Introduction to Anatomy & Physiology: Structure, Organization, and Terminology

Anatomy and Physiology: Definitions and Relationship

Overview of Anatomy and Physiology

Anatomy and physiology are foundational sciences in understanding the human body. Anatomy focuses on the structure of body parts, while physiology explores their functions and how they work together to sustain life.

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

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

• Key Principle: Structure determines function; the way a body part is built influences what it can do.

Divisions of Anatomy

Macroscopic (Gross) Anatomy

Gross anatomy examines structures visible to the naked eye and can be subdivided based on the focus of study.

• Regional Anatomy: Looks at all structures in a particular area of the body (e.g., abdomen, leg).

• System Anatomy: Focuses on one system (e.g., cardiovascular, muscular).

• Surface Anatomy: Studies internal structures as they relate to the overlying skin (e.g., visible muscle masses or veins).

Microscopic Anatomy

Microscopic anatomy deals with structures too small to be seen without magnification.

• Cytology: Study of cells.

• Histology: Study of tissues.

Developmental Anatomy

Developmental anatomy traces structural changes throughout the life span.

• Embryology: Study of developmental changes that occur before birth.

Tools and Techniques in Anatomy

Basic Anatomical Terminology and Methods

Understanding anatomy requires familiarity with specific terminology and the use of various tools and techniques.

• Palpation: Feeling organs with your hands.

• Auscultation: Listening to organs with a stethoscope.

• Imaging Technology: Non-invasive methods to view inside the body, such as X-ray, MRI, CT, and ultrasound.

Levels of Structural Organization in the Human Body

Hierarchy of Organization

The human body is organized into increasingly complex levels, each building upon the previous.

• Chemical Level: Atoms and molecules.

• Cellular Level: Cells and their organelles.

• Tissue Level: Groups of similar cells performing a common function.

• Organ Level: Contains two or more types of tissues working together.

• Organ System Level: Organs that work closely together to accomplish a common purpose.

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

Major Organ Systems and Their Functions

Overview of Organ Systems

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

• Integumentary System: Forms the external body covering, protects deeper tissues, synthesizes vitamin D, and houses sensory receptors and sweat/oil glands.

• Skeletal System: Protects and supports body organs, provides a framework for muscles, forms blood cells, and stores minerals.

• Muscular System: Allows manipulation of the environment, locomotion, and facial expression; maintains posture and produces heat. Additional info: Muscular system includes skeletal, cardiac, and smooth muscle types.

• Nervous System: Fast-acting control system; responds to internal and external changes by activating appropriate muscles and glands.

• Endocrine System: Glands secrete hormones that regulate growth, reproduction, and metabolism.

• Cardiovascular System: Blood vessels transport blood, which carries oxygen, nutrients, and wastes; heart pumps blood.

• Lymphatic System: Picks up fluid leaked from blood vessels, returns it to blood, disposes of debris, and houses white blood cells.

• Respiratory System: Keeps blood supplied with oxygen and removes carbon dioxide.

• Digestive System: Breaks down food into absorbable units; eliminates indigestible foodstuffs.

• Urinary System: Eliminates nitrogenous wastes; regulates water, electrolyte, and acid-base balance.

• Reproductive System: Produces offspring; testes produce sperm and male sex hormones, ovaries produce eggs and female sex hormones.

Anatomical Terminology: Directions and Planes

Importance of Anatomical Terms

Precise anatomical terminology is essential for describing locations, directions, and movements of body parts, facilitating clear communication among health professionals.

• Anatomical Position: Standard reference position: body erect, feet slightly apart, palms facing forward, thumbs pointing away from the body.

• Directional Terms: Describe the location of one body structure relative to another (e.g., lateral, medial, proximal, distal, superficial, deep).

• Right and Left: Always refer to the subject's right and left, not the observer's.

Body Planes and Sections

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

• Sagittal Plane: Vertical plane dividing the body into right and left parts.

• Midsagittal (Median) Plane: Sagittal plane that lies exactly in the midline.

• Parasagittal Plane: Sagittal plane offset from the midline.

• Frontal (Coronal) Plane: Vertical plane dividing the body into anterior (front) and posterior (back) parts.

• Transverse (Horizontal) Plane: Horizontal plane dividing the body into superior (top) and inferior (bottom) parts.

• Oblique Section: Cuts made at angles other than 90°, less commonly used.

Body Cavities and Membranes

Major Body Cavities

The body contains internal cavities that protect organs and allow for organ movement and expansion.

• Dorsal Body Cavity: Protects the nervous system; includes cranial cavity (encases brain) and vertebral (spinal) cavity (encases spinal cord).

• Ventral Body Cavity: Houses internal organs (viscera); includes thoracic cavity (pleural cavities, mediastinum, pericardial cavity) and abdominopelvic cavity (abdominal and pelvic cavities).

Serous Membranes

Serous membranes are thin, double-layered structures that cover organs and line cavities, reducing friction.

• Parietal Serosa: Lines cavity walls.

• Visceral Serosa: Covers organs within the cavity.

• Serous Fluid: Lubricating fluid secreted by both layers, filling the space between them.

Specific serous membranes include:

• Pleura: Surrounds lungs.

• Pericardium: Surrounds heart.

• Peritoneum: Surrounds abdominopelvic organs.

Abdominopelvic Regions and Quadrants

Quadrants

Medical personnel often use four quadrants to describe locations in the abdominopelvic cavity.

Quadrant	Location
Right Upper Quadrant (RUQ)	Upper right section
Left Upper Quadrant (LUQ)	Upper left section
Right Lower Quadrant (RLQ)	Lower right section
Left Lower Quadrant (LLQ)	Lower left section

Regions

Anatomists use nine regions for more precise localization.

Region	Location
Umbilical	Center, around navel
Epigastric	Above umbilical
Pubic (Hypogastric)	Below umbilical
Right Inguinal (Iliac)	Lower right
Left Inguinal (Iliac)	Lower left
Right Lateral (Lumbar)	Middle right
Left Lateral (Lumbar)	Middle left
Right Hypochondriac	Upper right
Left Hypochondriac	Upper left

Other Body Cavities

Open and Closed Cavities

In addition to the main closed body cavities, the body contains several other cavities.

• Open Cavities: Exposed to the environment (oral, digestive, nasal, orbital, middle ear).

• Closed Cavities: Not exposed to the environment (synovial cavities around joints).

Additional info: Synovial fluid in joint cavities reduces friction and allows smooth movement.