Pregnancy and Parturition Flashcards
Implantation
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
Stages of implantation
- 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. - Following that, blastocyst is no longer easily flushed from the lumen of the uterus.
- Gives rise to fetus portion of the placenta and becomes outermost layer of the placenta.
- Attach to the uterus, absorbs nutrients from uterus, allows maternal/fetal gas exchane produces hormones.
Superficial fuses to endometrium
Chrion fuses to endometrium.
The blastocyst remains in the uterine cavity (pigs, horses, carnivore)
Interstitial
Embyo invades endometrium and develops in endometrium
Rodents, primates
Placentation
The development of extra-embryonic membrane
Fetal placenta
Collective name of the membrane which consist of the chorion, allantois and amnion
Chorion
Outermost-associate with endometrium
Amnion
Envelops the fetus and contains amniotic fluid in the amniotic cavity
Allantoic cavity/Urachus
Space between the two layers of allantois
Allantois outer layer
Fused to chorion
Inner layer of allantois
Fused to the amnion
Functions of the fetal placenta
yolk sac - early supply
amnion - fetal protection
Allantois - fetal blood supply and waste
Chorion- maternal link
Yolk sac
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
AMNION
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
Allantois
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
Chorion
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
Diffuse placenta
Horse, pig
When attachment (extension of chorionic villi) of fetal membranes to the endometrium is continuous throughout the entire surface of the fetal membrane
Cotyledonary placenta
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
Zonary placenta
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
Discoidal placenta
Attached as disk-shaped area
Singlle placenta
Discoid in shape
Primates and rodents
Gestation
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
Why last 3rd of pregnancy fast
greater maintenance of dam, growth of fetus and for lactation
> greater requirement for nutrients
Relaxin hormone
Causes connective tissue to stretch uterine muscle
Causes pelvic canal to expand during gestation
Estrogen
From placenta.
Synergistic action with prostaglandin for mammary development
Placental lactogen
Mammary development and fetal growth
Fetal Nutrition
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
Factors affecting pregnancy
DAM
shorted if young dams
Factors affecting pregnancy
FETUS
no of fetus
males are born earlier
larges-sized is born earlier
Hormones
Factors affecting pregnancy
GENETIC
Breed of progeny
EG: angus vs hereford, bos taurus vs bos indicus
Factors affecting pregnancy
ENVIRONMENT
High temperature can reduce gestation length
More stress, earlier born
Nutrition
Pregnancy diagnosis
- Hormonal diagnosis - plasma progesterone levels between 18-25 days after mating or insemination (low=not, high=yes).
- Rectal palpation - left hand into rectum and feel cervix (in centre of pelvic cavity=no, in abdominal cavity=yes) Accuracy after 5-6 weeks
- Abdominal ballottement
- Ultrasound technique- accuracy from day 60
- X-ray
- Laparotomy
- Laparoscopy
Parturition/labor
Physiological process by which pregnant uterus delivers fetus and placenta from maternal organism
Hormone changes during parturition
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
Prior to parturition
+ adrenal cortisol > +estrogen concentration > increased synthesis in uterus of oxytocin receptors > stimulate +production of PGF2a and PGE2 > cause uterine contraction during labour
Signs of parturitiom
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
Dilation of cervix
- 2-6 hours, cow heifers 12 hours
- Uterine contractions become coordinated and regular due to decline in progesterone, estrogen & PGF2a induced
- Fetus pushed against cervix-amnion, stimulate oxytocin release, chriallantoic membrane may break, dilates cervix
- Pressure of fetus on cervix stimulates oxytocin release and reflex contraction of abdominal muscle
Expulsion of fetus
cow - 5-2 hours
- Strong uterine contraction due to synergistic actions of high estrogen, PGF2a and oxytocin
- Strong abdominal muscle contractions
- Amino ruptures, lubricates vagina & vestibules
- Contraction force the calf legs and head to spread in cervix
- Fetus passes through vagina-vestibule
Expulsion of the placenta (4-5 hours, cow)
- Uterine contraction continue
- Blood forced from cotyledon villi-shrinkage separates cotyledon and caruncle
- Contraction push placenta out
Fetus discharged
- Dam gets up and licks fetus nudges new born
- Separation of villi from uterus
- Fetal membranes discharged
- New born goes for milk
Causes of retained placenta
Infection
Calving stress
Weak uterine contraction
Dystocia
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
Causes of dystocia
Feto-pelvic disproportion
Fetal malposition
Uterine inertia
Vulval or cervical stenosis
Uterine torsion
Involution
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
