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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]
This type of connective tissue is found mostly in the reticular layer (or deep layer) of the dermis. [3] It is also in the sclera and in the deeper skin layers. Due to high portions of collagenous fibers, dense irregular connective tissue provides strength, making the skin resistant to tearing by stretching forces from different directions.
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.
The shape of the simple columnar epithelium cells are tall and narrow giving a column like appearance. the apical surfaces of the tissue face the lumen of organs while the basal side faces the basement membrane. [1] The nuclei are located closer along the basal side of the cell. [1]
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).
In a multicellular organism, an organ is a collection of tissues joined in a structural unit to serve a common function. [1] In the hierarchy of life, an organ lies between tissue and an organ system. Tissues are formed from same type cells to act together in a function. Tissues of different types combine to form an organ which has a specific ...
Histogenesis is the formation of different tissues from undifferentiated cells. [1] These cells are constituents of three primary germ layers , the endoderm , mesoderm , and ectoderm . The science of the microscopic structures of the tissues formed within histogenesis is termed histology .
Cell junctions [1] or junctional complexes are a class of cellular structures consisting of multiprotein complexes that provide contact or adhesion between neighboring cells or between a cell and the extracellular matrix in animals. [2] They also maintain the paracellular barrier of epithelia and control paracellular transport. Cell junctions ...