BGDA Practical Placenta - Placental Functions

From Embryology
Revision as of 21:29, 2 June 2019 by Z8600021 (talk | contribs)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
BGDsmall.jpg
Practical 14: Implantation and Early Placentation | Villi Development | Maternal Decidua | Cord Development | Placental Functions | Diagnostic Techniques | Abnormalities


Term Placenta

Placenta term anatomy 01.jpg

Increase in placental weight by birth gestational age GA.

Placental mean weight graph01.jpg

Placenta Vasculature - MRI and CT

Term placenta viewed from the fetal side.[1]

Human placenta vascular MRI 02.jpg Human placenta vascular CT 01.jpg
Magnetic Resonance Angiography (MRA) Computed Tomography Angiography (CTA)
Legend
  • CA - chorionic artery
  • PSA - primary stem artery
  • SSA - secondary stem artery
  • TSA - tertiary stem artery

Exchange

Placenta oxygen exchange levels.jpg Placenta spiral artery conversion.jpg
  • oxygen, carbon dioxide, carbon monoxide
  • nutrients
    • water, glucose, vitamins
    • electrolytes
  • waste products
    • urea, uric acid, bilirubin.
  • hormones
    • mainly steroid, protein hormones poorly transported.
    • maternal thyroid hormone can slowly cross.
    • fetal insulin can impact on maternal diabetes.
  • maternal antibodies
    • maternal IgG antibodies are transferred from about week 13 GA across the placenta
    • from the maternal lacunae syncytiotrophoblast cell endosomes bind IgG through neonatal Fc receptors.
  • drugs and their metabolites
    • pre-existing maternal conditions
    • illegal drugs (fetal drug addiction)
  • infectious agents
    • cytomegalovirus, rubella, measles, malaria, listeria, microorganisms

Endocrine

Protein and steroid hormones.

  • Human chorionic gonadotrophin (hCG) - like leutenizing hormone, supports corpus luteum in ovary, pregnant state rather than menstrual, maternal urine in some pregnancy testing
  • Human chorionic somatommotropin (hCS) - or placental lactogen stimulate (maternal) mammary development
    • rise through pregnancy, stimulates maternal metabolic processes, breast growth
  • Human chorionic thyrotropin (hCT)
  • Human chorionic corticotropin (hCACTH)
  • Relaxin
  • Steroid Hormones - progesterone (maintains pregnancy), estrogens (fetal adrenal/placenta)

Placental Estrogen

Human-adrenal gland 01.jpg Fetal adrenal cortex produces dehydroepiandrosterone sulphate (DHEA-S) that is converted by the placenta into estrogens[2][3] Placental estrogen, mainly estriol, suppresses gonadotropin secretion from the maternal pituitary gland. Maternal estrogen levels are often a useful indicator of fetal well being.
  • Uterus - stimulates growth of the myometrium, antagonizes the myometrial-suppressing activity of progesterone.
  • Mammary Gland - stimulates mammary gland ductal and alveolar growth.
  • Fetal Ovary - stimulates development of female fetal ovary.[4]

A second role for fetal adrenal DHEA-S is possible regulation of the effects of glucocorticoids on the developing brain.[5]

Placental Metabolism

Synthesises - glycogen, cholesterol, fatty acids

  • provides nutrient and energy


Placental Functions Interactive Component

Attempt the Quiz - Placental Functions  
BGDsmall.jpg

Here are a few simple Quiz questions that relate to Placental Functions from the practical.

1

The difference in oxygen tension between the umbilical artery and umbilical vein is about:

  100 pO2 (torr)
  55 pO2 (torr)
  45 pO2 (torr)
  10 pO2 (torr)
  none of the above are correct

2

Which of the following hormones produced by the placenta is important for initially preserving the pregnancy?

