18: placentation Flashcards
1
Q
what is implantation?
what does it begin with?
A
formation of placenta
begins w attachment
2
Q
how many days after fertilization does the bovine implant?
A
18-20 d
3
Q
how many days after fertilization does the ovine implant?
A
14-16 d
4
Q
how many days after fertilization does the porcine implant?
A
16 d
5
Q
how many days after fertilization does the equine implant?
A
35 d
6
Q
how many days after fertilization [the LH surge] does the canine implant?
A
16 d
7
Q
t/f
in all species, a placenta is the same thing as a “fetal membrane” or an “afterbirth”
A
false
placenta has a maternal and a fetal portion so it is not completely expelled after birth
8
Q
t/f
a placenta is considered an organ, composed of fetal and maternal tissues
A
true
9
Q
in most species, when does the placenta separate into maternal and fetal tissues?
A
prior to expulsion of the fetal component
10
Q
in most species, what is the afterbirth made of?
A
the fetal component of the placenta
11
Q
what layer of the fetal envelope does the placenta usually involve?
A
the outer most layer / membrane of the fetal envelope
12
Q
is most domestic species, why is there little hemorrhage at birth?
what species are an exception?
A
b/c maternal tissue remains intact and uterine lining is NOT disrupted
dog, human and higher primates are the exception
13
Q
when does the fetal envelope form?
A
after the blastocyst is hatched
14
Q
what are the 2 layers of the bi lamina structure that encases the embryo?
A
single layer of blastomeres (trophoblastic cells) AND cells from the embryonic disk (which line the cavity)
15
Q
what layer do the embryonic disks form?
where is it located? [btwn what layers is it loc]
A
the mesoderm layer
loc btwn the endoderm and the ectoderm
16
Q
what are the layers of the tri lamina structure that develops in the embryo?
A
ectoderm
mesoderm
endoderm
17
Q
what tissues does the mesoderm give rise to?
A
blood vessels
18
Q
what does the development of blood vessels in the mesoderm allow?
A
sophisticated exchange btwn the embryo and the yolk sac contents
important for transport of nutrients, waste, metabolites, etc from the adjacent endometrium and into the yolk sac
19
Q
in day 30 of horse embryo dev, what important structure forms from the hindgut of the embryo?
A
the allantois
20
Q
where does the allantoic cavity go?
A
the space called the axo ceo
21
Q
why is it important that the allantoic membrane splits open?
unsure about what exactly splits open here…
A
to allow the allantoic membrane to expand
22
Q
what happens to the yolk sac cavity in most species?
A
it shrinks
23
Q
what does the outer trophoblastic membrane give rise to?
A
the chorionic mem [remains on the outer envelope]
24
Q
what forms the amnion?
A
the lateral outgrows of the embryo fold and develop to surround the embrryo - when the tips of these poles meet, the amnion forms to encase the embryo
25
in the equine, when the embryo fixes on day 16, what is always the orientation of the embryonic disk?
it is ALWAYS located ventrally
26
why is the embryonic disk always located ventral?
physics: part of the young embryo is encased in a bilamina and part is encased in a tri lamina
the area encased in the tri lamina is more stable
the uterine is very toned and its mem is thin at the bottom and thick at the top, so the developing embryo aligns so that its more stable area (trilamina) aligns with the part of the uterus that is less stable
27
what happens if the fluid and embryonic disk are not in the correct orientation on the u/s exam?
the pregnancy will not last b/c this is not a stable orientation
28
what happens to the allantois over time?
it becomes larger and surrounds the exo celo with time
29
what are the 3 classifications of the placenta based on shape?
codyledonary
diffuse
zonary
30
which layer forms the interdigitation with the endometrium to accomplish implantation and subsequent formation of the placenta?
the chorionic layer, the outer layer of trophoblastic cells
31
what must be synchronized in order for successful placentation to occur?
synchrony btwn the development of the conceptus and time since ovulation in the endometrium
32
t/f
if an event that is normally supposed to occur during the placentation process does not occurr, it will occur at a later time
false
events of placentation must occur at pre determined time intervals and if something does not occur, it will not occur later
33
when considering shape of the placenta, what does this dictate regarding interaction of maternal and fetal tissues?
