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HUMAN ANATOMY AND PHYSIOLOGY - UNIT 1: THE HUMAN ORGANISM

Anatomy and Physiology Essentials

  • Anatomy: How the body is structured; includes the shapes, sizes, and features of body parts.

    • Etymology: Ana means 'up' or 'apart,' and tomos means 'to cut'.

Types of Anatomy

  • Gross (macroscopic) anatomy: Structures you can see without a microscope.

  • Microanatomy (microscopic) anatomy: Structures you need a microscope to see.

    • Histology: The study of tissues.

    • Cytology: The study of individual cells.

    • Histopathology: The study of diseased tissues.

Other Ways to Study Anatomy

  • Regional anatomy: Looking at all the structures in one specific area of the body (like the chest or abdomen).

  • Systemic anatomy: Studying the anatomy of each organ system separately (like the digestive system).

  • Surface anatomy: Understanding how internal structures relate to what you can see on the surface of the body (e.g., knowing where to find McBurney’s point for the appendix).

Physiology

  • Physiology: How the body works; explains how and why body parts function.

  • Examples: How muscles contract, how the heart beats, how we breathe, and how digestion happens.

Structural Organization

  • Levels (largest to smallest):

    • Organism → Organ System → Organ → Tissue → Cell → Organelle → Molecule → Atom

  • Reductionism: Understanding complex systems by breaking them down into smaller parts and seeing how they fit together.

The Organ Systems (Overview)

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

    • Functions: Protects the body, makes vitamin D, prevents drying out and entry of germs, has sensory receptors.

  • Skeletal: 206 bones.

    • Functions: Protection, support, allows movement, stores minerals (like calcium).

  • Muscular: Over 600 muscles.

    • Functions: Movement, posture, generates heat.

  • Nervous: Brain, spinal cord, and nerves.

    • Functions: Fast control, monitors the environment, starts responses.

  • Endocrine: Glands that release hormones (pituitary, thyroid, etc.).

    • Functions: Long-term regulation, growth, reproduction, and metabolism.

  • Cardiovascular: Heart and blood vessels.

    • Functions: Pumps blood, transports nutrients, gases, wastes, and signals.

  • Lymphatic/Immune: Vessels, nodes, spleen, and bone marrow.

    • Functions: Returns leaked fluid, removes debris, defends against germs.

  • Respiratory: Nasal cavity, pharynx, trachea, bronchi, and lungs.

    • Functions: Gas exchange (oxygen in, carbon dioxide out), regulates blood pH.

  • Digestive: Mouth, esophagus, stomach, intestines, rectum, and related organs.

    • Functions: Breaks down and absorbs nutrients.

  • Urinary: Kidneys, ureters, bladder, and urethra.

    • Functions: Removes waste, regulates water, electrolytes, and acid-base balance.

  • Reproductive: Testes/penis in males, ovaries/uterus in females.

    • Functions: Produces gametes and hormones; females support the developing fetus and lactation.

Life Functions

  • Organization: Having boundaries to protect the inside.

  • Metabolism: All the chemical reactions in the body; using energy from food for movement, body functions, growth, and repair.

    • Anabolism: Building complex molecules.

    • Catabolism: Breaking down complex molecules to release energy.

  • Responsiveness: Sensing and reacting to changes inside or outside the body.

  • Movement: Moving around or internal movement (like blood flow).

  • Development: Cells becoming specialized (differentiation); growth (increasing in size); reproduction (making new organisms).

Homeostasis

  • Homeostasis: Keeping stable internal conditions despite external changes.

  • The cell’s environment: The fluid around cells must have the right nutrients and ions; homeostasis keeps this stable.

  • Negative feedback loop: A loop that restores balance.

    • Sensor detects a change → sends input to the control center (e.g., brain) → control center activates an effector → effector’s response restores balance.

    • Example: Blood pressure regulation.

    • Sensors detect BP changes → send info to the brain → brain tells heart/vessels to adjust BP.

  • Positive feedback loop: Amplifies a change until a specific endpoint (e.g., labor contractions, blood clotting).

Homeostasis in Practice

  • Most body processes aim to maintain homeostasis.

  • Key terms: Sensor, control center, effector, input, output, set point, error signal.

Body Directions and Regions

  • Directional terms:

    • Superior (cranial): Toward the head; Inferior (caudal): Toward the feet.

    • Anterior (ventral): Front; Posterior (dorsal): Back.

    • Medial: Toward the midline; Lateral: Away from the midline.

    • Proximal: Nearer to the point of attachment; Distal: Farther from the point of attachment.

    • Superficial: At the surface; Deep: Internal.

  • Regional terms: Terms for different body regions (cephalic, cervical, thoracic, abdominal, pelvic, limbs, etc.).

  • Body planes:

    • Sagittal: Divides body into right and left.

    • Midsagittal: Exactly in the midline.

    • Frontal (coronal): Divides body into front and back.

    • Transverse (horizontal): Divides body into top and bottom.

  • Planes in motion: Examples of activities in each plane (lunges, jumping jacks, twisting).

Body Cavities

  • Two main cavities: Dorsal (posterior) and Ventral (anterior).

  • Dorsal cavity: Contains the cranial cavity (brain) and vertebral cavity (spinal cord).

  • Ventral cavity: Contains the thoracic cavity (above the diaphragm) and abdominopelvic cavity (below the diaphragm).

  • Thoracic cavity: Contains pleural cavities (lungs) and mediastinum (heart).

  • Abdominopelvic cavity: Contains the abdominal cavity (stomach, intestines, liver) and pelvic cavity (bladder, rectum, reproductive organs).

  • Serous membranes: Cover organs (visceral), line cavities (parietal), with fluid in between to reduce friction.

Abdominopelvic Regions

  • 9 regions: Umbilical, Epigastric, Hypogastric (pubic), Left/Right Hypochondriac, Left/Right Lumbar, Left/Right Iliac (Inguinal).

  • 4 quadrants: RUQ, LUQ, RLQ, LLQ; used for quick localization of conditions.

Medical Imaging

  • X-ray: Good for bones; quick assessment of fractures and dental issues.

  • Computed Tomography (CT): Imaging by sections; good for bone, soft tissue, tumors, and infections.

  • Magnetic Resonance Imaging (MRI): Excellent for soft tissue; no radiation.

  • Positron Emission Tomography (PET): Shows physiological activity; useful for cancer, infections, and heart disease.

  • Ultrasonography (US): Noninvasive; used for fetal development and heart function.

Key Takeaways

  • Focus: The human body, with all its interconnected systems.

  • Core concepts: Anatomy (structure) and physiology (function);

  • Organization: From atoms to the entire organism.

  • Homeostasis: Keeping a stable internal environment.

  • Feedback mechanisms: How the body maintains balance.

  • Imaging: Used for diagnosis.

  • Essentials: Oxygen, nutrients, heat, water, ions, and atmospheric pressure.

  • Basic metrics: 206 bones, about 10^{14} cells