CHAP 1 Human Body Structure and Function

Introduction to the Human Body

• Studies of normal body structures and functions provide the foundation for medical sciences.

• Understanding the normal is essential to analyze diseases.

• This chapter introduces general scientific concepts relevant to the human body.

Anatomy and Physiology

• Anatomy: Study of the structure of the body; derived from Latin meaning "cutting" (dissection).

• Physiology: Study of how the body functions; "physio" means nature; "logic" means study.

• Anatomy and physiology are interrelated:

  • Example: The stomach’s shape is ideal for storing food due to its anatomical features, which also protect underlying tissues from digestive juices.

Levels of Organization

• Living organisms are structured from simple to complex levels:

  • Chemical Level: From water and salts to complex molecules (sugars, fats, proteins).

  • Cellular Level: Basic unit of life; specialized groups of cells form tissues (e.g., muscle, connective tissue).

  • Tissue Level: Groups of similar cells working together.

  • Organ Level: Organs consist of different tissues (e.g., the stomach has muscle and connective tissue).

  • System Level: Groups of organs working together (e.g., digestive system).

  • Organism Level: All systems combine to form a complete organism.

Body Systems

1. Integumentary System: Protects body; includes skin, hair, nails, sweat glands, and oil glands.

2. Skeletal System: Framework of 206 bones; supports and protects organs.

3. Muscular System: Attached muscles enable movement, maintain posture, and protect organs.

   • Types of muscles: skeletal, smooth (in organs), and cardiac (in heart).

4. Nervous System: Comprises the brain, spinal cord, and nerves; coordinates body activities.

5. Endocrine System: Glands (e.g., thyroid, pituitary) that secrete hormones for growth, metabolism, and reproduction.

6. Cardiovascular System: Includes heart and blood vessels; transports nutrients and wastes throughout the body.

7. Lymphatic System: Returns fluids to blood, plays a role in immunity (includes organs like spleen and tonsils).

8. Respiratory System: Facilitates gas exchange; includes lungs and airways.

9. Digestive System: Processes nutrients; includes mouth, stomach, intestines, and accessory organs (e.g., liver, pancreas).

10. Urinary System: Removes waste products and regulates fluid balance; includes kidneys, bladder.

11. Reproductive System: Consists of external and internal organs for offspring production.

Homeostasis

• Maintenance of a stable internal environment despite external changes (internal balance).

• Regulated Variables: Must remain within narrow ranges (temperature, blood pressure, etc.).

Negative Feedback Mechanism

• Primary method for maintaining homeostasis.

• Components of a negative feedback loop:

  1. Sensor: Detects changes in the regulated variable.

  2. Control Center: Compares input from sensor to a set point.

  3. Effector: Acts to restore the variable to its set point.

• Example: Body temperature regulation (thermostat analogy).

  • If temperature deviates from the set point, responses (like sweating or shivering) are activated to restore homeostasis.

Barriers and Fluid Distribution

• Body maintains homeostasis against external factors; skin acts as the primary barrier.

• Internal environment consists of intracellular fluid (inside cells) and extracellular fluid (outside cell environment).

Body Directions and Terms

• Standard anatomical position: Upright, facing front, arms at sides, palms forward.

• Directional Terms:

  • Superior: Above (e.g., heart above intestines).

  • Inferior: Below.

  • Anterior/Ventral: Front.

  • Posterior/Dorsal: Back.

  • Medial: Closer to the midline.

  • Lateral: Further from the midline.

  • Proximal: Closer to the origin/attachment.

  • Distal: Further from the origin/attachment.

Planes of Division

• Divisions to visualize internal structures:

  • Frontal: Divides into anterior and posterior.

  • Sagittal: Divides into right and left.

  • Transverse: Divides into superior and inferior.

Medical Imaging Techniques

1. Radiography: Uses X-rays to visualize internal structures; best for dense tissues like bones.

2. Computed Tomography (CT): Advanced imaging that provides detailed images of soft tissues.

3. Magnetic Resonance Imaging (MRI): Uses magnetic fields and radio waves for high-resolution soft tissue images.

Body Cavities

• Dorsal Cavity: Includes cranial cavity (brain) and spinal cavity (spinal cord).

• Ventral Cavity: Larger than dorsal; subdivided into thoracic cavity (heart, lungs) and abdominopelvic cavity.

  • Abdominal Cavity: Contains digestive organs.

  • Pelvic Cavity: Contains urinary and reproductive organs.

Medical Terminology

• Specialized vocabulary in health care:

  • Root: Main part of the word.

  • Prefix: Beginning of the word that modifies the root.

  • Suffix: Ending that modifies the root.

• Example: "gastrointestinal" combines root "gastro-" (stomach) with other components.

Conclusion

• Understanding body systems, homeostasis, and anatomical terminology is critical for further studies in anatomy and physiology.

• Negative feedback mechanisms are essential for maintaining health.

• Familiarity with medical imaging and body cavities aids in clinical assessments.