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Placenta Flashcards

1
Q

Placenta

A

Vascular organ in mammals that unites the extramebryonic membranes of the fetus to the maternal uterus for metabolic exchanges

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2
Q

When does the yolk sac start?

A

Starts when hypoblast delaminates and lines the bastocoel

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3
Q

What are the 4 membranes of the placenta?

A

Yolk sac, amnion, chorion, allantois

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4
Q

What are the functions of the placenta?

A

Protection
Nutritive
Excretory
Endocrine

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5
Q

Yolk sac

A

Endodermal lined cavity of gastrula
Continuous with embryonic gut
Transitory structure

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6
Q

Splanchnic mesoderm in relation to the yolk sac

A

It becomes vascular
At the first site of blood formation, it’s vessels connect yolk sac with embryo and form vitelline vessels

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7
Q

Yolk sac endoderm is source of ____________

A

Primordial germ cells

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8
Q

Trophoblast + somatic mesoderm =

A

Chorion

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9
Q

Hypoblast + splanchnic mesoderm =

A

Yolk sac

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10
Q

When do chorion and yolk sac separate?

A

As extraembryonic coelom forms

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11
Q

Amnion

A

Formed by folding of somatopleure (folds unite dorsally)
Avascular (no splanchnic mesoderm)

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12
Q

Function of amnion

A

Protective cushion that covers embryo and is fluid filled
Let’s embryo “float” and have limited movement

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13
Q

Chorion

A

Layer of somatopleure that surrounds extraembryonic membrane
Trophoblast and somantic mesoderm
Initially Avascular

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14
Q

Syncytiotrophoblast

A

When the trophoblast cells lose their cytoplasmic boundaries

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15
Q

Cytotrophoblast

A

When the trophoblast cells retain their cell boundaries

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16
Q

Allantois

A

Formed as evagination from hind gut
Made of endoderm and splashnic mesoderm
Expands into extraembryonic coelom

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17
Q

How is the allantois in domestic animals?

A

Becomes very large, fills and obliterates extraembryonic coelom
May fused with chorion

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18
Q

How do allantois vessels arise?

A

Splanchnic mesoderm of allantois and somatic mesoderm of chorion fuse and form the vessels

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19
Q

Umbilical vessels

A

Same as allantois vessels
Formed in the splanchnic mesoderm

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20
Q

When does amnion and chorion become vascularized?

A

Not until they fuse with allantois to form the alantochorione or alantoamnion placenta

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21
Q

Implantation

A

Attachment of the developing embryo to the wall of uterus and the formation of placenta

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22
Q

Until the placenta becomes functional, where does the embryo obtains nutrients?

A

Via diffusion from uterine milk

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23
Q

What are the different types of implantation?

A

Superficial: embryo in uterine lumen (domestic)
Interstitial: embryo embeds into uterine wall (primates)
Placenta

