Introduction to Anatomy & Physiology: Organization, Terminology, and Body Systems

Introduction to Anatomy & Physiology

Definitions and Scope

• Anatomy: The study of the structure of body parts and their relationships to one another. The term derives from the Greek word meaning "to dissect."

• Physiology: The study of the function of the body parts; how they work to carry out life-sustaining activities.

• Pathophysiology: The branch of science that describes the consequences of the improper functioning of body parts, often relating to disease or injury.

Levels of Organization in the Human Body

Hierarchical Structure

The human body is organized into several levels, each building upon the previous one to form a complete organism.

• Cells: The basic structural and functional units of life.

• Tissues: Groups of similar cells that perform a specific function.

• Organs: Structures composed of two or more tissue types that perform specific functions.

• Organ Systems: Groups of organs that work together to perform complex functions.

• Organism: The complete living being, composed of all organ systems working together.

Major Organ Systems

Overview of Human Organ Systems

The body contains several major organ systems, each with specialized functions essential for survival.

1. Integumentary System: Consists of the skin and related structures such as hair and nails. Provides protection, regulates temperature, and prevents water loss.

2. Skeletal System: Composed of bones, joints, and cartilage. Forms the framework of the body, supports movement, and protects internal organs.

3. Muscular System: Includes three types of muscle tissue:

   • Skeletal muscle: Voluntary movement.

   • Cardiac muscle: Found only in the heart, involuntary.

   • Smooth muscle: Involuntary, found in walls of internal organs.

4. Nervous System: Consists of the brain, spinal cord, and nerves. Responsible for control, coordination, and communication throughout the body.

5. Endocrine System: Composed of glands that secrete hormones, regulating processes such as growth, metabolism, and reproduction.

6. Circulatory (Cardiovascular) System: Includes the heart and blood vessels. Transports nutrients, gases, hormones, and wastes throughout the body.

7. Lymphatic System: Consists of lymph nodes, lymphatic vessels, and lymph. Important in immune defense and fluid balance.

8. Respiratory System: Composed of the lungs and respiratory tubes. Responsible for gas exchange (oxygen and carbon dioxide).

9. Digestive System: Includes organs designed to ingest food, break it down into absorbable units, and eliminate waste.

10. Urinary System: Consists of kidneys and other structures that remove waste products from the blood and excrete them as urine.

11. Reproductive System: Composed of organs that enable humans to reproduce.

Homeostasis

Maintaining Internal Balance

• Homeostasis: The maintenance of a stable internal environment despite changes in external conditions.

• Essential for normal body function and survival.

Anatomical Position

Standard Reference Position

• The body is standing upright, facing forward, arms at the sides with palms facing forward, and feet parallel.

• This position is used as a reference in describing the relation of body parts to one another.

Directional Terms

Describing Locations and Relationships

• Superior: Toward the head or upper part of a structure.

• Inferior: Away from the head or toward the lower part of a structure.

• Anterior (Ventral): Toward the front of the body.

• Posterior (Dorsal): Toward the back of the body.

• Medial: Toward the midline of the body.

• Lateral: Away from the midline of the body.

• Proximal: Closer to the point of attachment or origin.

• Distal: Farther from the point of attachment or origin.

• Superficial: Toward or at the body surface.

• Deep: Away from the body surface; more internal.

• Central: Located near the center of the body or an organ.

• Peripheral: Away from the center of the body or an organ.

• Ipsilateral: On the same side of the body.

• Contralateral: On the opposite side of the body.

Planes and Sections of the Body

Dividing the Body for Study

• Sagittal Plane: Divides the body into right and left portions. A midsagittal plane divides the body into equal right and left halves.

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

• Transverse (Horizontal) Plane: Divides the body into superior (upper) and inferior (lower) portions. Additional info: This plane is sometimes called the axial plane.

Regional Terms

Specific Areas of the Body

• Abdominal: Abdomen

• Antecubital: Front of the elbow

• Antebrachial: Forearm

• Axillary: Armpit

• Brachial: Arm

• Buccal: Cheek

• Carpal: Wrist

• Caudal: Toward the tail or inferior end

• Cephalic: Head

• Cervical: Neck

• Cranial: Skull

• Deltoid: Shoulder

• Digital: Fingers or toes

• Femoral: Thigh

• Gluteal: Buttock

• Inguinal: Groin

• Lumbar: Lower back

• Occipital: Back of the head

• Oral: Mouth

• Orbital: Eye socket

• Patellar: Front of the knee

• Pedal: Foot

• Popliteal: Back of the knee

• Pubic: Genital region

• Scapular: Shoulder blade

• Sternal: Breastbone

• Tarsal: Ankle

• Umbilical: Navel

• Vertebral: Spinal column

Cavities of the Body

Major Body Cavities and Their Subdivisions

• Dorsal Cavity: Located toward the back of the body.

  • Cranial cavity: Contains the brain.

  • Spinal cavity: Contains the spinal cord.

• Ventral Cavity: Located toward the front of the body.

  • Thoracic cavity: Contains the heart and lungs.

    • Mediastinum: Central compartment of the thoracic cavity, contains the heart, trachea, and esophagus.

    • Pleural cavity: Surrounds each lung.

  • Abdominopelvic cavity: Subdivided into:

    • Abdominal cavity: Contains digestive organs.

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

Feedback Mechanisms

Regulation of Body Processes

• Negative Feedback: A mechanism that reverses a deviation from the set point; maintains homeostasis. Example: Regulation of body temperature.

• Positive Feedback: A mechanism that amplifies a change; usually leads to a specific event. Example: Blood clotting or childbirth contractions.