> [!cite] Citation > Biga, Lindsay M., ed. *Anatomy & Physiology*. 2nd edition. Oregon State University (2019). https://open.oregonstate.education/anatomy2e/. EPUB/ONLINE. > [!abstract] Description > This publication is adapted from [Anatomy & Physiology](https://openstax.org/details/books/anatomy-and-physiology-2e/) by [OpenStax](https://openstax.org/), licensed under [CC BY](https://creativecommons.org/licenses/by/4.0/). Icons by [DinosoftLabs](https://thenounproject.com/creator/dinosoftlab/) from [Noun Project](https://thenounproject.com/) are licensed under [CC BY](https://creativecommons.org/licenses/by/4.0/). Images from [Anatomy & Physiology](https://openstax.org/details/books/anatomy-and-physiology-2e/) by [OpenStax](https://openstax.org/) are licensed under [CC BY](https://creativecommons.org/licenses/by/4.0/), except where otherwise noted. --- ‘It is difficult to study structure (anatomy) without knowledge of function (physiology) and vice versa.’ [[Biga, Anatomy and Physiology, 2019|(Biga et al. 2019, chap. 1.1)]] ^209fe6 ‘All matter in the universe is composed of one or more unique pure substances called elements. Examples of these elements are hydrogen, oxygen, carbon, nitrogen, calcium, and iron.’ [[Biga, Anatomy and Physiology, 2019|(Biga et al. 2019, chap. 1.2)]] ^392992 ‘Higher levels of organization are built from lower levels. Therefore, molecules combine to form cells, cells combine to form tissues, tissues combine to form organs, organs combine to form organ systems, and organ systems combine to form organisms.’ [[Biga, Anatomy and Physiology, 2019|(Biga et al. 2019, chap. 1.2)]] ^281047 ‘The smallest unit of any of these pure substances (elements) is an atom.’ [[Biga, Anatomy and Physiology, 2019|(Biga et al. 2019, chap. 1.2)]] ^531fa6 ‘**Atoms** are made up of subatomic particles such as the proton, electron and neutron.’ [[Biga, Anatomy and Physiology, 2019|(Biga et al. 2019, chap. 1.2)]] ^806a50 ‘The terms sex and gender are often used interchangeably, but these terms have different contexts and meanings.’ [[Biga, Anatomy and Physiology, 2019|(Biga et al. 2019, chap. 27.0)]] ^33b30b ‘Although the sexual system is often described as a binary of male and female, in reality there is a spectrum of anatomical and chromosomal variation found in the human population including intersex as well as genitalia considered ambiguous at birth.’ [[Biga, Anatomy and Physiology, 2019|(Biga et al. 2019, chap. 27.0)]] ^af1151 ‘\[Human] sexual anatomy has a long history of surgical intervention such a circumcision, vasectomy, tubal ligation and more recently, sex reassignment surgery.’ [[Biga, Anatomy and Physiology, 2019|(Biga et al. 2019, chap. 27.0)]] ^fc5c27 ‘Two or more atoms combine to form a molecule, such as the water molecules, proteins, and sugars found in living things. **Molecules** are the chemical building blocks of all body structures.’ [[Biga, Anatomy and Physiology, 2019|(Biga et al. 2019, chap. 1.2)]] ^fdb10a ‘An organism is a living being that has a cellular structure and that can independently perform all physiologic functions necessary for life.’ [[Biga, Anatomy and Physiology, 2019|(Biga et al. 2019, chap. 1.2)]] ^086bf7 ‘Gender is socially constructed and operates as a way to identify and categorize certain behavioral, cultural, and psychological traits as belonging to specific groups of people.’ [[Biga, Anatomy and Physiology, 2019|(Biga et al. 2019, chap. 27.0)]] ^a92bf5