Human Anatomy: The Human Body: An Orientation

Overview of Anatomy and Physiology

  • Anatomy: The study of the structure of the human body.
  • Physiology: The study of body function.
  • Subdisciplines of Anatomy:
    • Gross Anatomy: This category includes:
      • Regional Anatomy: Focusing on specific areas of the body.
      • Systemic Anatomy: Studying body systems.
      • Surface Anatomy: Examining the external form of the body and its relation to deeper structures.
    • Microscopic Anatomy:
      • Cytology: The study of cells.
      • Histology: The study of tissues.

Other Types of Anatomical Studies

  • Developmental Anatomy: Investigates the structural changes from fertilization through to adulthood.
  • Embryology: A subset of developmental anatomy that specifically examines the period from fertilization to week 88.
  • Comparative Anatomy: Involves the study of anatomical similarities and differences across different types of animals.

Characteristics of Life

  • Responsiveness: The ability to respond to changes in the environment and the capacity to make long-lasting adjustments.
  • Growth: An increase in total size, achieved through the increase in the size of individual cells and the number of cells.
  • Differentiation: The process where unspecialized cells become specialized cells for specific tasks.
  • Reproduction: The mechanism for the production of new generations of the same organism.
  • Movement:
    • Internal Movement: Processes occurring inside the body, such as digestion.
    • External Movement: Physical activities involving the whole body, such as walking.

Metabolism and Life Processes

  • Metabolism: The sum of all chemical reactions occurring within the body.
    • Anabolism: The metabolic process characterized by the building of complex molecules.
    • Catabolism: The metabolic process characterized by the breakdown of complex molecules.
  • Absorption: The specific process of bringing material into the body.
  • Respiration: Encompasses the absorption, transport, and use of oxygen (O2O_2) by cells.
  • Excretion: The process of removing waste products from the body.

The Hierarchy of Structural Organization

  • Chemical Level: The most basic level where atoms combine to form molecules. Molecules further combine to form macromolecules, which include carbohydrates, lipids, proteins, and nucleic acids.
  • Cellular Level: Cells and their functional subunits. A cell is considered the smallest level of organization that constitutes life. For example, phospholipid molecules are structural components forming the plasma membrane of a cell.
  • Tissue Level: Consists of a group of similar cells and associated extracellular material performing a common function. An example is epithelial tissue forming the inner lining of blood vessels.
  • Organ Level: A discrete structure composed of more than one tissue type (multiple tissue types) working together. Examples include the heart, liver, brain, femur, and blood vessels.
  • Organ System Level: A unified group of organs and tissues working together to perform a specific common purpose. The cardiovascular system is an example, consisting of the heart, blood, and blood vessels.
  • Organismal Level: The most complex level of organization representing the whole person. This level results from all simpler levels (organ systems) working interdependently to support a single living individual.

Overview of Organ Systems

  • Integumentary System:
    • Forms the external body covering.
    • Protects deeper tissues from injury.
    • Regulates body temperature.
    • Synthesizes Vitamin D.
    • Provides the site for cutaneous receptors (sensing pain, pressure, etc.) and contains sweat and oil glands.
  • Skeletal System:
    • Protects and supports body organs.
    • Provides a structural framework for muscles to cause movement.
    • Site where blood cells are formed within bones.
    • Stores minerals.
  • Muscular System (Axial and Appendicular muscles):
    • Allows for locomotion and movement of the body.
    • Provides support and maintains posture.
    • Produces heat and allows for facial expression.
    • Manipulation of the environment.
  • Nervous System:
    • Serves as the fast-acting control system of the body.
    • Responds to both internal and external changes.
    • Activates muscles and glands as needed.
  • Endocrine System:
    • Glands secrete hormones to regulate various processes.
    • Regulates growth, reproduction, and nutrient use.
    • Maintains temperature, day/night cycles, calcium levels, blood pressure, blood glucose, heart rate, and breathing.
  • Cardiovascular System:
    • Blood vessels transport blood throughout the body.
    • Blood carries oxygen (O2O_2), carbon dioxide (CO2CO_2), nutrients, and wastes.
    • The heart acts as a pump, moving blood through the vessels.
  • Lymphatic System / Immunity:
    • Picks up fluid leaked from blood vessels and returns it to the blood.
    • Disposes of debris within the lymphatic system.
    • Houses white blood cells (lymphocytes).
    • Mounts an immune attack against foreign substances.
  • Respiratory System:
    • Keeps blood continuously supplied with oxygen (O2O_2) and removes carbon dioxide (CO2CO_2).
    • Gas exchange occurs through the thin walls of air sacs in the lungs.
    • Responsible for the production of vocal sounds.
  • Digestive System:
    • Breaks down food into units that can be absorbed.
    • Obtains essential building blocks and nutrients for the body.
    • Eliminates indigestible products as feces.
  • Urinary System:
    • Eliminates nitrogenous wastes and other waste products from the blood.
    • Regulates the water, electrolyte, and acid-base balance of the blood.
    • Plays an important role in maintaining blood pressure and blood volume.
  • Reproductive System:
    • Primary function is to produce offspring via gametes (sperm and eggs).
    • Produces sex hormones.
    • Female: Structures serve as sites for fertilization and the development of the fetus. Mammary glands produce milk.
    • Male: Ducts and glands assist in the delivery of sperm to the female reproductive tract.
    • Conceptual Question: Is this system primarily for individual survival or population level survival?

