Introduction to Anatomy & Physiology

Overview of Anatomy and Physiology

Anatomy and physiology are foundational sciences for understanding the structure and function of the human body. Anatomy focuses on the physical structures, while physiology examines how these structures operate to sustain life. The principle of complementarity states that structure and function are interdependent: the form of a structure is directly related to its function.

• Anatomy: Study of internal and external body structures and their relationships.

• Physiology: Study of how living organisms perform vital functions.

• Complementarity: Specific functions are performed by specific structures.

Specialties of Anatomy

• Gross (Macroscopic) Anatomy: Study of large structures visible to the naked eye.

• Regional Anatomy: Focuses on specific body areas.

• Systemic Anatomy: Examines organ systems.

• Microscopic Anatomy: Studies structures only visible with magnification.

• Cytology: Study of cells.

• Histology: Study of tissues.

Specialties of Physiology

• Cell Physiology: Functions of cells and their chemical processes.

• Organ Physiology: Functions of specific organs.

• Systemic Physiology: Functions of organ systems.

• Pathological Physiology: Effects of diseases on organs or systems.

Levels of Organization in the Human Body

Hierarchical Structure

The human body is organized into six major levels, from the simplest chemical components to the complex organism.

• Chemical Level: Atoms and molecules (e.g., protein molecules).

• Cellular Level: Cells, the smallest living units.

• Tissue Level: Groups of cells working together (epithelial, connective, muscle, neural).

• Organ Level: Two or more tissues working together (e.g., heart).

• Organ System Level: Groups of organs interacting for a particular function (e.g., cardiovascular system).

• Organism Level: The individual life form.

Anatomical Terminology

Anatomical Position and Body Regions

Standard anatomical position is used as a reference for describing locations and relationships of body parts. The body is upright, hands at the sides, palms facing forward, and feet together.

• Anterior (front) and Posterior (back) views

• Supine: Lying face up

• Prone: Lying face down

Abdominopelvic Quadrants and Regions

The abdominopelvic area is divided for clinical and anatomical purposes.

• Quadrants: Right Upper (RUQ), Left Upper (LUQ), Right Lower (RLQ), Left Lower (LLQ)

• Regions: Epigastric, Right/Left hypochondriac, Umbilical, Right/Left lumbar, Hypogastric, Right/Left inguinal

Directional Terms

Directional terms are used to describe the relative location of body regions and structures.

• Superior: Toward the head

• Inferior: Toward the lower part

• Anterior (ventral): Nearer to the front

• Posterior (dorsal): Nearer to the back

• Medial: Nearer to the midline

• Lateral: Farther from the midline

• Ipsilateral: Same side

• Contralateral: Opposite sides

• Proximal: Nearer to the point of attachment

• Distal: Farther from the point of attachment

• Superficial: Toward or on the surface

• Deep: Away from the surface

Sectional Anatomy and Medical Imaging

Sectional anatomy involves slicing through three-dimensional objects to visualize internal organization, important for interpreting medical scans.

• MRI: Noninvasive, uses magnetic fields and radio waves, no radiation.

• PET: Uses radioactive substances, diagnoses various conditions.

• X-ray: High-energy electromagnetic radiation, penetrates solids.

• CT: Cross-sectional X-rays analyzed by computers, higher radiation dose than X-rays.

Sectional Planes

Sectional planes are used to describe slices through the body:

• Frontal (coronal) plane: Divides body into anterior and posterior portions.

• Sagittal plane: Divides body into left and right portions.

  • Midsagittal: Lies in the middle.

  • Parasagittal: Offset from the middle.

• Transverse (horizontal) plane: Divides body into superior and inferior portions.

Body Cavities

Major Body Cavities and Their Functions

Body cavities are closed, fluid-filled spaces lined by serous membranes, containing vital organs (viscera) of the trunk. They protect organs and allow changes in size and shape.

• Serous membrane (serosa): Lines cavities and covers organs; consists of parietal (lines cavity) and visceral (covers organ) layers; serous fluid reduces friction.

Thoracic and Abdominopelvic Cavities

• Thoracic cavity: Divided from abdominopelvic cavity by diaphragm; contains pleural (lungs), pericardial (heart), and mediastinum (connective tissue stabilizing organs).

• Abdominopelvic cavity: Extends from diaphragm to pelvis; contains abdominal, pelvic, and peritoneal cavities.

• Retroperitoneal space: Area between parietal peritoneum and back of body wall; contains pancreas and kidneys.

• Pelvic cavity: Contains reproductive organs, rectum, and urinary bladder.

Homeostasis

Concept of Homeostasis

Homeostasis refers to the continuous physiological processes that maintain a stable internal environment. Systems respond to changes to keep variables within normal ranges (e.g., body temperature, blood pressure).

• Receptor: Sensor that detects stimulus or change.

• Control center: Receives and processes information, sends commands.

• Effector: Cell or organ that carries out commands.

• Set point: Desired value for a variable.

Negative and Positive Feedback

• Negative feedback: Regulation that opposes variation from normal; effector negates original stimulus, maintaining variables within a normal range.

• Positive feedback: Regulation that enhances variation from normal; response amplifies original change, used for rapid completion of processes (e.g., blood clotting).

Summary Table: Levels of Organization

Key Terms and Definitions

• Anatomy: Study of body structure

• Physiology: Study of body function

• Homeostasis: Maintenance of stable internal environment

• Serous membrane: Double-layered membrane lining cavities

• Feedback: Regulatory mechanism (negative or positive)

Example: Homeostatic Regulation Equation

Homeostatic regulation can be described mathematically as:

$\text{Variable}_{\text{new}} = \text{Variable}_{\text{old}} + \text{Response}_{\text{effector}}$

This equation shows how the effector's response adjusts the variable toward the set point.

Additional info:

• Scientific method is used in diagnosis: observation, hypothesis, experimentation.

• Sectional anatomy is essential for interpreting medical imaging techniques.