Exam 3

Timing and percentage of loss due to embryo wastage in domestic species

• bovine

• ovine

• porcine

• equine

• bovine

  • days of gestation: 8-16

    • embryos lost: 25-40%

• ovine

  • days of gestation: 9-15

    • embryos lost: 25-40%

• porcine

  • days of gestation: 8-16

    • embryos lost: 25-40%

• equine

  • days of gestation: 30-36

    • embryos lost: 30-40%

Ectoderm (Inner cell mass) develops

skin, hair, hooves, horns, sweat glands( including mammary glands), nervous system, oral and nasal cavity, outer repro tract (vulva, vestibule, clitoris, glans penis)

Mesoderm (Inner cell mass) develops

heart and blood vessels, renal system, skeleton (including muscle), internal repro tract (gonads: female including ovaries, oviduct, uterus, cervix, and vagina & male including epididymis, vas deferens, and accessory glands

T/F: yolk sac does play a role in waste removal

true

Endoderm (Inner cell mass) develops

digestive system (including liver and pancreas), pulmonary system, major glands

Site of semen deposition in cow and sheep

vagina

site of semen deposition in horses

cervix

site of semen deposition in pigs

cervix or uterus

T/F: oogenesis can proceed without folliculogenesis

false

Stage of embryo development w/ first defined cells

a) morula

b) syngamy

c) blastocyst

d) zygote

e) none of the above

c) blastocyst

T/F: the second meiotic division takes place after ovulation in most farm species

true

a single cell embryo is called a

a) morula

b) syngamy

c) blastocyst

d) zygote

e) none of the above

d) zygote

which parts of the female would be a potential barrier to sperm movement

a) vagina

b) cervix

c) uterotubular junction (UTJ)

d) all of the above

e) none of the above

d) all of the above

T/F: under normal conditions, 99.5% of all oocytes will never be ovulated

true

T/F: heart is the first tissue to form in the embryo, but nervous system is the last to become fully functional

false

which of the following might be responsible for embryo mortality

a) genetics

b) low progesterone

c) uterine crowding

d) all of the above

e) none of the above

d) all of the above

the last organ to begin functioning is the

a) heart

b) lungs

c) brain

d) liver

e) none of the above

b) lungs

T/F: oogonia originate in the yolk sac

true

[what] is the placental hormone that regulates the growth of the fetus

a) progesterone

b) estrogen

c) relaxin

d) all of the above

e) none of the above

e) none of the above

T/F: in cattle, we would we have a retained placenta if animal has not passed placenta within 2 hours after birth of neonate

false

Which species we have talked about has a normal gestational length of ~280d

a) bovine

b) equine

c) ovine

d) porcine

e) none of the above

a) bovine

Which species we have talked about has a normal gestational length of ~114d

a) bovine

b) equine

c) ovine

d) porcine

e) none of the above

d) porcine

T/F: milk letdown is due to an arc reflex of oxytocin from mother due to neonate suckling

true

Which species we have talked about has a normal gestational length of ~340d

a) bovine

b) equine

c) ovine

d) porcine

e) none of the above

b) equine

Which semen analysis measures movement of sperm cells

a) volume

b) motility

c) morphology

d) concentration

e) none of the above

b) motility

Which semen parameter examines the shape of the sperm cells

a) volume

b) motility

c) morphology

d) concentration

e) none of the above

c) morphology

T/F: cryopreservation is currently the best method available for long term storage of male genetics

true

Which species routinely produces semen volumes around 1mL

a) porcine

b) canine

c) ovine

d) equine

e) none of the above

c) ovine

T/F: normal semen analysis has been assoc. w/ higher pregnancy rates

true

Which species requires surgical embryo transfer

a) cattle

b) pig

c) horse

d) sheep

e) none of the above

d) sheep

Which species shows no detectable signs of heat in absence of an intact male animal

a) cattle

b) sheep

c) horse

d) pig

e) none of the above

b) sheep

Which of the assisted reproductive technology (ART) procedures should be used as a routine treatment for infertile female domestic animals?

a) cryopreservation

b) superovulation

c) embryo transfer

d) all of the above

e) none of the above

e) none of the above

T/F: winking of the vulva is a common sign of standing heat in pigs

false

T/F: to be efficient, estrus detecting should be done during feeding

false

Oocyte is the

female gamete (inside of follicle)

spermatogenesis

physiological process of growing and maturing spermatozoa

what are the 2 similarities bt Oogenesis and Spermatogenesis

1. phase where chromosomal numbers are reduced (meiosis cell division)

2. undergo a metamorphic change in structure

Males have billions of copies (of sperm cells) per [what] while females have a few million eggs in her [what]

ejaculate; ovary

Embryo transfer

process of super-ovulating and retrieving embryos from a donor animal and transferring those embryos into a recipient

How about many embryos are retrieved when attempting embryo transfer

10-15

Follicles are located where and make functional eggs

on the ovary

T/F: of the 75,000 to 2 million primordial follicles only .05% will reach the point of developing into a Graafian follicle and ovulation

true

Steps of folliculogenesis

1. primary follicle (primary oocyte inside)

