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- Skeletal system. The skeletal system is composed of bones and cartilages. There are two parts of the skeleton; axial and appendicular. The axial skeleton consists of the bones of the head and trunk.
- Muscular system. The muscular system consists of all the body muscles. There are three muscle types; smooth, cardiac and skeletal muscles. Smooth muscle is found within walls of blood vessels and hollow organs such as the stomach or intestines.
- Cardiovascular system. The cardiovascular system is comprised of the heart and the circulatory system of blood vessels. The heart is composed of four chambers; two atria and two ventricles.
- Respiratory system. The respiratory system consists of a series of organs; the nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles and lungs (alveoli).
- Overview
- Chemical composition of the body
- Organization of the body
Chemically, the human body consists mainly of water and organic compounds—i.e., lipids, proteins, carbohydrates, and nucleic acids. The human body is about 60 percent water by weight.
What are the four main types of tissue in the human body?
The four main types of tissue in the human body are epithelial, muscle, nerve, and connective.
What are the nine major organ systems in the human body?
The nine major organ systems in the human body are the integumentary system, the musculoskeletal system, the respiratory system, the circulatory system, the digestive system, the excretory system, the nervous system, the endocrine system, and the reproductive system.
human body, the physical substance of the human organism, composed of living cells and extracellular materials and organized into tissues, organs, and systems.
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. 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 fats, phospholipids, and 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. So also is collagen, the fibrous, elastic material that makes up much of the body’s skin, bones, tendons, and ligaments. Proteins also perform numerous functional roles in the body. Particularly important are cellular proteins called enzymes, which 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 glycogen, a 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. Deoxyribonucleic acid (DNA) carries the body’s hereditary master code, the instructions according to which each cell operates. It is DNA, passed from parents to offspring, that dictates the inherited characteristics of each individual human. Ribonucleic acid (RNA), of which there are several types, helps carry out the instructions encoded in the DNA.
Along with water and organic compounds, the body’s constituents include various inorganic minerals. Chief among these are calcium, phosphorus, sodium, magnesium, and iron. Calcium and phosphorus, combined as calcium-phosphate crystals, form a large part of the body’s bones. Calcium is also present as ions in the blood and interstitial fluid, as is sodium. Ions of phosphorus, potassium, and magnesium, on the other hand, are abundant within the intercellular fluid. All of these ions play vital roles in the body’s metabolic processes. Iron is present mainly as part of hemoglobin, the oxygen-carrying pigment of the red blood cells. Other mineral constituents of the body, found in minute but necessary concentrations, include cobalt, copper, iodine, manganese, and zinc.
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, metabolism, response to stimuli, and, with some exceptions, reproduction. Although there are some 200 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:
1.epithelial tissues, which cover the body’s surface and line the internal organs, body cavities, and passageways
2.muscle tissues, which are capable of contraction and form the body’s musculature
3.nerve tissues, which conduct electrical impulses and make up the nervous system
4.connective tissues, which are composed of widely spaced cells and large amounts of intercellular matrix and which bind together various body structures
Bone and blood are considered specialized connective tissues, in which the intercellular matrix is, respectively, hard and liquid.
- The Editors of Encyclopaedia Britannica
- Cardiovascular system. The heart and blood vessels make up this system. The heart is a pump forcing blood into a network of blood vessels allowing it to travel to organs and delivery sites requiring oxygen gas for respirationnutrients and the removal of waste substances.
- Digestive system. This system resembles a long tube with attached organs. Ingested food is broken down into constituent nutrient molecules that are then absorbed into the bloodstream.
- Endocrine system. Composed of a number of small organs distributed throughout the body, the endocrine system coordinates the metabolic activity of body cells by interacting with the nervous system.
- Excretory system. The excretory system is composed of the kidneys (urine-forming organs), the bladder (temporary storage for urine) and channels for moving this liquid waste around.
Apr 5, 2024 · Skeletal: Our bodies are supported by the skeletal system, which contains between 206 and 213 bones in an adult human body, due to slight variations in people's anatomy, according to the medical ...
The human body is structured as a hierarchy of increasingly complex levels. The most basic unit in the hierarchy is the cell. Groups of similar cells form tissues. Groups of different tissues make up organs. Groups of organs are integrated into organ systems. Together, cells, tissues, organs, and organ systems form a multicellular organism.
It gives the body basic structure and the ability for movement. In addition to their structural role, the larger bones in the body contain bone marrow, the site of production of blood cells. Also, all bones are major storage sites for calcium and phosphate. This system can be split up into the muscular system and the skeletal system. [34 ...
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The human body is an incredibly complex structure, with cells, tissues, and organs assembled into highly organized systems that work together to perform an astonishing array of functions—from seeing and hearing to breathing and digesting food to running, playing a musical instrument, and problem-solving. Each of the major systems of the body is essential to the survival of the human organism ...
