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acbs 315 > Placentation, Gestation and Parturition > Flashcards

Placentation, Gestation and Parturition Flashcards

1
Q

What is the placenta and what does it facilitate?

A

Placenta: the organic metabolic interchange between conceptus and dam
-Facilitates the exchange of nutrients and wastes

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2
Q

The placenta is what kind of organ?

A

The placenta is an endocrine organ

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3
Q

The placenta produces hormones. What are the 2 functions of these hormones?

A
  1. maintain pregnancy

2. induce parturition

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4
Q

The fetal contribution of the placenta is from the ___?

A

chorion

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5
Q

The maternal contribution of the placenta is from the ___?

A

endometrium

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6
Q

Attachment vs. Implantation

These terms are often used interchangeably; are they the same?

A

no, different animals have attachment vs. implantation

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7
Q

Which animals have attachment of the embryo to the placenta?

A

Most domestic animal embryos attach

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8
Q

Which animals have implantation of the embryo to the placenta?

A

Primates are the only example of true implantation (embryo buries itself in the endometrium)

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9
Q

What is the functional unit of the placenta?

A

the chorionic villus

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10
Q

What are the chorionic villi? What does it protrude towards?

A
  • Finger-like villi

- protruding away from chorion towards the endometrium

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11
Q

What is the purpose of the chorionic villi?

A

Increases surface area to maximize exchange

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12
Q

2 ways to classify placentas

A
  1. chorionic villi distribution

2. number of tissue layers separating maternal and fetal blood

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13
Q

Four types of placenta based on chorionic villi distribution

A
  1. Diffuse
  2. Zonary
  3. Discoid
  4. Cotyledonary
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14
Q

Chorionic villi distribution in a diffuse placenta

A

Uniform distribution of chorionic villi across chorion

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15
Q

Which animals have a diffuse placenta?

A

Pig and mare

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16
Q

Chorionic villi distribution in a zonary placenta

A

Exchange region is a distinct band around the middle of conceptus

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17
Q

What animals have zonary placenta?

A

dogs and cats

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18
Q

In zonary placenta, there are 2 additional regions on each side of the exchange region/band. What are they?

A
  1. pigmented zone

2. transparent zone

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19
Q

Pigmented zone of zonary placenta is a local area of ___ and ___?

A

Hemorrhage and necrosis

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20
Q

What is the function of the pigmented zone of zonary placenta?

A

Function unknown but may involve iron transport

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21
Q

The transparent zone of the zonary placenta is poorly ___

A

vascularized

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22
Q

The discoid placenta has __-___ distinct discs where ___ are located

A

The discoid placenta has 1-2 distinct discs where chorionic villi are located

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23
Q

What animals have a discoid placenta?

A

rodents and primates

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24
Q

The cotyledonary placenta has structures called ___

A

Placentomes

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25
Q

What is the placentome in the cotyledonary placenta?

A

The point of interface between fetus and dam

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26
Q

What are the two components of the placentome in the cotyledonary placenta?

A
  1. fetal cotyledon

2. Maternal cotyledon

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27
Q

Where is the fetal cotyledon from?

A

the chorion

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28
Q

Where is the maternal cotyledon from?

A

The caruncles of the uterus

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29
Q

Many placentomes form in cattle and sheep: ___-___ placentomes

A

70-120 placentomes form in cattle and sheep

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30
Q

There is placental classification based on what?

A

The number of tissue layers separating maternal and fetal blood

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31
Q

In placental classification, what means the maternal side and what means the fetal side?

A

Prefix means maternal side

Suffix means fetal side

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32
Q

What are the three types of placental classification?

A
  1. Epitheliochorial
  2. Endotheliolchorial
  3. Hemochorial
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33
Q

Epitheliochorial placenta

What does “epithet” refer to?

A

Maternal epithelium: specifically in contact with chorion

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34
Q

How many layers are in the epitheliochorial placenta?

A

6 layers

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35
Q

Describe the properties of the 6 layers of the epitheliochorial placenta

A

The 6 layers are the least intermixed and the epithelium of the endometrium and chorion lie adjacent and intact

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36
Q

Endotheliolchorial placenta

What does “end” refer to?

