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human muscle system, the muscles of the human body that work the skeletal system, that are under voluntary control, and that are concerned with movement, posture, and balance. Broadly considered, human muscle—like the muscles of all vertebrates—is often divided into striated muscle (or skeletal muscle), smooth muscle, and cardiac muscle.
2024年5月16日 · A diagram of the human skeleton showing bone and cartilage. Protection of the heart, lungs, and other organs and structures in the chest creates a problem somewhat different from that of the central nervous system. These organs, the function of which involves motion, expansion, and contraction, must have a flexible and elastic protective covering.
2 天前 · Chemical composition of the body. Chemically, the human body consists mainly of water and of organic compounds —i.e., lipids, proteins, carbohydrates, and nucleic acids. Water is found in the extracellular fluids of the body (the blood plasma, the lymph, and the interstitial fluid) and within the cells themselves.
2024年4月9日 · dermis. human skin, in human anatomy, the covering, or integument, of the body’s surface that both provides protection and receives sensory stimuli from the external environment. The skin consists of three layers of tissue: the epidermis, an outermost layer that contains the primary protective structure, the stratum corneum; the dermis, a ...
Saint Lucia. Marigot Bay, Saint Lucia. Saint Lucia, island state in the Caribbean Sea. It is the second largest of the Windward group in the Lesser Antilles and is located about 24 miles (39 km) south of Martinique and some 21 miles (34 km) northeast of Saint Vincent. Saint Lucia.
2012年5月9日 · As the head of the government of the United States, the president is arguably the most powerful government official in the world. The president is elected to a four-year term via an electoral college system. Since the Twenty-second Amendment was adopted in 1951, the American presidency has been
2024年5月6日 · mitosis, a process of cell duplication, or reproduction, during which one cell gives rise to two genetically identical daughter cells. Strictly applied, the term mitosis is used to describe the duplication and distribution of chromosomes, the structures that carry the genetic information. A brief treatment of mitosis follows.
