The Human Body (part 1)

The Cell All mammals, including humans, are made up of basic building blocks called cell. Although many different types of cells are known, they differ according to function, they are all similar in their basic constituents. The different types of cell perform different jobs, so have different gross structures. The size of cells also varies, ranging from 200 nanometers to several centimeters in length. Most cells, however, fall within the range of 0.5 to 20 micrometers. The cell contains material used in chemical reactions that keep the cell functioning. It is surrounded by a semipermeable membrane. This membrane not only contains the cell material but also allows selective passage of metrials in and out of the cell. There may also be membrane structures inside of the cell that compartmentalized the various chemical reaction taking place. The structure of most cells includes a nucleus inside of the cell, separated from the surrounding cytoplasm by its own membrane. The nulceus contains the genetic coding or reproducible cells. Cells in the human body are quite numerous. It has been estimated that are approximately 75 trillion cells in the body, of which one-third (25 trillion) are red blood cells. The red blood cells are responsible for transporting oxygen to body tissues. Body Fluids The body is almost two-third fluid (actually, approximately 56 percent). Intracellular fluid contains large concentrations of potassium (K/Kalium), magnesium (Mg), and phosphat ion (PO4), while the extracellular fluid contains significant concentrations of sodium (Na/natrium), chloride (Cl), bicarbonat ions (HCO3), oxygen (O2), amino acids, glucose (CH12O6), and carbon dioxide (CO2). Musculoskeletal System The muscles and bones of the body provide locomotion, that is, the ability to move around and manipulate our surroundings. If it were not for locomotion, humans would be more dependent on the local environment. The human would not be able to move to avoid danger, find food and water, or erect shelter from the elements. Respiratory System The respiratory system takes oxygen into the body and gives off carbon dioxide waste products from the cells. The respiratory system includes the mouth, nose, trachea, or "wind pipe", bronchii, and the lungs. Deoxygenated blood from the right side of the heart passes through the lungs such that only 0.4 to 2.0 microns of membrane separates the air-carrying alveoli from pulmonary capillaries (i.e. tiny blood vessels). Gaseous oxygen diffuses across this membrane into the blood stream, while carbon dioxide comes out of the blood, into the alveoli, to be exhaled into the atmosphere.