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
2
Q
The placenta is what kind of organ?
A
The placenta is an endocrine organ
3
Q
The placenta produces hormones. What are the 2 functions of these hormones?
A
- maintain pregnancy
2. induce parturition
4
Q
The fetal contribution of the placenta is from the ___?
A
chorion
5
Q
The maternal contribution of the placenta is from the ___?
A
endometrium
6
Q
Attachment vs. Implantation
These terms are often used interchangeably; are they the same?
A
no, different animals have attachment vs. implantation
7
Q
Which animals have attachment of the embryo to the placenta?
A
Most domestic animal embryos attach
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)
9
Q
What is the functional unit of the placenta?
A
the chorionic villus
10
Q
What are the chorionic villi? What does it protrude towards?
A
- Finger-like villi
- protruding away from chorion towards the endometrium
11
Q
What is the purpose of the chorionic villi?
A
Increases surface area to maximize exchange
12
Q
2 ways to classify placentas
A
- chorionic villi distribution
2. number of tissue layers separating maternal and fetal blood
13
Q
Four types of placenta based on chorionic villi distribution
A
- Diffuse
- Zonary
- Discoid
- Cotyledonary
14
Q
Chorionic villi distribution in a diffuse placenta
A
Uniform distribution of chorionic villi across chorion
15
Q
Which animals have a diffuse placenta?
A
Pig and mare
16
Q
Chorionic villi distribution in a zonary placenta
A
Exchange region is a distinct band around the middle of conceptus
17
Q
What animals have zonary placenta?
A
dogs and cats
18
Q
In zonary placenta, there are 2 additional regions on each side of the exchange region/band. What are they?
A
- pigmented zone
2. transparent zone
19
Q
Pigmented zone of zonary placenta is a local area of ___ and ___?
A
Hemorrhage and necrosis
20
Q
What is the function of the pigmented zone of zonary placenta?
A
Function unknown but may involve iron transport
21
Q
The transparent zone of the zonary placenta is poorly ___
A
vascularized
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
23
Q
What animals have a discoid placenta?
A
rodents and primates
24
Q
The cotyledonary placenta has structures called ___
A
Placentomes
25
What is the placentome in the cotyledonary placenta?
The point of interface between fetus and dam
26
What are the two components of the placentome in the cotyledonary placenta?
1. fetal cotyledon
| 2. Maternal cotyledon
27
Where is the fetal cotyledon from?
the chorion
28
Where is the maternal cotyledon from?
The caruncles of the uterus
29
Many placentomes form in cattle and sheep: ___-___ placentomes
70-120 placentomes form in cattle and sheep
30
There is placental classification based on what?
The number of tissue layers separating maternal and fetal blood
31
In placental classification, what means the maternal side and what means the fetal side?
Prefix means maternal side
| Suffix means fetal side
32
What are the three types of placental classification?
1. Epitheliochorial
2. Endotheliolchorial
3. Hemochorial
33
Epitheliochorial placenta
| What does "epithet" refer to?
Maternal epithelium: specifically in contact with chorion
34
How many layers are in the epitheliochorial placenta?
6 layers
35
Describe the properties of the 6 layers of the epitheliochorial placenta
The 6 layers are the least intermixed and the epithelium of the endometrium and chorion lie adjacent and intact
36
Endotheliolchorial placenta
| What does "end" refer to?
Maternal endometrium
37
In an endotheliochorial placenta, the ___ (minus the epithelium) is in contact with the chorion
endometrium
38
How many layers in an endotheliochorial placenta?
5 layers
39
Why are there not 6 layers in the endotheliochorial placenta?
the endometrial epithelium is eroded
40
Hemochorial placenta
| What does "hemo" refer to? (What is in contact with the chorion?)
Maternal blood
41
How many layers are in hemochorial placenta?
3 layers
42
Out of the 3 types of placentas, based on the number of tissue layers separating maternal and fetal blood, which is the most intimate?
Hemochorial chorionic epithelium is in direct contact with the maternal blood
43
Ruminant placentas have ___ ____ cells, which originate from trophoblasts
binucleate giant cells which originate from trophoblasts
44
In ruminants, binucleate giant cells migrate from the ___ epithelium to the ___ epithelium
Chorionic epithelium to the endometrial epithelium
45
Binucleate giant cells in ruminants secrete ____, which do what?
Binucleate giant cells in ruminants secrete hormones which facilitate pregnancy
46
What specific hormones do binucleate giant cells secrete (4)?
Placental lactogen
Pregnancy specific protein B
Progesterone
Estrogen
47
What are the 3 mechanisms for placental exchange?
1. simple diffusion
2. facilitated diffusion
3. active transport
48
Simple diffusion
transport via a concentration gradient
49
Example of simple diffusion
gases and water
50
Facilitated diffusion
utilizes specific carrier molecules
51
Example of facilitated diffusion
glucose and amino acids
52
Active transport
Utilizes energy to move molecules
53
Example of active transport
ATP hydrolysis to move sodium, k and ca
54
What nutrient is a major source of energy for the placenta and is from maternal circulation?
glucose
55
Ketosis
Condition where body fat is utilized for energy during glucose deprivation
56
When does ketosis occur? What is generated?
