L10.3 Role of the placenta Flashcards Preview

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Flashcards in L10.3 Role of the placenta Deck (16):
1

Role of the placenta

  • Central regulator of pregnancy outcomes
  • Interface b/w mother and fetus
    • Exchange nutrients and gases
    • Barrier
    • Immune function
    • Hormone production
  • Important in separating maternal and fetal circulations

2

4 methods of placental transport

  • Passive diffusion
    • O2, steroid hormones
    • Fetal waste - urea, creatinine
  • Facilitated diffusion
    • Glucose through GLUT transporters
  • Active transport
    • AA, folate, micronutrients
  • Vesicular transport
    • For very large molecules - i.e. immunoglobulins
    • Captured by microvilli

3

Placenta as a GC barrier

  • Glucocorticoid barrierPlacenta actively metabolise GC → acts as a barrier
    • Express 11β-HSD2 which converts GC into inactive metabolites
    • Cortisone → coritsol

4

Immune regulation of the placenta

  • Modulate immune system to prevent rejection
  1. Secretes neurokinin B → binds phosphocholoines → assists in dampening immune system
  2. Inhibit maternal T-cells → lymphocytic suppressors
  3. IgG AB crosses placenta and provide immunity

5

Endocrine regulation of the placenta

  • Produces GF, lactogens, FG
  • Regulates maternal insulin levels, ↑blood glucose/FA
  • Progesterone secretion → maintain endometrial lining and prevents preterm labour
  • Leptin → regulating maternal appetite
  • Vasodilators/angiogenic factors

6

Placental development

  • Starts dev early in pregnancy and important for implantation
  • Day 7/8 = implantation
    • Free floating blastocyst comes into contact and invades uterine lining
      • Allows placentation to occur

7

3 ways of placental development going wrong

  1. Placenta previa
    • When placenta implants → covers cervix → fetus have no pathway to pass out through
    • Need C-section
  2. Placenta Accreta
    • Placenta invades beyond uterus and obstruct other structures
    • Causes severe blood loss during delivery
  3.  IUGR

8

Conditions affecting placental development

  • Pre-eclampsia
  • Diabetes
  • Malnutrition
  • *Essentially maternal stress

9

Placenta classification according to maternal layers

  • Epitheliochorial (lower primates)
    • Mother and fetus have complete capillary network
  • Endotheliochorial (carnivores - dogs/cat)
    • Fetus capillaries sitting in bath of blood
  • Hemochorial (higher primates - i.e. humans)
    • Maternal blood directly with fetal chorion

10

Placenta classified according to shape

  • Discoid (humans, mouse)
  • Multicotyledonary (sheep)
    • Many implantation sites around the uterus
  • Diffuse (horse)
    • Encapsulates the whole fetus
  • Zonary (cat/dog)
    • Ring of placenta

11

Placenta classified according to fetal layers

  • Hemomonochorial (human)
    • One type of fetal cell layer
    • The syncitiotrophoblast → what transports nutrients from mother to fetus
  • Hemodichorial
    • Syncitiotrophoblast + cytotrophoblast
  • Hemotrichorial (rodent)
    • 2 syncitiotrophoblast + syncitial giant layer → creates a labyrinth for exchange
    • Junctional zone above allows for hormone production

12

Zones in rats and humans comparatively

  • Villous region both in human and rat (Called labyrinth zone in rats)
  • Extravillous = maternal uterus which interacts with placenta
  • 3 zones in rats and 2 in humans

13

Effect of famine on placental size

  • Placenta ↓SA (more affected in boys than girls)
  • Babies were lighter
    • Glucose intolerance → CV/obesity risk ↑

14

What is the Placental ratio and it's significance

  • Given fetal body weight → there is an optimal placental weight
    • Large = inefficient
    • Small = poor development

15

Altered placenta development results in:

  1. Impaired placental structure → altered SA for transport
  2. Dysregulated nutrient transport
  3. Impaired endocrine functions (IGF, leptin)
  4. Dysregulated placental barrier → fetal GC exposure ↑ risk of disease

16

Difference b/w males and females

  • Overdose of GC/ethanol given:
    • Females → good response → upregulate HSD11B2
    • Males → bad response → dysregulated
  • Hypoxia → impaired GC barrier in females but not males