Introduction to Anatomy & Physiology

Overview of Anatomy and Physiology

Anatomy is the study of the structures that make up the body and how those structures relate to each other. The term derives from the Greek meaning "to cut up." Anatomy is divided into:

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

• Microscopic Anatomy: Study of structures only visible with a microscope.

Physiology is the study of how the body functions and carries out the activities of life.

Levels of Organization

Hierarchy of Structural Organization

The human body is organized into a hierarchy of structural levels, each building upon the previous:

• Atoms: Smallest units of matter; combine to form molecules.

• Molecules: Combinations of atoms; form the chemical building blocks of cells.

• Cells: Smallest living units; contain organelles formed from molecules.

• Tissues: Groups of similar cells performing related functions. Four main types:

  • Epithelial

  • Connective

  • Muscular

  • Nervous

• Organs: Composed of two or more tissue types; perform specific functions (e.g., kidney, liver, brain, heart).

• Organ Systems: Groups of organs working together for related functions (e.g., respiratory system, cardiovascular system).

Example: The heart (organ) is made of muscle, connective, and nervous tissue, and is part of the cardiovascular system (organ system).

Anatomical Position and Body Orientation

Standard Anatomical Position

The anatomical position is the reference posture for describing body parts and positions:

• Standing upright

• Feet together

• Palms facing forward

Other positions:

• Supine: Lying face up

• Prone: Lying face down

Body Divisions

• Axial: Head, chest, abdomen, pelvis

• Appendicular: Limbs (arms and legs)

Body Planes

Major Anatomical Planes

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

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

  • Midsagittal: Equal left and right halves.

  • Parasagittal: Unequal left and right halves.

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

Anatomical Directions

Directional Terms

Directional terms describe the locations of structures relative to other structures or locations in the body:

• Superior (Cranial): Toward the head; above. Example: The leg is superior to the foot.

• Inferior (Caudal): Toward the feet; below. Example: The foot is inferior to the leg.

• Anterior (Ventral): Toward the front. Example: The nose is anterior to the ears.

• Posterior (Dorsal): Toward the back. Example: The ears are posterior to the nose.

• Medial: Toward the midline. Example: The heart is medial to the lungs.

• Lateral: Away from the midline. Example: The eyes are lateral to the nose.

• Proximal: Closer to the trunk or point of attachment. Example: The elbow is proximal to the wrist.

• Distal: Farther from the trunk or point of attachment. Example: The wrist is distal to the elbow.

• Superficial (External): Nearer to the surface. Example: The skin is superficial to the muscles.

• Deep (Internal): Farther from the surface. Example: The muscles are deep to the skin.

Abdominopelvic Quadrants and Regions

Quadrants

The abdominopelvic area is divided into four quadrants for clinical and anatomical reference:

• Right Upper Quadrant (RUQ)

• Left Upper Quadrant (LUQ)

• Right Lower Quadrant (RLQ)

• Left Lower Quadrant (LLQ)

Regions

For more precise localization, the abdominopelvic area is divided into nine regions:

• Right hypochondriac

• Epigastric

• Left hypochondriac

• Right lumbar

• Umbilical

• Left lumbar

• Right inguinal (iliac)

• Hypogastric

• Left inguinal (iliac)

Body Cavities

Major Body Cavities and Their Contents

• Dorsal Cavity:

  • Cranial cavity: Contains the brain

  • Spinal cavity: Contains the spinal cord

• Ventral Cavity:

  • Thoracic cavity:

    • Pleural cavities: Surround the lungs

    • Pericardial cavity: Surrounds the heart

    • Mediastinum: Partition between the lungs

  • Abdominopelvic (Peritoneal) cavity:

    • Abdominal cavity: Contains digestive organs and many glands

    • Pelvic cavity: Contains urinary bladder and reproductive organs

Note: The thoracic and abdominal cavities are separated by the diaphragm.

Anatomical Landmarks

Common and Anatomical Terms for Body Regions

Organ Systems of the Human Body

Overview of Major Organ Systems

• Integumentary System: Skin, hair, nails, and exocrine glands (sweat and sebaceous glands).

• Skeletal System: Bones, cartilage, tendons, ligaments.

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

• Nervous System: Central nervous system (brain and spinal cord) and peripheral nervous system.

• Endocrine System: Pituitary, thyroid, parathyroid, pineal, adrenal glands, pancreas, ovaries, testes.

• Cardiovascular System: Heart, blood vessels, and blood.

• Lymphatic System: Lymphatic vessels, nodes, spleen, and thymus.

• Respiratory System: Lungs, alveoli, bronchi, trachea, larynx, pharynx, nasal cavity, diaphragm.

• Digestive System: Oral cavity, pharynx, esophagus, stomach, small and large intestines, liver, pancreas, gallbladder.

• Urinary System: Kidneys, ureters, urinary bladder, urethra.

• Reproductive System:

  • Male: Testes, prostate gland, Cowper’s glands, seminal vesicles, ductus deferens, penis.

  • Female: Ovaries, uterine tubes, uterus, vagina.

Example: The respiratory system includes the lungs, trachea, and diaphragm, working together to facilitate gas exchange.

Additional info: Understanding these foundational concepts is essential for further study in anatomy and physiology, as they provide the framework for describing the structure and function of the human body in health and disease.