where the layer of tissue come together and interact
i.e. overall diffuse attachment or patchy/regional attachment
34
how is the ruminant placenta shape classified?
describe it.
cotyledonary
regional attachment only
35
what is the maternal portion of a Ru placenta called?
and the fetal portion?
what is the unit as a whole called?
maternal: caruncle
fetal: cotyledon
together: placentome
36
t/f
regions of the endometrium that are a caruncle are predetermined locations
true
37
t/f
if a caruncle is damaged, the dam will adapt to the loss or compensate by developing placental at a different location in the endometrium
false
there is a limited number of predetermined caruncles in the endometrium
the Ru cannot attach anywhere or make up new attachment locations if some are lost/damaged
38
t/f
a maiden heifer does not have caruncles in her endometrium - they develop at the time of preg
false
a maiden heifer has a set number of caruncles
39
what species have a diffuse attachment to placenta?
pig
camelid
horse
40
t/f
in species with diffuse placental attachments, if one area is damaged, the dam can compensate and attachment can occur in other areas of the endometrium
true
41
describe zonary placental attachment
placental attachment in a distinct band of tissue
not predetermined, but develops where the conceptus dictates
42
what is the nature of the placental classification scheme based on origin?
which fetal tissue participates in the formation of the placenta
43
based on origin, what type of placenta do humans have?
what is the significance?
humans have one envelope surrounding the fetus that forms from the chorion, amnion and allantois
makes amniocentesis tap possible - there is just one cavity that doctors can penetrate to harvest fetal cells
44
based on origin, what type of placenta do domestic animals have?
chorioallantoic placenta
the amnion is a separate cavity
45
what is the basis of placental classification based on invasiveness?
how many layers separate the maternal and fetal blood [the fetal envelope and the maternal endometrium]
46
what type of invasive placenta do most domestic animals have?
horse, pig, cow, partly the sheep and goat
epitheliochorial
47
what type of invasive attachment do sheep and goats [and partly the cow] have?
partly epitheliochorial and partly syndesmochorial
48
how many tissue ayers comprise an epitheliochorial placenta?
what are the layers?
6
```
endothelium of maternal blood vessels
CT
epithelium of uterine layer
intact chorionic epithelium
CT
endothelium of fetus
```
49
what is the special adaptation of the epitheliochorial placenta that forms the syndesmochorial placenta?
chorionic cells invade the endometrium to form a single layer of epithelial cells separating maternal and fetal components
50
describe the structure of the endotheliochorial placenta?
maternal epithelium and CT layers break down
4 layers: fetal endothelium, fetal CT, fetal epithelium and maternal endothelium
51
what species have an endothelial chorial placenta?
carnivores
52
what is the structure of a hemochorial placenta?
endothelium of maternal vessels breaks down so the chorionic epithelium is bathed in free maternal blood
53
what species have a hemochorial placenta?
dogs, cats
| rodents, monkeys, humans
54
what type of placentation lends to a very bloody birth?
what type is less bloody?
hemochorial placenta is very bloody
epitheliuchorial is less bloody - 2 layers of epithelium peel away from each other
55
why are puppies delivered 1 at a time? even during assissted c section this is important
b/c if all are removed at once, clotting factors will be consumed leading to a consumption coagulopathy
one at a time allows body time to clot and respond before more hemorrhage occurs
56
in an epitheliochorial placenta, endometrial glands are often juxtapositioned near a specially adapted area in the chorioallantois called what?
what is the function?
the areolae - pouches which capture the endometrial glandular secretions
allows the secretions to be absorbed into the fetal circulation
57
what special feature of the syndesmochorial placenta in the cow results in ability to detect preg at day 20/21?
binucleated or multinucleated cells form when cells migrate from the chorion and into the endometrium to form a mixture of fetal and maternal cells
they secrete pregnancy associated glycoproteins (PAGs)
58
describe binucleate cell structure:
- bi or multi nucleated
| - contain extensive secretory granules
59
in terms of invasiveness, what classifications does dog placenta have?
endotheliocchorial and hemochorial placenta
60
what are the classifications of placenta based on placental vasculature of the dam?
villous
| labyrinthine
61
what is the more common vasculature attachment in placentas of domestic animals?
