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REPRO > Prefertilisation sperm events > Flashcards

Prefertilisation sperm events Flashcards

1
Q

Where is sperm deposited in the ewe?

A

Vagina

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2
Q

Where is sperm deposited in the cow?

A

Vagina

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3
Q

Where is sperm deposited in the mare?

A

Uterus

- Initially deposited in cranial vaginally but will flow through open cervix to uterus

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4
Q

Where is sperm deposited in the sow?

A

Cervix/uterus

- Corkscrew penis and counter-corkscrew cervix, engage during copulation, long tract

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5
Q

Where is sperm deposited in camelids?

A

Uterine/cervix/vagina

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6
Q

Where is sperm deposited in the bitch?

A

Vagina (a lot will end up in uterus due to open cervix)

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7
Q

Describe structure and function of the head of spermatozoa

A
  • Contains nucleus/DNA

- Acrosomal enzymes

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8
Q

Describe structure and function of the middle piece of spermatozoa

A
  • Full of mitochondria
  • ATP generation
  • Microtubules
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9
Q

Describe the structure and function of tail of spermatozoa

A
  • Propels sperm/movement
  • 3mm minimum
  • Allows for directional movement
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10
Q

What features develop as part of the maturation process in the epididymis?

A

Develop the ability to be motile

  • The ability to fertilise
  • cytoplasmic droplets
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11
Q

What features are acquired in the head of the epididymis?

A

The ability to move and fertilise

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12
Q

Where does the cytoplasmic droplet develop?

A

Throughout the migration of the sperm through the epididymis

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13
Q

Explain the importance of the epididymal tail

A
  • Can store a large number of spermatozoa

- Allows more frequent ejaculation

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14
Q

How do sperm move?

A
  • rotation of head
  • Tail moving in wave like motion top to bottom
  • Low amplitude initially
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15
Q

Describe the structure of the flagella of sperm

A
  • Dentral axoneme with dyneins running length of flagellum
  • Outer dense fibres surrounding axoneme in midpiece and central piece
  • Fibrous sheath in principle piece
  • Mitochondrial sheath in midpiece
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16
Q

Describe the structure of the central axoneme

A
  • Anchored in centriole
  • has pair of central microtubules
  • Outer ring of 9 pairs of outer microtubules (symmetrical)
  • Dyneins bound to each outer doublet
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17
Q

Explain how the dyneins work to make the flagellum move following ejaculation

A
  • Bind to each outer double
  • Extend motor domains towards adjacent outer doublet
  • Outer doublets slide over each other
  • Leads to bending of axoneme
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18
Q

Describe hyperactivated movement of spermatozoa

A
  • Moves asymmetrically, high amplitude, straight in oviductal mucus, whiplash
  • Facilitates sperm-oocyte contact
  • Go in circles
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19
Q

When does hyperactivated movement of the sperm occur?

A

After capacitation

20
Q

What is the function of the seminal plasma?

A
  • Not essential for fertilisation

- Aids transport of sperm through urethra of male and then female tract

21
Q

How does seminal plasma carry out its function?

A
  • Nutritional support (fructose, glucose in horse)
  • Buffering capacity
  • Antioxidants (ascorbic acid)
  • Prostaglandins
22
Q

What is the function of the prostaglandins in the seminal plasma?

A
  • Stimulates muscuar activity in female tract
  • May help move sperm towards uterus
  • Cervix may filter out some PGs
23
Q

Give an overview of the journey taken by the spermatozoa following copulation

A
  • Immediate transport
  • Cervix
  • Tansport through uterus
  • Oviduct
  • Fertilisation
24
Q

How can spermatozoa be lost following copulation?

