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Aerenchyma in stem cross section of a typical wetland plant. Aerenchyma or aeriferous parenchyma [1] or lacunae, is a modification of the parenchyma to form a spongy tissue that creates spaces or air channels in the leaves, stems and roots of some plants, which allows exchange of gases between the shoot and the root. [2]
In biology, tissue is an assembly of similar cells and their extracellular matrix from the same embryonic origin that together carry out a specific function. [1] [2] Tissues occupy a biological organizational level between cells and a complete organ. Accordingly, organs are formed by the functional grouping together of multiple tissues. [3]
It also serves to regulate blood flow and tissue perfusion, thereby affecting blood pressure and responses to inflammation which can include edema (swelling). Most vessels of the microcirculation are lined by flattened cells of the endothelium and many of them are surrounded by contractile cells called pericytes. The endothelium provides a ...
There are four basic types of animal tissues: muscle tissue, nervous tissue, connective tissue, and epithelial tissue. [5] [9] All animal tissues are considered to be subtypes of these four principal tissue types (for example, blood is classified as connective tissue, since the blood cells are suspended in an extracellular matrix, the plasma). [9]
Epithelium or epithelial tissue is a thin, continuous, protective layer of cells with little extracellular matrix. An example is the epidermis, the outermost layer of the skin. Epithelial (mesothelial) tissues line the outer surfaces of many internal organs, the corresponding inner surfaces of body cavities, and the inner surfaces of blood vessels.
Developmental psychobiology posed this question since the lack of knowledge about the precise coordination of all cells, even those not related anatomically, in space and time during the embryonic period does not allow us to understand what forces at the cellular level coordinate four very general classes of tissue deformation, namely: tissue ...
Dense connective tissue also known as fibrous tissue [8] is subdivided into dense regular and dense irregular connective tissue. [9] Dense regular connective tissue, found in structures such as tendons and ligaments, is characterized by collagen fibers arranged in an orderly parallel fashion, giving it tensile strength in one direction. Dense ...
Some metabolic pathways flow in a 'cycle' wherein each component of the cycle is a substrate for the subsequent reaction in the cycle, such as in the Krebs Cycle (see below). Anabolic and catabolic pathways in eukaryotes often occur independently of each other, separated either physically by compartmentalization within organelles or separated ...