Comprehensive Introduction to Human Anatomy and Physiology

Definition and Etymology of Human Anatomy

  • Human Anatomy Definition: The study of the structures of the human body. This discipline involves the identification and description of internal and external structures. It encompasses two primary sub-disciplines: histology and gross anatomy.

  • Etymology (Word Roots): Anatomical names often derive from Latin and Greek. Understanding the root meanings (etymology) is essential for learning.

    • Anatomy: Derived from the Greek language.

      • ana: Means "up" or "apart."

      • tome: Means "a cutting."

      • Literal Meaning: "Cutting up or apart."

    • Significance of Dissection: Dissection is the literal process of cutting apart and is fundamental to the study of anatomy.

Classifications of Anatomy

  • Gross Anatomy (Macroscopic Anatomy):

    • Scope: The study of structures visible to the naked eye.

    • Examples: Bones and muscles.

    • Methods: Involves dissection or noninvasive methods to examine regions.

    • Objective: To understand the larger structures of organs, organ systems, and their interconnections.

  • Microscopic Anatomy (Histology):

    • Scope: The study of tissues and structures too small to be seen without magnification.

    • Etymology:

      • histo: Means "tissue."

      • ology: Means "study."

    • Methodology: Requires the use of light or electron microscopes. Microscopy involves studying prepared cells and tissues through specific histological techniques.

    • Tissue Preparation (Sectioning and Staining):

      • Sectioning: Tissue is treated with preserving agents and cut into very thin slices.

      • Staining: Commonly uses Hematoxylin and Eosin (H&EH\&E) to add visual contrast.

      • Chemistry: Stains generate different colors and intensities based on tissue chemistry (e.g., lipids, proteins, acidity, or alkalinity).

Anatomical Nomenclature and Vocabulary

  • Techniques for Learning: Associating root terms with familiar concepts is recommended.

    • Example: hypo (below/under) + chondro (cartilage). Hypochondral refers to the region under the ribs (which contain cartilage).

    • Anecdote: A "hypochondriac" (one who believes they are ill) often gestures toward their "tummy" or hypochondral region.

  • Grammatical Constructs: Endings change to indicate part of speech.

    • Noun vs. Adjective: Cranium (noun) vs. Cranial (adjective).

  • Diminutives: Modifying words to convey smallness.

    • Rule of Thumb: Generally, the longer the word, the smaller the structure.

    • Example: Organ vs. Organelle (literally "teeny tiny little organ").

  • Eponyms vs. Descriptive Terms:

    • Eponyms: Structures named after the person who discovered them. These must be capitalized as they are proper names.

    • Descriptive Terms: Preferred in modern practice as they indicate function, location, or shape.

    • Table of Common Examples (Eponym vs. Descriptive Name):

      • Eustachian tube: Auditory tube (indicates sound/ear location).

      • Achilles tendon: Calcaneal tendon of the heel.

      • Bowman's capsule: Glomerular capsule of the nephron (kidney).

      • Cowper's gland: Bulbourethral gland (male reproductive system).

      • Fallopian tubes: Uterine tubes (female reproductive system).

      • Graafian follicle: Mature follicle (female egg cell).

      • Kupffer cell: Macrophages of the liver.

      • Islets of Langerhans: Pancreatic islets (hormone production).

      • Meissner's corpuscle: Tactile corpuscle (touch sensation in the dermis).

      • Nissl bodies: Ribosomes within nerve cell bodies.

      • Sphincter of Oddi: Hepatopancreatic sphincter (controls bile and pancreatic juice flow).

      • Pacinian corpuscle: Lamellated corpuscle (pressure sensation deep in the dermis).

      • Node of Ranvier: Myelin-sheath gaps along myelinated axons.

      • Canal of Schlemm: Scleral venous sinus (drains aqueous humor from the eyeball).

Functional Anatomy and Organization

  • Functional Anatomy: The study of the correlation between structure (anatomy) and function (physiology). Form (shape) indicates function.

