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Lymphatic vessels of the human heart: precollectors and collecting vessels. A morpho-structural study
1Department of Biomedical Sciences, University of Siena, Italy. sacchi@unisi.it
Insights
This study details the structure of human heart lymphatic vessels, revealing their unique ultrastructure adapted for cardiac dynamics. These findings offer new insights into cardiac lymphatic function and development.
Area of Science:
- Cardiovascular Anatomy
- Lymphatic System Research
- Ultrastructural Biology
Background:
- Limited data exists on the structural and ultrastructural characteristics of human heart lymphatic outflow vessels.
- Previous knowledge primarily focused on topographic and distributional aspects.
Purpose of the Study:
- To elucidate the structural and ultrastructural features of the lymphatic outflow vessels in the human heart.
- To understand the adaptation of these vessels to the dynamic cardiac environment.
Main Methods:
- Analysis of heart tissue fragments from dilated cardiomyopathy patients using light and transmission electron microscopy.
- Three-dimensional reconstructions from serial semithin sections.
- Detailed ultrastructural examination of endothelial cells, basement membrane, and surrounding tissues.
Main Results:
- Identified precollectors and collecting vessels as initial lymphatic routes, characterized by discontinuous musculature and structural similarities.
- Observed unique ultrastructural features including abundant Weibel-Palade bodies, discontinuous basement membranes, and frequent anchoring filaments.
- Noted that cardiac contractions likely drive lymph flow due to the vessels' limited musculature.
Conclusions:
- Human heart lymphatic vessels exhibit an ultrastructure adapted to the heart's dynamic forces.
- The findings support the ontogenetic hypothesis of lymphatic vessel formation from mesenchymal lacunae.
- This research provides a foundational understanding of cardiac lymphatic anatomy and function.
Abstract:
Only topographic and distributional data are available on the lymphatic outflow vessels of the human heart. Here we describe their structural and ultrastructural features. Fragments of the atria, ventricles and fat surrounding the major coronary branches were obtained from hearts of dilated cardiomyopathy patients. Serial semithin sections were observed under light microscopy and used for tridimensional reconstructions. Ultrathin sections were observed by transmission electron microscopy. Precollectors, the initial lymphatic outflow routes of the heart, are small valved vessels with irregular, discontinuous musculature. They originate in the subepicardial region from a network of epicardial, and from scattered myocardial absorbing lymphatic vessels and drain into the collecting vessels accompanying the major coronary branches. Collecting vessels are larger but structurally similar to precollectors. Wall musculature is independent of the size of the vessel. Their ultrastructure is the same as that of precollectors. Endothelial cells have many Weibel-Palade bodies, cytoplasmic filaments and focal adhesions. The basement membrane is discontinuous and anchoring filaments are frequent and conspicuous. The subendothelial layer contains much elastin. Human heart collecting vessels and precollectors may only be distinguished by their size. The scarcity of musculature suggests that lymph progression in this district is mainly ensured by cardiac revolutions. Their ultrastructural features are determined by adaptation to dynamic forces. The architecture of these vessels (random, disorderly, discontinuous, lacking any exact plan) and their large variations in caliber are in line with the ontogenetic hypothesis that peripheral lymphatic vessels originate from the coalescence of mesenchymal lacunae.