An Introduction to the Human Body

By the end of this section, students should be able to:
- Compare and contrast anatomy and physiology.
- Discuss the fundamental relationship between anatomy and physiology.

Defined as the scientific study of the body's structures.
Structures vary in size:
- Some are small, observable only with a microscope.
- Others are larger, can be seen, manipulated, measured, and weighed.
Etymology:
- The word "anatomy" comes from a Greek root meaning "to cut apart".
Historical Study Methods:
- Early human anatomy studies included external observations and analyses of soldier injuries.
- With time, physicians were permitted to conduct dissections of deceased bodies to enhance knowledge.
- Dissection allowed for observing structures' attributes and their interrelationships.
Dissection remains vital in:
- Medical schools
- Anatomy courses
- Pathology labs.

Developed as a means to observe structures within living individuals.
Techniques allow visualization of internal structures, such as tumors and fractures.

Gross Anatomy:
- Studies larger structures visible without magnification.
- Also called macroscopic anatomy.
Microscopic Anatomy:
- Studies structures observable only with a microscope.
- Includes:
- Cytology: Study of cells.
- Histology: Study of tissues.
Technological Advancements:
- Improvements in microscopy have enabled observation of smaller biological structures.

Regional Anatomy:
- Will study the interrelationships of structures in a specific body region (e.g., the abdomen).
Systemic Anatomy:
- Examines the structures within discrete body systems working together for a specific function (e.g., muscular system).

Physiology is defined as:
- Scientific study of the chemistry and physics of body structures.
- Focused on how structures function cohesively to sustain life.
Foundational focus on homeostasis:
- Homeostasis: The state of steady internal conditions maintained by living entities.
Physiological study includes:
- Observation (naked eye and microscopes).
- Manipulations and measurements.
- Laboratory experiments to reveal functions of structures and chemical compounds in the body.
Like anatomists, physiologists often specialize in specific branches:
- Neurophysiology: Studies brain, spinal cord, and nerves for functions like vision and movement.

**Form and Function:
- Example:** The eyelid is structured for rapid movement, showcasing how anatomy supports function.
- The relationship underscores the significance of understanding physiology when studying anatomy.
For instance:
- Understanding the hand’s structure necessitates knowledge of its functional roles in people’s tool manipulation.

Basic building blocks of matter include:
- Subatomic Particles: Protons, electrons, neutrons.
- Atoms: Smallest unit of elements (e.g. hydrogen, oxygen, carbon).
- Molecules: Formed from two or more atoms (e.g. water, proteins).
Cells are the smallest independently functioning units of an organism; even single-celled organisms such as bacteria consist of one cell.
Human cellular structures typically contain:
- Flexible membranes enclosing cytoplasm and organelles performing life functions.

Tissue: A group of similar cells (sometimes different types) working together for a specific purpose.
Organ: Distinct body structure composed of two or more tissue types performing particular functions.
Organ System: A collection of organs working together to addressing physiological needs.
The human body comprises 11 distinct organ systems.

Definition: Process by which the body maintains a stable internal environment.
Set Point: Optimal physiological values around which normal ranges fluctuate.
Negative Feedback: Mechanism that opposes changes from the set point (e.g., insulin release for high blood glucose).
**Components of Negative Feedback Loop:
- Sensor:** Monitors a physiological value.
- Control Center: Compares the value to a normal range; activates effectors as necessary.
- Effector: Causes change to restore normal range.

Body temperature regulation:
- High temperature results in dilation of blood vessels and sweating to cool the body.
Positive Feedback: Amplifies change, leading the system further away from homeostasis; typical examples include childbirth and blood clotting processes.

Specialized terminology increases precision in anatomical descriptions and reduces errors.
Anatomical Position: Standardized position for anatomical reference; body standing upright, feet shoulder-width apart, palms facing forward.

Dorsal Cavity: Protects brain and spinal cord.
- Subdivided into cranial and spinal cavities.
Ventral Cavity: Contains thoracic and abdominopelvic cavities; accommodates organ expansion.
Serous Membranes: Thin membranes covering organs and lining cavities, minimizing friction during organ movement (e.g., pleura, pericardium, peritoneum).

Historical context of human anatomy studies includes limited knowledge until dissection became more accepted.
X-Rays:
- Discovered by Wilhelm Röntgen in 1895.
- Reveal hard structures (e.g., bones) through high energy electromagnetic radiation.
Computed Tomography (CT): Non-invasive imaging technique analyzing several cross-sectional X-rays for detailed visualization.
Magnetic Resonance Imaging (MRI): Uses magnetic fields and radio waves; not exposed to radiation; excellent for soft tissue visualization.
Positron Emission Tomography (PET): Visualizes organ function through radiopharmaceuticals.
Ultrasonography: High-frequency sound waves generate real-time images; least invasive imaging technique.

Understanding anatomy and physiology is foundational for healthcare and biological sciences.
Strong emphasis on the integration of form and function across various levels of complexity, emphasizing the importance of both disciplines in informing and understanding human biology.