Pregnancy and Parturition

Question 1

Implantation

Answer 1

First stage in development of the placenta
Occurs when the embryo become fixed in position and forms a physical and functional contact with the uterus
2-5 weeks after fertilisation
Blastocyst undergo implantation or elongates rapidly to fill the uterine lumen

Question 2

Stages of implantation

Answer 2

1. Attachment
   - Close interaction of embyonic trophoblast and endometrial epithelial cells that is known as adhesion or attachment
   - Involves a tight intertwining of microvilli on the maternal and embryonic cells.
2. Following that, blastocyst is no longer easily flushed from the lumen of the uterus.
3. Gives rise to fetus portion of the placenta and becomes outermost layer of the placenta.
4. Attach to the uterus, absorbs nutrients from uterus, allows maternal/fetal gas exchane produces hormones.

Question 3

Superficial fuses to endometrium

Answer 3

Chrion fuses to endometrium.
The blastocyst remains in the uterine cavity (pigs, horses, carnivore)

Question 4

Interstitial

Answer 4

Embyo invades endometrium and develops in endometrium
Rodents, primates

Question 5

Placentation

Answer 5

The development of extra-embryonic membrane

Question 6

Fetal placenta

Answer 6

Collective name of the membrane which consist of the chorion, allantois and amnion

Question 7

Chorion

Answer 7

Outermost-associate with endometrium

Question 8

Amnion

Answer 8

Envelops the fetus and contains amniotic fluid in the amniotic cavity

Question 9

Allantoic cavity/Urachus

Answer 9

Space between the two layers of allantois

Question 10

Allantois outer layer

Answer 10

Fused to chorion

Question 11

Inner layer of allantois

Answer 11

Fused to the amnion

Question 12

Functions of the fetal placenta

Answer 12

yolk sac - early supply
amnion - fetal protection
Allantois - fetal blood supply and waste
Chorion- maternal link

Question 13

Yolk sac

Answer 13

Early nutrient supply for early embryo
Picks up uterine secretions from endometrium to stimulate early embryonic development
Site of primodial germ cells
It regresses as the allantois development
Contains blood vessel
Connected to the fetal intestine

Question 14

AMNION

Answer 14

Develops form trophoblast and mesoderm
Non- vascular
Fluid filled - produced by fetus, reservoir for urine and waste
Protective cushion, protects fetus from injury and external shock
Ruptures at birth
Provides lubrication for parturition
Prevents lungs from collapsing and opens digestive tract

Question 15

Allantois

Answer 15

Originates from mesoderm and rises from hindgut
Fuses with chorion
Carries blood vessels of placenta
Umbilical cord attaches fetus to allantois
The blood vessels acts as a carrier of nutrients and waste products between fetus and mother

Question 16

Chorion

Answer 16

Developed from trophoblast and endoderm
Give rise to fetus portion of the placenta and becomes outermost layer of the placenta
-Attaches to uterus, absorb nutrients from uterus, allows maternal/fetal gas exchanges, produces hormones
Dont contain blood vessels

Question 17

Diffuse placenta

Answer 17

Horse, pig
When attachment (extension of chorionic villi) of fetal membranes to the endometrium is continuous throughout the entire surface of the fetal membrane

Question 18

Cotyledonary placenta

Answer 18

Ruminants
Mushroom-like from the endometrium
Multiple, discrete area of attacment called cotyledons formed by interactions of patches of allantochorion with endometrium
The fetal cotyledons are attached to the maternal caruncles, a combination known as placentome

Question 19

Zonary placenta

Answer 19

Placenta takes the form of a complete or incomplete band of tissues surrounding the fetus
Attached by girdle-like band tha encircles the placenta
Carnivores like dogs and cats, seals, bears and elephants

Question 20

Discoidal placenta

Answer 20

Attached as disk-shaped area
Singlle placenta
Discoid in shape
Primates and rodents

Question 21

Gestation

Answer 21

Period of time during which fetus develops, dividing via mitosis inside the female
The fetus receives all nutrion and oxygenated blood from the female, filtered through thep placenta, which is attached to the fetus’s abdomen via an umbilical cord

Question 22

Why last 3rd of pregnancy fast

Answer 22

greater maintenance of dam, growth of fetus and for lactation
> greater requirement for nutrients

Question 23

Relaxin hormone

Answer 23

Causes connective tissue to stretch uterine muscle
Causes pelvic canal to expand during gestation

