21 - Sperm in the Female Tract Flashcards
Slide 5
look
Role of vagina wrt sperm
- retrograde loss of sperm
- phagocytosis
- entrance into cervix
Role of cervix wrt sperm
- “privileged pathways” of sperm movement
- removal of non-motile and abnormal sperm
Role of uterus wrt sperm
- capacitation initiated
- phagocytosis
Role of oviduct wrt sperm
- capacitation completed
- phagocytosis
Steps in fertilization
- Acrosome reaction
- Sperm binds and penetrates oocyte
- Male and female pronuclei develop
- Zygote formed
Estrogenic effect on hypothalamus? Brain?
Hypo/pit: increase GnRH = LH surge
Brain: mating behaviour (lordosis), phonation (vocalization)
Estrogenic effects on reproductive tract
Increased:
- blood flow
- leukocytes
- mucosal secretion (lubricate, pheromones)
- growth uterine glands
- smooth muscle tone (contract to help sperm move to fert site)
- genital swelling
Role of leukocytes in fem repro tract? When does it occur
- prevent infection
- protect against foreign materials
Within 6-12h after intro of sperm into uterus
Control vs phenylephrine/ergonovine effects on sperm transport
Control: saline injection, 90,000 sperm AI, fertilization = 16%
Phenylephrine injection causes muscle contraction led to an increase in fertilization rate (52%)
Ergonovine = 63% fertilization rate
90,000 sperm AI
Two types of cervical mucus forms/functions
- Sialomucin: low viscosity mucus found within cervical crypts (folds). Sperm are able to move through it towards the uterus
- Sulfomucin: high viscosity mucus found at the ends of the cervical folds. Sperm that remain in cervical lumen are stuck to sulfomucin and do not enter uterus
Slide 11
What types of sperm move through the cervix
Viable sperm (ie motile & morphologically normal) are better able to gain access to this “privileged pathway”
Slide 12
Characteristics of copulation in diff species**
Two types of AI in cattle? Effectiveness?
Insert as soon as gun passes cervix (into uterine body) or go into uterine horn (using ultrasound scanner)
Uterine body deposition is just as efficient as cornual. Cervical deposition not effective (sperm is expelled)
Slide 13, 14
How does AI work in pigs
Semen deposition into cervix
AI gun/syringe needs to have a tip that can enter cervix (spiral tip)
Needs to be fresh semen (not frozen) and a high volume to achieve fertilizations (far distance to oocytes, multiple oocytes)
Slide 15
How does AI work in horses
Finger to help insert AI gun
Cervix can be tricky, unexperienced technician can cause damage
Slide 16
How does AI work in dogs
Repro tract goes upwards towards dorsal part of body
Use fingers to accommodate AI gun/access vagina
With AI, low volume of semen doses deposited, much will be lost due to gravity or lost to leukocytes
Try to go as close to or past the cervix if possible
Slide 18
Slide 18
Ai in sheep
What is sperm capacitation
The process whereby sperm acquire fertility through interactions w the female repro tract
Ejaculated sperm not yet able to fertilize oocyte. Gain full ability once exposed to appropriate factors
Sperm decapacitation / capacitation steps
In epididymus, egg-binding proteins added to sperm head membrane
Heads of ejaculated sperm then coated with de-capacitation factor that masks EBP
Capacitation factors produced by fem repro tract remove decapacitation factors
Exposed EBP interact w oocyte to initiate fertilization (acrosome reaction)
Events leading to fertilization ** (sperm in oviduct)
- Hyperactive motility (change from linear to rapid “figure-8” like movement
- Binding to zona pellucida
- Acrosome reaction
(only capacitated sperm do this)
Three glycoproteins of the zona pellucida
ZP1 (structural)
ZP2 (structural)
ZP3 (binds to proteins on sperm membrane)
2 zona binding sites on sperm’s oocyte binding proteins
- Primary zona binding region (ZBR)
- Acrosome reaction promoting region (ARPR)
Slides 23, 25
Zona pellucida binding, acrosomal reaction**
What is the acrosome?
Membrane-bound lysosome containing hydrolytic enzymes required for penetration of the oocyte zona pellucida at fertilization
Acrosomal enzymes: acrosin, zona lysin, esterases
What is the acrosome reaction
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
Steps 1 and 2 in sperm-oocyte interaction (fertilization)
1: acrosome-reacted sperm penetrates the zona pellucida
2:
- sperm enter the perivitelline space & bind to the vitelline membrane
- zona pellucida undergoes biochemical changes to prevent other sperm from penetrating (ZONA BLOCK)
Steps 3 and 4 in sperm-oocyte interaction (fertilization)
3:
- 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
4:
- cytoplasm shrinks
- second polar body pushed into perivitelline space
- DNA decondenses to form the male and female pronuclei
Steps 5 and 6 in fertilization
5: syngamy occurs (male and female pronuclei merge)
6: single diploid (2N) nucleus forms and fertilization is complete to give a zygote
Slides 26, 29, 31, 32
Oocyte, embryo