A
  • Retrograde transport
  • Phagocytosis after period of time
  • Loss through vagina and vulva
  • Once sperm enters uterus, recognised as foreign so induces immune response
  • Neutrophil infiltration into uterus following insemination rapid
25
Q

Describe the function of the secretion of mucus within the cervix following insemination

A
  • Sialomucin (low viscosity) and sulphomucin (high viscosity)
  • Creates spermatozoa reservoir and removes non-motile sperm
  • Only vigorous sperm can utilise the privileged pathways
  • Non-motile sperm are likely to get stuck meaning they can be removed
  • Acts as reservoir as sperm stick to lining and are tehn released over time = sustained flow of sperm to uterus
26
Q

Describe the transport of sperm through the uterus to the oviduct

A
  • Rapid transport minutes after copulation
  • Likely to be in oviduct before egg, fertilisation unlikely
  • Sustained release from cervix means more likley to fertilise
  • Elevated tone and motility of mscularis of female tract
27
Q

What stimulates the increased tone and motility of the muscularis of the female tract following copulation?

A
  • Oestradiol
  • Oxytocin
  • PGs from seminal fluid
28
Q

Describe the uterine sperm reservoir found in dogs

A
  • 2nd fraction of ejaculate is sperm rich fraction
  • At tips of uterine horns, sperm bind to epithelial cells in sperm reservoir
  • Aided by seminal proteins
  • Reduces polyspermy
  • Sperm remain function for many days
  • Is the main site of capacitation
29
Q

Describe the release of sperm from the reservoir in the oviduct

A
  • Released around ovulation swim towards ampulla region
  • Thought to be due to chemotaxis/thermotaxis
  • Release triggered by secretion of oviductal factors under influence of hormones e.g. oestradiol
30
Q

Describe the sperm and oocyte meeting

A
  • Sperm released from oviductal lining around ovulation
  • Swim through isthmus and into ampulla
  • Met in the ampulla
31
Q

What is capacitation?

A

The second stage of sperm maturation, renders sperm able to fertilise

32
Q

Where does capacitation occur?

A

In the oviduct, likely as cohorts

33
Q

What are the 4 steps involved in capacitation?

A
  • Removal of decapacitation factors
  • Membrane destabilisation
  • Detachment from the oviductal epithelium
  • Transient hyperactivity
34
Q

How does membrane destabilisation in capacitation occur?

A
  • Ion movement

- Influx of HCO3-/Ca2+

35
Q

Describe the removal of decapacitation factors

A
  • Sperm has proteins on head at end of epididymis
  • Add seminal plasma so more proteins bind
  • at correct time, all of these will be removed, exposing head of sperm and allowing fertilisation
36
Q

Describe the transient hyperactivity of sperm

A
  • Due to exposure of surface proteins that bind to oocyte (ZP proteins)
  • Enables acrosome reaction to take place
  • Short life span
37
Q

Describe the structure of the oocyte

A
  • Central ooplasm (egg itself)
  • Surrounding that is glycoprotein band = zona pellucida
  • Surrounding that are cumulus cells
38
Q

Describe the components of the zona pellucida

A
  • 3 glycoproteins
  • ZP1: minor component
  • ZP2: structural component
  • ZP3: receptor
39
Q

Describe the ZP3 receptor

A
  • Species specific
  • Recognises proteins of sperm
  • Primary zona binding region (ZBR)
  • Acrosome reaction promoting region (ARPR)
40
Q

What prevents the sperm of one species binding to the egg of another?

A

The specificity of the ZP3 receptors

41
Q

When does the acrosome reactions take place?

A
  • After capacitation

- Initiated by sperm binding to the ZP

42
Q

Describe the acrosome reaction

A
  • Release of acrosomal hydrolytic enzymes
  • Digestion of ZP (acrosin)
  • Localised small hole
  • Sperm migrates through (requires hyperactivation of flagellum)
  • Fusion of plasma membranes takes place
43
Q

What are the steps in oocyte activation?

A
  • Ovulation inducing completion of meiosis I in oocyte
  • Sperm binding to oocyte
  • cortical/zona reaction
  • Membranes fuse to start fertilisation
44
Q

What is induced by the sperm binding to the oocyte?

A
  • Influx of Ca2+ ions
  • Completion of meiossi II
  • Cortical reaction
45
Q

Describe the cortical/zona reaction

A
  • Zona pellucida hardens
  • Sperm receptros (ZP3) destroyed
  • Major block of polyspermy

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