A

Maternal endometrium

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37
Q

In an endotheliochorial placenta, the ___ (minus the epithelium) is in contact with the chorion

A

endometrium

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38
Q

How many layers in an endotheliochorial placenta?

A

5 layers

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39
Q

Why are there not 6 layers in the endotheliochorial placenta?

A

the endometrial epithelium is eroded

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40
Q

Hemochorial placenta

What does “hemo” refer to? (What is in contact with the chorion?)

A

Maternal blood

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41
Q

How many layers are in hemochorial placenta?

A

3 layers

42
Q

Out of the 3 types of placentas, based on the number of tissue layers separating maternal and fetal blood, which is the most intimate?

A

Hemochorial chorionic epithelium is in direct contact with the maternal blood

43
Q

Ruminant placentas have ___ ____ cells, which originate from trophoblasts

A

binucleate giant cells which originate from trophoblasts

44
Q

In ruminants, binucleate giant cells migrate from the ___ epithelium to the ___ epithelium

A

Chorionic epithelium to the endometrial epithelium

45
Q

Binucleate giant cells in ruminants secrete ____, which do what?

A

Binucleate giant cells in ruminants secrete hormones which facilitate pregnancy

46
Q

What specific hormones do binucleate giant cells secrete (4)?

A

Placental lactogen
Pregnancy specific protein B
Progesterone
Estrogen

47
Q

What are the 3 mechanisms for placental exchange?

A
  1. simple diffusion
  2. facilitated diffusion
  3. active transport
48
Q

Simple diffusion

A

transport via a concentration gradient

49
Q

Example of simple diffusion

A

gases and water

50
Q

Facilitated diffusion

A

utilizes specific carrier molecules

51
Q

Example of facilitated diffusion

A

glucose and amino acids

52
Q

Active transport

A

Utilizes energy to move molecules

53
Q

Example of active transport

A

ATP hydrolysis to move sodium, k and ca

54
Q

What nutrient is a major source of energy for the placenta and is from maternal circulation?

A

glucose

55
Q

Ketosis

A

Condition where body fat is utilized for energy during glucose deprivation

56
Q

When does ketosis occur? What is generated?

A

Ketosis can occur in late gestation or during lactation; generates ketone bodies (used for energy; excess production can be toxic = acetone or alcohol smell on breath)

57
Q

T or F: most maternal proteins cross the placenta

A

FALSE. Most maternal proteins do NOT cross the placenta

58
Q

How does the fetus get proteins? Where does it get amino acids from?

A

The fetus synthesizes its own proteins from amino acids provided by the dam

59
Q

Provide some examples of small molecular weight substances that can easily cross the placenta

A

Steroids and catecholamines (epinephrine and norepinephrine)

60
Q

Teratogenic

A

ability of a substance to induce birth defects

61
Q

Why should substances such as alcohol, mercury, and various illicit drugs be avoided during pregnancy?

A

They are small molecular weight toxic substances that are easily able to cross the placenta and induce birth defects

62
Q

Can microorganisms such as viruses and bacteria transfer through the placenta?

A

Yes. It allows mother to fetus disease transfer

63
Q

What hormone is produced by the placenta in mares?

A

Equine chorionic gonadotropin (ECG)

64
Q

Equine Chorionic Gonadotropin is produced by __ __ between days __-__ of pregnancy in the mare

A

ECG produced by endometrial cups between days 35-60 days of pregnancy

65
Q

What happens to the endometrial cups in mares after day 60 of pregnancy?

A

Cups slough off after day 60

66
Q

Major functions of ECG

What structures are specifically stimulated? What hormone production is increased?

A
  1. Increases ovarian progesterone production during pregnancy
    - stimulates primary CL (CL created form ovulated follicle)
    - Stimulates accessory CL (mare ovulates and develops CL while pregnant)
67
Q

In other species, what is ECG used for?

A

Used for super ovulation in other species; has FSH-like action in other species (only has a LH-like action in the mare)

68
Q

Human chorionic gonadotropin (hCG) is from __ cells of the __

A

hCG is from trophoblastic cells of chorion

69
Q

What does hCG stimulate (hint: what hormone is made)

A

stimulates CL to make progesterone

70
Q

In many species, the __ is an important source of progesterone

A

placenta

71
Q

Which hormone is a requirement for CL during pregnancy?

