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Reproductive System > Placenta > Flashcards

Placenta Flashcards

1
Q

What are the parts of the placenta?

A

Fetal part
Maternal part

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2
Q

What type of an organ is the placenta?

A

Fetomaternal organ

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3
Q

What are the parts of the placenta derived from?

A
  • Fetal part: from the chorionic sac (the outermost fetal membrane)
  • Maternal part: from the endometrium (innermost layer of the uterine wall)
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4
Q

Outline implantation

A
  • begins at day 6 of pregnancy
  • trophoblast cells interact with endometrial lining of uterus after losing the Zona pellucida
  • blastocyst embeds into the endometrium where it interacts with the increased vasculature + secretory glands in the endometrium
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5
Q

When does implantation begin?

A

Day 6 of pregnancy

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6
Q

What is decidualisation?

A

Process by which stromal cells differentiate into highly specialised secretory epitheleoid cells called decidual cells

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7
Q

Function of decidual cells

A
  • Control depth of invasion of trophoblast
  • protect conceptus from maternal immune rejection
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8
Q

When does decidualisation occur?

A

During the secretory phase

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9
Q

What happens if implantation occurs where there are no decidual cells?

A

No control over the extent of invasion or rejection from maternal immune system

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10
Q

What happens when implantation occurs in the correct place but the decidual reaction is suboptimal?

A

Complications in the pregnancy:
- not maintained (miscarriage or infertility)
- placental insufficiency e.g. pre eclampsia

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11
Q

Normal location of implantation

A

Upper posterior uterine wall

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12
Q

Normal invasion location

A

Within the stratum/decidual functionalis

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13
Q

Outline the attachment of the blastocyst

A
  • trophoblastic cells have microvilli which attach to pinopodes on endometrium
  • stronger connection made between integrins + receptors on endometrium
  • blastocyst is attached to endometrium of uterus
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14
Q

What does the trophoblast differentiate into?

A

Cytotrophoblast
Syncytiotrophoblast

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15
Q

What produces hCG?

A

Syncytiotrophoblast

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16
Q

When does placenta formation start?

A

Second week of pregnancy

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17
Q

What happens in the case of a disease placenta or failed implantation of placenta?

A

Miscarriage
(Embryo isn’t provided nutrients and oxygen)

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18
Q

What part of the embryo becomes the placenta?

A

Trophoblast

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19
Q

Describe the layers of chorionic villia

A
  • syncytiotrophoblast (outer layer)
  • cytotrophoblast
  • core of extra embryonic mesoderm with fetal vessels
20
Q

Formation of the primary villus

A
  • cytotrophoblast send projections through the syncytiotrophoblast
  • intervillus space between the projections
  • forms a cytotrophoblastic shell
21
Q

Formation of secondary villus

A
  • extra embryonic mesoderm invades into the primary villli
  • this forms the 3 layered secondary villus
22
Q

What happens at the same time as secondary villus formation?

A

The connecting stalk differentiates to form umbilical vessels
2 arteries + a vein

23
Q

Formation of the tertiary villus

A

Chorionic vessels grow up into villus

24
Q

What is a cotyledon?

A

Decidual cells of endometrium invaginate into placenta causing septae which separate tertiary villi into groups

25
Q

How does the placenta change throughout pregnancy?

A
  • initially, barrier between fetal and maternal blood is thick which a full layer of cytotrophoblast + syncytiotrophoblast
  • as pregnancy progress, the barrier thins by reducing the cytotrophoblast cells to optimise transport
26
Q

Changes in the embryonic spaces during pregnancy

A
  • yolk sac disappear
  • amniotic sac enlarges
  • chorionic sac is occupied by expanding amniotic sac
27
Q

Outline the umbilical vessels

A
  • two umbilical arteries: deoxygenated blood + waste products from fetus to placenta
  • one umbilical vein: oxygenated blood + nutrients from placenta to fetus
28
Q

What conditions can occur due to implantation at incorrect site?

A

Ectopic pregnancy
Placenta praevia

29
Q

What conditions occur if implantation is too shallow?

A

Placental insufficiency
Pre-eclampsia

30
Q

What conditions occur if implantation is too deep?

A

Placenta accreta
Placenta increta
Placenta precreta

Increasing depth (alphabetic order)

31
Q

Three functions of the placenta

A

Endocrine function
Metabolic changes
Transport function

32
Q

Describe the endocrine function of the placenta

A
  • syntiotrophoblasts produces human chorionic gonadotropin hCG
  • hCG sustains the corpus luteum in the 1st trimester
    .
  • placenta also produces steroid hormones at the start of the 2nd trimester
  • placenta takes over the role of the corpus luteum
  • produces enough oestrogen + progesterone to keep the HPG axis in the ‘pregnancy state’
33
Q

What hormones are produced by the placenta?

A

Human chorionic gonadotropin hCG
Oestrogen
Progesterone

34
Q

Describe the metabolic function of the placenta

A
  • progesterone increases maternal appetite > increased fat deposition to support the fetus + breastfeeding
  • human placental lactose hPL creates diabetogenic state to cause insulin resistance in mother > increases glucose availability to fetus
35
Q

What hormone is related to gestational diabetes?

A

Human placental lactogen hPL

36
Q

What are the three ways transport occurs in the placenta?
Examples of substances for each

A
  • Simple diffusion: e.g. water, gases, electrolytes
  • Facilitated diffusion: e.g. glucose
  • Active transport: e.g. amino acids
37
Q

How is the rate of exchange in gas exchange limited between mother and baby?
What is needed?

A

Flow limited
Adequate uteroplacental circulation is needed

38
Q

What specific immunoglobulin crosses the placenta?

A

IgG

39
Q

What are teratogens?

A

Substances that cause congenital disorders in developing fetus
e.g. alcohol, drugs, medications

40
Q

When do teratogens have the greatest effect?

A
  • Early pregnancy
  • Especially embryonic stage (3-8 weeks) as organs systems are most at risk of damage
41
Q

Why is hCG pregnancy specific?

A

It is produced by the syncytiotrophoblast

42
Q

What system is at a continual risk of damage by teratogens during development?

A

Central nervous system
Long development

43
Q

Function of human placental lactogen

A
  • Puts mother in diabetogenic state
  • causes insulin resistance in mother
  • increases glucose availability to fetus
44
Q

What are TORCH infections?

A

Infections that can pass across the placenta

Toxoplasmosis
Other- syphilis, HIV
Rubella
Cytomegalovirus
Herpes simplex

45
Q

What antibody can pass from the mother to the fetus?
By what process does this happen?

A

IgG
Receptor mediated endocytosis

46
Q

How soon after fertilisation can hCG be detected reliably in maternal urine?

A

14 days

Reproductive System (20 decks)

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