Lecture 12

What type of placenta do ruminants have?

Syneptiheliochorial, cotyledonary, villous, partially or non-deciduate.

What forms the attachment in ruminants' placenta?

Cotyledons attach to the maternal epithelium via caruncles.

When does placental attachment start in sheep vs cattle?

Around day 16 for sheep and day 25 for cattle

When is placental attachment well established in sheep vs cattle?

By day 430 in sheep and 40 in cattle .

What is a placentome?

The placental unit consisting of fetal cotyledon and maternal caruncle.

How many placentomes do sheep vs cattle typically have?

8 to 100 placentomes in sheep and 70-120 in cattle

What is the shape of the caruncle in cattle? vs sheep 

Convex shape in cattle and sheep goes from convex to concave

What is the origin and function of binucleate giant cells?

They originate from trophoblast cells and invade endometrial epithelium, constituting about 20% of the bovine placenta. This is typically where erosion occurs in the placenta

When do binucleate giant cells appear in sheep vs cattle?

Around day 14 in sheep and day 18-20 in cattle

What major products do binucleate giant cells secrete?

Proteins, estrogen, and progesterone.

What is the timing for amniogenesis in bovines?

Occurs between days 13 and 16.

What are amnionic plaques

These are found on amniotic ectoderm around the umbilical stalk and are small white clusters of keratinisation of the amnion

What are necrotic tips in placenta? Which species have them

Incidental findings at the end of the allantochorion due to faster trophoblast elongation than blood supply.

Ruminants and pigs

What is the function of the urachus?

It connects the apex of the bladder to the umbilical cord and empties urine into the allantois.

What is the type of placenta in equines?

Epitheliochorial, diffuse, villous, non-deciduate.

What is interdigitation in equine placentas

It refers to the complex, finger-like projections of the chorion that invade the endometrial tissue which is distributed over the enter surface of the chorioallantois

When do chorionic villi start interdigitating in equines?

Around day 35.

What are the areas between villi called in equine placentas

Arcades

Where are villli not normally found in the equine female system

Only not found in cervix, tips of uterine horn and near remnant of endometrial cups

What is the chorionic girdle and what is the sinus terminalis

The chorionic girdle is a band of trophoblasts that forms around the embryo in equines that later become invasive. The sinus terminalis refers to the a large fetal blood vessel where the umbilical cord inserts

What are endometrial cups in equines?

Invasive trophoblasts cells within the endometrium which make little “glands” which secrete equine chorionic gonadotropins (ecG) → aids in recruitment, development and luteinisation of additional follicles

When is ecG production highest in equines?

Between days 60-80.

What is a notable feature of the yolk sac in equines?

It remains relatively large and can be seen as a remnant at term.

When does placentogenesis occur in equines

Amniogenesis occurs between day 17 and day 22

The allantois starts to form around day 22 is vascularised by day 25

Placenta doesn’t really start functioning until around 35 days

What is unique about the amnion and umbilical cords in equines

There is no mesoamnion/raphe and the umbilical cords are very long with an intra and extra amnionic portion due to the lack of raphe.

The amnion itself is also the first thing seen in parturition as it surrounds foetus entirely

What are hippomanes

Amorphous, khaki-brown colour lumps tat are often freely flowing around the allantoic cavity formed from foetal waste products

What is the characteristic of porcine placenta?

Epitheliochorial, diffuse, folded, non-deciduate.

When do chorionic folds first appear in porcine pregnancies?

Around the fourth week (21-28 days).

What is the paraplacental zone in porcines and carnivores

a smooth zone next to placental zone with no folds or areolae

What are areolae in porcine placentation?

Small, round, grey, thickened foci on chorion that contain secretory gland products called histiotrophs

What type of placenta do carnivores have?

Endotheliochorial, zonary, labyrinthe, deciduate.

What are marginal haematomas?

Haemophagus regions where extravasated maternal blood is phagocytosed by fetal trophoblast cells causing degeneration of maternal endothelium

What is uteroverdin and its significance?

A substance related to bilirubin found in marginal haematomas, possibly aiding in iron transfer and causing the haematomas to appear green