Placental Development and Gestation in Different Species

What is implantation in the context of embryonic development?

Intimate contact between the embryo and uterine mucosa, involving initial sticky attachment.

What type of nutrition is utilized during pre-attachment development?

Histotrophic nutrition, which uses cytoplasmic stores, maternal mRNA, and uterine gland secretions.

What is the primary mode of nutrition after attachment?

Hemotrophic nutrition via the placenta.

List four functions of the placenta.

1. Nutrient transfers 2. Waste removal 3. Protection from shock 4. Hormone production

When does placenta formation begin in pigs?

Starts on day 13 and is complete by days 18-24.

What are the classifications of placental layers?

1. Epitheliochorial (6 layers) 2. Endotheliochorial (5 layers) 3. Hemochorial (3 layers)

Which species have an epitheliochorial placenta?

Horses and pigs.

What is syncytialization in ruminants?

The differentiation of trophoblast giant cells that secrete pregnancy-associated glycoproteins (PAGs).

What is the gestation length for cows?

282 days (approximately 9 months).

How does uterine capacity affect fetal growth?

It influences litter size and survival; a larger uterus can support more growth.

What is the gestation length for elephants?

616 days (approximately 2 years).

What is the significance of maternal recognition of pregnancy?

It is essential for the embryo and uterus to communicate during pre-attachment development.

What are the types of implantation?

1. Noninvasive (central) 2. Invasive

What characterizes a noninvasive implantation?

The conceptus attaches to the uterine surface without deeply invading maternal tissue.

What is the gestation length for humans?

284 days (approximately 9 months).

What is the gestation length for mares?

340 days (approximately 11 months).

How does placental size influence fetal growth?

Larger placental size can enhance nutrient transfer, thus promoting growth.

What is a discoid placenta?

A disc-shaped attachment area found in primates and rodents.

What is a zonary placenta?

A band or girdle-shaped placenta found in carnivores like dogs and cats.

What factors affect gestation length?

Fetal sex, dystocia, litter size, dam age, genetics, and season.

What is the role of pregnancy-associated glycoproteins (PAGs)?

They serve as pregnancy markers secreted by trophoblast giant cells in ruminants.

What is the gestation length for mice?

21 days, which is very fast.

What is the classification of a cotyledonary placenta?

It has discrete placentomes/cotyledon-caruncle attachments, typical in ruminants.