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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
Q

Describe adeciduate

A

Pig, horse, cow, sheep, and goat

Endometrium is left intact at time of placenta expulsion

26
Q

What are the placental functions?

A

Metabolic exchange
Substitutes for fetal GI tract, lung, kidney, liver, and endocrine glands
Produce hormones

27
Q

What do the hormones produced by the placenta do?

A

Stimulate ovarian function
Maintain pregnancy
Stimulate mammary function
Assist in delivery of fetus

28
Q

What is the role of the placenta in pregnancy maintenance?

A

None in bitch, queen, camels, sow, and doe

Placenta takes over from primary (ovarian) source in cow, ewe, and mare

29
Q

When does the placenta take over in cows? Ewes? Mares?

A

6-8 mos
50 days
70 days

30
Q

What is unique to a pregnant mare? What does it do?

A

Endometrial cups

Produce eCG

31
Q

Describe placental circulation

A

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
Q

What is freemartinism?

A

Blood can be co-mingled between twins of cattle

33
Q

What is the gestation length of a cow?

A

283 days

34
Q

What is the gestation length of a mare?

A

Approximately 344, but it is the most variable

35
Q

When does placental takeover of P4 production in cows and mares?

A

150 days

36
Q

What are the origins of amniotic fluid?

A

Fetal urine
Secretions from respiratory tract and buccal cavity
Maternal circulation

37
Q

What are the functions of amniotic fluid?

A

Protects fetus from external shock
Prevents adhesion between fetal skin and amniotic membrane
Assists in dilating cervix and lubricating birth passages during birth

38
Q

What are the origins of allantoic fluid?

A

Fetal urine

Secretory activity of allantoic membrane

39
Q

What are the functions of allantoic fluids?

A

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
Q

What are the functions of fetal fluids?

A

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
Q

What can be present in fetal fluids?

A

Hippomanes

42
Q

What species has allantoic caliculi?

A

Horse

43
Q

What are the stages of parturition?

A

1: Initiation of myometrial contractions
2: Expulsion of fetus
3: Expulsion of fetal membranes

44
Q

What occurs in stage I of parturition?

A

P4 block have been removed via PGF

P4 converted to estrogen

45
Q

What occurs in stage II of parturition?

A

Strong myometrial and abdominal contractions expel fetus

46
Q

What are the mechanical forces of the dilation of cervix (stage I of labor)?

A

Regular uterine contractions

47
Q

What is the period of dilation of cervix?

A

Beginning of uterine contractions until cervix is fully dilated and continuous with vagina

48
Q

What are related events to dilation of cervix?

A

Maternal restlessness
Elevated pulse and respiratory rates
Changes in fetal position and posture

49
Q

What are mechanical forces of expulsion of fetus (stage II of labor)?

A

Strong uterine and abdominal contractions

50
Q

What is the period of expulsion of fetus?

A

From complete cervical dilation to end of delivery of fetus

51
Q

What are related events to expulsion of fetus?

A

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
Q

What are the mechanical factors of expulsion of fetal membranes (stage III of labor)?

A

Uterine contractions decrease in amplitude

53
Q

What is the period of expulsion of fetal membranes?

A

Following delivery of fetus to expulsion of fetal membranes

54
Q

What are related events to expulsion of fetal membranes?

A

Maternal straining ceases
Loosening of chorionic villi from maternal crypts
Inversion of chorioallantois
Straining and expulsion of fetal membranes

55
Q

Know parturition cascade

A

Know parturition cascade

56
Q

What happens with myometrial contractions?

A

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
Q

Describe the immune status of the fetus

A

Fetus synthesizes little to no antibodies

Acquires antibodies from dam in utero or from colostrum

58
Q

What is the immune status related to?

A

Impermeability of epitheliochorial placenta to antibodies

Physiology (70 decks)

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