T4: Placentation Flashcards
how many days does the cow have for implantation
30-35
how many days does the sow have for the implantation
12-20
how many days does the ewe have for implantation
18-20
how many days does the mare have for implantation
50-60
what is superficial implantation
chorion fuses to endometrium (majority of species)
what is interstitial implantation
embryo invades endometrium (day 8) and develops in the endometrium (humans)
what is implantation
attachment of the placenta to the uterus
what is the origin and functions of the yolk sac
origin: early entodermal layer
Functions: vestigial
what is the origin and function of the amnion
origin: cavitation from inner cell mass
function: encloses fetus in a fluid filled cavity
what is the origin and function of allantois
origin: diverticulum of hindgut
function: blood vessels connect fetal with placental circulation
what is the origin and function of the chorion
origin: trophoblastic capsule of blastocyst
function: encloses embryo and other fetal membranes
what is the origin and function of umbilical cord
origin: amion wraps about the yolk stalk
function: encloses allantoic vessels and acts as the vascular link between mother and fetus
what does the ICM become and trophoblast become after the first differentiation event
ICM= embryo
Trop= fetal portion of placenta
what occurs during the second differentiation of embryo development
-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
what happens after the primitive endoderm completes it’s growth
it forms a cavity called a yolk sac. This cavity does not contain actual yolk.
describe how amnionic folds form
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
what is fused to make the chorion
the mesoderm and trophectoderm
what is happening when the primitive gut forms/ allantois
-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
describe the final stage of the of the development for the structures
-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)
what are the four placental membranes
chorion, yolk sac, amnion, allantois
what is the function of the yolk sac for the embryo
-early nutrient supply for early embryo
-picks up uterine secretions form endometrium to stimulate early embryonic development
what is the function of the amnion for the embryo
-protects fetus from injury, provides lubrication for parturition, reservoir for urine and wastes
-prevents the lungs from collapsing and opens digestive tract
what is the function of the allantois for the embryo
-fuses with chorion (chorio-allantoic placenta)
-carries blood vessels of placenta reservoir for nutrients and wastes
-umbillical cord attaches fetus to allantois
what is the function of the chorion for the embryo
-attaches to uterus, absorbs nutrients from uterus
-allows maternal/fetal gas exchanges
-produces hormones
what is the role of the chorion villus (chorionic villi)
increases surface area and important for fetal interaction, exchange of nutrients
what type of animals have a epitheliochorial placenta/ how many layers separating the fetal and maternal sections
-pig, horses, and ruminants
-6 layers
6. chorionic capillaries
5. chorionic intersitium
4. chorionic epithelium
3. endometrial epithelium
2. endometrial interstitium
1. endometrial capillaries
what species have a endotheliochorial placenta and how many layers
-dogs and cats
-5 layers
5. chorionic capillaries
4.chorinoic interstitium
3.chorionic epithelium
2. endometrial interstitium
1. endometrial capillaries
what is the fetal and maternal portions
fetal: chorion
maternal: endometrium
what species have a hemochorial placenta and how many layers
primates and rodents
-3 layers, most invasive
3. chorionic capillaries
2. chorionic interstitium
1. chorionic epithelium
describe the diffuse placenta for the sow
-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.
describe the diffuse placenta for the mare
-consists of many microcotyledons distributed over the entire surface of the chorion “microzones” of chronic villi
-these are the site of fetal-maternal exchange
what does the zonary placenta consist of and where is this found
transfer zone, pigmented zone, relatively nonvascular zone, the alllantochorion (band-like zone of chorionic villi)
-found in the dogs and cats
what species has the discoid placenta/ what is it
-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
describe the cotyledonary placenta/ what species
-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)
what species has a convex cotyledon
-cow, giraffe
-spread is upward, protrude towards the lumen of the uterus (caruncular tissue points down like)
what species has a concave cotyeldon
-sheep, goat
-chorionic tissues pushes inward (caruncular tissue points up)
what are binucleate giant cells/where do they come from
-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
describe the fetal nutrition for farm animals (placenta)
- 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
describe the fetal nutrition for farm animals
-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)
what comes first in the development of extraembryonic membranes in mammals
- ICM = embryo
- Primitive endoderm forms= comprising the yolk sac (surrounds it)
- trophoblast=trophectoderm
- mesoderm forms underneath embryo
- mesoderm + trophectoderm = chorion (will eventually attach to fetus)
- amnion= surrounds the amnionic cavity (made from the chorion)
what is the fusion of the allantois and chorion/ what is it
allantochorion/ fetal contribution to the placenta
what are endometrial cups and where are they found
-mare placenta
-discrete areas that range in diameter, has both trophoblastic and endometrial origin
-produce equine chorionic gonadotropin (eCG)
describe the overview of classifications for placentas/ what are they classified by
-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)