  • Levels of Organization (Simplest to Most Complex):

    • A. Atoms

    • B. Molecules

    • C. Organelles

    • D. Cells

    • E. Tissues

    • F. Organs

    • G. Organ systems

    • H. Organism

  • Basic Functions of Living Organisms:

    • Responsiveness

    • Growth

    • Differentiation

    • Metabolism

    • Movement

    • Reproduction

    • Excretion

Organ Systems of the Human Body

  • Tissues: The four primary types are Epithelium, Connective, Muscular, and Nervous.

  • Integumentary: Skin, hair, nails, and glands.

  • Skeletal: Bones, cartilage, and articulations.

  • Muscular: Skeletal, cardiac, and smooth muscles.

  • Nervous: Nerves, glial cells, Central Nervous System (CNS), Peripheral NS, and Autonomic NS.

    • Special Senses: Eyes, ears, touch, olfaction (smell), equilibrium, and taste.

  • Endocrine: Primary and secondary endocrine glands.

  • Cardiovascular: Heart, arteries, capillaries, and veins.

  • Lymphatic: Lymph ducts, nodes, organs, and tissues.

  • Respiratory: Lungs and the bronchial tree.

  • Digestive: Mouth, esophagus, stomach, small intestine, colon, liver, and pancreas.

  • Urinary: Kidney, ureters, urinary bladder, and urethra.

  • Reproductive:

    • Female: Ovary, uterine tube, uterus, and vagina.

    • Male: Testes, epididymis, ductus deferens, glands, urethra, and penis.

Body Regions and Planes

  • Abdominopelvic Quadrants:

    1. Right Upper Quadrant (RUQ)

    2. Left Upper Quadrant (LUQ)

    3. Right Lower Quadrant (RLQ)

    4. Left Lower Quadrant (LLQ)

  • Descriptive Abdominopelvic Regions (99 total):

    1. Right and Left Hypochondriac

    2. Right and Left Lumbar

    3. Right and Left Iliac (Inguinal)

    4. Epigastric

    5. Umbilical

    6. Hypogastric

  • Planes of the Body:

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

    • Transverse (Cross or Horizontal) Plane: Divides the body into superior (top) and inferior (bottom) portions.

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

      • Mid-sagittal: Equal left and right portions.

      • Para-sagittal: Unequal left and right portions.

Anatomical Landmarks (Landmark to Layperson Terminology)

  • Cranium (Cranial): Skull / Head

  • Oris (Oral): Mouth

  • Oculus (Orbital/Ocular): Eye

  • Bucca (Buccal): Cheek

  • Auris (Otic): Ear

  • Mentis (Mental): Chin

  • Cervicis (Cervical): Neck

  • Acromion (Acromial): Shoulder

  • Thoracis (Thoracic): Chest / Thorax

  • Pectus (Pectoral): Chest

  • Abdomen (Abdominal): Belly

  • Umbilicus (Umbilical): Navel

  • Coxal: Hip

  • Pelvis (Pelvic): Pelvis

  • Inguen (Inguinal): Groin

  • Pubis (Pubic): Pubic area

  • Gluteus (Gluteal): Buttock

  • Axilla (Axillary): Armpit

  • Brachium (Brachial): Arm

  • Antecubitis (Antecubital): Front of elbow

  • Olecranon (Olecranal): Elbow / Back of elbow

  • Antebrachium (Antebrachial): Forearm

  • Carpus (Carpal): Wrist

  • Manus (Manual): Hand

  • Palma (Palmar): Palm

  • Pollex: Thumb

  • Digits (Phalanges): Fingers or Toes

  • Femur (Femoral): Thigh

  • Patella (Patellar): Knee / Kneecap

  • Popliteus (Popliteal): Back of knee

  • Crus (Crural): Leg (front)

  • Sura (Sural): Calf (back)

  • Tarsus (Tarsal): Ankle

  • Calcaneus (Calcaneal): Heel

  • Pes (Pedal): Foot

  • Dorsum: Top of foot / Back

  • Planta (Plantar): Sole of foot

  • Hallux: Great toe

  • Lumbus (Lumbar): Loin / Lower back

  • Sacrum (Sacral): Sacrum

Body Cavities and Membranes

  • Function of Cavities: Contain, compartmentalize, and protect organs while allowing interconnection.

