Introduction to Anatomy & Physiology

Structure and Function

Anatomy and physiology are foundational sciences for understanding the human body. Anatomy describes the structures of the body, including their composition, location, and relationships. Physiology focuses on the functions of these anatomical structures.

• Anatomy: What structures are made of, where they are located, and how they relate to each other.

• Physiology: How anatomical structures function individually and together.

Anatomy Subtypes

Anatomy is divided into several specialized fields, each focusing on different levels of structural detail.

• Microscopic Anatomy: Study of structures observed with a microscope.

• Cytology: Study of body cells.

• Histology: Study of tissues.

• Gross (Macroscopic) Anatomy: Study of structures visible without magnification.

• Systemic Anatomy: Study of each functional body system.

• Regional Anatomy: Study of all structures in a specific region.

• Embryology: Study of developmental changes from conception to birth.

Physiology Subtypes

Physiology examines the function of body systems and their components.

• Cardiovascular Physiology: Functioning of the heart, blood vessels, and blood.

• Neurophysiology: Functioning of nerves and nervous system organs.

• Respiratory Physiology: Functioning of respiratory organs.

• Reproductive Physiology: Functioning of reproductive hormones and cycles.

• Pathophysiology: Relationship between organ system function and disease or injury.

Levels of Organization

Hierarchical Structure of the Human Body

The human body is organized into six distinct levels, each increasing in complexity.

• Chemical (Molecular) Level: Atoms and molecules (e.g., hydrogen, collagen molecule).

• Cellular Level: Groups of molecules forming cells (e.g., osteocyte).

• Tissue Level: Groups of similar cells working together (e.g., osseous tissue).

• Organ Level: Different tissues forming organs (e.g., femur).

• System Level: Organs working together in systems (e.g., skeletal system).

• Organismal Level: The complete human body.

Example: Organization Quiz

Arrange from smallest to largest: Collagen Molecule → Osteocyte → Osseous Tissue → Femur → Skeletal System → Human

Organ Systems of the Human Body

Overview of Organ Systems

Organs that work together are grouped into organ systems. Each system has major organs and specific functions.

• Examples: Skeletal system (bones), muscular system (muscles), cardiovascular system (heart, blood vessels), etc.

• Students should know each system’s major organs and their functions.

Metabolism

Anabolic and Catabolic Reactions

Metabolism refers to all chemical reactions in the body, including both building (anabolic) and breaking down (catabolic) processes.

• Anabolic Reactions: Build larger molecules from smaller ones; require energy.

• Catabolic Reactions: Break down larger molecules into smaller ones; release energy.

Key Metabolic Reactions

• Decomposition (Catabolism): Breaks chemical bonds; hydrolysis (adding H2O); energy released.

• Synthesis (Anabolism): Forms chemical bonds; dehydration synthesis (removing H2O); energy required.

Metabolic Equations

Characteristics of Life

Essential Functions

Living organisms exhibit several essential characteristics.

• Responsiveness: Ability to adjust to changes in internal and external environments.

• Development: All changes the body undergoes throughout life.

• Reproduction: Formation of new organisms or cells for growth, repair, and maintenance.

• Growth: Assimilation of materials and increase in size.

• Movement: Change in position of body parts.

Homeostasis

Definition and Components

Homeostasis is the maintenance of a constant internal environment. It is regulated by feedback mechanisms.

• Sensors (Receptors): Detect changes in stimulus.

• Control (Integration) Center: Interprets stimulus and initiates commands.

• Effector: Carries out commands from the control center.

Regulation of Homeostasis

• Nervous System: Provides quick responses.

• Endocrine System: Uses hormones for regulation.

Feedback Mechanisms

• Negative Feedback: Returns the body to homeostasis; normal range is achieved. Examples: heat/sweat, cold/shivering, glucose/insulin.

• Positive Feedback: Moves the body away from homeostasis; speeds up processes. Examples: labor, blood clotting.

Negative Feedback Loop

• A stimulus causes deviation from a set point.

• Physiological processes resist the deviation, returning the body to homeostasis.

• Example: Regulation of body temperature.

Positive Feedback Loop

• Results in a change in the body’s status, rather than a return to homeostasis.

• Example: Childbirth.

Anatomical Position and Directions

Anatomical Position

The standard reference position for the human body is:

• Body erect

• Feet apart

• Hands at sides, palms forward

• Eyes looking forward

Directional Terms

Directional terms describe the location of structures relative to each other.

• Anterior: Front of the body

• Posterior: Back of the body

• Superior: Toward the head

• Inferior: Away from the head

• Medial: Toward the midline

• Lateral: Away from the midline

• Proximal: Toward attachment of limbs to body

• Distal: Away from attachment of limbs to body

• Superficial: Closer to the surface

• Deep: Further from the surface

Example: Directions Quiz

The patella is proximal to the tarsals and distal to the thigh.

Planes and Sections

Body Planes

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

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

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

• Transverse Plane: Divides the body into superior and inferior parts.

Body Cavities

Dorsal and Ventral Cavities

The body contains two main cavities:

• Dorsal Cavity: Includes cranial and spinal cavities.

• Ventral Cavity: Includes thoracic and abdominopelvic cavities.

Serous Membranes

Serous membranes line body cavities and cover organs, consisting of two layers:

• Parietal Layer: Lines the cavity.

• Visceral Layer: Covers the organ.

Thoracic Cavity

• Pleural Cavities: Contain the lungs; lined by visceral and parietal pleura.

• Mediastinum: Contains trachea, esophagus, thymus gland.

• Pericardial Cavity: Contains the heart.

Abdominopelvic Cavity

• Peritoneum: Two-layered serous membrane enclosing the peritoneal cavity.

• Parietal Peritoneum: Lines the internal body wall.

• Visceral Peritoneum: Covers the organs.

• Peritoneal Cavity: Space containing serous fluid between layers.

Quiz Example

What separates thoracic cavity from abdominal cavity? D. Diaphragm

Abdominal Regions and Quadrants

Regions and Quadrants

The abdominopelvic cavity is divided for clinical and anatomical reference.

• Nine Abdominal Regions: Used for detailed anatomical study.

• Four Abdominal Quadrants: Used for clinical reference.

Quiz Example

The epigastric region is superior to the umbilical region.

Summary Table: Levels of Organization

Summary Table: Directional Terms