
  1. Excitement phase - due to psychogenic and/or somatogenic stimuli
  2. Plateau phase
  3. Orgasm phase
  4. Resolution - return to haemodynamic norm followed by a refractory period in males
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14
Q

Which nervous system causes erection in males?

A
  • Parasympathetic
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15
Q

What are the stimulants for erection?

A
  • Psychogenic
  • Tactile (sensory afferents of penis and perineum)
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16
Q

What are the efferents for erection?

A
  • Somatic and autonomic
  • Pelvic nerve (PNS)
  • Pudendal nerve (somatic)
  • Causes haemodynamic changes
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17
Q

What does erection involve?

A
  • Straightening of coiled helicine arteries
  • Allows blood to fill the corpus cavernosum
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18
Q

Describe blood flow in the flaccid penis?

A
  • Arterio-venous anastomoses allows blood to bypass corpus cavernosum
19
Q

Describe blood flow to the penis during erection

A
  • Smooth muscle in helicine arteries relaxes and straightens
  • Blood flows into corpus cavernosum
  • Bulbospongiosus and ischiocavernosus muscles compress venous plexus
  • This retains blood in the penis
20
Q

Which nerves provide parasympathetic innervation to the penis?

A
  • Fibres from lumbar and sacral spinal levels
  • Pelvic nerve and pelvic plexus
  • Cavernous nerve to corpora and vasculature
21
Q

Outline the neurophysiology of erection

A
  • Inhibition of sympathetic arterial vasoconstrictor nerves
  • Activation of PNS
  • Activation of non-adrenergic, non-cholinergic, autonomic nerves to arteries
  • NO released
22
Q

What are the effects of NO on erection

A
  • Post-ganglionic fibres release ACh
  • ACh binds to M3 receptor on endothelial cells
  • Causes a rise in Ca2+ concentration, activation of NOS and formation of NO
  • NO diffuses into vascular smooth muscle and causes vasodilation
  • This leads to erection
    (NO is also released directly from nerves)
23
Q

What causes erectile dysfunction?

A
  • Psychological (descending inhibition of spinal reflexes)
  • Vascular - CVD, DM, HTN
  • Anatomical
  • Neurogenic - peripheral (polyneuropathy/DM) or central (spinal cord lesion/MS)
  • Hormonal
  • Drugs
24
Q

Which nervous system causes emission and ejaculation?

A
  • Sympathetic
25
Q

What happens in emission of semen?

A
  • Movement of semen into prostatic urethra
  • Contraction of smooth muscle in prostate, vas deferens and seminal vesicles
26
Q

What happens in ejaculation?

A
  • Expulsion of semen
27
Q

What happens to facilitate ejaculation?

A
  • Contraction of glands and ducts
  • Bladder internal sphincter contracts
  • Prevents retrograde ejaculation
  • Rhythmic striatal muscle contractions of pelvic floor and perineal muscles (ischiocavernosus and bulbospongiosus)
28
Q

How does the character of cervical mucus change over the course of the menstrual cycle?

A
  • Oestrogen alone causes thin and stretchy mucus
  • Oestrogen and progesterone forms thick and sticky mucus (forms a plug)
29
Q

Outline capacitation of sperm?

A
  • Further maturation of sperm in female productive tract (6-8 hours)
  • Sperm cell membrane changes to allow fusion with oocyte cell surface
  • Tail movement changes from beat to whip-like action
  • Now capable of undergoing acrosome reaction
30
Q

How long can sperm survive once they’ve left the body?

A
  • 48-72 hours
31
Q

How long do oocytes survive after ovulation?

A
  • 6-24 hours
32
Q

How long is the fertile period?

A
  • Sperm deposition up to 3 days prior to ovulation or day of ovulation
33
Q

How do oocytes move after ovulation?

A
  • Beating cilia and peristalsis of uterine tube
34
Q

What is the acrosome?

A
  • Derived from golgi region of developing spermatid
  • Contains enzymes
  • Necessary for fertilisation
35
Q

What is the acrosome reaction?

A
  • Sperm pushes through corona radiata
  • Binding of sperm surface receptor to ZP3 glycoprotein of zona pellucida
  • Triggers acrosome reaction
  • Digestion of zona pellucida
36
Q

What is the cortical reaction?

A
  • One sperm penetrates zona pellucida
  • Plasma membranes fuse
  • Blocks polyspermy
37
Q

What does fertilisation trigger?

A
  • Series of calcium waves activated
  • Meiosis II continues
  • Pronuclei move together
  • Mitotic spindle forms leading to cleavage
38
Q

Describe the cells of the morula

A
  • Each cell is totipotent
39
Q

Outline what happens in IVF

A
  • Oocytes fertilised in vitro
  • Divide to the 4 or 8 cell stage
  • Morula is then transferred into uterus
40
Q

What is Pre-implantation genetic diagnosis?

A
  • Cell safely removed from morula
  • Tested for serious heritable conditions
  • Prior to transfer of embryo
41
Q

What is the process of hatching?

A
  • Occurs after formation of blastocyst
  • Blastocyst hatches from zona pellucida
  • Now can enlarger without constraint
  • Can interact with uterine surface to implant
42
Q

Outline the process of implantation

A
  • Outer cell mass (trophoblast) interacts with endometrium
  • Endometrium controls degree of invasion
43
Q

What happens in ectopic implantation?

A
  • Implantation occurs at sites other than endometrium lined uterine cavity
  • Invasion not controlled
44
Q

What causes placenta praevia?

A
  • Implantation in lower uterine segment

Reproductive systems (20 decks)

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