villous
62
describe villous vasculature of placenta
maternal villi interdigitate with fetal villous
each villous has a blood vessel
63
describe labyrinthine vasculature:
villi is bathed in the blood of the dam
64
what species have labyrinthine vasculature:
dog
| human
65
what classifications exist in terms of intimacy with endometrium?
what does it mean?
adeciduate
deciduate
describes if the maternal tissue is shed together with fetal membranes during stage 3 of labor
66
what is an adeciduate attachment?
endometrial epithelium is left intact
67
what is a deciduate attachment?
endometrial epithelium is shed / interrupted during birth
68
does adeciduate or deciduate attachment lead to more hemorrhage?
deciduate
69
cow placenta:
| shape classification?
cotyledonary
70
cow placenta:
| tissue origin classification
chorio-allantoic
71
cow placenta:
| tissue layer classification
epitheliochorial
72
cow placenta:
| vasculature classification
villous
73
cow placenta:
| intimacy with endometrium classification
adeciduate
74
in the bovine, is the amnion attached to the allanto-chorion?
what are the implications / significance of this arrangement?
yes - the amnion is partially attached to the allanto-chorion
in order for the calf to be born, the chorio-allantois must rupture, releasing the allantoic fluid, AND the amnion must break b/c it is still attached to the uterus
75
t/f
the calf is never born w/in its amniotic cavity
true
the amnoin must rupture for the calf to exit b/c the amnoin is partially attached to the allanto-chorion membrane
76
what is the consistency of the amniotic fluid in the ruminant?
what is its purpose?
thick and slick
the purpose is to lubricate the birth canal well for the calf to pass
77
what is the shape of the equine placenta?
diffuse
78
what is the origin of the layers of the equine placenta?
chorio-allantoic
79
what is the classification of the equine placenta based on number of layers?
epitheliochorial
80
what is the vasculature classification of the equine placenta?
villous
81
what is the classification of the equine placenta based on the intimacy with the endometrium?
adeciduate
82
t/f
the amnion is attached to the allanto-chorion in the equine placenta.
what are the significance of the arrangement?
false
in the equine, the amnion is NOT attached to the allanto-chorion
the significance of the arrangement is that the allantois breaks during birth but the amnion does not - the foal is delivered encased in its amnion
83
what is the function of the amnion in the horse?
lines the birth canal so that the foal can slide through its own amniotic membrane
84
when does the amnion rupture in the birth of a foal?
when the foal is about 3/4 the way through the birth canal
85
t/f
like the ruminant amnion, the equine amnion is a viscous material
false
the equine amnion is not viscous - there for it is easy to pull a foal out of the mare with your hands [calves are too slick to pull with your bare hands]
86
t/f
in the equine, the only communication btwn the outer most mem of the fetal envelope and the fetus itself is the umbilical cord
true
b/c the amnion is not attached to the allantois
87
in the equine, with the separation of the amniotic and allantoic cavities, what is the function of each separate cavity?
- allantois = waste storage
| - amnion = shock absorber against trauma to the fetus
88
in the allantois, where does waste that cannot be passed to maternal circulation go?
what is the clinical significance of this?
dead cells, meconium, etc forms concretions that become macroscopically evident and form structures called HIPPOMANES
the size of the hippomane can indicate how long she carried the pregnancy
important for evaluating for fescue toxicosis, b/c the mare will carry the foal over term and the hippomane will be larger than normal
89
what are allantoic pouches?
| what is their significance
in the equine: pedunculated pouches that hang from the allantoic surface into the allantoic fluid
no signifncance known
90
what are extre ceolemic pouches and what is their significance?
the exoceolome is the potential space btwn the allantois and chorion
the pouches do not indicate an abnormality or disruption of preg - commonly found
91
what are the umbilical vessels present in the horse?
how does this differ form most domestic animals
2 umbilical veins, which fuse to form 1
2 umbilical arteries
most animals have a duplicated vascular system with 4 vessels total
92
in the equine, what is the only area where there is not vascular attachment btwn the chorion and endometrium?
inner opening of the cervix
93
what is the cervical star?
the mirror image of the lack of vascular attachment that occurs over the inner opening of the cervix - can be seen on the placenta as a pale avillous scar on chrionic surface, amidst vascular tissue
94
t/f
there can be multiple areas similar to the cervical star throughout the placenta
false
not normally - if there are other avillous areas, that indicates that there was damage to that area of the uterus, preventing chorionic attachment
95
when looking at fetal membranes after parturition, what tells you a lot about the health of the endometrium?