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
T or F: most maternal proteins cross the placenta
FALSE. Most maternal proteins do NOT cross the placenta
58
How does the fetus get proteins? Where does it get amino acids from?
The fetus synthesizes its own proteins from amino acids provided by the dam
59
Provide some examples of small molecular weight substances that can easily cross the placenta
Steroids and catecholamines (epinephrine and norepinephrine)
60
Teratogenic
ability of a substance to induce birth defects
61
Why should substances such as alcohol, mercury, and various illicit drugs be avoided during pregnancy?
They are small molecular weight toxic substances that are easily able to cross the placenta and induce birth defects
62
Can microorganisms such as viruses and bacteria transfer through the placenta?
Yes. It allows mother to fetus disease transfer
63
What hormone is produced by the placenta in mares?
Equine chorionic gonadotropin (ECG)
64
Equine Chorionic Gonadotropin is produced by __ __ between days __-__ of pregnancy in the mare
ECG produced by endometrial cups between days 35-60 days of pregnancy
65
What happens to the endometrial cups in mares after day 60 of pregnancy?
Cups slough off after day 60
66
Major functions of ECG
| What structures are specifically stimulated? What hormone production is increased?
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
In other species, what is ECG used for?
Used for super ovulation in other species; has FSH-like action in other species (only has a LH-like action in the mare)
68
Human chorionic gonadotropin (hCG) is from __ cells of the __
hCG is from trophoblastic cells of chorion
69
What does hCG stimulate (hint: what hormone is made)
stimulates CL to make progesterone
70
In many species, the __ is an important source of progesterone
placenta
71
Which hormone is a requirement for CL during pregnancy?
Progesterone. It is always important in early pregnancy
72
Why do some species no longer need the CL in late pregnancy?
The placenta makes enough progesterone at that point
73
The lute-placental shift occurs in species where the __ is not needed for full gestation
CL
74
In some species where the luteo-placental shift is present, is the CL required? Does it still produce progesterone?
Even though CL is not required, it still produces progesterone through the pregnancy
75
When does the placenta take over (the luteo-placental shift) in ewes? Women? Cows? Sows?
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
In what species is the CL required for the entire pregnancy?
sow
77
The placenta secretes somatomammortropin. What does this do (2)?
1. promotes growth of fetus (somatotropic)
| 2. Stimulates mammary gland of mother (lactogenic)
78
3 stages of parturition
1. initiation of myometrial contractions
2. expulsion of fetus
3. expulsion of fetal membranes
79
What must happen for the initiation of myometrial contractions to occur? why?
The progesterone levels must fall (progesterone inhibits myometrial contractions)
80
What hormone inhibits myometrial contractions?
progesterone
81
Initiation of myometrial contractions: STEP 1
the fetus produces ___
adrenal corticotropin
82
ACTH from the fetus stimulates __ release by the __ glands (a stress hormone)
ACTH stimulates cortisol release by the adrenal glands
83
Initiation of myometrial contractions: STEP 2
What are the effects of cortisol (2 specific things are stimulated)
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
Cortisol stimulates the synthesis of enzymes that convert __ into __. Why is this important?
Progesterone is converted into estradiol because placenta levels need to fall in order for myometrial contractions to occur
85
Cortisol causes regression of the CL which allows __ levels to fall
progesterone
86
Initiation of myometrial contractions: STEP 3
Removal of __ block
progesterone
87
How is "progesterone block" removed?
Estradiol and PGF2a initiate contractions
88
Estradiol and PGF2a initiate contractions, which force the fetus against the ___
cervix
89
When the fetus is pushed against the cervic, __ is released via a ___ reflex
Oxytocin is released via a neuroendocrine reflex
90
___ facilitates myometrial contractions and is used to induce labor
oxytocin
91
Oxytocin establishes a ___ feedback loop. Explain
Oxytocin establishes a POSITIVE feedback loop; more oxytocin= more contractions = more cervical pressure = more oxytocin
92
Epulsion of the fetus- what 3 things are important for relaxation and lubrication of the birth canal
1. relaxin
2. mucus secretion
3. membrane rupture
93
Relaxin is a hormone produced by the __ or the __
CL or the placenta
94
Relaxin "___" the birth canal
relaxes
95
__ promotes mucus secretion, removes cervical plug and lubricates the birth canal
estradiol
96
Entrance of the fetus: 1. fetus becomes __, which causes fetal movement
hypoxic
97
Fetal movement caused by hypoxia causes further __ contractions and abdominal contractions also occur
myometrial contractions
98
Dystocia means:
difficult birth
99
Dystocia is usually associated with complications during the __ stage
second
100
Causes of dystocia (3)
1. too large fetus
2. improper rotation of fetus
3. multiple births in monotonous species
101
Expulsion of fetal membranes: 1. __ __ must dislodge from the maternal side
chorionic villi
102
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
Vasoconstriction - myometrial contractions continue, allowing the placenta to be expelled
