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Physiology > Exam 5: Placentation, Gestation, and Parturition > Flashcards

Exam 5: Placentation, Gestation, and Parturition Flashcards

1
Q

What is the placenta?

A

Fusion of fetal membranes to endometrium

Organ of physiologic exchange

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2
Q

What does the size and function of the placenta change with?

A

Stage of pregnancy

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3
Q

When is the placenta expelled?

A

After parturition

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4
Q

How is the placenta classified?

A

Gross shape and distribution of villi
Microscopic structure of feto-maternal barrier
Loss of maternal tissue at parturition

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5
Q

What is the function of villi?

A

To bring fetal vessels into close proximity to maternal blood vessels

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6
Q

What kind of placenta do mares and sows have?

A

Diffuse

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7
Q

What kind of placenta do ewes, does, and cows have?

A

Cotyledonary

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8
Q

What kind of placenta do bitches and queens have?

A

Zonary

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9
Q

What kind of placenta do primates and rodents have?

A

Discoid

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10
Q

Describe diffuse placenta

A

Attachement dispersed everywhere

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11
Q

Describe cotyledonary placenta

A

Multiple focal areas of attachment

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12
Q

Describe zonary placenta

A

Placenta attaches in a specific circular zone all around the fetus

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13
Q

Describe discoid placenta

A

Very large, single area of attachment where all of the exchange occurs

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14
Q

What forms placentomes?

A

The fusing of fetal cotyledons and maternal carunlces

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15
Q

What are maternal caruncles?

A

Specialized projections of uterine mucosa

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16
Q

What are the maternal caruncles like in the cow?

A

Convex

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17
Q

What are the maternal caruncles like in the ewe and doe?

A

Concave

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18
Q

What is the name given to the functional unit of a cotyledonary placenta?

A

Placentome

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19
Q

What are the degrees of invasiveness?

A

Epitheliochorial
Endotheliochorial
Hemochorial

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20
Q

Describe epitheliochroial

A 
Pig, horse, cow, ewe, and doe
Least intimate (more layers), both maternal and fetal epithelium
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21
Q

Describe endotheliochorial

A

Dog and cat
Complete erosion of endometrial epithelium
Fewer layers

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22
Q

Describe hemochorial

A

Primates and rodents
Chorionic epithelium is in direct apposition to maternal pools of blood
Most intimate

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23
Q

What are the degrees of intimacy?

A

Deciduate

Adeciduate

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24
Q

Describe deciduate

A

Dog, cat, rodents, and primates

Portion of endothelium is shed with placenta

25
Describe adeciduate
Pig, horse, cow, sheep, and goat | Endometrium is left intact at time of placenta expulsion
26
What are the placental functions?
Metabolic exchange Substitutes for fetal GI tract, lung, kidney, liver, and endocrine glands Produce hormones
27
What do the hormones produced by the placenta do?
Stimulate ovarian function Maintain pregnancy Stimulate mammary function Assist in delivery of fetus
28
What is the role of the placenta in pregnancy maintenance?
None in bitch, queen, camels, sow, and doe | Placenta takes over from primary (ovarian) source in cow, ewe, and mare
29
When does the placenta take over in cows? Ewes? Mares?
6-8 mos 50 days 70 days
30
What is unique to a pregnant mare? What does it do?
Endometrial cups | Produce eCG
31
Describe placental circulation
Two circulation parallel to each other Blood does not intermingle between dam and fetus Is close enough for gas and nutrient exchange to occur
32
What is freemartinism?
Blood can be co-mingled between twins of cattle
33
What is the gestation length of a cow?
283 days
34
What is the gestation length of a mare?
Approximately 344, but it is the most variable
35
When does placental takeover of P4 production in cows and mares?
150 days
36
What are the origins of amniotic fluid?
Fetal urine Secretions from respiratory tract and buccal cavity Maternal circulation
37
What are the functions of amniotic fluid?
Protects fetus from external shock Prevents adhesion between fetal skin and amniotic membrane Assists in dilating cervix and lubricating birth passages during birth
38
What are the origins of allantoic fluid?
Fetal urine | Secretory activity of allantoic membrane
39
What are the functions of allantoic fluids?
Brings allantochorion into close apposition with endometrium during initial steps of attachment Stores fetal excretory products not readily transferred back to the mother Helps to maintain osmotic pressure of fetal plasma
40
What are the functions of fetal fluids?
Protect and bathe the fetus Lubrication of birth canal Elimination of waste Maintains osmotic pressure of fetal plasma and prevents fluid loss of maternal circulation
41
What can be present in fetal fluids?
Hippomanes
42
What species has allantoic caliculi?
Horse
43
What are the stages of parturition?
1: Initiation of myometrial contractions 2: Expulsion of fetus 3: Expulsion of fetal membranes
44
What occurs in stage I of parturition?
P4 block have been removed via PGF | P4 converted to estrogen
45
What occurs in stage II of parturition?
Strong myometrial and abdominal contractions expel fetus
46
What are the mechanical forces of the dilation of cervix (stage I of labor)?
Regular uterine contractions
47
What is the period of dilation of cervix?
Beginning of uterine contractions until cervix is fully dilated and continuous with vagina
48
What are related events to dilation of cervix?
Maternal restlessness Elevated pulse and respiratory rates Changes in fetal position and posture
49
What are mechanical forces of expulsion of fetus (stage II of labor)?
Strong uterine and abdominal contractions
50
What is the period of expulsion of fetus?
From complete cervical dilation to end of delivery of fetus
51
What are related events to expulsion of fetus?
Maternal recumbency and straining Rupture of allantochorion and escape of fluid from vulva Appearance of amnion at vulva Rupture of amnion and delivery of fetus
52
What are the mechanical factors of expulsion of fetal membranes (stage III of labor)?
Uterine contractions decrease in amplitude
53
What is the period of expulsion of fetal membranes?
Following delivery of fetus to expulsion of fetal membranes
54
What are related events to expulsion of fetal membranes?
Maternal straining ceases Loosening of chorionic villi from maternal crypts Inversion of chorioallantois Straining and expulsion of fetal membranes
55
Know parturition cascade
Know parturition cascade
56
What happens with myometrial contractions?
Uterus is transformed from P4 dominated relaxed state to an active state PGF synthesis and release is increased Act jointly to initiate uterine contractions needed to dilate the cervix and deliver the fetus
57
Describe the immune status of the fetus
Fetus synthesizes little to no antibodies | Acquires antibodies from dam in utero or from colostrum
58
What is the immune status related to?
Impermeability of epitheliochorial placenta to antibodies

Physiology (70 decks)

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