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

Form (Anatomy) Determines Function (Physiology)

Definitions and Principles

• Anatomy: The study of the structure of body parts and their relationships to one another.

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

• In this textbook, reference values are based on a reference male (70 kg) and reference female (57 kg).

• Anatomical variability: Over 90% of anatomical structures match textbook descriptions, but minor variations (e.g., nerves or blood vessels out of place, missing small muscles) exist. Extreme variations are rare and usually incompatible with life.

• Sex: Biological attributes based on chromosomes, gene expression, and hormone action, reflected in reproductive anatomy and physiology (male or female).

• Gender: Psychosocial construct including behaviors, expressions, and identities (e.g., man, woman, transgender, non-binary).

Topics of Anatomy

Subdivisions of Anatomy

• Gross (macroscopic) anatomy: Study of large body structures visible to the naked eye.

  • Regional anatomy: All structures in a particular area.

  • System anatomy: One system at a time (e.g., cardiovascular, nervous).

  • Surface anatomy: Internal structures as related to overlying skin (e.g., visible muscle masses, veins).

• Microscopic anatomy: Structures too small to be seen with the naked eye.

  • Cytology: Study of cells.

  • Histology: Study of tissues.

• Developmental anatomy: Structural changes throughout the lifespan.

  • Embryology: Developmental changes before birth.

Studying Anatomy

• Requires understanding anatomical terminology and the ability to observe, manipulate, palpate (feel organs), and auscultate (listen with a stethoscope).

• Medical imaging (e.g., X-ray, MRI, CT, ultrasound) allows non-invasive internal visualization.

Topics of Physiology

Subdivisions of Physiology

• Based on organ systems, e.g.:

  • Renal physiology: Kidney function.

  • Neurophysiology: Nervous system function.

  • Cardiovascular physiology: Heart and blood vessel function.

• Often focuses on cellular or molecular events—how chemical reactions in cells underlie body functions.

• Requires understanding of basic chemical and physical principles (e.g., electrical currents, pressure, levers).

Complementarity of Structure and Function

• Anatomy and physiology are inseparable; function always reflects structure.

• The principle of complementarity: What a structure can do depends on its specific form.

• Example: Teeth with flat surfaces are suited for grinding food; sharp teeth are for tearing.

The Body's Organization Ranges From Atoms to the Entire Organism

Levels of Structural Organization

• Chemical level: Atoms and molecules.

• Cellular level: Cells and their organelles.

• Tissue level: Groups of similar cells.

• Organ level: Two or more tissue types.

• Organ system level: Organs working together.

• Organismal level: All organ systems combined to make the whole organism.

The Body's Organ Systems and Their Major Functions

• There are 11 organ systems:

  1. Integumentary

  2. Skeletal

  3. Muscular

  4. Nervous

  5. Endocrine

  6. Cardiovascular

  7. Lymphatic

  8. Respiratory

  9. Digestive

  10. Urinary

  11. Reproductive

• Each system has specialized functions but works cooperatively with others to maintain life.

What Are the Requirements for Life?

• All living organisms carry out vital functions and require certain substances and conditions to survive.

Necessary Life Functions

• Maintaining boundaries: Separation between internal and external environments (e.g., plasma membranes, skin).

• Movement: Of body parts (skeletal muscles), substances (cardiac muscle, blood), and cells (e.g., white blood cells).

• Responsiveness (excitability): Ability to sense and respond to stimuli (e.g., withdrawal reflex, breathing rate changes).

• Digestion: Breakdown of ingested food into simple molecules for absorption.

• Metabolism: All chemical reactions in body cells, including:

  • Catabolism: Breakdown of molecules.

  • Anabolism: Synthesis of molecules.

  • Cellular respiration: Use of nutrients and oxygen to make ATP. Equation: $\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{ATP}$

• Excretion: Removal of wastes (e.g., urea, carbon dioxide, feces).

• Reproduction: Cellular level (cell division for growth/repair); organismal level (offspring production).

• Growth: Increase in size of a body part or organism.

Examples of Interrelationships Among Body Organ Systems

• Organ systems work together to maintain life; all cells depend on organ systems for survival needs.

• Example: The digestive system provides nutrients, which the cardiovascular system distributes to body cells.

Survival Needs

• Nutrients: Carbohydrates (energy), proteins (cell building), fats (energy storage), minerals/vitamins (chemical reactions, structure).

• Oxygen: Essential for energy release from food; survival without oxygen is limited to a few minutes.

• Water: Most abundant chemical in the body; solvent for reactions, base for secretions/excretions.

• Normal body temperature: Must be maintained near 37°C (98.6°F) for optimal chemical reactions.

• Appropriate atmospheric pressure: Required for adequate breathing and gas exchange in the lungs.

Homeostasis Is Maintained by Negative Feedback

Definition and Principles

• Homeostasis: Maintenance of relatively stable internal conditions despite environmental changes; a dynamic equilibrium.

• Law of mass balance: The amount of a substance taken in must equal the amount lost to maintain constancy.

• All organ systems contribute to homeostasis.