T4: Placentation

Question 1

how many days does the cow have for implantation

Answer 1

30-35

Question 2

how many days does the sow have for the implantation

Answer 2

12-20

Question 3

how many days does the ewe have for implantation

Answer 3

18-20

Question 4

how many days does the mare have for implantation

Answer 4

50-60

Question 5

what is superficial implantation

Answer 5

chorion fuses to endometrium (majority of species)

Question 6

what is interstitial implantation

Answer 6

embryo invades endometrium (day 8) and develops in the endometrium (humans)

Question 7

what is implantation

Answer 7

attachment of the placenta to the uterus

Question 8

what is the origin and functions of the yolk sac

Answer 8

origin: early entodermal layer
Functions: vestigial

Question 9

what is the origin and function of the amnion

Answer 9

origin: cavitation from inner cell mass
function: encloses fetus in a fluid filled cavity

Question 10

what is the origin and function of allantois

Answer 10

origin: diverticulum of hindgut
function: blood vessels connect fetal with placental circulation

Question 11

what is the origin and function of the chorion

Answer 11

origin: trophoblastic capsule of blastocyst
function: encloses embryo and other fetal membranes

Question 12

what is the origin and function of umbilical cord

Answer 12

origin: amion wraps about the yolk stalk
function: encloses allantoic vessels and acts as the vascular link between mother and fetus

Question 13

what does the ICM become and trophoblast become after the first differentiation event

Answer 13

ICM= embryo
Trop= fetal portion of placenta

Question 14

what occurs during the second differentiation of embryo development

Answer 14

-the primitive endoderm begins to form beneath the inner cell mass and grows downward forming a lining on the inner surface of the trophoblast.
-mesoderm begins to develop between the primitive endoderm and the embryo

Question 15

what happens after the primitive endoderm completes it’s growth

Answer 15

it forms a cavity called a yolk sac. This cavity does not contain actual yolk.

Question 16

describe how amnionic folds form

Answer 16

the mesoderm continues to grow, forming a sac that surrounds the yolk sac and pushes against the trophectoderm (previously the trophoblastic cells), the newly formed mesodermal sac pushes against the trophectoderm and begins to fold up/ wing like folds

Question 17

what is fused to make the chorion

Answer 17

the mesoderm and trophectoderm

Question 18

what is happening when the primitive gut forms/ allantois

Answer 18

-the mesoderm now completely surrounds the yolk sac and the developing allantois
-allantois is derived form the primitive gut that collects embryonic wastes
-the mesoderm continues to fuse with the cells of the trophectoderm to form the chorion.
-the amnionic folds continue to grow upward around the emberyo

Question 19

describe the final stage of the of the development for the structures

Answer 19

-amnionic folds have completely fused resulting in the formation of a double sac around the embryo
-the inner sacs consists of trophectoderm and mesoderm = amnion
-it creates the amnionic activity cavity
-the chorion completely surrounds the entire conceptus
-the allantois continues to expand and begins to fill-in the spaces of the cavity
-allantois and the chorion will fuse forming the allantochorion (yolk sac continues to regress)

Question 20

what are the four placental membranes

Answer 20

chorion, yolk sac, amnion, allantois

Question 21

what is the function of the yolk sac for the embryo

Answer 21

-early nutrient supply for early embryo
-picks up uterine secretions form endometrium to stimulate early embryonic development

Question 22

what is the function of the amnion for the embryo

Answer 22

-protects fetus from injury, provides lubrication for parturition, reservoir for urine and wastes
-prevents the lungs from collapsing and opens digestive tract

Question 23

what is the function of the allantois for the embryo

Answer 23

-fuses with chorion (chorio-allantoic placenta)
-carries blood vessels of placenta reservoir for nutrients and wastes
-umbillical cord attaches fetus to allantois

Question 24

what is the function of the chorion for the embryo

Answer 24

-attaches to uterus, absorbs nutrients from uterus
-allows maternal/fetal gas exchanges
-produces hormones

Question 25

what is the role of the chorion villus (chorionic villi)

Answer 25

increases surface area and important for fetal interaction, exchange of nutrients

Question 26

what type of animals have a epitheliochorial placenta/ how many layers separating the fetal and maternal sections

