Chapter 1 – The Human Body: An Orientation (Anatomy & Physiology Study Notes)

Chapter 1 – The Human Body: An Orientation

Anatomy vs. Physiology

Anatomy and physiology are foundational sciences in understanding the human body. Anatomy focuses on the structure of body parts, while physiology examines their function. The two are closely linked by the principle of complementarity, which states that structure and function are interdependent.

• Anatomy: Study of body structure (gross, microscopic, developmental).

• Physiology: Study of body function (e.g., cardiovascular, renal physiology).

• Principle of Complementarity: Structure determines function and vice versa.

Levels of Organization

The human body is organized in a hierarchical manner, from the simplest chemical level to the complex organismal level.

1. Chemical: Atoms and molecules

2. Cellular: Cells and organelles

3. Tissue: Similar cells together

4. Organ: Two or more tissues

5. Organ system: Organs working together

6. Organism: The human body as a whole

11 Organ Systems

The body is composed of eleven organ systems, each with specific functions essential for survival.

• Integumentary: Skin, nails, hair; protection, vitamin D synthesis, sensory reception.

• Skeletal: Bones; support, movement, mineral storage, blood formation.

• Muscular: Muscles; movement, posture, heat production.

• Nervous: Brain, spinal cord, nerves; fast control, response to changes.

• Endocrine: Glands; slow control, hormones, growth, metabolism.

• Cardiovascular: Heart, blood vessels; transport oxygen, CO2, nutrients, waste.

• Lymphatic/Immune: Lymph nodes, spleen; fight infection, return fluid to blood.

• Respiratory: Lungs; oxygen in, CO2 out.

• Digestive: Stomach, intestines; break food into nutrients.

• Urinary: Kidneys, bladder; remove nitrogen waste, balance water.

• Reproductive: Testes/ovaries; make offspring.

Necessary Life Functions

To maintain life, the body must perform several essential functions.

• Boundaries: Skin, membranes (separate internal from external environment).

• Movement: Muscles, food, blood.

• Responsiveness: Sense and respond to changes (stimuli).

• Digestion: Break down food for absorption.

• Metabolism: All chemical reactions in the body (anabolism + catabolism).

• Excretion: Removal of wastes (feces, urine, CO2).

• Reproduction: Production of cells and offspring.

• Growth: Increase in size and number of cells.

Survival Needs

The body requires certain materials and conditions to survive.

• Nutrients: Food, vitamins, minerals.

• Oxygen: Required for energy production.

• Water: Most abundant substance in the body.

• Normal body temperature: Affects chemical reactions.

• Atmospheric pressure: Needed for breathing.

Homeostasis

Homeostasis is the body's ability to maintain a stable internal environment despite external changes. It is regulated by feedback systems.

• Parts of control system:

  • Receptor: Detects change.

  • Control Center: Determines set point and response.

  • Effector: Carries out the response.

• Negative feedback: Reverses change (e.g., sweating when hot).

• Positive feedback: Strengthens change (e.g., labor contractions, blood clotting).

Anatomical Terms

Standard anatomical terms describe body positions, directions, and regions to avoid confusion.

• Position: Anatomical position is standing, palms forward, feet apart.

• Directional terms:

  • Superior/Inferior: Above/below

  • Anterior/Posterior: Front/back

  • Medial/Lateral: Toward/away from midline

  • Proximal/Distal: Nearer/farther (limbs)

  • Superficial/Deep: Surface/inside

Body Planes

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

• Sagittal: Left vs. right

• Frontal (coronal): Front vs. back

• Transverse: Top vs. bottom

• Oblique: Diagonal

Body Cavities

Body cavities protect organs and allow them to change shape and size.

• Dorsal (back): Cranial (brain), vertebral (spinal cord)

• Ventral (front): Thoracic (heart, lungs), abdominopelvic (digestive, bladder, reproductive)

• Other cavities: Oral, nasal, orbital (eyes), ear, synovial (joints)

• Serous membranes:

  • Parietal serosa: Lines cavity wall

  • Visceral serosa: Covers organ

  • Serous fluid between layers reduces friction

Abdominopelvic Regions

The abdominopelvic cavity is divided for clinical and anatomical reference.

• Quadrants: RUQ (right upper), LUQ (left upper), RLQ (right lower), LLQ (left lower)

• Nine regions: Right/left hypochondriac, right/left lumbar, right/left iliac, epigastric, umbilical, hypogastric