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Microanatomy > Placenta > Flashcards

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
Q

Cat implantation

A

Gestation pd: 63 days
Implantation begins: 11-12 days
Implantation completed: 16-17 days

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26
Q

Cattle implantation

A

Gestation pd: 227-290
Implantation begins: 28-32
Implantation completed: 40-45

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27
Q

Dog implantation

A

Gestation pd: 61
Implantation begins: 14-17
Implantation completed: 20-21

28
Q

Horse implantation

A

Gestation pd: 330-345
Implantation begins: 35-40
Implantation completed: 95-105

29
Q

Sheep implantation

A

Gestation pd: 144-152
Implantation begins:14-16
Implantation completed: 28-34

30
Q

Swine implantation

A

Gestation pd: 112-115
Implantation begins: 12-13
Implantation completed: 24-26

31
Q

Placental classification based on fetal extra-embryonic membranes

A

Choriovitelline (yolk sac placenta)
Alantochroine
Alantoamnione

32
Q

Choriovitelline

A

Transitory
Yolk sac contacts the chorion
Vitelline vessels transfer waste/ nutrients

33
Q

How is choriovtelline important to the horse?

A

Delayed extraembryonic mesoderm formation and implantation

34
Q

Alantochorione

A

Permanent placenta (horse, dog)
Allantois + chorion
Umbilical vessels vascularize the chorion and allantois
2 bags burst at parturition

35
Q

Alantoamnione

A

Cow, pig
Allantois fuses dorsally with the amnion
1 bag bursts at parturition

36
Q

Placenta classification based on source of nutrition

A

Histiotrophic
Hemotrophic

37
Q

Histotrophic

A

Nutrients derived from uterine secretions via diffusion

38
Q

Hemotrophic

A

Nutrient transfer between maternal and fetal capillaries

39
Q

Placenta classification based on degree of destruction at parturition

A

Non-deciduate
Deciduate

40
Q

Non-deciduate

A

Materal and fetal membranes separate without endometrial loss
Ruminants, pigs, horses

41
Q

Deciduate

A

Materal tissue is lost and hemorrhage may occur
Rodents, primates, carnivores (somewhat)

42
Q

Placental classification based on gross shape of hemotrophic transfers area

A

Diffuse
Cotyledenous (placentome)
Zonary
Discoid

43
Q

Diffuse

A

Exchange occurs over most of the surface of the chorion
Horse, pig
Microcotlyedenous

44
Q

Cotyledenous

A

Special points of contact on uterus (caruncle or maternal cotyledon) and chorion (cotyledons or fetal cotyledons)

45
Q

Placentome

A

Ruminants: Caruncle (maternal coryledon) + fetal cotyledon
Cattle: convex (70-120)
Sheep: concave (90-100)

46
Q

Zonary

A

Area of exchange in form of “ring- like” band extending around entire circumference (carnivores)

47
Q

Discoid

A

Exchange site is round/oval (rodents and primates)

48
Q

Placenta classification based on histology

A

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
Q

Placenta specifics in pigs

A

Diffuse
Epitheliochorial
Amniochorion
Areoli
Necrotic tips

50
Q

Epitheliochorial

A

Uterine epithelium is in contact with chorionic epithelium
All 6 layers present
Horse, pig

51
Q

Amniochorion

A

Fusion between amnion and chorion
Pig, ruminants

52
Q

Areoli

A

Histiotrophic areas (potential space between the trophoblast and uterine epithelium)
Located opposite of the uterine glands

53
Q

Necrotic tips

A

Vascularization of the extreme ends of chorion is lost and tips necrotic

54
Q

Function of necrotic tips

A

Prevents BVs from adjacent embryos from coming close enough to fuse

55
Q

Placenta specifics in horses

A

Diffuse
Epitheliochorial
Yolk sac/ chorion functions 3-4 weeks
Allantois becomes functional at 5 weeks
Endometrial cups
Hippomanes

56
Q

Diffuse in horse placentas

A

Microcotyledenous; ducts of endometrial glands empty into spaces between microcolyledon

57
Q

Endometrial cups

A

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
Q

Hippomanes

A

Amorphous, debris, mucoprotein and calcium phosphate
In pig and ruminant but not as common

59
Q

Placenta specifics in ruminants

A

Cotyledenous (placentomes present)
Syndesmochorial
Amniochorion dorsally
Allantochorion ventrally and laterally

60
Q

Placental specifics in carnivores

A

Zonary
Endotheliochorial
Green band/ marginal area

61
Q

Syndesmochorial

A

Uterine CT is in contact with chorionic epithelium
5 layers present
In epitheliochorial
Ruminants

62
Q

Endotheliochorial

A

Uterine BVs are in contact with chorionic epithelium
5 layers present

63
Q

Green band/ marginal area

A

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
Q

What is the function of Green band/ marginal area

A

Source of iron for the fetus in cats
Brown and not present until 53 days of gestation

65
Q

Hemochorial

A

Blood of uterine vesseles is in direct contact with chorionic epithelium
3 layers presents
Man

66
Q

Hemeondothelial

A

Blood of uterine vessels is in contact with chorionic capillaries
One layer present
Rodent
In hemochorial

Microanatomy (18 decks)

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