Anatomy and Physiology > Gestation > Flashcards

Gestation Flashcards

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1
Q

Sperm formation and transport

A

-sperm made in parenchyma of testes
-made via convoluted seminiferous tubules and drain into rete testes within mediastinum
-then drains to efferent ducts
-then to ductus epididymis (where it is stored and matures)
-then goes to Vas deferens
-where sperm transported from epididymis —> urethra —> copulation

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2
Q

Embryogenesis simple

A

Blastomere —> morula —> blastocyst

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3
Q

What covers the outer area of blastocyst?

A

Trophoblasts

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4
Q

Function of trophoblasts

A

Develops into foetal portion of the placenta
-forms 2 foetal membranes called the amnion and chorion

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5
Q

What does the inner cell mass of blastocyst develop into?

A

Develops into the embryo

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6
Q

What is a hatched blastocyst?

A

A rapidly growing blastocyst that hatches from the zona pelllucida and forms a hatched blastocyst which is no free floating in the uterus

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7
Q

Name stages of embryogenesis

A

1.oocyte
2.fertilisation
3.ootid
4.zygote
5.two-celled stage
6.four-celled stage
7.eight-called stage
8.morula
9.early blastocyst
10.hatching blastocyst
11.hatched blastocyst

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8
Q

Four foetal membranes in animals

A

Chorion
Yolk sac
Amnion
Allantois

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9
Q

Where are foetal membranes derived from?

A

Zygote

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10
Q

Outermost layer of foetal membranes

A

Chorion

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11
Q

Innermost layer of foetal membranes

A

Amnion

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12
Q

Chorion function

A

-principal membrane involved in exchange of nutrients and gas and waste exchange
-key role in protecting the embryo from maternal immunosurveillance
-role in synthesis and secretion of hormones and proteins to help maintain pregnancy

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13
Q

Amniotic sac function

A

-where embryo develops
-fluid in amniotic cavity provides buoyancy to foetus and protects it from mechanical impact
-provides nutrition and maintains temperature
-role in developing lungs and organs in foetus

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14
Q

Allantois function

A

-primarily involved in removal of waste products and excretory products
-some function in gaseous exchange

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15
Q

What do the Allantois and chorion do?

A

Allantois grows until it reaches and fuses with chorion to form chorioallantoic membrane

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16
Q

Why do Allantois and chorion join?

A

Allantois contributes to vascular portion of the chorioallantoic placenta and so involved in foetal and maternal exchange

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17
Q

Overview of development of foetal membranes (gastrulation)

A

1.endoderm forms beneath the inner cell mass and grows downwards to form lining on the inner surface of the trophoblastic cells on outer edge
2.eventually it will fuse and form the yolk sac
3.at the same time, mesoderm starts to develop between primitive endoderm and embryo
4.mesoderm grows into that space and pushes around the yolk sac to form wing like amniotic folds
5.mesoderm completely surrounds yolk sac and fuses with cells of trophoectoderm and forms the chorion
6.at the same time, Allantois forms
7.yolk sac starts to regress and Allantois gets bigger
8.allantois eventually makes contact with chorion and forms allantochorion
9.amniotic folds create double layered membrane and gives us amniotic cavity as well

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18
Q

Why is formation of extra embryonic membranes important?

A

Allow embryo to actually be able to attach to the uterus of the dam

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19
Q

Name 1-7

A

1.amniotic cavity
2.amnion
3.chorion
4.yolk sac
5.allantoic membrane
6.allantois
7.chorioallantoic membrane

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20
Q

Placenta - metabolic interchange

A

-facilitate gas and nutrient exchange
-excretory products

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21
Q

Placenta - endocrine organ

A

Hormone production for:
-maintenance of pregnancy
-induction of parturition
- suppress new oestrus cycles
-stimulate mammary function
-influence foetal growth
-stimulate ovarian function