2. secondary and tertiary stages

3. Graafian follicle

Graafian follicle has several structures. Describe them

1. highly structured relationship bt outer layers of theca and inner layers of granulosa separated by basement membrane

2. basement membrane creates a physical barrier that allows fluids to pool and final structures of follicle to form, creates a blood barrier

3. as follicle develops, egg develops its own barrier, Zona Pellucida

Zona Pellucida

protein structure surrounding oocyte that serves a barrier to fertilization

During embryo development (i.e embryonically), the first form of egg cells which contain 2 sets of chromosomes identical to other cells of the body is called what

Oogonium

Oogonium undergo [mitosis or meiosis?] to create 75,000 to 2 million primary oocytes

mitosis

T/F: the mitotic divisions in oogonium continue after birth and number of potential oocytes increases

false;

• the mitotic divisions CEASE BEFORE BIRTH

• potential oocytes becomes FIXED and begin decreasing even before birth

What is one of the reasons why a female only has a set amount of oocytes (most before birth)

the mitotic divisions underwent by oogonium to create primary oocytes CEASES

• once this stops, there will ONLY be meiosis from this point

T/F: females will lose eggs before birth (once mitotic divisions cease!) because the hormone-independent phase has primordial follicles trying to grow and develop and they will become atretic esp if they are trying to grow before puberty

true

T/F: some oocytes that attempt to continue development before puberty will become atretic and some will be viable

false; ALL of the oocytes will become atretic if they try to develop before puberty

If the female has hit puberty and has the right set of hormones, will the follicles and oocytes continue to develop in a normal fashion

yes

What is a large difference in male and female reproductive systems (spermatogenesis and oogenesis)

Order in which they go through meiosis and metamorphosis

• males go through spermatocytogenesis first then through spermiogenesis

• Spermatogonia goes from 2N to N (chromosomal change) → sperm shape (metamorphic change)

• Oogonia go from small to bigger shape (metamorphic change) → 2N to N (chromosomal shape)

Male reduces gametes’ chromosome number first then transforms its shape to look like a sperm cell which means what

a) nothing

b) makes more copies

c) can’t make more copies

d) none of the above

b) makes more copies

Female changes shape of gamete first (zona pellucida around the structure) and then goes through what

a) meiosis

b) mitosis

c) spermatocytogenesis

d) none of the above

a) meiosis

T/F: the difference bt the order of meiosis and metamorphosis in male repro and female repro leads to both males and females having limited gametes

false;

• males remain fertile for their entire lives

  • chromosome reduced (meiosis) then sperm shape made → more copies of sperm being made

• females have limited gametes

  • changes shape with zona pellucida going around the structure then meiosis

Metamorphic change of the oocyte (Females)

1. follicle is developing from primary to secondary stage of development, egg will begin to enlarge; increase cytoplasm and organelles

2. once 2X or 3X bigger: develop the zona pellucida, granulosa cells known as corona radiata

3. this arrangement = very large cell, only nutrients the embryo will have until the outer wall, zona pellucida, attaches to the uterine wall

Meiosis in the egg is how many steps

2 step

• 2 part meiosis: cell is waking up

Meiosis I in oocyte

• cell begins growing w/o duplication of chromosomes

• arms of paired chromosomes will exchange genetic material in process called crossover: exchange of genetic material bt paired chromosomes

• ends with production of 2 nuclei each w/ 1 set of chromosome (haploid)

  • these nuclei are genetically diff

• one of these nuclei will be “thrown out”

  • polar body

• remaining nuclei is called secondary oocyte

Crossover

exchange of genetic material bt paired chromosomes

T/F: crossover leads to genetic recombination → survival of fittest

true

T/F: many high tech procedures require healthy, mature oocytes

true

Meiosis II in oocyte

• still need to become mature

  • there will be no meiosis 2 and we are kinda stuck until next part!

• as sperm is crossing vitelline membrane, this triggers second meiotic division, and 2 haploid nuclei, called pronuclei, form

• one will be expelled and form a second polar body

• second one (mature ovum; haploid) will fuse w/ DNA from sperm during fertilization

Ooogenesis Picture and link to yt video

Usually, ovulation occurs after the peak of LH surge except for what species

a) bears

b) pigs

c) dogs

d) horse

d) horse

• ovulation occurs before peak of LH surge and will occur 1 or 2 days prior to end of estrus

Timing of ovulation in cow

10-12 hrs after end of estrus

Timing of ovulation in ewes

24-30 hrs from start of estrus

Timing of ovulation in sow

35-45 hrs from start of estrus

Timing of ovulation in mare

1-2 days before end of estrus

Medulla of the ovary

that portion of the ovary containing nerves and blood supply

Cortex of the ovary

that portion of the ovary containing the follicle and hormone production

T/F: in most domestic species, cortex is on the outside and medulla is on inside

true

T/F: Mares have the medulla on the outside and cortex on the inside

true

• ovulation fossa

Pattern to ovulation in species who ovulate after LH surge

1. LH surge triggered by high lvls of estrogen (from the ovary)

2. LH triggers 4 important changes within follicle

   1. saturation of LH receptors on theca cells will begin their transformation from theca to luteal cells

