Placentation Gestation Parturition Flashcards
What is Gestation?
Act of being carried in uterus between conception and birth
What is Oviparous?
Egg laying
WHat are Eutherian mammals?
Mammals with a placenta
What is implantation?
Attachment of placental membranes to the endometrium
What is the definition of placenta?
Endorcrine organ of matabolic exchange between conceptus and dam (mom)
What is parturition?
Giving birth to young
What are the final prepartum steps of reproduction?
- Formation of placenta
- Placenta acquires endocrine function
- Initiation of parturition
What are the types of placentation?
- Implantation
- Attachment
What does implantation mean?
- Conceptus buries into uterine endometrium
- Totally invasive or semi-invasive
What is attachment?
Placenta attaches to uterine epithelium
What does the transient organ of pregnancy do?
Provides metabolic interface between conceptus & dam
What does the transient endocrine gland do?
- Maintains pregnancy
- promotes fetal & mammary gland growth
- Introduction of parturition
The conceptus consists of the embryo and what other extra embryonic membranes?
- Amnion
- Allantois
- Chorion
What are chorionic villus?
- They are exchange apparatus, small finger-like projections
- They protrude away from the chorion toward the uterine endometrium
What are diffuse placentas?
- They have a uniform villi distribution (in pig and mare)
In mares how do diffuse placentas work?
- They are further classified as microcytyledons due to microzones of chorionic villi
- Have endometrial cups produced by equine chorionic gonadotropin (eCG)
- Cups developn between 35-60 days of pregnancy and are then sloughed
- Conceptus does not attach until day 24
What is the zonary aspect of the placenta?
- Band like zone of chorionic villi
- Villi forms zone around the middle of conceptus
What is the Discoid aspect of the placenta?
- Two or more adjacent discs that provide nutrient exchange
- Villi form a regionalized disc
How does fetal circulation happen?
Vessels from the exchange zone (EZ) merge into umbilical vessels that supply the fetus with blood
What is the cotylendonary aspect of the placenta?
- Numerous button-like cotyledons (ruminants)
- Villi located on button-like structures called cotyledons
What is the cotyledon? How is it formed?
- It is a placental unit of trophoblast origin that has vessels and tissues
- Formed by the help of outter derm cells
What are caruncles?
The maternal cotyledon that comes from the uterus
What is the placentome?
- The point of interface consisting of a fetal cotyledon and maternal cotyledon
- Major site of nutrient exchange
What is the fetal cotyledon?
Trophoblastic origin, contributed by chorion
What is the maternal cotyledon?
Caruncular region of uterus
How many cotyledons do sheep and cattle have? When is their initial attachment? when is attachment established?
- 90-100 cotyledons (sheep)
- 70-120 cotyledons (cattle)
- Day 16 = initial attachment (sheep)
- Day 25 = initial attachment (cattle)
- Day 30 (sheep)
- Day 40 (cattle)
What type of caruncles do sheep have and cattle?
- Sheep have concave caruncles
- Cattle have convex caruncles
What type of caruncles do sheep have and cattle?
- Sheep have concave caruncles
- Cattle have convex caruncles
How do cotyledons change ? what is is that changes?
- Changes through increasing conceptus age
- Increases diameter, placental surface area and nutrient transfer
What does epitheliochorial mean?
- Means maternal side “epithelio”
- Means fetal side “chorial” the least intimate
What does epitheliochorial mean?
- Means maternal side “epithelio”
- Means fetal side “chorial” the least intimate
How many layers do epitheliochorial have?
They have 6 layers of tissue
What does syndesmochorial mean?
Endometrial epitheliums transiently erodes & regrows
What are binucleate giant cells from trophoblasts?
- They are large cells with 2 nuclei
- Transfer complex molecules
- produces steroids like P4 and E2
What are endothelicohorial placentas?
- Complete erosion of endometrial epithelium & underlying interstitium
- They have 5 layers
What are endothelicohorial placentas?
- Complete erosion of endometrial epithelium & underlying interstitium
- They have 5 layers
What are hemochorial placentas?
- Chorionic epithelium in direct apposition to maternal pools of blood
- Placenta bathed in blood
- Maternal and fetal blood do not make contact
Which animals have the epitheliochorial, syndesmochorial, endotheliochorial, hemochorial placentas.
- Sow, mare, can include cow (E)
- Ruminants (S)
- Dogs and cats (Endo)
- Primates and rodents (H)
What are some primary functions of the placenta?
- Transmits & provides nutrients
- Exchange of water and gasses
- Excretion of fetal waste
- Modifies fetal & maternal metabolism, maintenance of pregnancy
What are some characteristics of the placental circulation?
- Fetal & maternal circulations (seperate and parallel ‘do not mix’)
- Inteface between circulations allows for exchange (maternal substrates and gasses for fetal growth, fetal waste elimination)
How does O2 and CO2 play a role between the placenta of the dam and the fetus?
- Fetus requires O2 for survival and metabolism
- CO2 removed from fetal to maternal circulation
How does glucose play a role in the placenta between the damn and the fetus?
It is converted to fructose by the placenta
How do amino acids play a role in the placenta between the dam and the fetus?
It is converted to proteins by the fetus
How are lipid transport limited apply to the placenta between the dam and the fetus?
They are free fatty acids trasnferred across placenta -> fetal fat
How do antibodies play a role in placenta between the dam and the fetus?
- In ruminants, sow, mare, cats, dogs they do not cross the placenta barrier (newborn gets anitbodies via colostrum)
- In humans, rodents they do cross the placental barrier
How are vitamins regulated by the placenta? What are the difference between the B,C and A,D,E vitamins?
- They are transferred across the placenta
- B, C vitamins are water soluble and cross more easily
- A,D,E vitamins are lipid soluble and they cross more slowly
How are minerals regulated by the placenta?
They are trasnferred across the placenta (they are under fetal control)
What are some examples of toxic/potentially pathogenic substances?
- Ethyl alcohol
- Lead
- Phosphorous
- Mercury
- Opiate drugs
- barbiturates
- antibiotics
- Viruses
- Bacteria
What are teratogenic substances?
They are abnormal developments (birth defects)
The placenta is a major endocrine organ, what does its hormones provide that access both fetal and maternal circulation?
- Maintains pregnancy
- Impacts ovarian function
- Increases fetal growth
- Drives mammary function
- Assists in parturition
What is PMSG?
Pregnant mare syrum gonadotropin, this is an old term.
What homrones does the mare placenta produce? What is it produced by?
- Produces eCG (pregnant mare serum gonadotropin-PMSG)
- Produced by transient endometrial cups
What are lutetrophic actions?
- Maintains CL of pregnancy & progesterone secretion
- Initiates accesory CL formation (she will ovulate again)
- Increased progesterone to assist in maintaining pregnancy.
What does the placenta have that makes it powerful?
- Powerful FSH actions
- Induces superovulation (cows, sheep, rabbit)
What does hCG stand for and what are they produced by?
- hCG stands for human chorionic gonadotropin
- Produced by trophoblast cells of chorion
What happens when hCG is given to a non-primate?
It induces ovulation
What is the purpose of the placental progesterone? Over what time what occurs in certain animals?
- The blockage of myometrial contractions
- CL produces P4 to maintain pregnancy but in cows,ewe and women the placenta take over P4 production
Which animal require CL for their entire gestation?
- Sow
- Rabbit
- Cow (8 months)
Which animals secrete placental lactogen?
- Rats
- Mice
- Sheep
- Cows
- Humans (for mammary development)
What are lactogenic actions?
They stimulate mammary glands of the dam
