Anatomy Basics: Organization, Planes, Cavities, and Homeostasis

  • Organization: atoms → cells → organelles → tissues → organs → organ systems → body.
  • Cells and organelles: nucleus, cell membrane, cytoplasm; organelles include mitochondria, nucleus, lysosome, ribosome, endoplasmic reticulum.
  • Tissues and hierarchy: tissues form organs; organs form systems; systems form the body. Systems can have multiple organs; endocrine system has many organs.
  • Body basics: skin is the largest organ.
  • Anatomical position: standing, feet forward, palms forward; serves as a universal reference point.
  • Directional terms:
    • Anterior (front) vs. Posterior (back)
    • Superior (top) vs. Inferior (bottom)
    • Medial (toward midline) vs. Lateral (away from midline)
    • Proximal (closer to trunk) vs. Distal (farther from trunk)
    • Bilateral (both sides) vs. Unilateral (one side)
    • Ipsilateral (same side) vs. Contralateral (opposite sides)
  • Planes and sections:
    • Sagittal plane: divides left and right; midsagittal = along midline.
    • Frontal/Coronal plane: divides anterior and posterior.
    • Transverse (axial) plane: divides superior and inferior; also called cross-section.
    • Oblique plane: at an angle.
    • Longitudinal vs. transverse (cross) sections depend on cutting direction.
  • Planes in practice: cross sections are transverse; longitudinal cuts run along the long axis.
  • Body cavities and membranes:
    • Thoracic cavity (includes pleural cavities around lungs and pericardial cavity around heart) and mediastinum.
    • Diaphragm separates thorax from abdomen.
    • Abdominal cavity and pelvic cavity; pelvic line separates abdomen from pelvis.
    • Pleural cavities = lungs; pericardial cavity = heart.
    • Visceral membranes (cover organs) vs. Parietal membranes (lining cavities).
    • Cavity fluid (reduces friction): pericardial fluid in the pericardial cavity.
  • Abdominal regions and quadrants:
    • Nine-region scheme (e.g., epigastric, umbilical, hypogastric; right/left hypochondriac; right/left lumbar; right/left iliac/inguinal; pubic region).
    • Four-quadrant scheme: Right Upper, Left Upper, Right Lower, Left Lower.
    • Landmarks: umbilical region at the center; right/left iliac (inguinal) regions; epigastric, hypogastric, and hypochondriac regions.
  • Axes and skeleton:
    • Axial skeleton (blue in diagrams): skull, vertebral column, rib cage.
    • Appendicular skeleton (yellow): limbs and girdles.
  • Homeostasis and feedback:
    • Negative feedback: corrects toward a set point (e.g., temperature regulation).
    • Positive feedback: reinforces a process (e.g., oxytocin during childbirth).
    • Sensor (e.g., hypothalamus) → integrator → effector pathway; hormones commonly act via endocrine axes (hypothalamus → pituitary → target organ).
    • Set point: normal value; deviations trigger corrective responses.
  • Physiology vs pathology:
    • Physiology: normal function; Pathophysiology: disease-related dysfunction.
    • Cancer: tumors can be benign or malignant; caused by genetic mutations; malignant tumors can metastasize.
    • Aging: changes across systems; atrophy is tissue loss or wasting.
  • Quick study tips observed: after each chapter, check quick-check items; use structured plans and, when possible, reference exam-style resources (e.g., UWorld) for alignment with boards.
  • Terminology highlights from the lecture:
    • Parietal vs. Visceral: parietal lines the cavity; visceral covers the organ.
    • Apex (apex) of the heart: the farthest point from the base; base is opposite.
    • Dorsal (back) vs. Ventral (front); Supine (face up) vs. Prone (face down).
    • Proximal, Distal, Medial, Lateral, Midline, Bilateral, Ipsilateral, Contralateral.
    • Internal/external terms: intra- (inside), extra- (outside); intrace llular vs extracellular fluids (ICF vs ECF).
  • Summary takeaway: memorize the hierarchical organization, key directional terms, planes and sections, cavity anatomy and membranes, region/quadrant naming, and the basics of homeostasis and endocrine control for quick recall during exams.