AGR 506

Gestation

Period that a female is pregnant between conception and parturition

Implantation

Attachment of placental membranes to endometrium in most animals

Placenta

Organ of metabolic exchange between fetus and dam consisting of a portion of embryonic origin (chorin) and portion of maternal origin (endometrium)

Parturation

process of giving birth

Chorion

-outermost extraembryonic membrane derived from trophoblast ectoderm

-develops villi that will form fetal sites of placental attachment

Amnion

-Embryonic membranes formed from chorion that surrounds and encloses fetus for protection

Allantois

Extraembryonic membrane formed from embryonic ectoderm that serves as liquid waste storage for developing fetus

Chorionic Villus

Small, fingerlike projections found on surface of chorion that interface with maternal placenta, fictional unit of fetal placenta

Teratogenic

Causing physical defects in developing conceptus

Dystocia

difficult parturation

Cotyledon

Points of attachment fetal and maternal placenta, consisting of maternal cotyledon contributed by caruncular areas of uterus and fetal cotyledon by chorion of conceptus

Caruncle

In ruminants, a button like area of the uterine endometrium that forms maternal side of the cotyledonary placenta

T/F:

The Chorionic villi provides surface area so exchange is maximized.

True

T/F:

Placentas are classified by distribution of chronic villi on their surface.

True

What are the 4 types of placentas?

-Diffuse

-Zonary

-Discoid

-Cotyledonary

What is a diffuse placenta dn what animals have it?

-Uniform distribution of chorionic villi that covers surface of chorion

-Piga and Horses

What is a Zonary Placenta and what animals have it?

-Band like zone of chorion villi

-Cats and dogs

What is a Discoid placenta and what animals have it?

-Regionalized disc

-Rodents and primates

What is a Cotyledonary placenta and what animals have it?

-Numerous, discrete button like structures

-Ruminants

What is a Placentome?

Fetal chorion + maternal caruncle

T/F:

Placentas can also be classified by the number of placental layers that separate fetal blood from maternal blood.

True

what range of placental layers are there?

3-6

How many layers does a Epitheliochorial placenta have and what animals have them?

-6 layers

-Pigs, horses, ruminants

How many layers does a endotheliochorial placenta have and what animals have it?

-5 layers

-Dogs and cats

How many layers does a Hemochorial placenta have and what animals have it

-3 layers

-Primates and Rodents

What does the placenta do?

-Regulates exchange between the fetus and dam

-Simple diffusion of gases and water from high to low concentration

-Facilitated diffusion using carrier molecules like glucose

-Active transport with sodium, potassium, and calcium

Why is glucose important?

It is a major energy source for the fetus

What does the Placenta secrete?

Progesterone and estrogens

What does progesterone do for the placenta?

-Obligated for ealy embryonic development by providing stimulus for elevated secretion by endometrial glands and inhibits myometrial contractions

What is another name for placental lactogen?

Somatomammotropin

What is the purpose of Placental lactogen?

-Promote growth of fetus (somatotropic)

-Stimulates mammary gland of dam (lactogenic)

T/F:

The degree of somatotropic vs lactogenic effects in species are all the same.

False

What does placental relaxin do?

-Softens pelvic ligament

-Facilitates expulsion of fetus

What is the gestation period for Alpacas and Llama?

11.3-11.4

What is the gestation period for a bitch and Queen?

2 months (65 days)

What is the gestation period for a camal?

12.3 months

What is the gestation period for a cow and women?

9 months

What is the gestation for Ewe and Goat?

5 months

What is the gestation of a Mare?

11 months

What is the gestation period for a rabbit?

1 month

What is the gestation for a Sow?

3.8 months

T/F:

Parturition is Simple cascade of physiologic events.

False, its complex

What does the fetal pituitary secrete to trigger parturition?

Adrenal corticotropin (ACTH)

What endocrine changes occur in the dam during parturition?

-Removal of myometrial progesterone block to enable contractions

-Increase in reproductive tract secretion

Due to fetal cortisol promoting synthesis of enzymes, what do they convert progesterone to?

Estradiol

What happens during stage one of parturition?

-Initionates myometral contractions (removal of progesterone block)

-Fetus pushes toward cervix and enters cervical canal at the end of this stage

-Fetus initiates stage one

What happens during stage two of parturition?

-Expulsion of fetus

-Increased estrogen=increased secretion=washed out cervical seal of pregnancy and lubricant

-Most common time for Dystocia

What happens during stage 3 of parturition?

-Expulsion of fetal membrane