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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]
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]
All of the special connective tissue types have been included as a subset of fascia in the fascial system, with blood and lymph classed as liquid fascia. [14] [15] Bone and cartilage can be further classified as supportive connective tissue. Blood and lymph can also be categorized as fluid connective tissue, [2] [16] [17] and liquid fascia. [14]
Simple cuboidal epithelium is a type of epithelium that consists of a single layer of cuboidal (cube-like) cells which have large, spherical and central nuclei.. Simple cuboidal epithelium is found on the surface of ovaries, the lining of nephrons, the walls of the renal tubules, parts of the eye and thyroid, and in salivary glands.
In the theory of symbiogenesis, a merger of an archaean and an aerobic bacterium created the eukaryotes, with aerobic mitochondria, some 2.2 billion years ago. A second merger, 1.6 billion years ago, added chloroplasts, creating the green plants. [31] Eukaryotic cells were created some 2.2 billion years ago in a process called eukaryogenesis.
Simple squamous epithelium falls under the physiological category of exchange epithelium due to its ability to rapidly transport molecules across the tissue layer. To facilitate this movement, some types of simple squamous epithelium may have pores between cells to allow molecules to move through it, creating a leaky epithelium.
At a tissue level, ignoring the means of control, morphogenesis arises because of cellular proliferation and motility. [9] Morphogenesis also involves changes in the cellular structure [10] or how cells interact in tissues. These changes can result in tissue elongation, thinning, folding, invasion or separation of one tissue into distinct layers.
When the animal is born (or hatches from its egg), it has all its body parts and from that point will only grow larger and more mature. By contrast, plants constantly produce new tissues and structures throughout their life from meristems [5] located at the tips of organs, or between mature tissues. Thus, a living plant always has embryonic ...