Units of Measurement

  • Medicine utilizes the metric system as the standard system of measurement.
  • It is a universal system easily converted by units of 1010.
  • Distance: Measured in Meters (with subdivisions like centimeter, decimeter, micrometer, etc.).
  • Volume: Measured in Liters (subdivision: milliliter).
  • Mass: Measured in Grams (subdivision: kilogram).

The Language of Anatomy and Human Body Structural Plan

  • Introduction: Anatomical language is used for precise communication to provide exact information. Terms are rooted in Latin and Greek.
  • Human Body Structural Plan:
    • Backbone: Part of the central structure.
    • Tube-within-a-tube: Refers to the inner tube (the digestive tract) and the outer tube (the body wall).
    • Bilateral Symmetry: The body has distinct left and right sides.
  • Regional Terms:
    • Axial Region: Represents the axis of the body, including the head, neck, and trunk.
    • Appendicular Region: Includes the appendages (limbs).
  • Standard Directional Terms: Used by professionals to describe the location of one body part relative to another.

Anatomical Landmarks and Position

  • Anatomical Position: A standardized reference point where the individual is standing with feet flat on the floor, hands at the sides, and palms facing forward (anterior).
  • Supine: Lying down face-up while in the anatomical position.
  • Prone: Lying down face-down while in the anatomical position.

Regional Terms - Specific Locations

  • Axial Region - Cephalic (Head): Frontal (forehead), Orbital (eye), Nasal (nose), Oral (mouth), Mental (chin), Otic (ear), Occipital (back of head).
  • Axial Region - Cervical: Neck.
  • Axial Region - Thoracic: Sternal, Axillary (armpit), Mammary (breast).
  • Axial Region - Abdominal: Umbilical.
  • Axial Region - Pelvic: Inguinal (groin).
  • Axial Region - Pubic: Genital.
  • Axial Region - Back (Dorsum): Scapular (shoulder blade), Vertebral (spine), Lumbar (lower back), Sacral (between hips), Gluteal (buttock), Perineal (between anus and external genitalia).
  • Appendicular Region - Upper Limb: Acromial (shoulder), Brachial (arm), Antecubital (front of elbow), Olecranal (back of elbow), Antebrachial (forearm), Carpal (wrist).
  • Appendicular Region - Manus (Hand): Pollex (thumb), Palmar, Digital (fingers), Metacarpal (back of hand).
  • Appendicular Region - Lower Limb: Coxal (hip), Femoral (thigh), Patellar (kneecap), Popliteal (back of knee), Crural (leg/shin), Sural (calf), Fibular/Peroneal (side of leg).
  • Appendicular Region - Pedal (Foot): Tarsal (ankle), Metatarsal, Digital (toes), Hallux (great toe), Calcaneal (heel), Plantar (sole).

Standard Directional Terms

  • Superior (Cranial): Toward the head end or upper part of a structure; above. (Example: The head is superior to the abdomen).
  • Inferior (Caudal): Away from the head end or toward the lower part of a structure; below. (Example: The intestines are inferior to the liver).
  • Anterior (Ventral): Toward or at the front of the body; in front of. (Example: The sternum is anterior to the heart).
  • Posterior (Dorsal): Toward or at the back of the body; behind. (Example: The vertebra is posterior to the heart).
  • Medial: Toward the middle or midline of the body; on the inner side of. (Example: The heart is medial to the lungs).
  • Lateral: Away from the midline of the body; on the outer side of. (Example: The thumb is lateral to the pinky).
  • Ipsilateral: Located on the same side of the body. (Example: The right hand and right foot are ipsilateral).
  • Contralateral: Located on the opposite side of the body. (Example: The right hand and left foot are contralateral).
  • Proximal: Nearer to the point of origin of a body part or the point of attachment of a limb to the body trunk. (Example: The elbow is proximal to the wrist).
  • Distal: Farther from the origin of a body part or attachment point. (Example: The knee is distal to the thigh).
  • Superficial (External): Toward or on the surface of the body. (Example: The skin is superficial to skeletal muscles).
  • Deep (Internal): Away from the body surface; more internal. (Example: The lungs are deep to the skin).
  • Note on Terminology: In humans, "anterior" and "ventral" are synonymous, as are "posterior" and "dorsal." However, in four-legged animals, "ventral" refers to the "belly" (inferior surface) and "dorsal" refers to the back (superior surface).