  • Dorsal Body Cavity (Posterior):

    1. Cranial Cavity: Enclosed by skull bones; houses the brain. The brain is protected by meningeal layers and bathed in Cerebrospinal Fluid (CSF).

    2. Spinal Cavity: Enclosed by the vertebral column; contains the spinal cord. Protected by spinal meninges and CSF.

  • Ventral Body Cavity (Anterior): Separated into two divisions by the diaphragm.

    1. Thoracic Cavity: Enclosed by the ribcage.

      • Pleural Cavities: Two cavities containing the Right and Left lungs; surrounded by pleural fluid.

      • Mediastinum: Area between the lungs; contains the thymus gland, trachea, esophagus, aorta, major veins, and nerves.

      • Pericardial Cavity: Located within the mediastinum; contains the heart bathed in pericardial fluid.

    2. Abdominopelvic Cavity: Subdivided by an imaginary plane.

      • Abdominal Cavity: Contains stomach, small intestine, liver, gallbladder, pancreas, spleen, and most of the colon (viscera).

      • Pelvic Cavity: Situated in the bony pelvic basin; contains the urinary bladder, rectum, lower colon, and reproductive organs.

  • Serous Membranes: Lined all ventral internal body cavities (pericardium, pleura, and peritoneum). They provide a moist, slippery surface to reduce friction between moving surfaces.

Anatomical Position and Directions

  • Standard Anatomical Position: A universal frame of reference where the subject is standing upright, feet together, facing forward, arms at sides with palms facing forward (anterior).

    • Supine: Palms facing forward (or lying on the back).

    • Prone: Palms facing posterior (or lying on the stomach).

  • Anatomical Directions:

    • Superior / Inferior: Above / Below.

    • Posterior / Anterior: Back / Front.

    • Dorsal / Ventral: Back / Front (used interchangeably with posterior/anterior in humans).

    • Deep / Superficial: Away from surface / Toward surface.

    • Distal / Proximal: Further from point of attachment / Closer to point of attachment.

    • Lateral / Medial: Away from midline / Toward midline.

Cytology: Review of the Cell

  • Cell Population: The human body contains approximately 5050 to 60×101260 \times 10^{12} (trillions) of cells. They act as a coordinated community.

  • Health vs. Disease: In healthy states, cells cooperate. In disease states, cells may compete, destroy others, or Provide no function.

  • Cell Variety: There are approximately 200200 different types of cells (e.g., hepatocytes in the liver, neurons in nervous tissue, osteocytes in bone, adipocytes in fat).

  • Cell Membrane (Plasma Membrane):

    1. Boundary: Separates internal and external environments.

    2. Adhesion: Allows attachment to other membranes.

    3. Receptors: For hormones, neurotransmitters, and signals.

    4. Markers: Identifying markers for other cells.

  • Special Cell Features:

    • Cilia: Hair-like structures on the apical (exposed) surface used for moving substances (e.g., mucus) across the surface.

    • Microvilli: Membrane extensions that increase surface area for absorption.

    • Flagellum: Whip-like structure for cell movement (e.g., spermatozoa).

  • Cell Membrane Permeability:

    • Impermeable: Restricts all molecules.

    • Selectively Permeable: Allows specific molecules to pass (standard for plasma membranes).

    • Highly Permeable: Allows almost everything to pass.

  • Cell Attachments and Junctions:

    • Tight Junction: Near the apical surface of epithelium; creates a water-tight seal.

    • Desmosome: Lightly tacks cells together; usually near the basal end.

    • Hemidesmosomes: Tethers cells to the basement membrane.

    • Gap Junction: Physical opening allowing direct communication of ions between cells.

Cell Naming Conventions

  • -cyte: Suffix indicating a mature cell that resides in and maintains tissue (e.g., chondrocyte, hepatocyte, adipocyte).

  • -blast: Suffix indicating a cell that "builds" or makes something (e.g., fibroblast makes fibers).

  • -clast: Suffix indicating a cell that breaks down structures (e.g., osteoclast breaks down bone matrix).

  • Note: Adipocytes specifically store triglycerides (fat).