  Human chorionic gonadotrophin
  Human chorionic somatommotropin
  Human chorionic thyrotropin
  Human chorionic corticotropin

3

Which of the following hormones produced by the placenta is important for later preserving the pregnancy?

  progesterone
  Human chorionic somatommotropin
  Human chorionic gonadotrophin
  Human chorionic thyrotropin
  Follicle Stimulating Hormone
  Relaxin

4

Which of the following options are the roles of placental estrogens.

  stimulates growth of the maternal uterus myometrium
  antagonizes the maternal uterus myometrial-suppressing activity of other hormones
  stimulates maternal mammary gland ductal growth
  stimulates maternal mammary gland alveolar growth
  stimulates development of female fetal ovary

5

The placenta is said to have a "metabolic" role in the synthesis compounds except for:

  glycogen
  dehydroepiandrosterone-sulphate
  cholesterol
  fatty acids


BGDsmall.jpg
Practical 14: Implantation and Early Placentation | Villi Development | Maternal Decidua | Cord Development | Placental Functions | Diagnostic Techniques | Abnormalities

Additional Information: endocrine placenta


BGDsmall.jpg
Practical 14: Implantation and Early Placentation | Villi Development | Maternal Decidua | Cord Development | Placental Functions | Diagnostic Techniques | Abnormalities


Additional Information

Additional Information - Content shown under this heading is not part of the material covered in this class. It is provided for those students who would like to know about some concepts or current research in topics related to the current class page.


  1. Rasmussen AS, Lauridsen H, Laustsen C, Jensen BG, Pedersen SF, Uhrenholt L, Boel LW, Uldbjerg N, Wang T & Pedersen M. (2010). High-resolution ex vivo magnetic resonance angiography: a feasibility study on biological and medical tissues. BMC Physiol. , 10, 3. PMID: 20226038 DOI.
  2. Rainey WE, Rehman KS & Carr BR. (2004). The human fetal adrenal: making adrenal androgens for placental estrogens. Semin. Reprod. Med. , 22, 327-36. PMID: 15635500 DOI.
  3. Parker CR. (1999). Dehydroepiandrosterone and dehydroepiandrosterone sulfate production in the human adrenal during development and aging. Steroids , 64, 640-7. PMID: 10503722
  4. Albrecht ED & Pepe GJ. (2010). Estrogen regulation of placental angiogenesis and fetal ovarian development during primate pregnancy. Int. J. Dev. Biol. , 54, 397-408. PMID: 19876841 DOI.
  5. Quinn TA, Ratnayake U, Dickinson H, Castillo-Melendez M & Walker DW. (2016). The feto-placental unit, and potential roles of dehydroepiandrosterone (DHEA) in prenatal and postnatal brain development: A re-examination using the spiny mouse. J. Steroid Biochem. Mol. Biol. , 160, 204-13. PMID: 26485665 DOI.

Drugs

Abnormal Development - Drugs

The placenta and fetal tissues may deal with drugs differently from adult target tissues. In particular, drugs are "cleared", metabolised and excreted, at a different rate in both the fetus and in newborn infants. In general there is a much lower rate of clearance.

Adam MP, Polifka JE & Friedman JM. (2011). Evolving knowledge of the teratogenicity of medications in human pregnancy. Am J Med Genet C Semin Med Genet , 157C, 175-82. PMID: 21766440 DOI.

van Gelder MM, Roeleveld N & Nordeng H. (2011). Exposure to non-steroidal anti-inflammatory drugs during pregnancy and the risk of selected birth defects: a prospective cohort study. PLoS ONE , 6, e22174. PMID: 21789231 DOI.

Salisbury AL, Ponder KL, Padbury JF & Lester BM. (2009). Fetal effects of psychoactive drugs. Clin Perinatol , 36, 595-619. PMID: 19732616 DOI.



BGDsmall.jpg
Practical 14: Implantation and Early Placentation | Villi Development | Maternal Decidua | Cord Development | Placental Functions | Diagnostic Techniques | Abnormalities