ANAT2341 Lab 4 - Implantation and Villi Development

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ANAT2341 Lab 4: Introduction | Implantation and Villi | Decidua and Cord | Abnormal Placenta | Cardiovascular | Online Assessment | Group Project

Implantation

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Human Embryo Day 8 to 9

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 Implantation  Chorionic Cavity  Week 3  Amniotic Cavity
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Villi Development

Chorionic Villi

Primary villi

Week 2 - first stage of chorionic villi development, trophoblastic shell cells (syncitiotrophoblasts and cytotrophoblasts) form finger-like extensions into maternal decidua.

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Secondary villi

Week 3 - second stage of chorionic villi development, extraembryonic mesoderm grows into villi, covers entire surface of chorionic sac.

Basal region will form chorionic plate.

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Tertiary villi

Week 4 - third stage of chorionic villi development, mesenchyme differentiates into blood vessels and cells, forms arteriocapillary network, fuse with placental vessels, developing in connecting stalk.

  • stem villi - or anchoring villi, cytotrophoblast cells attached to maternal tissue.
  • branched villi - grow from sides of stem villi, region of main exchange, surrounded by maternal blood in intervillous spaces.
  • terminal villi - not active outgrowths caused by proliferation of the trophoblast. Passive protrusions induced by capillary coiling due to growth of the fetal capillaries within the mature intermediate villi (third trimester).
  • chorionic plate - region of membrane at the base of the villi through which placental arteries and vein passes.
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Anchoring Villi

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Floating Villi

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Chorionoic Villi Location

Originally villi cover entire chorionic surface and then become restricted to decidua basalis region forming 2 regions:

  1. Frondosum - "leafy" where villi are mainly located.
  2. Capsularis - smooth chorion, where villi are absent or not abundant.
Embryo-membranes stage 11.jpg Stage18 bf10.jpg
Week 4 (Stage 11)
Week 7 (Stage 18)


ANAT2341 Lab 4: Introduction | Implantation and Villi | Decidua and Cord | Abnormal Placenta | Cardiovascular | Online Assessment | Group Project

Additional Information

Human Villi Timeline

The placental vill development data below is based upon a recent immunochemistry confocal laser scanning microscope (CLSM) study.[1]

Note that the paper uses clinical gestational age (GA) from last menstrual period (LMP) and has been corrected for post-conception (fertilization) age, approximately 14 days later.

Fertilization Age

(weeks)

Gestational Age

(weeks)

Vessel Lumen Diameter

(range in microns, µm)

Features
3 to 4 5 and 6 10 - 15
  • a complex network of cords and vessels with redundant connections
  • network comprises mainly cords, already connected together
  • vessels and cords are connected to each other without any interruptions
  • chorionic villus dominated by this network of vascular elements
  • vessels and cords are located centrally as well as peripherally and as a consequence contact the overlying trophoblastic layer
5 to 6 7 and 8 10 - 26
  • villi dominated by capillary network of vessels and cords
  • capillary network contains more vessels than cords
7 to 8 9 and 10 60 - 75 two central vessels

26 - 34 capillary network

  • villi have two large centrally located vessels
  • surrounded by and connected to a peripheral capillary network
  • capillary network contains vessels with a lumen in tight contact with overlying trophoblastic layer
  • villous projections also contain blind ending capillary sprouts
9 to 10 11 and 12 70 - 90 two central vessels

26 - 34 capillary network

  • immature intermediate villi characterized by two large vessels surrounded by a capillary network
  • capillary network has few cords
  • blind ending capillary sprouts off the capillary network

Reference

  1. <pubmed>17545656</pubmed>



ANAT2341 Lab 4: Introduction | Implantation and Villi | Decidua and Cord | Abnormal Placenta | Cardiovascular | Online Assessment | Group Project
2012 Course: Week 1 Lecture 1 Lecture 2 Lab 1 | Week 2 Lecture 3 Lecture 4 Lab 2 | Week 3 Lecture 5 Lecture 6 Lab 3 | Week 4 Lecture 7 Lecture 8 Lab 4 | Week 5 Lecture 9 Lecture 10 Lab 5 | Week 6 Lecture 11 Lecture 12 Lab 6 | Week 7 Lecture 13 Lecture 14 | Lab 7 | Week 8 Lecture 15 Lecture 16 Lab 8 | Week 9 Lecture 17 Lecture 18 Lab 9 | Week 10 Lecture 19 Lecture 20 Lab 10 | Week 11 Lecture 21 Lecture 22 Lab 11 | Week 12 Lecture 23 Lecture 24 Lab 12


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Cite this page: Hill, M.A. (2021, October 15) Embryology ANAT2341 Lab 4 - Implantation and Villi Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/ANAT2341_Lab_4_-_Implantation_and_Villi_Development

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© Dr Mark Hill 2021, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G