UNM BIOL 2210 Learning Objectives - Fall 2025 Skeletal System & Articulations Study Guide

UNM BIOL 2210 Learning Objectives - Fall 2025 Skeletal System & Articulations Study Guide

1. General functions of bone & the skeletal system

  • Major Functions of the Skeletal System

    • Protection:

    • Protects underlying organs and holds organs in place.

    • Mineral Storage:

    • Acts as a storehouse for essential minerals such as calcium, phosphorus, and magnesium salts.

    • Blood Cell Formation:

    • Facilitates the process called hematopoiesis, occurring in red bone marrow.

    • Fat Storage:

    • Serves as reserve storage of fat in yellow bone marrow, which cells use as fuel.

    • Muscle Attachment:

    • Acts as the site of attachment for the majority of skeletal muscles responsible for movement.

    • Support:

    • Provides structural framework, supporting the weight of the body.

2. Structural components – microscopic anatomy

  • Cellular and Extracellular Components of Bone Tissue

    • Cell Types:

    • Osteoblasts:

      • Found in the inner periosteum and endosteum, responsible for building bone by secreting the organic matrix and forming the inorganic matrix.

    • Osteocytes:

      • Formed from osteoblasts when surrounded and trapped by the bone matrix; they maintain the ECM and recruit osteoblasts to areas under tension.

    • Osteoclasts:

      • Large multinucleated cells located in shallow depressions on bone surfaces, responsible for breaking down bone to release nutrients into the bloodstream; they secrete H+ ions creating an acidic environment to break down bone.

    • Extracellular Matrix (ECM):

    • Inorganic Matrix (65% of bone weight):

      • Composed mainly of calcium salts and phosphorus in the form of hydroxyapatite crystals; vital for bone rigidity against compression.

    • Organic Matrix (35% of bone weight):

      • Known as osteoid, primarily consisting of collagen fibers, whose alignment with hydroxyapatite crystals significantly enhances the hardness of bones. Contains protein fibers, proteoglycans, glycosaminoglycans, glycoproteins, and bone-specific proteins like osteocalcin.

    • Role of Glycosaminoglycans and Proteoglycans:

      • Assist in drawing water from blood vessels and cells via osmosis, helping the tissue resist compression; glycoproteins bind hydroxyapatite with bone cells.

    • Types of Cartilage in the Skeletal System:

    • Hyaline Cartilage: Found in joints and ribs; resists compressive stress.

    • Fibrocartilage: Found in intervertebral disks; absorbs compressive forces.

    • Elastic Cartilage: Found in the external ear; provides structure with flexibility.

    • Roles of Dense Regular and Irregular Connective Tissue:

    • Dense Regular Collagenous CT:

      • Provides extreme tensile strength in one direction.

    • Dense Irregular Collagenous CT:

      • Provides tensile strength in multiple directions.

3. Structural components – gross anatomy

  • Components of a Long Bone:

    • Regions: Periosteum, endosteum, perforating fibers, articular cartilage, compact bone, spongy bone, medullary cavity, diaphysis, nutrient artery, epiphysis, epiphyseal line, epiphyseal plate, red and yellow marrow.

  • Functions of Structural Components:

    • Each component plays a critical role in the overall function and stability of long bones.

4. Physiology of embryonic bone formation (ossification, osteogenesis)

  • Cellular Roles in Bone Formation:

    • Osteogenic Cells, Osteoblasts, Chondroblasts, and Osteoclasts:

    • Osteoblasts develop from mesenchymal cells and initiate the secretion of organic matrix within the primary ossification center; this matrix then calcifies, trapping the osteocytes.

    • Osteoblasts lay down early spongy bone trabeculae, leading to the formation of periosteum and subsequent compact bone.

  • Primary vs. Secondary Bone:

    • Primary Bone: Formed during fetal development, replaced by secondary bone after resorption.

    • Secondary Bone: Forms after embryonic development, where compact bone forms before spongy bone.

  • Intramembranous vs. Endochondral Ossification:

    • Intramembranous Ossification: Directly forms bone without a cartilage model.

    • Endochondral Bone Formation: Uses a cartilage scaffold for gradual ossification.

5. Physiology of bone growth, repair, & remodeling

  • Chondroblasts, Osteoblasts, and Osteoclasts in Bone Dynamics:

    • Longitudinal Growth: Chondrocytes proliferate, enlarge, and undergo calcification leading to the growth in bone length.

    • Appositional Growth: Osteoblasts add new layers of bone, affecting diameter while osteoclasts remodel inner circumferential lamellae.

