Fertilization

Why is semen deposition so important in the sow?

Makes the journey easier because uterine horn very defined

Semen deposition differs by species. Name the THREE regions where semen can be deposited.

Cranial vagina

Cervix

Cervical lumen -> Uterus

The bull, ram, cat, and human all have rapid ejaculation, so it ends up in the —-.

The dog, stallion, and boar are prolonged, so it ends up in the —-.

Vagina

Uterus

Name the THREE animals with a fibroelastic penis.

Bull

Rm

Boar

Name the FOUR animals with a musculocavernous penis.

Stallion

Dog

Cat

Human

Where does fertilization occur specifically?

Ampulla of oviduct

What are the TWO phases of sperm transport to the egg? Indicate which can and which cannot fertilize.

Rapid transport: CANNOT fertilize

Sustained transport: CAN fertilize

What phase has sperm reach the site of fertilization in less than 5 minutes and reaches not of their own accord?

Rapid transport phase

What phase is reliant on uterine contractions and relies on sperm motility?

Sustained transport phase

Name the FOUR major barriers to fertilization.

Vagina

Cervix

Oviduct

Fertilization (already occurred)

True or False: Vaginal pH is basic.

False! Vaginal pH is ACIDIC.

Name THREE major vaginal barriers to fertilization.

Vaginal pH

Retrograde transport

Phagocytosis by leukocytes

During phagocytosis by leukocytes, high levels of —- sequester —- to the vagina, which attack foreign materials introduced into the reproductive tract.

Estradiol

Neutrophils

Name the TWO major ways semen fights against the vaginal barriers.

Semen is divided into "fractions"

Seminal fluid is very BASIC

True or False: In semen fractions, there is always a "sperm-rich" fraction that carries the majority of the sperm and some have a post-sperm fraction that is highly viscous and acts to block the vaginal canal to prevent retrograde loss.

True!

During estrus, the cervix secretes mucus. Name the TWO common types and define them.

Sialomucin: LOW viscosity; basal area of cervix

Sulfomucin: HIGH viscosity; apical area of cervix; tips of cervical folds

What is the major function overall of the cervical barriers?

Slow down sperm transport and remove non-motile/abnormal sperm

True or False: Semen fraction numbers are species dependent

True!

What is where sperm must reside in the reproductive tract for a minimum period of time to obtain the ability to fertilize?

What phase can it only occur in?

Capacitation

Sustained transport phase

Capacitation is dependent upon what?

Semen deposition location

(Shallower the deposition, the shallower the capacitation)

Name the TWO important functions of capacitation.

Removal of surface molecules of sperm head (expose molecules needed for binding to egg)

Increases motility of sperm tail

Put the following steps in order once capacitation is complete:

Sperm engulfed

Hyperactive motility

Acrosomal reaction

Formation of male pronucleus

Sperm-oocyte membrane fusion

Binding to zona pellucida

Pentration of zona pellucida

Decondensation of sperm nucleus

Hyperactile motility -> Binding to zona pellucida -> Acrosomal reaction -> Penetration of zona pellucida -> Sperm-oocyte membrane fusion -> Sperm engulfed -> Decondensation of sperm nucleus -> Formation of male pronucleus

Why is the acrosome so important?

Release enzymes that chew through cumulus oocyte complex with hyaluronidase and proteolytic enzymes

What does the plasma membrane of sperm contain? Which ones provide structural integrity of the zona? Which ones bind the proteins on the spermatozoal plasma membrane?

Zona pellucida binding proteins (ZP1, ZP2, ZP3)

ZP1 and ZP2

ZP3

Why does the sperm only dissolve a tiny hole in the zona pellucida and not the whole thing?

Must remain intact from fertilization to blastocyst stage to prevent embryo from blebbing off

How does an egg prevent polyspermy?

Transports cortical granules to the egg periphery after ovulation and releases them to harden the zona

True or False: Most eggs that have multiple sperm that bind fail to develop.

True!

The sperm nucleus is protected by —- crosslinks, which are very condensed and rendered inert. —- from oocyte cytoplasm breaks down these crosslinks.

What is the result from here?

Disulfide

Glutathione

Decondense sperm nucleus and free up nuclear material

True or False: In pronuclei fusion, the sperm is broken down into male pronucleus via Glutathione and migrates towards the female pronucleus for fusion.

True!

Describe where AI occurs in the cow, sow, mare, and bitch.

Cow: Grab cervix and deposit to uterus

Sow: Starts cervix and ends uterus

Mare: Directly into uterine body

Bitch: Vagina/sometimes cervix; 2 fractions with semen-rich first then semen extender

Name the THREE ways you can inseminate and define them.

Transcervical: bypass cervix to deposit in uterus (cow)

Intracervical: semen delivered into cranial half of cervix (sow)

Intravaginal: semen deposited into cranial vagina (bitch/queen)