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Anatomy and Physiology Lecture Notes

Chapter 1 Study Notes

Introduction to Anatomy and Physiology

  • Anatomy: The study of the structure of body parts at various levels.
    • Levels of Anatomy:
    • Gross Anatomy: Study of larger structures without a microscope.
    • Histology: Microscopic structure of tissues.
    • Cytology: Study of cells.
  • Physiology: The study of the function of body parts.
    • Each structure is custom-modeled to carry out a particular function.
    • Example: The nose is lined with hairs to perform a filtering function.

Anatomical Position

  • Defined as:
    • Body Facing Observer: The subject stands facing the observer.
    • Arms at Side: The arms are positioned downward along the sides of the body.
    • Palms Facing Forward (Supinated): The palms face anteriorly.
    • Note: This position may not be comfortable as hands naturally hang partially cupped towards the thigh.
  • Importance: Understanding the anatomical position is fundamental for correctly using directional terms.

Definitions of Limbs

  • Arm: The segment from the shoulder to the elbow on the Upper Extremity.
  • Forearm: The segment from the elbow to the wrist on the Upper Extremity.
  • Thigh: The segment from the hip to the knee on the Lower Extremity.
  • Leg: The segment from the knee to the ankle on the Lower Extremity.

Directional Terms (Anatomical Directions)

Note: (L) = Latin, (G) = Greek

  1. Dorsal: Back side (dorsal (L) = the back).
  2. Ventral: Belly side (ventral (L) = the belly).
  3. Anterior: The part which goes first (anterior is synonymous with ventral in bipeds).
    • Etymology: ante (L) = before; ped (L) = foot.
  4. Posterior: The part which follows (posterior = dorsal).
    • Etymology: post (L) = after, behind.
  5. Superior: Towards the head or above another structure.
  6. Inferior: Away from the head or below another structure.
  7. Lateral: Away from the midline.
  8. Medial: Towards the midline.
  9. Proximal:
    • a) Nearer to the point of attachment of an extremity to the trunk.
    • b) Nearer to the point of reference (origin).
    • Example: The arm (humerus) is proximal to the forearm (radius).
  10. Distal:
    • a) Further from the attachment of an extremity to the trunk.
    • b) Further from the point of reference (origin).
  11. Ipsilateral: On the same side of the body.
    • Example: Gall bladder (R) and appendix (R) are ipsilateral.
  12. Contralateral: On opposite sides of the body.
    • Example: Spleen (L) and appendix (R) are contralateral.

Body Planes and Sections

  • Plane: An imaginary flat surface.
  • Section: A flat surface resulting from a cut or image made through a structure.
    1. Sagittal Plane: Divides the body into right and left portions.
    2. Frontal Plane (Coronal Plane): Divides the body into front and back (anterior and posterior) sections.
    3. Transverse Plane (Cross Section): Divides the body into superior and inferior portions along a horizontal plane.
      • Analogy for understanding: A slice of bread is a cross-section of a loaf of bread.

Body Cavities

  • Overview: Body cavities that do not open to the outside are lined with moist serous membranes.
  • Dorsal Body Cavity: The back side of the body.
    • Cranial Cavity: Contains the brain covered with meninges.
    • Vertebral (Spinal) Canal: Contains the spinal cord covered with meninges.
  • Ventral Body Cavity: The belly side of the body.
    • General Characteristics:
    • The organs inside are collectively called viscera (L = organs).
    • Lined with serous membranes:
      • Parietal: Lines the wall of the cavity.
      • Visceral: Covers the organs of the cavity.
    • Examples of serous membranes:
      • Pleura: Associated with the lungs.
      • Pericardium: Associated with the heart.
      • Peritoneum: Associated with the abdominal organs.
  • Diaphragm: Divides the thoracic cavity from the abdominopelvic cavity; unique to mammals.

