Placentation

What are egg laying mammals called?

Monotremes

True or False: The majority of the animals discussed have a chorioallantoic placenta.

True!

What kind of placenta does a marsupial have?

Choriovitelline

True or False: The placenta is considered both a metabolic and endocrine organ.

True!

What is the major role of the placenta?

Exchange of hormones, gas, nutrients between conceptus and dam

The placenta is composed of TWO parts. Describe each component and where it comes from.

Fetal: chorion

Maternal: after attachment; modifications of uterine environment during window of receptivity

Name the FOUR major extra embryonic membranes of the pre-attached embryo.

Yolk sac

Chorion

Amnion

Allantois

What creates the organ that will eventually become the mature placenta?

When allantois fuses to create allantochorion

What is the functional unit of the placenta that determines placenta type?

What does it provide?

Chorionic villus

Increased surface area to maximize exchange

How are placentas classified?

Distribution of chorionic villi

Name the FOUR major classifications of placentas and the major animal representatives that utilize them.

Diffuse: horse/pig

Cotyledonary: ruminants

Zonary: dog/cat

Discoid: primates/rodents

True or False: In the sow, chorionic villi are closely spaced and uniformly distributed over the entire space of the chorion.

True!

When is initial atatchment of the placenta in the sow? When is the placenta established?

Day 12

Day 18-20 post-ovulation

The mare placenta is made of "microzones" of chorionic villi known as what?

When is the placenta estaqblished?

Microcotyledons

36-38 days post-ovulation

Where do the endometrial cups arise from in the mare?

Chorionic girdle

When do endometrial cups develop in the mare?

Day 25 (mature Day 50-70)

What do the endometrial cups produce in the mare? What does this stimulate?

PMSG

CL to double in size (accessory CL to increase P4)

When does the placenta take over primary P4 secretion in the mare?

Day 100

Why are endometrial cups so important in the mare?

Maintain P4 for pregnancy until placenta takes over at Day 100

What kind eCG levels determine in the blood?

If she spontaneously aborted before Day 35 (low levels) or after Day 35 (high levels)

Zonary placentas have a band-like zone of chorionic villi called what?

What is the second region at either end of the original band? Why are they important?

Transfer zone

Paraploacenta/pigmented zone

Ion transport from dam to fetus

What are the third regions of the zonary placenta? Why is it important?

Clear region

Direct absorption of materials from uterine lumen

The discoid placenta is a —- —- containing all of the chorionic villi in one place to form the maternal-fetal interface that interacts directly with maternal blood.

Round disc

What are the fetal and maternal portions of the cotyledonary placenta? What is their fusion called?

Fetal: Cotyldone

Maternal: caruncle

Placentome

Cotyledons are of —- origin and comprised of blood vessels and connective tissue.

Trophoblastic

True or False: Cattle have 70-120 cotyledons, convex shape, and established by day 40 post-ovulation.

True!

Ewe placenta is very similar to the cow. How is it different? (2)

Concave in size instead of convex

90-100 cotyledons

(It is also established D40 post-ovulation though)

Name the major animal groups with the THREE additional placental classifications based on layers.

Epitheliochorial: cow/pig/horse

Endotheliochorial: dog/cat

Hemochorial: human/rodent

Define the THREE layer classifications and order them in order of easiest for passage to hardest.

Hemochorial: one layer; open capillary

Endotheliochorial: one layer; closed capillary

Epitheliochorial: two layers; closed capillary

How many degrees of separation are seen in the THREE placenta layer types?

Epi: 6

Endo: 5

Hemo: 3

What animals have NO (nondeciduate), moderate (deciduate), and extensive (deciduate) loss of maternal tissue at birth?

None: pig/mare/ruminant

Moderate: dog/cat

Extensive: primate/rodent

Name the THREE major methods of placental transfer and the TWO major substances they transport.

Simple diffusion: gas and water

Facilitated diffusion: glucose and amino acids

Active transport: sodium and potassium

Antibody transfer is a phenomenon of what placenta type?

Hemochorial

(Huge benefit because IgG readily crosses border- immune support for baby)

When does the placenta take over P4 production in the cow, ewe, mare, and woman?

Cow: 6-8 months

Ewe: 50 days

Mare: 100 days

Woman: 60-70 days

What hormone other than P4 can the placenta also secrete? Provide TWO reasons this is important.

Estradiol

Mammary gland development

Rise signals beginning of parturition period

In what THREE animals is gestation so short that the CL can maintain P4 levels throughout the entire pregnancy rather than utilizing the placenta?

Bitch

Sow

Queen