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22
Q

Placenta - immunity

A

Antibodies pass across the placental barrier to provide the foetus with some form of immunity

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23
Q

Name 1-5

A

1.villi from chorion
2.amniotic sac
3.chorioallantois
4.foetus
5.amnion

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24
Q

Function of villi from chorion

A

Project out into wall of uterus to hold it in place

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25
Function of progesterone produced from placenta
-maintains pregnancy by supporting endometrium -suppresses contractility of the uterine smooth muscle until parturition
26
Function of oestrogens produced by placenta
-also stimulate growth of myometrium and antagonise any myometrial suppressing activity of the progesterone (why it comes in stage before parturition) -role in stimulating mammary gland development
27
Placentation v implantation
Placentation = formation and attachment of the placenta to the uterus Implantation = attachment of the placental membranes to the endometrium surface rather than actually implanting
28
3 stages of implantation
Apposition Adhesion Attachment
29
Implantation - apposition
Blastocyst or foetal membranes become closely apposed to uterine lining (epithelium)
30
Implantation - adhesion
A complex biochemical interaction between molecules on the trophoblast and epithelium
31
Implantation - attachment
Firm attachment or invasion of trophoblast into uterus
32
Implantation in domestic animals
Foetus will develop inside the uterine cavity and there is no real penetration of the endometrium by the embryo
33
Implantation in humans and rats
Embryo implants itself on the wall of endometrium and gets buried in that and develops inside the wall
34
Function of implantation
To obtain that very close apposition between embryonic and maternal tissue so they can transfer gases, waste etc.
35
Why is implantation dependent on different species?
-for type of implantation that occurs -timing of implantation - how long it’s implanted for
36
Classification of placental types
1.foetal membranes 2.the shape of the placenta and the distribution of contact sites between fetal membranes and endometrium (described morphologically depending on distribution of villi) 3.the number of layers of tissue between maternal and fetal vascular systems (classified based on type of implantation)
37
Placenta type 1 - foetal membranes
Two types that form: -choriovitelline (non mammals and marsupials) - when yolk sac involved -chorioallantoic (ruminants, pigs)
38
Foetal membranes in horses, carnivores and rodents
Choriovitelline and then chorioallantoic
39
Placental type 2 - shape and point of villus contact
4 types: -discoid (rodents) -cotyledonary (ruminants) -zonary (dogs and cats) -diffuse (horses and pigs)
40
Shape and point of villus contact - discoid
1-2 points of contact, discoid in shape -dense common area where placenta contacts the uterus
41
Shape and point of villus contact - cotyledonary
-multiple discrete areas of attachment (cotyledons) which interact with endometrium (caruncles) to form placentome
42
Shape and point of villus contact - zonary
Prominent band of tissue surrounding fetus
43
Shape and point of villus contact - diffuse
Almost entire surface of allantochorion involved
44
Name a,b,c,d
A. Diffuse B. Cotyledonary (multi cotyledonary) C. Zonary D. Discoid
45
6 layers spreading maternal and foetal blood
3 layers of foetal embryonic membranes -endothelium lining of capillaries -connective tissue -epithelium 3 layers on maternal side -endothelium -stroma/connective tissue -epithelium
46
Diagram of cell layers at maternal and foetal interface
47
Foetal membranes of dog
-choriovitelline then chorioallantoic (because yolk sac decreases) -zonary, central -endotheliochorial (endothelial cells of maternal blood vessels still in tact and what chorion interact with
48
What type of shape are these placentas?
Zonary -ring goes all the way round in dogs but not in cats
49
Name 1+2
1.zonary placenta 2.chorioallantois
50
Name shape of placenta
Diffuse epitheliochorial placenta of pig
51
Name shape of placenta
Epitheliochorial, diffuse placenta of horse (Choriovitelline then chorioallantoic)
52
