Anatomy | Research & Encyclopedia Articles

Anatomy

Anatomy is the study of the structure of plants and animals. This study can be divided into two fields, gross anatomy (or macroscopic anatomy) and microscopic anatomy. Gross anatomy focuses on the study of structures which can be seen by the naked eye. Microscopic anatomy can be further subdivided into histology, which is the study of tissues, and cytology, which is the study of cells.

Study of gross anatomy began much earlier than that of microscopic anatomy, which could not develop until the invention of the microscope. A primitive study of anatomy began with the teachings of Aristotle, who argued that each organ had its own function, which could be determined by observing its structure. The first school of anatomy was found later in the third century B.C. by Herophilius of Chalcedon, who encouraged his students to dissect human bodies. Herophilus is credited both with determining that the brain controls the nervous system and with distinguishing between voluntary and involuntary nerves. Another Greek physician from the same century, Erasistratus, also performed human dissections and described theories relating the arteries with the lungs, the direction of circulation from the veins to the arteries, and described the functions of the trachea and epiglottis. The Greek physician Galen (c. 130-200B.C.) correlated the works of Aristotle and other early physicians with his own experiments and animal dissections. He is credited with showing that arteries carry blood and not air, discovering the function of the kidneys, and adding to general knowledge of the nervous system. Unfortunately, his work was undisputed for years which hampered further discoveries in the field of anatomy for centuries.

The first post-classical medical schools in the West were founded in the Middle Ages, although researchers trusted the Greek medical texts before their own dissections. With the Renaissance came a renewed interest in anatomy. Leonardo da Vinci studied the muscular structure of humans and animals in his artwork. The first truly systematic studies of the human body began shortly thereafter, but were discouraged due to religious conflicts concerning the morality of dissecting human bodies. Andreas Vesalius was considered one of the founders of modern anatomy with his work On the Structure of the Human Body in 1543, only to be rewarded a death sentence during the Inquisition for his work. His advances lived on in his students, such as Michael Servetus, who discovered pulmonary circulation; and Realdo Columbus, who actually coined the term circulation.

The seventeenth century brought about many discoveries in gross anatomy with the founding of several medical schools and many advances in technology. Human dissections were common in medical schools and an understanding of human anatomy was well under way. The invention of the compound microscope at this time brought about the study of microscopic anatomy. Marcello Malpighi observed the movement of blood through capillaries and studied lung and gland structure. Anthoni van Leewenhoek helped discover microorganisms. Jan Swammerdam observed red blood cells and Robert Hooke coined the term cell. These discoveries led to the cell theory in the eighteenth and nineteenth centuries and served as a basis for the modern study of anatomy.

An underlying theme in the study of anatomy which has led to many of the modern theories is that structure is almost always related to function. For example, the structure of a bird's beak is related to the kind of food it eats, whether it picks berries or cracks open seeds. Another example is the structure of white blood cells. These cells have tiny projections on their surface, which helps them "grab" microorganisms, viruses, and cell particles which are then destroyed. The study of the structure of plants and animals, and how this structure is related to function, led to the branch of anatomy known as comparative anatomy.

Comparative anatomy is used to test Charles Darwin's theory of evolution. Many studies in comparative anatomy have provided strong evidence for this theory. Structures in different organisms are compared, and organisms with more similar structures are considered to be more closely related evolutionarily. Comparative anatomy helps classify organisms into taxonomic categories and makes it possible to construct evolutionary trees. Structures that are studied are classified as either homologous or analogous. Homologous structures are the same in evolutionary origin, although presently are different in structure and function. Examples of homologous structures are the forelimbs in the wing of a bat, the fin of a porpoise, and the leg of a horse. Analogous structures have similar structure and function but different evolutionary origins, for example the eyes of vertebrates and octopuses. Another structure which an organism may have is a vestigial organ, which is underdeveloped and perhaps useless in an organism, but may be fully developed and functional in related organisms. An example of a vestigial organ is the human appendix.

The study of human anatomy has led to extensive knowledge about the many systems of the human body. The systems that are studied in human anatomy are: the endocrine system, which includes the hormone-releasing glands; the reproductive system, which includes the structures involved in the production of offspring; the skeletal system, which includes the bones of the body; the urinary system, or those structures concerned with the excretion of waste from the body; the digestive system, which consists of those organs which break down food into useable energy for the body; the circulatory system, which consists of the heart and blood vessels; the lymphatic system, which helps defend the body against invasion by disease-causing agents; the muscular system, which includes the muscles of the body; and the nervous system, which controls the actions and reactions of the body. Developments in microscopic techniques have led to significant understanding of human anatomy on both a gross and a cellular level.