Introduction to Human Anatomy and Physiology

Definition of Human Anatomy: Human anatomy is the scientific study of the body's structures.
Etymology: The word "anatomy" is derived from a Greek root that means "to cut apart."
Scale of Observations: * Some structures are very small and can only be observed and analyzed with the assistance of a microscope. * Other larger structures can be easily seen, manipulated, measured, and weighed.
Historical Development of Anatomy: * Initial studies were conducted by observing the exterior of the body and examining injuries and wounds, such as those sustained by soldiers. * Later, physicians were permitted to perform dissections on the bodies of the dead to expand their anatomical knowledge.
Dissection: * Dissection involves cutting structures apart to observe their physical attributes and their spatial relationships to one another. * The practice remains a standard in medical schools, anatomy courses, and pathology laboratories.
Clinical Imaging Techniques: * Modern imaging techniques allow clinicians to visualize structures within the living body without dissection. * Examples of structures visualized in vivo include cancerous tumors and fractured bones.

Gross Anatomy (Macroscopic Anatomy): * The prefix "macro-" means "large." * Gross anatomy is the study of larger structures of the body that are visible without the aid of magnification. * Example: The study of the brain (Figure 1.2 a).
Microscopic Anatomy: * The prefix "micro-" means "small." * This field is the study of structures that can only be observed with the use of a microscope or other magnification devices. * With the advancement of microscope technology, anatomists can observe structures ranging from slices of large organs (like the heart) to the three-dimensional structures of large molecules. * Cytology: A sub-discipline of microscopic anatomy focusing specifically on the study of cells. * Histology: A sub-discipline of microscopic anatomy focusing specifically on the study of tissues. * Micrograph Detail: A micrograph of nerve cells from the brain is cited with a magnification of $LM \times 1600$ .

Regional Anatomy: * This approach involves the study of the interrelationships of all structures located within a specific body region. * Example: The study of the abdomen. * Regional anatomy helps researchers and students appreciate how different structures, such as muscles, nerves, and blood vessels, work together to serve a specific part of the body.
Systemic Anatomy: * This approach focuses on the structures that comprise a discrete body system. * A body system consists of a group of structures that work together to perform a unique body function. * Example: A systemic study of the muscular system would involve considering every skeletal muscle in the human body.

Definition of Human Physiology: Physiology is the scientific study of the chemistry and physics of the structures of the body and how they collaborate to support the functions of life.
Focus on Homeostasis: A primary focus of the study of physiology is the body's tendency toward homeostasis. * Definition of Homeostasis: The state of steady internal conditions maintained by living things.
Methods of Physiological Research: * Physiology encompasses observations made both with the naked eye and with microscopes. * It involves manipulations and precise measurements. * Current advancements in the field generally rely on carefully designed laboratory experiments intended to reveal the functions of specific structures and chemical compounds.
Specialization in Physiology (Neurophysiology): * Neurophysiology is the study of the brain, spinal cord, and nerves. * It examines how these structures work together to perform complex functions such as vision, movement, and thinking.
Levels of Physiological Analysis: * Researchers may work at the organ level (e.g., exploring the functions of different brain regions). * Researchers may work at the molecular level (e.g., exploring how electrochemical signals travel along nerves).

General Principle: In all living things, form is closely related to function. Anatomical study is most effective when the form of a structure is continually related to the function it supports.
Example: The Eyelid: * Macroscopic Level: The eyelid is a thin flap that can snap down to clear away dust particles and retreat almost instantaneously to allow for vision. * Microscopic Level: This quick action and retreat are made possible by the specific arrangement and function of the nerves and muscles serving the eyelid. * Molecular Level: The function of these nerves and muscles depends on the interactions of specific molecules and ions, where even the three-dimensional structure of molecules is essential to their function.
Example: The Human Hand: * It is difficult to appreciate the unique arrangement of bones in the human hand without understanding its function. * The hand's ability to manipulate tools (e.g., pens, cell phones) is rooted in the unique alignment of the thumb in opposition to the four fingers. * This specific structural arrangement (opposition) allows for the ability to pinch and grasp objects and perform tasks like typing text messages.