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Slide 100: Umbilical cord
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H/E
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This specimen is a cross section through the umbilical cord.
This is a cross section through the umbilical cord. The three large blood vessels are used as examples of smooth muscle.
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General description
At low magnification:
At low magnification, the umbilical cord appears as a round structure covered by a simple squamous epithelium known as the amniotic epithelium. Three primary structures are visible: two arteries (umbilical arteries) and one vein (umbilical vein). These vessels are embedded in a gelatinous substance called Wharton's jelly, which fills the space between the vessels and the surrounding epithelium. The cord is typically surrounded by a thin layer of amnion.
Cells Present:
- Fibroblast-like cells: Located within Wharton's jelly, these cells produce the extracellular matrix.
- Endothelial cells: Line the lumens of the umbilical arteries and vein.
- Smooth muscle cells: Found in the walls of the umbilical arteries and vein, contributing to the structural integrity and contractility of the vessels.
- Mesenchymal stem cells: Present in Wharton's jelly, these multipotent cells can differentiate into various cell types.
Tissues Present:
- Wharton's jelly: A specialized connective tissue composed of a mucous substance rich in proteoglycans, providing structural support and protection for the vessels.
- Amniotic epithelium: A single layer of epithelial cells covering the outer surface of the umbilical cord.
- Smooth muscle tissue: Found in the walls of the umbilical arteries and vein, allowing the vessels to maintain their structure and regulate blood flow.
Functions of structures, cells, and tissues:
- Umbilical arteries and vein: The arteries carry deoxygenated blood from the fetus to the placenta, while the vein carries oxygenated blood back to the fetus.
- Wharton's jelly: Protects the vessels from compression, preventing disruption of blood flow between the fetus and placenta.
- Amniotic epithelium: Serves as a protective barrier and plays a role in the exchange of gases and nutrients.
- Smooth muscle cells: Help maintain vessel integrity and regulate the passage of blood through the umbilical cord.
The umbilical cord is involved in the exchange of gases, nutrients, and waste between the fetus and the placenta, ensuring proper fetal development.
Identify:
Macroscopic
Microscopic
Longitudinally sectioned smooth muscle fibers. Cross sectioned smooth muscle fibers. In the tissue and between the blood vessels the following:
Draw and annotate:
The three components of gelatinous connective tissue in the correct ratio. Draw an additional fibroblast showing its microscopic detail (at higher magnification).
A few longitudinal and cross sectioned smooth muscle fibers. Note the shape and different diameters of the smooth muscle fibers.
Reflection:
- What is the shape of the fibroblasts and their nuclei? Compare this to the smooth muscle present in the blood vessel.
- How is the collagen arranged? Compare to irregular dense connective tissue.
- How do the collagen fibers appear? Compare to irregular dense connective tissue.
- How does the amorphous substance appear and how does it stain?
- What is characteristic of the cellular and nuclear shapes of smooth muscle fibres? Do all muscle fibres have the same diameter? Explain.
- How does the nucleus appear in a contracted smooth muscle fibre?
- What is found between the muscle fibers?
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