Question 24

Estrogen

Answer 24

From placenta.
Synergistic action with prostaglandin for mammary development

Question 25

Placental lactogen

Answer 25

Mammary development and fetal growth

Question 26

Fetal Nutrition

Answer 26

Blood gas exchange at chorion- endometrium attachment
Placenta highly permeable to water and electrolytes stored in and exchange between allantoic and amniotid fluids
Placenta converts glucose to fructose
Allow storage in allantoic fluid
Fetal fat formed from fatty acids transferred across the placenta
- omega 3 & 6 fatty acid
- DHA
Fetus makes protein from transferreda amino acids
Water soluble vitamins cross placenta easier than fat soluble vitamins
Minerals are transferred across placenta
Antibodies dont cross placenta - newborn will get these antibodies from colostrum

Question 27

Factors affecting pregnancy
DAM

Answer 27

shorted if young dams

Question 28

Factors affecting pregnancy

FETUS

Answer 28

no of fetus
males are born earlier
larges-sized is born earlier
Hormones

Question 29

Factors affecting pregnancy
GENETIC

Answer 29

Breed of progeny
EG: angus vs hereford, bos taurus vs bos indicus

Question 30

Factors affecting pregnancy

ENVIRONMENT

Answer 30

High temperature can reduce gestation length
More stress, earlier born
Nutrition

Question 31

Pregnancy diagnosis

Answer 31

1. Hormonal diagnosis - plasma progesterone levels between 18-25 days after mating or insemination (low=not, high=yes).
2. Rectal palpation - left hand into rectum and feel cervix (in centre of pelvic cavity=no, in abdominal cavity=yes) Accuracy after 5-6 weeks
3. Abdominal ballottement
4. Ultrasound technique- accuracy from day 60
5. X-ray
6. Laparotomy
7. Laparoscopy

Question 32

Parturition/labor

Answer 32

Physiological process by which pregnant uterus delivers fetus and placenta from maternal organism

Question 33

Hormone changes during parturition

Answer 33

Progesterone- reduce rapidly 1-2 days before parturition
Prolactin - Increase rapidly 1-2 days b4 parturition
Relaxin - increase to max 1 day before parturition, relax pelvic area
Estogen and FSH - increase to stimulate birth, assist in the production of uterine muslce contractile proteins b4 parturition
Estrogen - signal secretion of PGF2 alpha that occur in the immediate prepartum period
Fetal cortisol - increase rapidly, more compared to maternal cortisol, determines when is parturition

Question 34

Prior to parturition

Answer 34

+ adrenal cortisol > +estrogen concentration > increased synthesis in uterus of oxytocin receptors > stimulate +production of PGF2a and PGE2 > cause uterine contraction during labour

Question 35

Signs of parturitiom

Answer 35

Frequently adopt posture of urination
Myometrium contracts
Rhythmic contraction of uterus
Fetal positioning
Restless
Nesting behaviour
Enlargement of mammary gland, teats
Chorion-allantois ruptures
Dam recumbent

Question 36

Dilation of cervix

Answer 36

1. 2-6 hours, cow heifers 12 hours
2. Uterine contractions become coordinated and regular due to decline in progesterone, estrogen & PGF2a induced
3. Fetus pushed against cervix-amnion, stimulate oxytocin release, chriallantoic membrane may break, dilates cervix
4. Pressure of fetus on cervix stimulates oxytocin release and reflex contraction of abdominal muscle

Question 37

Expulsion of fetus
cow - 5-2 hours

Answer 37

1. Strong uterine contraction due to synergistic actions of high estrogen, PGF2a and oxytocin
2. Strong abdominal muscle contractions
3. Amino ruptures, lubricates vagina & vestibules
4. Contraction force the calf legs and head to spread in cervix
5. Fetus passes through vagina-vestibule

Question 38

Expulsion of the placenta (4-5 hours, cow)

Answer 38

1. Uterine contraction continue
2. Blood forced from cotyledon villi-shrinkage separates cotyledon and caruncle
3. Contraction push placenta out

Question 39

Fetus discharged

Answer 39

• Dam gets up and licks fetus nudges new born
• Separation of villi from uterus
• Fetal membranes discharged
• New born goes for milk

Question 40

Causes of retained placenta

Answer 40

Infection
Calving stress
Weak uterine contraction

Question 41

Dystocia

Answer 41

Abnormal or difficulty childbirth or labour
- prolonged spontaneous calving or prolonged or severe assisted extraction
- due to incoordinate uterine activity, abnormal fetal lie or presentation, absolute or relative cephalopelvic disproportion

Question 42

Causes of dystocia

Answer 42

Feto-pelvic disproportion
Fetal malposition
Uterine inertia
Vulval or cervical stenosis
Uterine torsion

Question 43

Involution

Answer 43

process the uterus returns to its non-pregnant size after parturition
cow - 21 to 35 days
ewe and sow - 24 to 28 days
bitch - 12 weeks