Midterm 3 - Lecture 22 Flashcards

1
Q

What happens to sperm in the vagina?

A
  • retrograde loss of sperm
  • phagocytosis
  • entrance into the cervix
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2
Q

What happens to sperm in the cervix?

A
  • “privileged pathways” of sperm movement
  • removal of non-motile and abnormal sperm
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3
Q

What happens to sperm in the uterus?

A
  • capacitation initiated
  • phagocytosis; majority of sperm attacked and defeated
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4
Q

What happens to sperm in the oviduct?

A
  • capacitation completed
  • phagocytosis
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5
Q

What happens to sperm during fertilization?

A
  • acrosome rxn
  • sperm binds to and penetrates oocyte
  • male and female pronuclei develop
  • zygote formed
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6
Q

What are the estrogenic effects on the reproductive tract?

A
  • increase blood flow
  • increase leukocytes
  • increase mucosal secretion
  • increase growth of uterine glands
  • increase smooth muscle tone (gamete transport)
  • genital swelling
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7
Q

What do leukocytes prevent? When is there an increase?

A
  • prevent infection
  • within 6-12 hours after the introduction of sperm into the uterus there is a large infiltration of neutrophils from the uterine mucosa into the uterine lumen
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8
Q

What is the role of the cervix?

A
  • the cervix is a barrier to sperm transport, but also plays a role in sperm selection
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9
Q

How does cervical mucus vary in form and fxn?

A
  1. Sialomucin
    - low viscosity mucus found within the cervical crypts (folds of the cervix surface)
    - sperm that work their way into the cervical crypts are able to move through to the sialmucin and are moved towards the uterus
  2. Sulfomucin
    - high viscosity mucus found at the ends of the cervical folds
    - sperm that remain in the cervical lumen are stuck to the sulfomucin and do not enter the uterus
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10
Q

What are viable sperm better able to gain access to?

A

privileged pathway

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11
Q

What is sperm capacitation?

A
  • the process whereby sperm acquire fertility through interactions with the female reproductive tract
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12
Q

Are ejaculated sperm able to fertilize an oocyte?

A

ejaculated sperm are not yet able to fertilize an oocyte; gain full ability to fertilize once they have been exposed to appropriate factors/enviro

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13
Q

What are the steps of sperm capacitation?

A
  • in the epididymus “egg-binding proteins” are added to the sperm head membrane that allow them to bind to an oocyte
  • heads of ejaculated sperm are coated with de-capacitation factors that mask egg-binding proteins
  • capacitation factors produced by the female repro tract remove decapacitation factors
  • exposed egg-binding proteins able to interact with oocyte and initiate fertilization (acrosome rxn)
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14
Q

What are the 3 events leading to fertilization?

A
  1. Hyperactive motility
    - change from linear to rapid “figure-8” like movement
  2. Binding to the Zona Pellucida
  3. Acrosome Rxn

*only capacitated sperm are able to achieve these milestones

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15
Q

What 3 glycoproteins does the zona pellucida consist of?

A
  1. ZP1 - structural protein
  2. ZP2 - structural protein
  3. ZP3 - binds to proteins on the sperm membrane
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16
Q

What do sperm oocyte binding proteins contain?

A

2 zona pellucida binding sites
1. primary zona binding region (ZBR)
2. acrosome reaction promoting region (ARPR)

17
Q

What is the acrosome?

A
  • membrane-bound lysosome containing hydrolytic enzymes required for penetration of the oocyte zona pellucida at fertilization
18
Q

Acrosome rxn

A
  • plasma membrane overlying the acrosome fuses with the outer acrosomal membrane
  • fusion of the 2 membranes leads to vesiculation that allows for the release of the acrosomal enzymes
19
Q

6 sequential steps in fertilization

A
    • acrosome-reacted sperm penetrates the Zona Pellucida
    • sperm enter the perivitelline space and bind to the vitelline membrane
    • zona pellucida undergoes biochemical changes to prevent other sperm from penetrating = zona block
    • sperm is engulfed by oocyte cytoplasm and passes through the vitelline membrane
    • additional alteration in oocyte membranes (vitelline block) is evoked to prevent other sperm from entering
    • cytoplasm shrinks
    • second polar body pushed into the perivitelline space
    • DNA decondenses to form the Male and Female Pronuclei
  1. Syngamy occurs = male and female pronuclei merge

6.
- single diploid (2N) nucleus forms and fertilization is complete to give a zygote