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The uniformity of both specific types of molecules (the biomolecules) and of certain metabolic pathways are invariant features among the wide diversity of life forms; thus these biomolecules and metabolic pathways are referred to as "biochemical universals" [4] or "theory of material unity of the living beings", a unifying concept in biology ...
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]
This was ultimately concluded by plant scientist Matthias Schleiden [5] and animal scientist Theodor Schwann in 1838, who viewed live cells in plant and animal tissue, respectively. [ 3 ] 19 years later, Rudolf Virchow further contributed to the cell theory, adding that all cells come from the division of pre-existing cells. [ 3 ]
Animal tissues are grouped into four basic types: connective, muscle, nervous, and epithelial. [4] Collections of tissues joined in units to serve a common function compose organs. While most animals can generally be considered to contain the four tissue types, the manifestation of these tissues can differ depending on the type of organism.
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.
He coined the term cell (from Latin cellula, meaning "small room" [41]) in his book Micrographia (1665). [ 42 ] [ 40 ] 1839: Theodor Schwann [ 43 ] and Matthias Jakob Schleiden elucidated the principle that plants and animals are made of cells, concluding that cells are a common unit of structure and development, and thus founding the cell theory.
Usage of the term to describe large molecules varies among the disciplines. For example, while biology refers to macromolecules as the four large molecules comprising living things, in chemistry , the term may refer to aggregates of two or more molecules held together by intermolecular forces rather than covalent bonds but which do not readily ...
[2] [3] [4] Regeneration can either be complete [5] where the new tissue is the same as the lost tissue, [5] or incomplete [6] after which the necrotic tissue becomes fibrotic. [ 6 ] At its most elementary level, regeneration is mediated by the molecular processes of gene regulation and involves the cellular processes of cell proliferation ...