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Bone is a form of connective tissue found in the body, composed largely of hardened hydroxyapatite-containing collagen. In larger mammals, it is arranged in osteon regions. Bone matrix allows mineral salts such as calcium to be stored and provides protection for internal organs and support for locomotion.
Non-cellular life, also known as acellular life, is life that exists without a cellular structure for at least part of its life cycle. [1] Historically, most definitions of life postulated that an organism must be composed of one or more cells, [2] but, for some, this is no longer considered necessary, and modern criteria allow for forms of life based on other structural arrangements.
A plant cell wall was first observed and named (simply as a "wall") by Robert Hooke in 1665. [3] However, "the dead excrusion product of the living protoplast" was forgotten, for almost three centuries, being the subject of scientific interest mainly as a resource for industrial processing or in relation to animal or human health.
The U.S. space agency's robotic OSIRIS-REx spacecraft in 2020 collected the samples from the near-Earth asteroid, a rocky remnant of a larger celestial body that had formed near the dawn of the ...
Some eukaryotic cells (plant cells and fungal cells) also have a cell wall. Inside the cell is the cytoplasmic region that contains the genome (DNA), ribosomes and various sorts of inclusions. [2] The genetic material is freely found in the cytoplasm. Prokaryotes can carry extrachromosomal DNA elements called plasmids, which are usually circular.
Unlike plant cells, animal cells have neither a cell wall nor chloroplasts. Vacuoles, when present, are more in number and much smaller than those in the plant cell. The body tissues are composed of numerous types of cells, including those found in muscles, nerves and skin.
Mesenchyme (/ ˈ m ɛ s ə n k aɪ m ˈ m iː z ən-/ [1]) is a type of loosely organized animal embryonic connective tissue of undifferentiated cells that give rise to most tissues, such as skin, blood or bone. [2] [3] The interactions between mesenchyme and epithelium help to form nearly every organ in the developing embryo. [4]
The cell wall is the relatively rigid structure surrounding the plant cell. The cell wall provides lateral strength to resist osmotic turgor pressure, but it is flexible enough to allow cell growth when needed; it also serves as a medium for intercellular communication. The cell wall comprises multiple laminate layers of cellulose microfibrils ...