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The human skin is the outer covering of the body and is the largest organ of the integumentary system. The skin has up to seven layers of ectodermal tissue guarding muscles, bones, ligaments and internal organs. Human skin is similar to most of the other mammals' skin, and it is very similar to pig skin.
Each of these variables is controlled by one or more regulators or homeostatic mechanisms, which together maintain life. Homeostasis is brought about by a natural resistance to change when already in optimal conditions, [2] and equilibrium is maintained by many regulatory mechanisms; it is thought to be the central motivation for all organic ...
Optimal bone health is characterized by adequate bone mineral density (BMD) and proper bone microarchitecture, which together contribute to bone strength. [2] Osteoporosis, a skeletal disorder characterized by compromised bone strength and increased risk of fractures, is a major concern in bone health, particularly among older adults.
Tissue growth is the process by which a tissue increases its size. In animals, tissue growth occurs during embryonic development, post-natal growth, and tissue regeneration. The fundamental cellular basis for tissue growth is the process of cell proliferation, which involves both cell growth and cell division occurring in parallel. [1] [2] [3] [4]
In humans with non-injured tissues, the tissue naturally regenerates over time; by default, new available cells replace expended cells. For example, the body regenerates a full bone within ten years, while non-injured skin tissue is regenerated within two weeks. [2] With injured tissue, the body usually has a different response.
Simplified control circuit of human thermoregulation. [8]The core temperature of a human is regulated and stabilized primarily by the hypothalamus, a region of the brain linking the endocrine system to the nervous system, [9] and more specifically by the anterior hypothalamic nucleus and the adjacent preoptic area regions of the hypothalamus.
In normal skin, the rate of keratinocyte production equals the rate of loss, [4] taking about two weeks for a cell to journey from the stratum basale to the top of the stratum granulosum, and an additional four weeks to cross the stratum corneum. [2] The entire epidermis is replaced by new cell growth over a period of about 48 days. [13]
Bone tissue is removed by osteoclasts, and then new bone tissue is formed by osteoblasts. Both processes utilize cytokine (TGF-β, IGF) signalling.In osteology, bone remodeling or bone metabolism is a lifelong process where mature bone tissue is removed from the skeleton (a process called bone resorption) and new bone tissue is formed (a process called ossification or new bone formation).