A

Progesterone. It is always important in early pregnancy

72
Q

Why do some species no longer need the CL in late pregnancy?

A

The placenta makes enough progesterone at that point

73
Q

The lute-placental shift occurs in species where the __ is not needed for full gestation

A

CL

74
Q

In some species where the luteo-placental shift is present, is the CL required? Does it still produce progesterone?

A

Even though CL is not required, it still produces progesterone through the pregnancy

75
Q

When does the placenta take over (the luteo-placental shift) in ewes? Women? Cows? Sows?

A

Ewe- placenta takes over at ~ 50 days

Women- 60-70 days

Cow- placenta takes over 6-8 months

**Sow- CL is required for full pregnancy

76
Q

In what species is the CL required for the entire pregnancy?

A

sow

77
Q

The placenta secretes somatomammortropin. What does this do (2)?

A
  1. promotes growth of fetus (somatotropic)

2. Stimulates mammary gland of mother (lactogenic)

78
Q

3 stages of parturition

A
  1. initiation of myometrial contractions
  2. expulsion of fetus
  3. expulsion of fetal membranes
79
Q

What must happen for the initiation of myometrial contractions to occur? why?

A

The progesterone levels must fall (progesterone inhibits myometrial contractions)

80
Q

What hormone inhibits myometrial contractions?

A

progesterone

81
Q

Initiation of myometrial contractions: STEP 1

the fetus produces ___

A

adrenal corticotropin

82
Q

ACTH from the fetus stimulates __ release by the __ glands (a stress hormone)

A

ACTH stimulates cortisol release by the adrenal glands

83
Q

Initiation of myometrial contractions: STEP 2

What are the effects of cortisol (2 specific things are stimulated)

A
  1. Stimulates synthesis of enzymes that convert progesterone into estradiol (therefore, estradiol rises and progesterone falls)
  2. Stimulates PGF2a release form the placenta, causing CL regression; placenta levels fall even further
84
Q

Cortisol stimulates the synthesis of enzymes that convert __ into __. Why is this important?

A

Progesterone is converted into estradiol because placenta levels need to fall in order for myometrial contractions to occur

85
Q

Cortisol causes regression of the CL which allows __ levels to fall

A

progesterone

86
Q

Initiation of myometrial contractions: STEP 3

Removal of __ block

A

progesterone

87
Q

How is “progesterone block” removed?

A

Estradiol and PGF2a initiate contractions

88
Q

Estradiol and PGF2a initiate contractions, which force the fetus against the ___

A

cervix

89
Q

When the fetus is pushed against the cervic, __ is released via a ___ reflex

A

Oxytocin is released via a neuroendocrine reflex

90
Q

___ facilitates myometrial contractions and is used to induce labor

A

oxytocin

91
Q

Oxytocin establishes a ___ feedback loop. Explain

A

Oxytocin establishes a POSITIVE feedback loop; more oxytocin= more contractions = more cervical pressure = more oxytocin

92
Q

Epulsion of the fetus- what 3 things are important for relaxation and lubrication of the birth canal

A
  1. relaxin
  2. mucus secretion
  3. membrane rupture
93
Q

Relaxin is a hormone produced by the __ or the __

A

CL or the placenta

94
Q

Relaxin “___” the birth canal

A

relaxes

95
Q

__ promotes mucus secretion, removes cervical plug and lubricates the birth canal

A

estradiol

96
Q

Entrance of the fetus: 1. fetus becomes __, which causes fetal movement

A

hypoxic

97
Q

Fetal movement caused by hypoxia causes further __ contractions and abdominal contractions also occur

A

myometrial contractions

98
Q

Dystocia means:

A

difficult birth

99
Q

Dystocia is usually associated with complications during the __ stage

A

second

100
Q

Causes of dystocia (3)

A
  1. too large fetus
  2. improper rotation of fetus
  3. multiple births in monotonous species
101
Q

Expulsion of fetal membranes: 1. __ __ must dislodge from the maternal side

A

chorionic villi

102
Q

In order for fetal membrane to be expelled, chorionic villi must dislodge from the maternal side of the placenta. This is caused by __ of arteries in the villi

A

Vasoconstriction - myometrial contractions continue, allowing the placenta to be expelled

acbs 315 (3 decks)

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