ANAT2341 Lab 4 - Decidua and Cord

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

Uterus

Human placenta classified as Haemochorial where the chorion comes in direct contact with maternal blood.

Menstrual Changes

  • Endometrium - 3 layers in secretory phase of menstrual cycle: compact, spongy, basal
  • Myometrium - muscular layer outside endometrium, contracts in parturition
  • Perimetrium - tunica serosa of the uterus continuous with the peritoneal wall

Endometrial Layers

  • Compact - implantation occurs in this layer, dense stromal cells, uterine gland necks, capillaries of spiral arteries.
  • Spongy - swollen stromal cells, uterine gland bodies, spiral arteries.
  • Basal - not lost during menstruation or childbirth, own blood supply.

Uterine glands

  • still well-developed and highly active at 6 weeks (GA).
  • gradually regress in length and epithelium height as the first trimester advances.

Decidual Reaction

Maternal Decidua and anchoring villi

Process (decidualization) of endometrial stromal cells (fibroblast-like) change in morphology (polygonal cells) and protein expression and secretion.

  • occurs initially at site of implantation and includes both cellular and matrix changes
  • reaction spreads throughout entire uterus, not at cervix
  • deposition of fibrinoid and glycogen and epithelial plaque formation (at anchoring villi)
  • presence of decidual cells are indicative of pregnancy

Fibrinoid layer - (Nitabuch's layer) is thought to act to prevent excessively deep implantation.

Artery Dilatation - due to extravillous trophoblast cells invading uterine wall and maternal spiral arteries replacing both smooth muscle with fibrinoid material and part of vessel endothelium. There is also a proliferation of maternal blood vessels.

Cervix - at mouth of uterus, secretes mucus (CMP), forms a plug/barrier, mechanical and antibacterial.

Decidua

Historic drawing decidua parts

The endometrium becomes the decidua and forms 3 distinct anatomical regions (at approx 3 weeks)

  • Decidua Basalis at implantation site
  • Decidua Capsularis enclosing the conceptus
  • Decidua Parietalis the remainder of uterus
    • Decidua Capsularis and Parietalis fuse eventually fuse and uterine cavity is lost by 12 weeks
    • decidua capsularis then degenerates

Fibrinoid

Exist as 2 forms of extracellular matrix:

  1. Fibrin-type fibrinoid is a maternal blood-clot product which replaces degenerative syncytiotrophoblast
  2. Matrix-type fibrinoid is secreted by invasive extravillous trophoblast cells.

Fibrinoid layer (Nitabuch's layer) is thought to act to prevent excessively deep implantation.

Decidualization

Process of endometrial stromal cells (fibroblast-like) change in morphology (polygonal cells) and protein expression and secretion (specific decidual proteins: prolactin, insulin-like growth factor binding protein-1, tissue factor, interleukin-15, and VEGF).

  1. Estrogen and progesterone - receptive phase, luminal and glandular epithelial cells change in preparation for blastocyst adplantation.
  2. Human Chorionic gonadotropin - luminal epithelium endoreplication leading to epithelial plaque formation.
  3. Human Chorionic gonadotropin - trophoblast invasion and decidualization of human stromal fibroblasts.

Maternal Blood Vessels

Artery Dilatation - Due to extravillous trophoblast cells invading uterine wall and maternal spiral arteries replacing both smooth muscle with fibrinoid material and part of vessel endothelium. There is also a proliferation of maternal blood vessels.

Uterine and Placental Vasculature in Non-pregnant, Pregnant and immediate Post-partum State

Uterine and placental vasculature.jpg


Diagrammatic representation of uterine and placental vasculature (red shading = arterial; blue shading = venous) in the non-pregnant, pregnant and immediate post-partum state.

  • Normal pregnancy is characterized by the formation of large arterio-venous shunts that persist in the immediate post-partum period.
  • Extravillous cytotrophoblast invasion in normal pregnancy (diamonds) extends beyond the decidua into the inner myometrium resulting in the formation of funnels at the discharging tips of the spiral arteries.
  • Pregnancies complicated by severe preeclampsia are characterized by minimal arterio-venous shunts, and thus narrower uterine arteries.


Placental Cord

Placental cord cross-section

The placental cord (umbilical cord) is the connecting region between the functional placenta and the embryo/fetal umbilical region. The human cord varies physically in overall length, increasing to about 60 to 70 cm at term, degree of coiling, number of vessels and insertion site on the placenta. This extraembryonic structure contains the placental blood vessels and allantois.

Normally a pair of placental arteries are wrapped around a single (left) placental vein. A persistent right umbilical vein is thought to be a rare anomaly.

Placental Arteries and Vein

Placental cord vessels 02.jpg Placental cord vessels 01.jpg


Week 8

Stage 22 image 086.jpg Stage 22 image 090.jpg

Cord Histology

Virtual Slide - Virtual Slides - Placenta Please note that there are additional slides listed in the current set, only the first placenta slide and the cord cross-section will be covered in detail in the practical class.


Placental cord ultrasound 03.jpg

Ultrasound image of transverse scan through the cord show the method of estimation of the cross-sectional area.

Wharton's Jelly

Placental cord cross-section
  • placental cord connective tissue (substantia gelatinea funiculi umbilicalis)
  • amorphous substance containing glycosaminoglycans, proteoglycans and hyaluronic acid.
  • cells similar to smooth muscle that allows a contractile function.
  • network of collagen that form canaliculi and perivascular spaces.
  • maintain blood flow to the fetus during placental cord compression during pregnancy or delivery.

First described and named after Thomas Wharton (1614–1673) an English physician and anatomist.


Hofbauer Cells

  • located the core of placental villi
  • macrophages with micropinocytotic activity and phagocytosis ability
  • possible paracrine role for early stages of placental vasculogenesis
  • express angiogenic growth factors (VEGF)

Cord Length

The following are lengths and classifications at term.

  • Normal range - 50 to 60 cm.
  • Short cord - less than 35 cm.
  • Long cords - over 70 cm can be associated with wrapping around the fetus and other abnormalities.


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


Additional Information

Other changes

  • Endoreplication - rounds of nuclear DNA replication without intervening cell or nuclear division (mitosis).
  • Cytokines - of maternal origin also act on placental development.
  • Natural Killer (NK) cells - 30% of all the decidual cells towards the end of the first trimester of pregnancy. These lymphocytes are present in the maternal decidua in large numbers (70%, normal circulating blood lymphocytes 15%) close to the extravillous trophoblast cells. Have a cytolytic potential against virus-infected and tumor-transformed cells.

Historic Drawings


ANAT2341 Lab 4: Introduction | Implantation and Villi | Decidua and Cord | | Abnormal Placenta | Cardiovascular | Online Assessment | Group Project
2014 Course: Week 2 Lecture 1 Lecture 2 Lab 1 | Week 3 Lecture 3 Lecture 4 Lab 2 | Week 4 Lecture 5 Lecture 6 Lab 3 | Week 5 Lecture 7 Lecture 8 Lab 4 | Week 6 Lecture 9 Lecture 10 Lab 5 | Week 7 Lecture 11 Lecture 12 Lab 6 | Week 8 Lecture 13 Lecture 14 | Lab 7 | Week 9 Lecture 15 Lecture 16 Lab 8 | Week 10 Lecture 17 Lecture 18 Lab 9 | Week 11 Lecture 19 Lecture 20 Lab 10 | Week 12 Lecture 21 Lecture 22 Lab 11 | Week 13 Lecture 23 Lecture 24 Lab 12 | Student Projects - Group 1 | Group 2 | Group 3 | Group 4 | Group 5 | Group 6 | Group 7 | Group 8 | Moodle