the appearance of the chorion
96
what is the chorionic gircle?
the first efforts of the embryo to form villous attachment with the endometrium
from this point, binucleat cells invade the endometrium and become endometrial cups
97
what is the significance of the fact that fetal tissue completely embeds itself in the maternal tissue?
constitutes a spontaneously and successful tissue transplant - maternal tissue and fetal tissue tolerate each other [until a certain point in the preg]
98
what occurs when the maternal tissue rejects the endometrial cups part of the way through parturition?
- mare will reject endometrial cups with a massive inflammatory response around each cup
cups are pushed towards the lumen of the uterus, into the fetal layer
the cups form little pouches in the chorion, which remain as little pockets
99
when the equine embryo is lifted, around day 35, what is its orientation?
embryo moves from ventral to dorsal
yolk sac is dorsal and becomes smaller
allantois is ventral
100
what connects the embryo to the top of the fetal membranes?
sinus terminalis
101
how long does the yolk sac remain present?
until the birth of the foal
102
what is the least differentiated tissue w/in the full term conceptus?
remnant of the yolk sac
103
what is the importance of collecting umbilical cord blood from the yolk sac remnant?
the primitive cells are pluripotent stem cells which may be used in future therapies
104
where is the ossified yolk sac remnant?
what does the ossified yolk sac remnant contain?
it is attached to the sinus terminalis, loc where the yolk sac remnant is
contains all adult tissues - bone, cartilgae, blood vessels - except nervous tissue
105
what is the shape of the ovine and cap placenta?
cotyledonary
106
ov and cap placenta:
| layer origin classification?
chorio-allantoic
107
ov and cap placenta:
| number of layers classification?
epitheliochorial and syndesmochorial
108
ov and cap placenta:
| vasculature classification?
villous
109
ov and cap placenta:
| intimacy with endometrium classification?
adeciduate
110
in the ov and cap, is the amnion attached to the allanto-chorionic mem, like in the bovine?
yes
111
on u/s, what do ov and cap placentomes look like?
a donut - b/c they are formed like a cup inside out
112
porcine placenta:
| shape classification
diffuse
113
porcine placenta:
| layer origin classification?
chorio-allantoic
114
porcine placenta:
| layer number classification?
epitheliochorial
115
porcine placenta:
| vasculature classification?
villous
116
porcine placenta:
| classification based on intimacy with endometrium
adeciduate
117
in the porcine placenta, is the amnion attached to the allanto-chorion, as in the bovine?
YES
piglets are unlikely to suffocate
118
canine placenta:
| layer origin classification?
chorio-allantoic
119
canine placenta:
| shape classification?
zonary
120
canine placenta:
| layer number classification?
endotheliochorial
| and hemochorial
121
canine placenta:
| vasculature classification?
labyrinthine
122
canine placenta:
| classification based on intimacy with maternal endometrium?
deciduate
123
in the canine, is the amnion attached to the allanto-chorion, as in the bovine?
NO
124
what region of the canine placenta is labyrinthine vasculature?
regions of hematoma on either side of the placental zonary band
125
t/f
puppies often born w/in the amnion
true
126
camelidae placenta:
| layer origin classification
chorio-allantoic
| and chorio-amniotic
127
camelidae placenta:
| shape classification
diffuse
128
camelidae placenta:
| layer number classification
epitheliochorial
129
camelidae placenta:
| vasculature classification?
villous
130
camelidae placenta:
| classification based on intimacy with endometrium?
adeciduate
131
in the camelid, what is the orientation of the allantois and the amion?
what membrane lies btwn them?
the 2 fluid cavities are side by side
- amniochorion and amnioallantoic and allantochorion membranes all lie next to each other
132
what cavity is ruptured before a camelid is born?
| what is the fluid inside like?
amnion breaks
very little amniotic fluid present
133
what are 2 ways the camelid placenta has evolved to fit the cold native environment of camelids?
- little amniotic fluid so the birthing bed is dry for the neonate
- 4th fetal envelope: the epidermal membrane - a continuation of the GIT - which covers entire fetus to keep its [well developed] fur dry at time of birth
