Introduction to Anatomy & Physiology: Organization, Terminology, and Body Systems

Anatomy & Physiology Overview

Definition and Scope

Anatomy is the study of the structures of the body, while physiology focuses on the functions and activities of those structures. Anatomy can be divided into gross anatomy (structures visible to the naked eye) and microscopic anatomy (structures seen only with a microscope).

• Gross Anatomy: Study of body structures visible without a microscope.

• Microscopic Anatomy: Study of structures that require magnification to be seen.

• Physiology: Study of body functions and processes.

Levels of Organization

Hierarchical Structure

The human body is organized into several levels, each building upon the previous:

• Chemical Level: Atoms and molecules form the basis of all matter.

• Cellular Level: Cells are the smallest living units; organelles within cells perform specialized functions.

• Tissue Level: Groups of similar cells form tissues. Four main types: epithelial, connective, muscle, and nervous.

• Organ Level: Organs are structures composed of different tissue types working together for specific functions (e.g., heart, liver).

• Organ System Level: Groups of organs working together to perform complex functions (e.g., respiratory system).

• Organismal Level: The complete living individual, made up of all organ systems.

Anatomical Position and Terminology

Standard Reference Position

The anatomical position is the standard reference for describing locations and directions on the body:

• Standing upright

• Facing forward

• Arms at sides, palms forward

Key directional terms:

• Superior: Toward the head

• Inferior: Toward the feet

• Anterior (ventral): Toward the front

• Posterior (dorsal): Toward the back

• Medial: Toward the midline

• Lateral: Away from the midline

• Proximal: Closer to the trunk or point of attachment

• Distal: Farther from the trunk or point of attachment

• Superficial: Nearer to the surface

• Deep: Farther from the surface

Body Planes and Sections

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

• Sagittal Plane: Divides body into left and right halves

• Mid-sagittal Plane: Divides body into equal left and right halves

• Parasagittal Plane: Divides body into unequal left and right halves

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

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

Body Cavities and Quadrants

Major Body Cavities

The body contains several major cavities that house organs:

• Dorsal Cavity: Includes cranial cavity (brain) and spinal cavity (spinal cord)

• Ventral Cavity: Includes thoracic cavity (lungs, heart) and abdominopelvic cavity (digestive, urinary, reproductive organs)

Body Cavities Table

Cavity	Main Contents
Cranial	Brain
Spinal	Spinal cord
Thoracic	Lungs, heart
Abdominal	Digestive organs, many glands
Pelvic	Urinary bladder, reproductive organs

Abdominal Quadrants and Regions

The abdomen is divided for clinical and anatomical reference:

• Quadrants: Right Upper, Left Upper, Right Lower, Left Lower

• Regions: Right hypochondriac, epigastric, left hypochondriac, right lumbar, umbilical, left lumbar, right iliac (inguinal), hypogastric, left iliac (inguinal)

Surface Anatomy Terminology

Common Anatomical Terms

Specific terms are used to describe regions of the body:

• Head: Cephalic

• Face: Facial

• Forehead: Frontal

• Eye: Ocular or orbital

• Cheek: Buccal

• Nose: Nasal

• Mouth: Oral

• Neck: Cervical

• Chest: Thoracic

• Abdomen: Abdominal

• Pelvis: Pelvic

• Arm: Brachial

• Forearm: Antebrachial

• Wrist: Carpal

• Hand: Manual

• Fingers: Digital or phalangeal

• Thigh: Femoral

• Knee (front): Patellar

• Knee (back): Popliteal

• Leg: Crural

• Ankle: Tarsal

• Foot: Pedal

Homeostasis and Feedback Mechanisms

Balance of Body Functions

Homeostasis is the maintenance of a stable internal environment. The body uses feedback systems to regulate homeostasis:

• Negative Feedback: Opposes changes to restore balance (e.g., temperature regulation).

• Positive Feedback: Amplifies changes (e.g., blood clotting).

The Scientific Method in Anatomy & Physiology

Systematic Approach

The scientific method is used to investigate and understand body functions:

• Observation: Gathering data

• Hypothesis: Testable explanation

• Experimentation: Testing the hypothesis

• Control Group: Standard for comparison

• Theory: Well-supported explanation

• Law: Hypothesis with high confidence

Major Body Systems

Overview of Organ Systems

The human body is composed of several organ systems, each with specific functions:

• Integumentary System: Skin, hair, nails, sweat and sebaceous glands

• Muscular System: Skeletal muscles, smooth muscles, cardiac muscle

• Skeletal System: Bones, cartilage, tendons, ligaments

• Nervous System: Brain, spinal cord, nerves

• Endocrine System: Glands (pituitary, thyroid, adrenal, etc.)

• Cardiovascular System: Heart, blood vessels, blood

• Respiratory System: Lungs, airways, diaphragm

• Digestive System: Oral cavity, esophagus, stomach, intestines, liver, pancreas, gallbladder

• Urinary System: Kidneys, ureters, bladder, urethra

• Reproductive System: Male: testes, prostate, penis; Female: ovaries, uterus, vagina

Additional info:

• Atrophy: Wasting away of tissue; decrease in size or function, often due to degeneration.