Lecture Notes 10/1/2025

Examination Policies and Practices

  • Assurance of Exam Integrity
    • Confirmation that exam questions will remain unchanged.
    • Mandatory disclosure of exam questions to students.

Bone Structure and Dynamics

  • Overview of Bone Softness and Strength
    • Discussion of bone density and potential issues when bones are too soft.
    • Warning that lower limb bones support the weight of the upper body.
    • Consequence for short bones leading to bowing, similar to a ballerina's posture.

Bone Anatomy

  • Patterns in Bone and Tissue
    • Comparison of bone patterns to tree whorls, reflecting growth patterns and age.
    • Explanation of the osteocyte's location in lacunae and within concentric lamellae.
  • Bone Structure Components
    • Description of osteons, their concentric layers, and structural arrangement.
    • Identification of central canals and their role as conduits for blood vessels; central canals also referred to as Haversian canals.
    • Discussion of spongy bone as highlighted through holes in bone layers.
    • Description of the periosteum, noting its two layers:
    • Outer layer producing perforating fibers.
    • Inner layer housing stem cells.
    • Mention of interstitial lamellae found between osteons, and circumferential lamellae surrounding bones.

Blood Vessel Interaction

  • Overview of Blood Supplies to Bone Tissue
    • Distinctive coloring for arteries (red) and veins (blue) regarding blood flow.
    • Description of branches from central canals termed "perforating branches".

Bone Type and Functionality

  • Differentiation between Types of Bone
    • Explanation of trabecular and cortical bone.
    • Discussion of red bone marrow and its misconceptions, emphasizing its role in red blood cell production.
    • Clarification that adult bone marrow transitions primarily to yellow marrow, which is comprised mainly of fat cells.

Calcium Dynamics and Ossification

  • Ectopic Ossification

    • Clarification on the meaning of ectopic (abnormal) ossification.
    • Identification of potential locations for ossification outside normal bone (e.g., lungs, brain, eye tissues, muscles, tendons, arteries).
    • Differentiation from atherosclerosis, which refers to cholesterol concentrations in arteries.

  • Calcium Phosphate Crystallization

    • Explanation of initial crystal formation attracting further calcium deposits.
    • Mention of how calcium phosphate solutions form in wildlife and their implications for ossification processes.

Bone Resorption Mechanism

  • Acidic Interaction with Bone
    • Description of resorption facilitated by osteoclasts utilizing hydrochloric acid to break down bone tissues.
    • Discussion on the role of osteocytes in maintaining bone equilibrium.

Homeostasis and Calcium Regulation

  • Normal Blood Calcium Levels

    • Definition: Homeostasis refers to the body's need for balance.
    • Normal blood calcium range: 9.2 - 10.4 ext{ mg/dL}
    • Explanation of conditions:
    • Hypercalcemia (high blood calcium) when levels exceed 10.4 ext{ mg/dL}.
    • Hypocalcemia (low blood calcium) reflects deficiencies.

  • Hormonal Regulation of Calcium

    • Discussion of three key hormones affecting calcium metabolism:
    1. PTH (Parathyroid Hormone): Causes bone resorption, increases blood calcium levels by acting on bones, kidneys, and intestines.
    2. Calcitonin: A weaker hormone that primarily encourages calcium deposition into bones when levels are too high.
    3. Calcitriol (Vitamin D): Activates absorption of calcium in the intestines and promotes reabsorption in the kidneys, functional only when converted to its active form in the kidneys.

Vitamin D Metabolism

  • Steps of Vitamin D Activation
    • Initiation occurs in the skin with 7-dehydrocholesterol exposure to UV light converting into cholecalciferol (Vitamin D3).
    • Transformation in the liver to calcidiol via hydroxylation.
    • Activation in the kidneys, converting to calcitriol, its bioactive form.

Classification and Types of Fractures

  • Stress vs. Pathological Fractures
    • Stress fractures arise from direct physical force (e.g., strikes, car accidents).
    • Pathological fractures occur without excessive force (e.g., during routine activities like coughing).
  • Types of Fractures
    • Nondisplaced fractures where the bone maintains its alignment.
    • Displaced fractures where bone shifts out of alignment
    • Comminuted fractures displaying severe fragmentation.

Summary of Fracture Assessment

  • Classification can be based on the fracture line, displacement, and comminution.