   2. binding will trigger these converting cells to release proteolytic enzymes, weaken the bond bt follicular cells and basement membrane

   3. trigger the local release of prostaglandins, which will stimulate contractions at the base of the follicle and cause shifts in blood flow

   4. maturation of the oocyte cytoplasm, nucleus, and vitelline membrane to make fertilization possible

Rupture of follicle caused by (steps of ovulation)

1. pressure from contractions

2. weakened basement membrane

3. rift in follicle wall

4. oocyte will be extruded

5. oocyte into the waiting fimbria

Where will the rupture of the follicle occur

anywhere in the cortex*

• *except the hilus: depression or pit at the part of an organ where vessels and nerves enter

Where will the rupture of the follicle NOT occur

the hilus of the cortex

T/F: single ovulators, the maturation and ovulatory event is totally random bt 2 ovaries and cannot be predicted by previous cycle

true

Where do the female’s gametes go before fertilization

AIJ

Sperm cell pathway in male tract

epididymis → vas deferens → pelvic urethra → penile urethra before introduced to female tract

What causes movement of the sperm through the female repro tract (towards AIJ for fertilization)

contractions of the female tract

• NOT the sperms’ tail!

T/F: contractions of muscles of female tract move sperm cells to AIJ and not the sperm cells’ tail

true

T/F: Female tract creates barriers for sperm and facilitate its movement.

true

• ex: cow, male deposits 4-5 billion sperms in vagina, only few 100-1000 arrive at the AIJ

Sperm move up what structure (specifically) to wait for an egg

AIJ (remember this is a physiological location not PHYSICAL)

T/F: Sperm can swim for days in female tract but 24-48hrs become biochemically nonfunctional

true

• oviduct is the most ideal environment for prolonging sperm shelf life → sperm can wait up to 96 hrs waiting for oocyte to fertilize

In the female tract, the sperm will undergo what type of reaction and capacitation

acrosome rxn

T/F: once the sperm cells have gone through acrosome rxn and capacitation, the sperm has forever to fertilize the oocyte

false; it only has a limited number of hrs to fertilize the oocyte

What is the function lifespan of an oocyte and what will happen to the oocytes that aren’t fertilized within this lifespan

the lifespan of a functional oocyte is bt 6-10 hrs

• after this, egg cells that aren’t fertilized will be phagocytized (absorbed by the body)

Mature Oocyte Ready to be Fertilized Picture

Where does the final maturation of a sperm cell happen

within the female repro tract

Final Maturation of Sperm (Fertilization)

• Step 1-5

1. sperm cells undergo acrosome rxn and capacitation

2. hypermotility of sperm cells (maybe induced by chemical agents from egg) as it approaches egg

3. sperm cell forms loose assoc. w/ zona pellucida

4. enzymes in the acrosome digest a hole through the zona as the tail pushes the sperm head through into the perivitelline space

   • function of motility

5. several sperms could enter perivitelline space

What is the main function of the sperm cell’s tail

function of motility during fertilization

• tail will push sperm head through perivitelline space

under normal circumstances, how many sperm cells will lay down on the vitelline membrane and form an assoc. w/ membrane surface

1 sperm cell

What will the sperm cell laying down on vitelline membrane and forming an assoc. w/ membrane surface trigger

triggers membrane to phagocytize sperm (at least sperm head)

• this step is species dependent*

Fill in the Blanks

3 important events in fertilization

1. cortical granules will migrate and fuse with the vitelline membrane, releasing their enzymes into perivitelline space and change [1.What] structure

2. enzymes will functionally change the zona because [2. Why?]

3. trigger [3. What process] in the oocyte nuclei. The first 2 events will lead to vitelline block, both the membrane and the zona will become resistant to any other sperm cells crossing their structure, preventing more than one sperm cell from entering the egg

1. vitelline membrane

2. no other sperm can get across it and into the perivitelline

3. meiosis 2

T/F: activation of the egg nuclei is essential for final steps of fertilization

true

Activation of egg to forming a zygote (Fertilization)

• Steps 1-6

1. Nuclei forms a visible nuclear membrane → duplicate in chromosomes → briefly returning oocyte to 2N cell

2. Meiosis II: nuclei splits to form 2 pronuclei (each haploid)

3. One of the 2 pronuclei migrates to become second polar body; the DNA from sperm will form male pronuclei

4. 2 remaining pronuclei (one from sperm and one from egg) will align together toward middle of oocyte

   1. Remember there were 2 pronuclei from the egg

   2. one of them becomes the second polar body and is EXPELLED

5. Male and female aligned fuse together in a process called Syngamy

6. Fertilization is complete: single cell w/ combo of male and female’s genetics → new genetic combo

   1. Zygote: a single cell formed at fusion of an egg and sperm cell

T/F: sometimes, you can see the the pronuclei from sperm and other pronuclei from the egg aligning together toward the middle of the oocyte under a microscope

true

Syngamy

fusing of pronuclei during fertilization

Zygote

a single cell formed at fusion of an egg and sperm cell