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ANSC 312 - Repro Physiology > Midterm 3 - Lecture 24 > Flashcards

Midterm 3 - Lecture 24 Flashcards

1
Q

Implantation/Attachment

A

joining of the extra-embryonic membranes to the uterine endometrium

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2
Q

Placentation

A

organization and physical relationship of embryonic/fetal membranes to the uterine endometrium that provides a site of metabolic exchange between the dam and embryo/fetus

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3
Q

Placenta

A

temporary organ of metabolic exchange btw the embryo/fetus and the dam consisting of tissues of embryonic origin and maternal origin

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4
Q

4 steps in pre-attachment embryonic development

A
  1. developing within the zona pellucida
  2. hatching from the zona pellucida
  3. maternal recognition of pregnancy
  4. extra-embryonic membranes
    - preparation for placentation and attachment to endometrium
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5
Q

Following hatching what happens prior to attachment?

A

“explosion” of embryonic tissue growth occurs to establish the extra-embryonic membranes

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6
Q

Why is the formation of the extra-embryonic membranes necessary?

A

to allow the developing embryo to attach to the uterus

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7
Q

What are the 4 extra-embryonic membranes?

A
  1. yolk sac
  2. chorion
  3. amnion
  4. allantois
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8
Q

Yolk sac

A
  • a transient membrane that regresses as the conceptus develops
  • formed from the primitive endoderm of the embryo
  • contributes primordial germ cells and early RBC
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9
Q

Chorion

A
  • outermost membrane that develops villi (chorionic villi) which attach to the endometrium to form fetal sites of placental attachment
  • formed from the trophoblast (ectoderm), primitive endoderm and mesoderm of the embryo
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10
Q

Amnion

A
  • liquid filled membrane enclosing the fetus the serves to protect the embryo against mechanical damage and prevent tissue adhesions
  • formed from the trophoblast (ectoderm), primitive endoderm and mesoderm of the embryo
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11
Q

Allantois

A
  • membrane that encloses a liquid waster storage reservoir for the developing embryo/fetus
  • formed from the primitive gut of the developing embryo
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12
Q

Origin of amnionic fluid

A
  • maternal circulation
  • secretions from fetal respiratory tract
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13
Q

Functions of amnionic fluid

A
  • protects fetus from mechanical damage
  • prevents adhesions
  • lubricates birth passage during parturition
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14
Q

Origin of allantoic fluid

A
  • fetal waste
  • secretions of allantoic membrane
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15
Q

Functions of allantoic fluid

A
  • positions allantochorion in contact with endometrium during attachment
  • stores fetal waste
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16
Q

Allantochorion

A

the fetal contribution to the fetal/maternal interface of the placenta

17
Q

Chorionic villi

A

small, finger-like projections on the surface of the allantochorion that serve as the interface btw the embryonic/fetal and maternal systems

18
Q

How are placentas classified?

A

according to the distribution of chorionic villi on their surface AND the number of tissue layers separating maternal and fetal blood

19
Q

What are the 4 different placenta chorionic villi distributions?

A
  1. diffuse
  2. cotyledonary
  3. zonary
  4. discoid
20
Q

What are the 3 different placenta maternal-fetal layers?

A
  1. epitheliochorial (6)
  2. endotheliochorial (~5)
  3. hemochorial (3)
21
Q

Diffuse

A

uniform distribution of chorionic villi that cover the surface of the chorion
- sows and mares

22
Q

Zonary

A

placenta has a band-like zone of chorionic microvilli
- bitch

23
Q

Discoid

A

placenta forms regionalized disc
- rodents and primates

24
Q

Cotyledonary

A

placenta has numerous discrete button-like structures referred to as cotelydons
- cows and ewes

25
Q

Epitheliochorial

A
  • 6 layers btw fetal and maternal blood
  • sows, mares, and ruminants
26
Q

Endotheliochorial

A
  • 5 layers between fetal and maternal blood
  • bitches and queens
27
Q

Hemochorial

A
  • 3 layers between fetal and maternal blood
  • primate and rodents
28
Q

Pig placenta

A

diffuse; epitheliochorial

29
Q

Mare placenta

A

diffuse; epitheliochorial

30
Q

Cow, sheep, goat placenta

A

cotyledonary; epitheliochorial

31
Q

Dog, cat placenta

A

zonary; endotheliochorial

32
Q

Primates, rodents placenta

A

Discoid; endotheliochorial

33
Q

Epitheliochorial placenta

A
  • both endometrial epithelium (maternal side) and epithelium of the chorionic villi (fetal side) are intact
  • in ruminants the endometrial epithelium periodically erodes and then re-grows allowing for occasional contact of maternal capillaries with chorionic epithelium = syndeschorial
34
Q

Binucleate giant cells

A
  • large cells with 2 nuclei formed in the placental tissues of ruminants
  • migrate from the chorionic epithelium and invade the endometrial epithelium
  • roles:
    1. transport complex molecules from the fetal to maternal placenta
    2. secretes steroids (P4)
35
Q

Endotheliochorial placenta

A
  • endometrial epithelium and interstitium are eroded
  • direct exposure of the maternal capillaries to the chorionic epithelium
36
Q

Hemochorial placenta

A
  • chorionic epithelium is in direct contact with maternal blood
  • nutrients and gases are exchanged directly btw maternal and fetal blood
37
Q

3 mechanisms of placental exchange

A
  1. Simple diffusion
    - gases and water move from high to low concentration
  2. Facilitated diffusion
    - specific carrier proteins facilitate the diffusion of important metabolic substances such as glucose and amino acids
  3. Active transport
    - sodium, potassium and calcium are moved across the placenta by transport pumps
38
Q

What does not cross the placenta?

A
  1. Proteins
    - fetus uses maternal AA to synthesize proteins
  2. Lipids
    - placenta hydrolyses triglycerides and maternal phospholipids to be used by the fetus
  3. Vitamins
    - fat soluble vitamins do not, water soluble vitamins cross with ease
  4. Hormones
    - large peptide hormones do not; small molecular wt hormones can
39
Q

What does cross the placenta?

A
  1. glucose
    - major source of energy for the fetus
    - derived from maternal circulation
    - glucose consumption is very high towards the end of gestation and can drain maternal system
  2. vitamins
    - water soluble cross
  3. Hormones
    - small molecular wt hormones cross
  4. viruses and bacteria

ANSC 312 - Repro Physiology (21 decks)

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