Answer 26

-pig, horses, and ruminants
-6 layers
6. chorionic capillaries
5. chorionic intersitium
4. chorionic epithelium
3. endometrial epithelium
2. endometrial interstitium
1. endometrial capillaries

Question 27

what species have a endotheliochorial placenta and how many layers

Answer 27

-dogs and cats
-5 layers
5. chorionic capillaries
4.chorinoic interstitium
3.chorionic epithelium
2. endometrial interstitium
1. endometrial capillaries

Question 28

what is the fetal and maternal portions

Answer 28

fetal: chorion
maternal: endometrium

Question 29

what species have a hemochorial placenta and how many layers

Answer 29

primates and rodents
-3 layers, most invasive
3. chorionic capillaries
2. chorionic interstitium
1. chorionic epithelium

Question 30

describe the diffuse placenta for the sow

Answer 30

-consists of many chorionic villi (areolae) evenly distributed over the entire surface of the chorion
-they penetrate into the endometrium forming the fetal-maternal interface.

Question 31

describe the diffuse placenta for the mare

Answer 31

-consists of many microcotyledons distributed over the entire surface of the chorion “microzones” of chronic villi
-these are the site of fetal-maternal exchange

Question 32

what does the zonary placenta consist of and where is this found

Answer 32

transfer zone, pigmented zone, relatively nonvascular zone, the alllantochorion (band-like zone of chorionic villi)
-found in the dogs and cats

Question 33

what species has the discoid placenta/ what is it

Answer 33

-consists of choriconic tissue that forms the fetal-maternal interface
-the vessels from the exchange zone merge to form the umbillical vessels that supply the fetus with blood
-the vasculature of the chorion (within the disc) is immersed in pools of blood, where metabolic exchange takes place
-found in primates/rodents

Question 34

describe the cotyledonary placenta/ what species

Answer 34

-cow
-characterized by “button-like” structures distributed across the surface of the chorion (fetal cotyledons)
-when they join with the maternal caruncle they form the placentome (convex and concave versions)

Question 35

what species has a convex cotyledon

Answer 35

-cow, giraffe
-spread is upward, protrude towards the lumen of the uterus (caruncular tissue points down like)

Question 36

what species has a concave cotyeldon

Answer 36

-sheep, goat
-chorionic tissues pushes inward (caruncular tissue points up)

Question 37

what are binucleate giant cells/where do they come from

Answer 37

-come from the trophectoderm
-migrate rom the chorion to the endometrial epithelium in ruminants
-thought to secrete placental lactogen and pregnancy specific protein B
- can be a pregnancy diagnosis measure

Question 38

describe the fetal nutrition for farm animals (placenta)

Answer 38

• blood gas exchange at chorion= endometrium attachments
  -placenta highly permeable to water and electrolytes (stored in and gas exchange between allantoic and amniotic fluids)
  -placenta converts glucose to fructose = allows for storage in allantoic fluid

Question 39

describe the fetal nutrition for farm animals

Answer 39

-fetal fat formed from fatty acids transferred across the placenta
-fetus make proteins from transferred amino acids
-water soluble vitamins cross the placenta easier than fat soluble
-minerals are transferred across the placenta = in domestic species
-antibodies to fight disease do not cross the placenta; the newborn will get these antibodies from the first milk (colostrum)

Question 40

what comes first in the development of extraembryonic membranes in mammals

Answer 40

1. ICM = embryo
2. Primitive endoderm forms= comprising the yolk sac (surrounds it)
3. trophoblast=trophectoderm
4. mesoderm forms underneath embryo
5. mesoderm + trophectoderm = chorion (will eventually attach to fetus)
6. amnion= surrounds the amnionic cavity (made from the chorion)

Question 41

what is the fusion of the allantois and chorion/ what is it

Answer 41

allantochorion/ fetal contribution to the placenta

Question 42

what are endometrial cups and where are they found

Answer 42

-mare placenta
-discrete areas that range in diameter, has both trophoblastic and endometrial origin
-produce equine chorionic gonadotropin (eCG)

Question 43

describe the overview of classifications for placentas/ what are they classified by

Answer 43

-classified by distribution of chorionic villi
-diffuse: uniform villi (pig, mare)
-zonary: band like zone (dog,cat)
-discoid: disc (rodent,primates)
-cotyledonary: button like (cotyledons, ruminants)