Thoracic Cavity

  • Pleural Cavity: Contains lungs and is lined with parietal and visceral pleura.
    • Historical etymology: Pleura (G) = side, rib.
  • Mediastinum: Mass of soft tissue between lungs from sternum to vertebral column, does NOT include lungs or bones:
    1. Anterior Mediastinum: Contains the Thymus.
    2. Middle Mediastinum: Contains the heart in its pericardial cavity, with parietal and visceral pericardium.
    3. Posterior Mediastinum: Contains the esophagus, trachea, and aorta.

Abdominopelvic Cavity

  • General Characteristics:
    • The walls are lined with parietal peritoneum, and organs are covered with visceral peritoneum.
  • Divisions:
    1. Abdominal Cavity: Contains most digestive organs.
    2. Pelvic Cavity: Everything below the pelvic brim.

Homeostasis

  • Definition: Maintenance of a stable (balanced) internal environment.
  • Primary Control Mechanism: Negative feedback mechanisms are the primary mechanism of control.
  • Stressors: Homeostasis is continually disturbed by stressors that create imbalances in extracellular fluid (ECF):
    • Examples of stressors include heat, cold, decreased O2, changes in blood pressure, changes in H+ levels, hormone imbalances, pain, loud noises, decreased glucose, infections, unpleasant thoughts, poisoning, etc.
  • Extracellular Fluid (ECF): Comprises 1/3 of body fluid and includes:
    1. Plasma: 20% of ECF, produces interstitial fluid (IF) at capillary beds by blood pressure.
    2. Interstitial Fluid (IF): 80% of ECF, fluid between cells in the body.
    3. Lymph: Less than 1% of ECF, constantly returns IF to the blood.
  • Intracellular Fluid (ICF): Comprises 2/3 of body fluid, fluid within cells.
  • Composition: Both ECF and ICF contain gases, nutrients, and electrolytes.
  • Major Systems Controlling Homeostasis:
    1. Nervous System: Fast, using nerve impulses.
    2. Endocrine System: Slower, using hormones that travel in the blood.
  • Negative Feedback: The output reverses the stimulus input (stressor).
  • Positive Feedback: Enhances (intensifies) the stimulus and continues until interrupted.
    • Examples: Labor contractions and blood clotting.
  • Pathologies: Disease conditions that result from disrupted homeostasis.

Medical Imaging

Overview of Imaging Modalities

  1. Conventional X-ray:

    • Uses ionizing radiation directed through the body.
    • Tissues absorb radiation based on densities.
    • Economical but may produce unclear images.
    • Uses low doses of X-rays (e.g., in mammograms and bone densitometry).
    • Contrast X-rays (e.g., angiograms, barium contrast x-rays).

  2. CT Scan (Computerized Tomography):

    • Uses series of X-rays arcing around the body producing images (CT scans).
    • Computer reconstructs images into multiple slices (tomograms).
    • Useful for detecting bone issues, soft tissue, blood vessels generally not visible by conventional X-ray.
    • 3D images can be constructed by stacking slices.

  3. MRI (Magnetic Resonance Imaging):

    • Does NOT use ionizing radiation.
    • More expensive than CT scans.
    • Uses low-energy radio waves within a strong magnetic field.
    • Aligns protons in atoms, especially those of water molecules.
    • Produces images by measuring the response of protons to radio waves.
    • Cannot be used on patients with certain metal objects (e.g., pacemakers, some tattoos).
    • More effective than CT for tumor detection and assessing joints/ligaments.

  4. PET Scan (Positron Emission Tomography):

    • Positrons are emitted from radioactive isotopes.
    • Radioisotopes attached to glucose molecules are injected into the blood.
    • As the radioisotopes circulate and metabolize, they emit gamma rays detected by the scanner.
    • Constructs multicolored images showing metabolic activity (useful for detecting cancer).
    • Also assesses brain function, particularly in Alzheimer’s disease.

  5. Ultrasound:

    • Uses high-frequency sound waves that echo off body tissues.
    • Observes fetuses, blood flow, and studies abdominal/pelvic organs.
    • Less effective for assessing lungs, brain, and spinal cord, especially in obese individuals or with scars.