BIOL 201 Lecture 7 Spring 2025

Lecture Overview

• Course: BIOL 201 Anatomy and Physiology I

• Lecture: 7 – Osteology, Axial Skeletal System

• Assignments Due: Interactive Reading Chapter 7, Quiz 6 by 2pm

Announcements

• Due date reminder for Interactive reading Chapter 7 and Quiz 6.

• Ongoing grading of previous exams; results expected by Tuesday.

Classification of Bones by Shape

• Categories of Bone Shapes:

  • Irregular Bones: Not fitting standard classifications; includes vertebrae and hip bones.

  • Cranial Bones: Forms the skull.

  • Long Bones: Found in limbs (e.g., femur, humerus).

  • Short Bones: Roughly cube-shaped; found in wrists and ankles.

  • Flat Bones: Such as ribs, sternum.

  • Sesamoid Bones: Small, round bones that form within tendons (e.g., patella).

Gross Anatomy of Bones

• Common Structure of Bones:

  • Compact Bone: Dense outer layer, appearing smooth.

  • Spongy Bone: Internal structure resembling a honeycomb, contains trabeculae and marrow.

    • Trabeculae: Interconnected plates creating a lightweight structure.

  • Medullary Cavity: Hollow space filled with yellow marrow, located in the diaphysis.

Structure of a Long Bone

• Components Include:

  • Diaphysis: Shaft of the bone

  • Epiphyses: Bone ends

  • Blood Vessels: Extensive vascularization of bones

  • Membranes:

    • Periosteum: Outer layer providing muscle attachment

    • Endosteum: Covers internal surfaces.

Microscopic Structure of Bone

• Osteon (Haversian System): Fundamental structural unit of compact bone.

  • Lamellae: Concentric rings of bone tissue.

  • Central Canal: Houses blood vessels and nerves.

  • Canaliculi: Tiny channels for nutrient exchange.

Chemical Composition of Bone

• Bone Structure: Cells separated by an extracellular matrix.

  • Organic Components (35%):

    • Cells: Osteoblasts, osteocytes, osteoclasts.

    • Osteoid: Collagen fibers providing strength.

  • Inorganic Components (65%):

    • Calcium Phosphate: Resists compression, essential for bone hardness.

Bone Markings

• Categories:

  • Projections for muscle, tendon, and ligament attachment: e.g., Trochanters, spines.

  • Surfaces forming joints: e.g., Heads, facets.

  • Depressions and openings: e.g., Fossae, foramina, grooves.

Bone Repair and Fracture Healing

• Fracture Steps:

  1. Hematoma formation

  2. Callus formation by endosteum and periosteum cells

  3. Bony callus formation by osteoblasts

  4. Remodeling phase to restore bone structure.

• Types of Fractures:

  • Transverse, displaced, compression, spiral, epiphyseal, comminuted, greenstick, Colles, Pott's fractures.

The Axial Skeleton

• Composition:

  • Total Bones: 80 named bones.

  • Includes:

    • Skull (22 bones)

    • Hyoid + auditory bones (6)

    • Vertebral column

    • Bony thorax

• Functions: Support for head, neck, trunk, and protection of vital organs.

Vertebral Column

• Structure: Comprises 26 bones in adults.

• Functions:

  • Supports weight of head, neck, trunk

  • Protects spinal cord

  • Attachment points for ribs and muscles.

• Curvatures:

  • Four distinct curves enhance resilience and flexibility:

    • Primary: Thoracic and sacral curvatures

    • Secondary: Cervical and lumbar curvatures.

  • Abnormal curvatures include scoliosis, kyphosis, and lordosis.

Development of the Skeleton

• Growth Patterns:

  • Skeleton grows until 18-21 years.

  • Childhood: Bone formation exceeds resorption.

  • Old Age: Resorption predominates, leading to bone mass decline.

Study Guide Questions

• Key concepts to understand from Chapters 6 and 7 include:

  1. Bone classification by shape and structure.

  2. Microscopic structure of bones, including functions of osteocytes, osteoblasts, osteoclasts.

  3. Differences between compact and spongy bone.

  4. Calcium homeostasis and its implications on total body health.

  5. Mechanisms of fracture repair and the healing process.

  6. The development of the axial skeleton and its functional anatomy.