Stem cells are a special form of human life:
As well as believing in the reality of Forms, Plato believed in the immortality of the human soul. The soul was, he thought, an entity that was fundamentally distinct from the body although it could be and often was affected by… Chemical composition of the body Chemically, the human body consists mainly of water and of organic compounds —i.
Water is found in the extracellular fluids of the body the blood plasmathe lymphand the interstitial fluid and within the cells themselves. It serves as a solvent without which the chemistry of life could not take place.
The human body is about 60 percent water by weight. Lipids —chiefly fatsphospholipidsand steroids —are major structural components of the human body. Fats provide an energy reserve for the body, and fat pads also serve as insulation and shock absorbers.
Phospholipids and the steroid compound cholesterol are major components of the membrane that surrounds each cell. Proteins also serve as a major structural component of the body.
Like lipids, proteins are an important constituent of the cell membrane.
In addition, such extracellular materials as hair and nails are composed of protein. Proteins also perform numerous functional roles in the body. Particularly important are cellular proteins called enzymeswhich catalyze the chemical reactions necessary for life. Carbohydrates are present in the human body largely as fuels, either as simple sugars circulating through the bloodstream or as glycogena storage compound found in the liver and the muscles.
Small amounts of carbohydrates also occur in cell membranes, but, in contrast to plants and many invertebrate animals, humans have little structural carbohydrate in their bodies. Nucleic acids make up the genetic materials of the body.
It is DNA, passed from parents to offspring, that dictates the inherited characteristics of each individual human. Chief among these are calciumphosphorussodiummagnesiumand iron. Calcium is also present as ions in the blood and interstitial fluidas is sodium.
Ions of phosphorus, potassium, and magnesium, on the other handare abundant within the intercellular fluid. Iron is present mainly as part of hemoglobinthe oxygen-carrying pigment of the red blood cells.
Other mineral constituents of the body, found in minute but necessary concentrations, include cobaltcopperiodinemanganeseand zinc. Organization of the body The cell is the basic living unit of the human body—indeed, of all organisms.
The human body consists of trillions of cells, each capable of growth, metabolismresponse to stimuli, and, with some exceptions, reproduction. Although there are some different types of cells in the body, these can be grouped into four basic classes. These four basic cell types, together with their extracellular materials, form the fundamental tissues of the human body: Bone and blood are considered specialized connective tissues, in which the intercellular matrix is, respectively, hard and liquid.
The most basic unit is the cell; groups of similar cells form tissues; groups of different tissues make up organs; groups of organs form organ systems; cells, tissues, organs, and organ systems combine to form a multicellular organism.
The next level of organization in the body is that of the organ. An organ is a group of tissues that constitutes a distinct structural and functional unit. Thus, the heart is an organ composed of all four tissues, whose function is to pump blood throughout the body.
Of course, the heart does not function in isolation; it is part of a system composed of blood and blood vessels as well. The highest level of body organization, then, is that of the organ system.
The body includes nine major organ systems, each composed of various organs and tissues that work together as a functional unit. The chief constituents and prime functions of each system are summarized below. Basic form and development In general structure, the human body follows a plan that can be described as a cylinder enclosing two tubes and a rod.
This body plan is most clearly evident in the embryo ; by birth, the plan is apparent only in the trunk region—i. The body wall forms the cylinder. The two tubes are the ventrally located alimentary canal i. Between the tubes lies the rod—the notochord in the embryo, which becomes the vertebral column prior to birth.
The terms dorsal and ventral refer respectively to the back and the front, or belly, of an animal. Within the embryo, the essential body parts are: Everything in the body derives from one of these six embryonic parts.Enzymes are incredibly efficient and highly specific biological heartoftexashop.com fact, the human body would not exist without enzymes because the chemical reactions required to maintain the body simply would not occur fast enough.
The endocrine system includes all of the glands of the body and the hormones produced by those glands. The glands are controlled directly by stimulation from the nervous system as well as by chemical receptors in the blood and hormones produced by other glands. The liver is a large organ located in the upper right side of the abdomen, where it is found mostly underneath the ribs.
It plays a very important role in maintaining the body's overall health. Most of the blood leaving the intestines travels through the liver, where it is filtered of both toxic chemicals and bacteria.
The liver uses nutrients in the blood to provide energy for the body by. Human body: Human body, the physical substance of the human organism. Characteristic of the vertebrate form, the human body has an internal skeleton with a backbone, and, as with the mammalian form, it has hair and mammary glands.
Learn more about the composition, form, and physical adaptations of the human body. human stem cell research and experimentation: all sides to the debate. The endocrine system is made up of glands that produce and secrete hormones, chemical substances produced in the body that regulate the activity of cells or organs.
These hormones regulate the body's growth, metabolism (the physical and chemical processes of the body), and sexual development and.