  • Hormonal Regulation of Skeleton Growth:

    • Growth Hormone: Stimulates mitosis of chondrocytes and osteogenic cells, enhancing growth.

    • Testosterone: Increases appositional growth and the rate of mitosis in the epiphyseal plate leading to growth spurts in males.

    • Estrogen: Promotes longitudinal growth and inhibits osteoclast activity; quicker closure of the epiphyseal plate compared to testosterone.

  • Regulatory Roles of Calcitonin, Parathyroid Hormone, and Calcitriol:

    • Parathyroid Hormone (PTH): Released when blood calcium levels are low, enhancing osteoclast activity to release calcium into the bloodstream.

    • Calcitonin: Released when calcium levels are high to decrease osteoclast activity.

    • Calcitriol (Vitamin D): Plays a critical role in calcium absorption; deficiency leads to brittle bones and weakness.

  • Contrast in Remodeling Processes:

    • Children: Focused on growth and rapid healing; faster than in adults.

    • Adults: Primarily repair and maintenance, slower and less detailed.

6. Organization of the skeletal system

  • Major Divisions of the Skeletal System:

    • Axial Skeleton:

    • Comprises 22 skull bones (cranial and facial), approximately 33 vertebral column bones (vertebrae, sacrum, coccyx), and 27 thoracic cage bones (12 pairs of ribs and sternum).

    • Appendicular Skeleton:

    • Includes pectoral girdle (clavicle, scapula), upper limb bones (humerus, radius, ulna), wrist and hand bones, pelvic girdle (both halves of pelvis, sacrum), and lower limb bones (femur, tibia, fibula, ankle, foot bones).

7. Gross anatomy of bones

  • Types of Bones by Shape:

    • Long Bones:

    • Longer than wide, serving as major support structures and allowing muscle attachments; spongy bone at the epiphysis, compact bone at diaphysis.

    • Short Bones:

    • Nearly equal in length and width (e.g., carpals), providing stability.

    • Flat Bones:

    • Thin (e.g., sternum, skull), protecting underlying organs.

    • Irregular Bones:

    • Complex shapes (e.g., vertebrae), allowing for protection of complex organs like the spinal cord.

    • Sesamoid Bones:

    • Round and flat (e.g., patella), acting as reinforcement for tendons.

  • Identification of Specific Bones:

    • Cranial Bones: Frontal, parietal, temporal, occipital, sphenoid, ethmoid.

    • Facial Bones: Maxilla, zygomatic, nasal, mandible.

    • Pectoral Girdle: Clavicle, scapula.

    • Thoracic Cage: Sternum, ribs.

    • Pelvic Bones: Coxal bone, sacrum, coccyx.

    • Vertebral Column: Cervical, thoracic, lumbar vertebrae, sacrum, coccyx.

    • Limb Bones: Upper limb (humerus, radius, ulna, carpals, metacarpals, phalanges), lower limb (femur, tibia, fibula, tarsals, metatarsals, phalanges).

8. Classification of Joints

  • Functional Classification Based on Movement:

    • Synarthrotic Joints: No movement, providing the greatest stability; examples include skull sutures, teeth sockets, first pair of ribs and sternum.

    • Amphiarthrotic Joints: Allow limited movement with significant stability; example include intervertebral disks.

    • Diarthrotic Joints: Freely movable joints allowing a variety of movements; examples include shoulder, knee, ankle, and hip joints.

  • Anatomical Classification Based on Structure:

    • Fibrous Joints: United by dense collagen fibers, functionally synarthroses or amphiarthroses; examples include skull sutures, gomphosis, syndesmosis.

    • Cartilaginous Joints: Comprised of cartilage, functionally synarthroses or amphiarthroses; examples include intervertebral disks.

    • Synovial Joints: Contain a joint space filled with synovial fluid allowing diarthrosis with the greatest degree of movement.

  • Relation of Functional and Anatomical Classifications:

    • Functional classifications directly correlate with the structural makeup of joints, indicating the degree of movement allowed based on how the joints are constructed.

9. Synovial Joints

  • Structural Components of Synovial Joints:

    • Includes accessory structures such as bursae, tendon sheaths, ligaments, all of which play roles in stability and movement.

  • Six Structural Types of Synovial Joints:

    • Each type has specific anatomical features, locations in the body, and corresponding movements:

    • Synovial joints allow for increased articulation and flexibility depending on the type of joint.

    • Anatomical Features:

    • Various features including the joint capsule, synovial membrane, and articular cartilage can be modified across the joint classifications to impact functionality.