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STRUCTURAL ORGANIZATION
Describing the anatomy and physiology of the human body according to the different hierarchical levels of its structural organization can greatly assist in explaining its functions. The five levels of organization help us to understand the anatomy and physiology of the body: Chemical > Cellular > Tissue > Organ > System > Organism (the body). body). Each subsequent level becomes increasingly complex. However, all levels function through the interaction of their constituent parts. In other words, chemical reactions contribute to cell function, cellular interactions contribute to tissue function, and so on. Chemical Chemical > Cellular > Tissue > Organ > System > Organism The chemical level is the most basic level of structural organization. The human body is made up of chemical elements called atoms. atoms. Oxygen, carbon, hydrogen, and nitrogen make up 96% of the body's mass. There are 22 other elements that also commonly occur in the human body, such as iron for example. Atoms Atoms comb combin ine e to fo form molecules, molecules, for example water, glucose, and DNA. The properties of different atoms, and therefore molecules, result in a wide array of chemical reactions, and this leads to a greater degree of complexity in the higher levels of structural organization. Cellular Chemical > Cellular > Tissue > Organ > System > Organism There are many different types of cells found in the body, such as sperm cells or nerve cells. The sum of the chemical reactions in a cell makes up its structure and function. Often these reactions are confined to specific regions within a cell, known as organelles. organelles. These are made of molecules organized into special functional units. Tissue Chemical > Cellular > Tissue > Organ > System > Organism There are four basic types of tissue grouped together by common features of structure and function: 1. Epithelial 2. Connective 3. Muscular Muscular 4. Nervous The function of a tissue is influenced not only by its constituent cells, but also by the extracellular material and intercellular connections. Organ Chemical > Cellular > Tissue > Organ > System > Organism An orga rgan is a structu structure re com compose posed d of two two or mo more diffe iffere ren nt type types of of tissu tissue e. Org Orga ans ha have spe specific cific functions and usually have recognizable shapes, such as the bean shape of a kidney. Organs found in the body include the heart, brain, stomach, skin, and bones.
System Chemical > Cellular > Tissue > Organ > System > Organism Related organs working for a common function is what constitutes a system. The digestive, nervous, and cardiovascular systems are all examples of this. A single organ however, can be part of one or more systems. For example, the pancreas belongs to both the endocrine and digestive systems. Some systems have organs that are in direct physical contact and thus function together, such as the organs of the digestive system, but others are related by functional or structural similarities and do not have direct contact, such as the glands that form the endocrine system.
