Introduction to Anatomy and Physiology

Anatomy is the study of the structures that make up the body and how those structures relate to each other. The term originates from the Greek meaning "to cut up." Anatomy is divided into gross anatomy (structures visible without a microscope) and microscopic anatomy (structures visible only with a microscope). Physiology is the study of how the body functions and carries out the activities of life.

Levels of Organization

Hierarchy of Structural Organization

The human body is organized into several levels, each building upon the previous:

• Atoms: The smallest units of matter; combine to form molecules.

• Molecules: Combinations of atoms; form the chemical building blocks of cells.

• Cells: The smallest living units in the body; contain organelles formed from molecules.

• Tissues: Groups of similar cells performing a specific function. Four main types:

  • Epithelial

  • Connective

  • Muscular

  • Nervous

• Organs: Structures composed of two or more tissue types working together (e.g., kidney, liver, brain, heart).

• Organ Systems: Groups of organs working together to perform related functions (e.g., respiratory system, cardiovascular system).

• Organism: The complete living being (e.g., a human), composed of multiple organ systems.

Organ Systems of the Human Body

Overview of Major Organ Systems

The body is organized into several major organ systems, each with specific structures and functions:

• Integumentary System: Skin, hair, nails, and exocrine glands (sweat and sebaceous glands).

• Skeletal System: Bones, cartilage, tendons, ligaments.

• Muscular System: Skeletal muscles, smooth muscles, cardiac muscle.

• Nervous System: Central nervous system (brain and spinal cord) and peripheral nervous system.

• Endocrine System: Pituitary, thyroid, parathyroid, pineal, adrenal glands, pancreas, ovaries, testes.

• Cardiovascular System: Heart, blood vessels, and blood.

• Lymphatic System: Lymphatic vessels, nodes, spleen, thymus.

• Respiratory System: Lungs, alveoli, bronchi, trachea, larynx, pharynx, nasal cavity, diaphragm.

• Digestive System: Oral cavity, pharynx, esophagus, stomach, small and large intestines, liver, pancreas, gallbladder.

• Urinary System: Kidneys, ureters, urinary bladder, urethra.

• Reproductive System:

  • Male: Testes, prostate gland, Cowper’s glands, seminal vesicles, ductus deferens, penis.

  • Female: Ovaries, uterine tubes, uterus, vagina.

Anatomical Position and Body Orientation

Standard Anatomical Position

The anatomical position is the standard reference for describing body parts and positions:

• Standing upright, feet together, arms at sides, palms facing forward.

• Supine: Lying face up in anatomical position.

• Prone: Lying face down in anatomical position.

• Axial: Refers to the head, chest, abdomen, and pelvis.

• Appendicular: Refers to the limbs (arms and legs).

• Right/Left: Always refers to the subject's right or left, not the observer's.

Anatomical Directions

Directional Terms

Directional terms are used to describe the locations of structures relative to other structures or locations in the body:

• Superior (cranial): Above; toward the head (e.g., the leg is superior to the foot).

• Inferior (caudal): Below; toward the feet (e.g., the foot is inferior to the leg).

• Anterior (ventral): Toward the front (e.g., the nose is anterior to the ears).

• Posterior (dorsal): Toward the back (e.g., the ears are posterior to the nose).

• Medial: Toward the midline (e.g., the heart is medial to the lungs).

• Lateral: Away from the midline (e.g., the eyes are lateral to the nose).

• Proximal: Nearer to the trunk or point of attachment (e.g., the elbow is proximal to the wrist).

• Distal: Farther from the trunk or point of attachment (e.g., the ankle is distal to the knee).

• Superficial (external): Nearer to or on the surface (e.g., the skin is superficial to the muscles).

• Deep (internal): Farther from the surface (e.g., the muscles are deep to the skin).

Anatomical Landmarks

Common and Anatomical Terms

Many body regions have both common and anatomical names. The following table summarizes key landmarks:

Planes of the Body

Body Planes and Sections

Body planes are imaginary lines used to divide the body for anatomical study:

• Transverse Plane (cross section): Divides the body into superior (upper) and inferior (lower) sections.

• Sagittal Plane: Divides the body into left and right halves.

• Midsagittal Plane: Divides the body into equal left and right halves.

• Parasagittal Plane: Divides the body into unequal left and right halves.

• Frontal (Coronal) Plane: Divides the body into anterior (front) and posterior (back) portions.

Body Cavities

Major Body Cavities and Their Contents

The body contains several major cavities that house and protect internal organs:

• Dorsal Cavity:

  • Cranial cavity: Contains the brain.

  • Spinal cavity: Contains the spinal cord.

• Ventral Cavity:

  • Thoracic cavity:

    • Pleural cavities: Surround the left and right lungs.

    • Pericardial cavity: Surrounds the heart.

    • Mediastinum: Partition area between the lungs.

  • Abdominopelvic (peritoneal) cavity:

    • Abdominal cavity: Contains digestive organs and many glands.

    • Pelvic cavity: Contains urinary bladder and reproductive organs.

Note: The thoracic and abdominal cavities are separated by the diaphragm.

Abdominopelvic Quadrants and Regions

Quadrants

The abdominopelvic area is divided into four quadrants for clinical reference:

• Right Upper Quadrant (RUQ)

• Left Upper Quadrant (LUQ)

• Right Lower Quadrant (RLQ)

• Left Lower Quadrant (LLQ)

Regions

For more precise localization, the abdominopelvic area is divided into nine regions:

• Right hypochondriac region

• Epigastric region

• Left hypochondriac region

• Right lumbar region

• Umbilical region

• Left lumbar region

• Right inguinal (iliac) region

• Hypogastric (pubic) region

• Left inguinal (iliac) region

Laboratory Application: Identifying Organs and Systems

Muscle Man and Torso Model

Students should be able to identify the following organs on anatomical models and state their corresponding organ systems:

Summary

• Understanding the levels of organization, anatomical terminology, and body orientation is foundational for studying human anatomy and physiology.

• Familiarity with organ systems and their major components is essential for identifying structures in laboratory settings.

• Mastery of anatomical directions, planes, and body cavities enables precise communication in clinical and academic contexts.

Additional info: For laboratory practice, students are encouraged to use interactive models and digital resources such as Practice Anatomy Lab (PAL) 4.0 to reinforce identification skills.