Name shape of placenta
Ruminants foetal membranes - chorioallantoic cotyledonary central epitheliochorial villus
53
Name 1-3
1.red patches = placentomes 2.cotyledon 3.caruncle
54
Maintenance of pregnancy
-progesterone required to maintain pregnancy -progesterone secreted by corpus luteum throughout pregnancy in some species -placenta takes over section of progesterone during gestation in some species -increase in the oestrogen:progesterone ratio induces parturition
55
Pregnancy in the bitch
-non seasonal, mono-oestrus -average interval between pro-oestrus periods = 7 months -progesterone is produced solely from the corpus luteum during pregnancy -similar length luteal phase in pregnant vs non pregnant bitch
56
Unique features of pregnancy in the bitch
-preovulatory rise in serum progesterone -serum progesterone concentration similar in pregnant vs non-pregnant -the absence of many pregnancy-specific proteins -exclusive placental production of relaxin -prefesterone only produced by corpus luteum throughout and not the placenta
57
Main leutrophic hormones to support corpus luteum
LH and prolactin
58
Why can’t progesterone identification be used to diagnose pregnancy in bitch?
Progesterone produced in luteal phase regardless if pregnant or not -few differences in luteal phase regardless if pregnant or not and so causes pseudopregnancy
59
Role of progesterone
-alter characteristics of mucosal secretions -decrease smooth muscle excitability -slow down passage of egg in uterine tubes to delay entry of embryos if present into the uterus and give them time to mature -closes cervix and prepare uterus to facilitate embryo
60
Ovulation in bitches
-oestrogen levels lower and progesterone levels start to rise at the time -progesterone derived from pre ovulatory follicular lutenising hormone in dogs -means that cells of follicle undergo lutenisation process to turn it into a corpus luteum and therefore producing the progesterone before she’s even ovulated
61
Where are progestagens produced?
Produced by CL and placenta in most species -just CL in dog
62
Function of progestagens
-stimulation of uterine secretions (histotroph) -suppress myometrial activity -mammary gland development -essential for pregnancy
63
Where are oestrogens produced?
Produced by foetal cotyledons/trophoblast cells
64
Function of oestrogens
-stimulate mammary development -stimulate placental growth -increase uterine blood flow -stimulate myometrial growth -preparation for parturition -no pregnancy specific oestrogen in dog
65
Where is relaxin produced?
Produced by the placenta in the dog -can be used for pregnancy diagnosis
66
Function of relaxin
-promotes progesterone secretion -softens connective tissue to enable foetal growth -relaxation of pelvis ligaments -parturition
67
What type of hormone is prolactin?
Leteotrophic -stimulated P4 production from CL
68
Function of prolactin
In mammary gland: -induces alveolar growth -lactogenesis -has role in maternal behaviour and maternal bond
69
What would happen if prolactin was inhibited during pregnancy?
-progesterone starts to decrease and prolactin increases to take over supporting CL and so any inhibition of prolactin = termination of luteal phase and therefore termination of pregnancy
70
Maternal recognition
-in absence of embryo, luteolysis is induced and causes decline in progesterone and return to oestrus -conceptus signals presence to dam - proteins and hormones -no maternal recognition in bitch or queen due to role of CL
71
Pregnancy diagnosis
-mammary glands (but keep pseudopregnancies in mind) -abdominal plalpation -radiography (45 days into pregnancy to see skeletons) -ultrasonography
72
Pregnancy in the Queen
-polyoestrus seasonal breeders (Feb-Sep) -induced ovulators -multiple pregnancies within a breeding season -can get pseudopregnancies too
73
Pregnancy in the Queen - progesterone
-rapids rise and divergent from non-pregnant at 21 days -placenta takes over 40-50 days -rapids fall prior to parturition
74
Luteal phase in queens pregnant vs non pregnant
Non pregnant luteal phase shorter than pregnant luteal phase
75
Luteotrophic factors of pregnancy in Queen
From fetus/placenta/uterus to maintain secretion of P4 from CL -potentially prolactin or relaxin
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