Body Planes and Sections

  • Sagittal Plane: Separates the body into left and right sides.
    • Midsagittal: Provides equal left and right sections.
    • Parasagittal: Offset sections parallel to the midline.
  • Frontal (Coronal) Plane: Separates the body into anterior (front) and posterior (back) sections.
  • Transverse (Horizontal) Plane: Separates the body into superior (top) and inferior (bottom) sections.
  • Oblique: Passes through at an angle that is between a transverse plane and either a sagittal or frontal plane.

Human Body Plan and Shared Vertebrate Features

  • All chordates/vertebrates share these features:
    • Tube-within-a-tube: Inner digestive tube and segmented outer tube.
    • Bilateral Symmetry.
    • Dorsal Hollow Nerve Cord: (Brain and spinal cord).
    • Notochord and Vertebrae: Provides axial support.
    • Pharyngeal Pouches: Found in embryos (around 55 weeks postconception).
    • Segmented Outer Layer: Including muscle segments (myotomes) between ribs.

Body Cavities and Subdivisions

  • Dorsal Body Cavity: Subdivided into:
    • Cranial Cavity: Contains the brain.
    • Vertebral Cavity: Contains the spinal cord.
  • Ventral Body Cavity: Subdivided into:
    • Thoracic Cavity: Discretely divided into:
      • Two lateral parts containing lungs, each surrounded by a Pleural Cavity.
      • Mediastinum: The central area containing the heart, which is surrounded by the Pericardial Cavity.
    • Abdominopelvic Cavity: Divided into two parts:
      • Abdominal Cavity: Contains digestive viscera such as the liver, stomach, and kidneys.
      • Pelvic Cavity: Lower portion containing the bladder, certain reproductive organs, and the rectum.

Serous Membranes and Cavities

  • Serous Cavities: Slit-like spaces lined by a serous membrane.
    • Visceral Layer: Lines the actual organ within the cavity.
    • Parietal Layer: Lines the wall of the body cavity itself.
  • Specific Serosae:
    • Pleura: Visceral and Parietal Pleura (Lungs).
    • Pericardium: Visceral layer of the serous pericardium and Parietal layer of the serous pericardium (Heart).
    • Peritoneum: Visceral and Parietal Peritoneum (Abdominal viscera/stomach/liver).
  • Serous Fluid: Produced by both layers of serous membranes to reduce friction as organs move.
  • Retroperitoneal: Organs located behind the peritoneum, such as the kidneys.

Abdominal Quadrants

Used by anatomists and clinicians to localize concerns within the abdomen:

  • Right Upper Quadrant (RUQ).
  • Left Upper Quadrant (LUQ).
  • Right Lower Quadrant (RLQ).
  • Left Lower Quadrant (LLQ).

Microscopy and Imaging Techniques

  • Microscopy: Examining structures too small for the naked eye.
    • Light Microscopy: Uses a beam of light; provides lower magnification.
    • Electron Microscopy: Uses beams of electrons; provides higher magnification.
    • Scanning Electron Microscopy (SEM): Provides three-dimensional pictures of whole, unsectioned surfaces (e.g., radula of sea hares).
  • Artifacts: Minor distortions of preserved tissues that occur during preparation; they are not exactly identical to living tissues.
  • X-Ray: Uses short electromagnetic waves. Ideal for bones and abnormally dense structures. Contrast media (like Barium) may be used for GI tract imaging.
  • Computed (Axial) Tomography (CT/CAT): Takes successive X-rays around a circumference; a computer creates a detailed picture of the section.
  • Angiography: Uses contrast dye to highlight vessel structures.
    • Digital Subtraction Angiography (DSA): Compares images before and after contrast injection to identify blockages or damage to vessel walls.
  • Positron Emission Tomography (PET): Detects radioactive isotopes injected into the body to form an image.
  • Sonography (Ultrasound): Uses high-frequency sound waves that echo off tissues.
  • Magnetic Resonance Imaging (MRI): Uses magnetic fields and radio waves to distinguish tissues based on relative water content; provides high-contrast images of soft tissues.

Key Requirements for Mastery

Students should be proficient in:

  • Subdivisions of anatomy.
  • Hierarchical levels of organization.
  • Human body plan characteristics.
  • Features of the anatomical position.
  • Comprehensive list of ALL regional and directional terms.
  • Identifying body planes and cavities.
  • Understanding various medical imaging techniques.