Repro 8: Maintenance of pregnancy

D

Which of the following is not a function of the placenta?

A) Nutrient exchange

B) Hormone production

C) Immunological barrier

D) Protein digestion in the fetal gut

C

Which of the following species has an epitheliochorial placenta?

A) Dog

B) Cat

C) Horse

D) Human

B

The type of placentation in ruminants is best described as:

A) Diffuse

B) Cotyledonary

C) Zonary

D) Discoid

D

Which placental layer is absent in endotheliochorial placentation?

A) Fetal endothelium

B) Chorionic epithelium

C) Fetal connective tissue

D) Maternal epithelium

A

What are binuclear giant cells?

A) Cells with two nuclei and an unusually large size

B) Cells with fragmented nuclei

C) Cells undergoing apoptosis

D) Cells lacking a nucleus

C

Which glycoprotein hormone family does eCG belong to?:

A) Insulin-like growth factors

B) Transforming growth factors

C) Gonadotropins

D) Thyroid hormones

B

Species with superficial implantation exhibit:

A) Hemochorial placentation

B) Epitheliochorial placentation

C) Hemoendothelial placentation

D) Endotheliochorial placentation

C

Binuclear giant cells in ruminants originate from:

A) Decidual cells

B) Theca cells

C) Fetal cells

D) Stromal cells

B

The receptor-binding affinity of eCG is species-dependent. In mares, it binds preferentially to:

A) Estrogen receptors

B) LH receptors

C) FSH receptors

D) Prostaglandin receptors

B

The trophoblast of the blastocyst is destined to become:

A) Inner cell mass

B) Chorionic epithelium

C) Endometrial epithelium

D) Peritubular myoid cells

A

What is a unique feature of eCG compared to other gonadotropins?

A) It has both FSH-like and LH-like activity

B) It only acts on equine species

C) It is secreted by the pituitary gland

D) It functions only during lactation

D

Early (first trimester) pregnancy would be terminated by ovariectomy in:

A) Cow

B) Horse

C) Rabbit

D) All of the above

B

In what species are secondary corpora lutea characteristic during pregnancy?

A) Cow

B) Mare

C) Bitch

D) Queen

B

In primates, the removal of both ovaries during late gestation will:

A) Prevent the maintenance of normal pregnancy

B) Not have any major effect on normal pregnancy maintenance

C) Lead to decrease in plasma concentration of hCG

D) Decrease myometrial contractility

B

In which species can placental luteotropin tolerate ovariectomy in late pregnancy?

A) Dog

B) Horse

C) Swine

D) Sheep

C

What is the primary role of the placenta in sheep?

A) Exchange of fetal waste products and nutrients

B) Synthesis of estrogen and progesterone late in pregnancy

C) Both A and B

D) None of the above

A

eCG has dual hormonal activity. What is its predominant function in non-equine species like cattle and sheep?

A) Acts primarily as FSH

B) Acts primarily as LH

C) Stimulates prolactin release

D) Inhibits ovulation

True

True or false?:

eCG has a longer half-life in circulation compared to FSH or LH due to its glycosylation.

False

True or false?:

eCG is species-specific and does not work effectively in non-equine animals.

A

Which species requires ovaries throughout pregnancy? The duration of its normal luteal phase and pregnancy are nearly identical.

A) Dog

B) Horse

C) Swine

D) Sheep

C

What are caruncles?

A) Structures found in the intestines

B) Parts of the placenta in certain animals

C) Specialized regions of the uterine lining

D) A type of gland in the skin

C

What structure does the fetal tissue attach to the caruncles in ruminants?

A) Allantois

B) Yolk sac

C) Chorion

D) Amnion

Fetal: Chorion (trophoblast cells) Maternal: Uterine endometrium

What are the fetal and maternal components of the placenta?

Fetal, maternal

Hormones of the placenta gain access to both the ___ and ___ circulation.

Stimulate ovarian function, maintain pregnancy, influence fetal growth, assist in parturition

Functions of placental hormones

Distribution of chorionic villi on surface, number of placental layers that separate fetal blood from maternal blood

Two ways that placenta are classified

Pigs, mares

Which species use a diffuse placenta?

Diffuse placenta

Uniform distribution of chorionic villi that cover the surface of the chorion

Large available surface area for physical interaction between the maternal and fetal tissues

Microcotyledons

Microzones of chorionic villi

Cows, ewes

What species use a cotyledonary placenta?

