Introduction to Anatomy & Physiology

Form (Anatomy) Determines Function (Physiology)

• Anatomy is the study of body structures and their relationships.

• Physiology is the science of how body parts function.

• Understanding anatomy is essential for understanding physiology, as the structure of a body part enables its function.

• Examples of physiology include cardiovascular physiology (heart and blood vessels), renal physiology (kidneys), and muscle physiology (muscle function).

• Physiological processes are explained by chemical and physical principles.

Major Subdivisions of Anatomy

• Gross Anatomy: Study of large body structures visible to the naked eye (e.g., heart, bones).

• Microscopic Anatomy: Study of structures too small to be seen without a microscope (e.g., cells, tissues).

• Developmental Anatomy: Study of structural changes throughout the lifespan (e.g., embryology).

Complementarity of Structure and Function

• The principle that anatomy and physiology are inseparable: what a body part can do depends on its structure.

• This is known as the complementarity of structure and function.

Levels of Structural Organization in the Human Body

From Atoms to the Entire Organism

• The body is organized into hierarchical levels, from simplest to most complex:

  1. Chemical Level: Atoms combine to form molecules.

  2. Cellular Level: Cells are made up of molecules.

  3. Tissue Level: Tissues consist of similar types of cells.

  4. Organ Level: Organs are made up of different types of tissues.

  5. Organ System Level: Organ systems consist of different organs that work together.

  6. Organismal Level: The human organism is made up of many organ systems.

• The 11 organ systems are: integumentary, skeletal, muscular, nervous, endocrine, cardiovascular, lymphatic, respiratory, digestive, urinary, and reproductive systems.

• The immune system is a functional system closely associated with the lymphatic system.

Requirements for Life

Vital Functional Activities and Survival Needs

• All living organisms carry out certain vital activities necessary for life:

  • Maintenance of boundaries (separating internal from external environments)

  • Movement

  • Responsiveness (ability to sense and respond to stimuli)

  • Digestion

  • Metabolism (all chemical reactions in the body)

  • Excretion (removal of wastes)

  • Reproduction

  • Growth

• Survival needs include:

  • Nutrients

  • Water

  • Oxygen

  • Appropriate temperature

  • Atmospheric pressure

Homeostasis

Dynamic Equilibrium and Feedback Mechanisms

• Homeostasis is the maintenance of a stable internal environment despite external changes.

• All body systems contribute to homeostasis, but the nervous and endocrine systems are most important.

• Homeostasis is necessary for health; its loss leads to disease.

Homeostatic Control Mechanisms

• Consist of three main components:

  1. Receptor(s): Detect changes (stimuli) in the environment.

  2. Control Center: Determines the set point and analyzes input; sends output to effector.

  3. Effector(s): Carry out the response to restore homeostasis.

Types of Feedback

• Negative Feedback: Reduces the effect of the original stimulus; essential for maintaining homeostasis.

  • Examples: Regulation of body temperature, heart rate, blood pressure, breathing rate and depth, blood glucose, and certain ions.

• Positive Feedback: Intensifies the initial stimulus, leading to an enhanced response; rarely contributes to homeostasis.

  • Examples: Blood clotting, labor contractions.

• Feedforward (Anticipatory) Response: Occurs in anticipation of a change to the internal environment.

Homeostatic Imbalance

• With age, the efficiency of negative feedback mechanisms declines, contributing to disease conditions.

Anatomical Terms: Body Directions, Regions, and Planes

Anatomical Position and Directional Terms

• In the anatomical position, the body is erect, facing forward, feet slightly apart, arms at sides with palms forward.

• Directional terms allow precise location of body parts:

  • Superior/Inferior (above/below)

  • Anterior/Posterior (front/back)

  • Ventral/Dorsal (belly side/back side)

  • Medial/Lateral (toward midline/away from midline)

  • Intermediate (between medial and lateral)

  • Proximal/Distal (closer to/farther from origin of body part or point of attachment)

  • Superficial/Deep (toward/away from body surface)

Regional Terms

• Used to designate specific areas of the body (e.g., brachial for arm, femoral for thigh).

Body Planes and Sections

• The body or its organs may be cut along planes to produce sections:

  • Sagittal Plane: Divides body into right and left parts.

  • Frontal (Coronal) Plane: Divides body into anterior and posterior parts.

  • Transverse (Horizontal) Plane: Divides body into superior and inferior parts.

Body Cavities and Membranes

Major Body Cavities

• The body contains two major closed cavities:

  • Dorsal Cavity: Subdivided into cranial (contains brain) and spinal (contains spinal cord) cavities.

  • Ventral Cavity: Subdivided into thoracic (houses heart and lungs) and abdominopelvic (contains liver, digestive organs, reproductive structures) cavities.

Membranes of the Ventral Cavity

• The walls of the ventral cavity and the surfaces of its organs are covered with thin membranes called serosae:

  • Parietal Serosa: Lines the cavity walls.

  • Visceral Serosa: Covers the organs within the cavity.

  • Serosae produce a thin fluid that decreases friction during organ functioning.

Abdominopelvic Regions and Quadrants

• The abdominopelvic cavity can be divided by four planes into nine regions or by two planes into four quadrants.

• There are several smaller body cavities, most of which are in the head and open to the exterior (e.g., oral, nasal, orbital, middle ear cavities).

Example: Application of Anatomical Terms

• When describing pain in the abdomen, a physician may refer to the right lower quadrant (RLQ) or the umbilical region to localize the area precisely.

Additional info: The above notes expand on the summary points by providing definitions, examples, and context for each concept, as would be expected in a mini-textbook introduction to Anatomy & Physiology.