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24
Q

_______ and _________ blood never mix

A

Maternal and fetal

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25
Cat implantation
Gestation pd: 63 days Implantation begins: 11-12 days Implantation completed: 16-17 days
26
Cattle implantation
Gestation pd: 227-290 Implantation begins: 28-32 Implantation completed: 40-45
27
Dog implantation
Gestation pd: 61 Implantation begins: 14-17 Implantation completed: 20-21
28
Horse implantation
Gestation pd: 330-345 Implantation begins: 35-40 Implantation completed: 95-105
29
Sheep implantation
Gestation pd: 144-152 Implantation begins:14-16 Implantation completed: 28-34
30
Swine implantation
Gestation pd: 112-115 Implantation begins: 12-13 Implantation completed: 24-26
31
Placental classification based on fetal extra-embryonic membranes
Choriovitelline (yolk sac placenta) Alantochroine Alantoamnione
32
Choriovitelline
Transitory Yolk sac contacts the chorion Vitelline vessels transfer waste/ nutrients
33
How is choriovtelline important to the horse?
Delayed extraembryonic mesoderm formation and implantation
34
Alantochorione
Permanent placenta (horse, dog) Allantois + chorion Umbilical vessels vascularize the chorion and allantois 2 bags burst at parturition
35
Alantoamnione
Cow, pig Allantois fuses dorsally with the amnion 1 bag bursts at parturition
36
Placenta classification based on source of nutrition
Histiotrophic Hemotrophic
37
Histotrophic
Nutrients derived from uterine secretions via diffusion
38
Hemotrophic
Nutrient transfer between maternal and fetal capillaries
39
Placenta classification based on degree of destruction at parturition
Non-deciduate Deciduate
40
Non-deciduate
Materal and fetal membranes separate without endometrial loss Ruminants, pigs, horses
41
Deciduate
Materal tissue is lost and hemorrhage may occur Rodents, primates, carnivores (somewhat)
42
Placental classification based on gross shape of hemotrophic transfers area
Diffuse Cotyledenous (placentome) Zonary Discoid
43
Diffuse
Exchange occurs over most of the surface of the chorion Horse, pig Microcotlyedenous
44
Cotyledenous
Special points of contact on uterus (caruncle or maternal cotyledon) and chorion (cotyledons or fetal cotyledons)
45
Placentome
Ruminants: Caruncle (maternal coryledon) + fetal cotyledon Cattle: convex (70-120) Sheep: concave (90-100)
46
Zonary
Area of exchange in form of "ring- like" band extending around entire circumference (carnivores)
47
Discoid
Exchange site is round/oval (rodents and primates)
48
Placenta classification based on histology
6 tissue layers: 3 each from maternal and fetal sides 1. Maternal capillary endothelium 2. Maternal CT 3. Uterine epithelium 4. Chorionic epithelium (trophoblast) 5. Fetal CT 6. Fetal capillary endothelium
49
Placenta specifics in pigs
Diffuse Epitheliochorial Amniochorion Areoli Necrotic tips
50
Epitheliochorial
Uterine epithelium is in contact with chorionic epithelium All 6 layers present Horse, pig
51
Amniochorion
Fusion between amnion and chorion Pig, ruminants
52
Areoli
Histiotrophic areas (potential space between the trophoblast and uterine epithelium) Located opposite of the uterine glands
53
Necrotic tips
Vascularization of the extreme ends of chorion is lost and tips necrotic
54
Function of necrotic tips
Prevents BVs from adjacent embryos from coming close enough to fuse
55
Placenta specifics in horses
Diffuse Epitheliochorial Yolk sac/ chorion functions 3-4 weeks Allantois becomes functional at 5 weeks Endometrial cups Hippomanes
56
Diffuse in horse placentas
Microcotyledenous; ducts of endometrial glands empty into spaces between microcolyledon
57
Endometrial cups
Chorionic trophoblast cells Secrete equine chorionic gonadotropin (eCG, FSH like function) Secretion at 35-40 days, peal at 60-80 days, stops at 140-150 days
58
Hippomanes
Amorphous, debris, mucoprotein and calcium phosphate In pig and ruminant but not as common
59
Placenta specifics in ruminants
Cotyledenous (placentomes present) Syndesmochorial Amniochorion dorsally Allantochorion ventrally and laterally
60
Placental specifics in carnivores
Zonary Endotheliochorial Green band/ marginal area
61
Syndesmochorial
Uterine CT is in contact with chorionic epithelium 5 layers present In epitheliochorial Ruminants
62
Endotheliochorial
Uterine BVs are in contact with chorionic epithelium 5 layers present
63
Green band/ marginal area
In dogs, edges of zonary placenta have a green band that represents extravasated blood into the space between the uterine surface and the chorionic epithelium
64
What is the function of Green band/ marginal area
Source of iron for the fetus in cats Brown and not present until 53 days of gestation
65
Hemochorial
Blood of uterine vesseles is in direct contact with chorionic epithelium 3 layers presents Man
66
Hemeondothelial
Blood of uterine vessels is in contact with chorionic capillaries One layer present Rodent In hemochorial

Microanatomy (18 decks)

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