Tissue conducting parenchyma

Hardwoods contain several cell types, specialized for different functions (Fig. 1-9). The supporting tissue consists mainly of libriform cells, the conducting tissue of vessels with large cavities, and the storage tissue of ray parenchyma cells. In addition, hardwood contains hybrids of the above-mentioned cells which are classified as fiber tracheids. Although the term fiber is frequently used for any kind of wood cells, it more specifically denotes the supporting tissue, including both libriform cells and fiber tracheids. In birch these cells constitute 65 to 70% of the stem volume. 

ERASISTRATUS OF KEOS (ca. 300-250 BC) Coined the term "parenchyma (i.e. poured out beside) for liver tissue, based on the belief that it was formed by coagulation of the blood released from the hepatic vessels. For him, however, liver parenchyma was a completely useless structure. He also described for the first time the "choledochos , which he believed absorbed the redundant and rather harmful bile (transported into the liver with the portal vein blood) from the intrahepatic bile ducts, and conducted it away. This separation of bile from blood in the liver was allegedly effected by the different viscosities of the two fluids and the different diameters of the adjacent ( ) intrahepatic bile ducts and blood vessels. Stoppage of the bile flow would lead to jaundice (obstructive icterus ) and inflammation of the liver. He attributed the dropsy commonly associated with liver disease to a hardening of the liver, which he termed "skirros this compressed the intrahepatic vessels, diverting the flow of the watery fluid into the abdomen. Based on this surmise, he rejected the practice of... 

The blade of the leaf consists of the framework, made dp of branching vessels of the petiole, which are woody tubes pervading the soft tissue called mesophyll, or leaf parenchyma, and serve not only as supports but as veins to conduct nutritive fluids. Veins are absent in simple leaves such as many of the Mosses. 

At the stem apex, alkaloids are present in all the young undifferentiated cells. According to Molle (6), the most recently formed cells have comparatively little, the precipitations increasing to a maximum density at a short distance behind the actual apex. The zone of tissue differentiation is also abundantly supplied, but as differentiation proceeds, alkaloids disappear from the vascular strands, and then from the central tissues of the pith. When differentiation is complete, the alkaloids are located principally in three concentric layers, in the epidermis and outer cortical layers just below it, in parenchyma within and adjacent to the phloem, and in the periphery of the pith just inside the xylem strands. The xylem parenchyma and medullary rays also possess alkaloids after they have disappeared from the conducting elements. 

The test usually conducted to determine body zinc is the measurement of plasma zinc concentration. However, plasma zinc concentrations do not seem to reflect the concentration found in the liver parenchyma (Goksu Ozsoylu, 1986 Sato et al., 2005). This may be explained by the fact that there are very efficient homeostatic mechanisms to correct plasma or serum zinc deficiencies, which makes it difficult to diagnose marginal deficiency by using this method. Therefore, the investigation of zinc concentration in liver tissue is important. 

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