Cotyledonary placenta

• Numerous, discrete button-like structures called cotyledons

  • Placentome (point of interface) consists of a fetal cotyledon contributed by the chorion and a maternal cotyledon originating from the caruncular regions of the uterus

Cotyledon

Placental unit of trophoblastic origin consisting of abundant blood vessels and connective tissue

Fetal cotyledon contributed by the chorion, maternal cotyledon originating from caruncular regions of uterus

What does the placentome (point of interface) of the cotyledonary placenta consist of?

Dogs, cats

Which species use a zonary placenta?

Zonary placenta

Have a band-like zone of chorionic villi

Rodents, primates

Which species use a discoid placenta?

Discoid placenta

Forms regionalized one or two discs

6

How many layers does the epitheliochorial placenta have?

Pigs, horses, ruminants

What species use an epitheliochorial placenta?

Epitheliochorial/syndesmochorial placenta

• Endometrial epithelium transiently erodes and then regrows

• Unique binucleate giant cells originate from trophoblast cells

Binucleate giant cells (BNGC)

20% of fetal placenta

Migrate from chorion to endometrial epithelium in ruminants —> Invade endometrium

These cells are thought to secrete placental lactogen and pregnancy specific protein B

Syncytium

Fusion of binucleate cells and uterine epithelium

Placental lactogens (protein hormones)

• May regulate maternal metabolism to facilitate fetal growth

• High levels in the last ⅓ of gestation

• High levels facilitate higher milk production

• Dairy cows have higher blood concentrations than beef cows

Pregnancy specific protein B

• Unique to ruminants

• Function uncertain

• Has been used to detect pregnancy

  • Cattle, sheep, deer

    • Can be used to detect pregnancy in cows after day 25

Dogs, cats

Which species use an endotheliochorial placenta?

5

How many layers does the endotheliochorial placenta have?

Primates, rodents

What species use a hemochorial placenta?

3

How many layers does the hemochorial placenta have?

Rabbits, rodents

What species use a hemoendothelial placenta?

1

How many layers does the hemoendothelial placenta have?

Gases, water

What is transported via simple diffusion in placental exchange?

Glucose, amino acids

What is transported via facilitated diffusion in placental exchange?

Sodium, potassium, calcium

What is transported via active transport in placental exchange?

Immunoglobulins

Maternal proteins do not cross the placental barrier except ___.

Lipids

What does not cross the placenta in placental exchange?

Vitamins, minerals

___ and ___ are transferred to the fetus in placental exchange.

Sheep

Which species?:

Progesterone source:
CL: up to day 55

Placental: 55-term (150 days)

Horse

Which species?:

Progesterone source:

• CL: up to day 150

• Placental: 150-term (340 days)

Human

Which species?:

Progesterone source:

• CL: up to day 35

• Placental: 35-term (280 days)

Rodents, rabbits

Which species?:

Ovary is required throughout pregnancy for production of estrogen and progesterone

Cattle, goats, pigs, cats, dogs

Which species?:

Ovary is responsible for progesterone, and placenta is responsible for estrogen

Prostaglandins (PGF2alpha)

• Stimulate contraction of uterine smooth muscle cells

• Potentiates the contractions induced by oxytocin

• Luteolysis

• Secretion of relaxin

Relaxin

• Glycoprotein

• Placental relaxin is produced in humans, mares, cats, dogs, pigs, and rabbits

• Relaxin acts on connective tissue, causing softening of the cervix and relaxation of pelvic ligaments

Equine chorionic gonadotropin (eCG)

• The placenta of the mare produces ___

  • Also called pregnant mare’s serum gonadotropin (PMSG)

Decrease, increases, accessory CL, placenta

Luteal progesterone synthesis during the first half of gestation in the mare:

• Primary CL: P4 from the primary corpus luteum increases rapidly after ovulation and then decreases. Without eCG, P4 would continue to ___, and the pregnancy would terminate.

• Primary CL + eCG: Upon stimulation by eCG, the primary CL is stimulated, and P4 in the maternal blood again ___. If eCG were not produced, P4 would continue to decrease.

• Accessory CL + eCG: As eCG continues to increase, ___ develops, and P4 increases until about day 100. After day 100, the ___ assumes the major P4 producing role.

LH, FSH

eCG exhibits __-like activity in the mare but ___-like actions when administered to females of other species.

Human chorionic gonadotropin (hCG)

What does the placenta of the primate produce?

2.5, CL, placenta

• Production of hCG and progesterone during pregnancy in woman

  • Human chorionic gonadotropin (hCG) peaks at about ___ months of gestation and then declines. This period of time is crucial for maintenance of pregnancy because the __ assumes primary responsibility for P4 secretion

  • At about 2.5 to 3 months of gestation, the ___ begins to assume the primary responsibility for P4 secretion and continues this role until the time of parturition. hCG increases slightly between months 6 and 9 because of the increased placental mass.