Early postnatal growth of the initial lymphatics in the ventral stripe of spinotrapezius muscle of the rat.

The aim of this study was the morphological description of the early postnatal growth of initial lymphatics in the ventral stripe of the spinotrapezius muscle of the rat. Electron-microscopically it was found that in the muscles of newborn rats no well-developed lymphatics were apparent, but the presence of specifically polarized mesenchymal cells in the close vicinity of central blood vessels was evident. In animals aged one-day through two-weeks-old, those modified mesenchymal cells continuously joined with one another, to form simple intercellular contacts and incomplete lymphatic lumina. Morphologically, they were well demarcated relative to the surrounding muscular interstitium. In three-week-old rats, all intramuscular lymphatics were well developed, including fine intraluminal valves, and their endothelial cells presented slight pinocytotic activity and a complete absence of a basal lamina. In growing lymphatic endothelial cells, no mitoses or signs of sprouting, typical for the growth of blood capillaries, were found. In conclusion, a possible morphological mechanism enabling the expansion of the growing lymphatic endothelial cells could be the specific remodeling of cytoplasmic vacuoles accumulated in the peripheral cellular processes.

Vasa vasorum of the human great saphenous vein.

The distribution of the vasa vasorum of the human great saphenous vein (GSV) was studied on veins taken both post-mortem and peroperatively. It was found that the stems of feeding vessels approach the venous wall at intervals of 1.5-2.5 cm; their smaller branches first passed the fascial compartments of the GSV and then entered the adventitia at intervals of 0.5-1.5 cm on both the stem and the largest tributaries of the GSV. In the stem regions vasa vasorum arteries and veins ran together but, between neighboring stems, isolated venae vasorum were regularly found which opened individually into terminal segments of the largest tributaries of the GSV. Neither by dissection nor by injection methods were venae vasorum found to open directly into the lumen of the GSV stem. The total thickness of the media ranged between 500 and 1300 micro m, according to the state of constriction of the venous wall before fixation. Two structurally different layers of GSV tunica media were present: an inner loose layer and an outer dense layer, both of similar thickness. The innermost capillaries of the vasa vasorum network were found in all cases on the border between the two layers of media. No lymphatic was found in any of the layers of GSV wall. From the findings the authors recommend extremely careful dissection of the GSV wall during in situ grafting surgery, to ensure the best viability of the venous wall.

Morphology and some biomechanical properties of human liver and spleen.

The aim of the study was an experimental determination of some morphological and mechanical properties of human liver and spleen (amount of collagen in organ capsules, their critical tension and density), followed by a definition of the threshold of critical acceleration, above which the organs can be injured during a car crash. Experiments were done on 33 fresh cadavers (18 males, 15 females; age 3 months to 88 years), and completed by sled tests on dummies testing the loads of both hypochondrial regions protected by air bags and/or seat belts. Results obtained were the following: (1). liver: capsule collagen 14-35%, critical tension 0.066-0.386 MPa, density 0.92-1.19 g/ml, critical acceleration 48-155 g; (2). spleen: capsule collagen 1.8-24.4%, critical tension 0.022-0.652 MPa, density 0.85-1.25 g/ml, critical acceleration 33-149 g. Loads of both hypochondrial regions measured on dummies during a predefined sled test were 34-67 g. Results obtained were evaluated qualitatively and discussed from the point of view of their possible use in future passive safety engineering and design calculations.