Skeletal System Overview
MODULE 3: Skeletal System
Course Information
Professor: Dr. Bianca Pedroza, PT, DPT, MS
Institution: Hillsborough Community College
Course: BSC 2085 Human Anatomy & Physiology
Overview of Related Chapters
Ch. 6: Bones & Skeletal Tissues
Ch. 7: The Skeleton
Ch. 8: Joints
Clinical Terms (Vocabulary)
Chapter 6: Bones & Skeletal Tissues
Achondroplasia: A genetic disorder resulting in dwarfism due to the abnormality of cartilage and bone development.
Bony Spur: A bony growth or protrusion that forms at a joint.
Ostealgia: Pain in a bone.
Osteitis: Inflammation of bone.
Osteogenesis Imperfecta: A genetic disorder characterized by fragile bones that break easily, often known as brittle bone disease.
Osteomyelitis: A severe bone infection, typically caused by bacteria.
Osteosarcoma: A type of bone cancer that typically starts in the osteoblasts.
Pathologic Fracture: A fracture that occurs in a bone that is weakened by disease.
Traction: A treatment method to relieve pressure and tension on the skeletal system by using weights or devices.
Chapter 7: The Skeleton
Chiropractic: A complementary and alternative medicine that focuses on the diagnosis and treatment of mechanical disorders of the musculoskeletal system.
Clubfoot: A congenital deformity in which the foot is twisted out of shape or position.
Laminectomy: A surgical procedure that involves the removal of the lamina, a part of the vertebra.
Orthopedist: A medical doctor specializing in diagnosing and treating skeletal disorders.
Pelvimetry: The measurement of the dimensions of the pelvis, often performed during pregnancy.
Spina Bifida: A birth defect that occurs when the spine does not close completely.
Spinal Fusion: A surgical procedure to join two or more vertebrae together to eliminate movement and reduce pain.
Chapter 8: Joints
Ankylosing Spondylitis: A type of arthritis that affects the spine, causing inflammation and pain.
Arthrology: The scientific study of joints and their functions.
Arthroplasty: Surgical reconstruction or replacement of a joint.
Chondromalacia Patellae: Softening of the cartilage on the underside of the kneecap.
Rheumatism: Pain and stiffness in the joints or muscles.
Synovitis: Inflammation of the synovial membrane, causing joint swelling and pain.
Introduction to Cartilage and Bone
The human skeleton begins as cartilages and fibrous membranes in the early development stages, later replaced predominantly by bone.
Adult skeleton retains a few cartilages primarily where flexibility is required.
Cartilage: Structure, Types, and Locations
Structure of Cartilage:
Composed mainly of water, allowing it to be resilient and regain its shape after compression.
Lacks nerves and blood vessels, which limits its ability to heal.
Surrounded by perichondrium (dense irregular connective tissue).
Contains chondrocytes housed in lacunae and a flexible extracellular matrix formed by chondroblasts.
Grows via:
Appositional Growth: Chondroblasts secrete new matrix along existing cartilage surfaces, expanding its width.
Interstitial Growth: Chondrocytes secrete matrix within cartilage, leading to growth in length.
Types of Cartilage
Hyaline Cartilage:
Most abundant type;
Provides support and flexibility;
Contains spherical chondrocytes and fine collagen fibers (microscopically undetectable);
Types include:
Articular Cartilage (joints at ends of bones)
Costal Cartilage (ribs & sternum)
Respiratory Cartilage (larynx & respiratory pathways)
Nasal Cartilage (external nose).
Elastic Cartilage:
More flexible, with elastic fibers;
Located at external ear and epiglottis.
Fibrocartilage:
High compressibility and tensile strength;
Composed of parallel rows of chondrocytes alternating with thick collagen fibers;
Found in menisci of knees and discs between vertebrae.
Perichondrium: Reinforces cartilage to resist expansion due to compression; also contains blood vessels for nourishment.
Bone: Structure, Types, and Locations
Bone Composition:
Osseous tissue prominently comprises bones, alongside nervous tissue, cartilage, dense connective tissue, and muscle/epithelial tissue in blood vessels.
Levels of Bone Structure:
Gross Anatomy:
Consists of compact and spongy bone, blood vessels, nerves, hemopoietic tissue, and bone markings.
Microscopic Anatomy:
Includes osteoprogenitor cells, osteoblasts, osteocytes, bone lining cells, and osteoclasts.
Chemical Composition:
Involves organic (living) and inorganic (mineralized) components.
Classification of Bones
By Shape:
Long Bones:
Cylinder-like; provides leverage.
Examples: Femur, tibia, fibula, humerus.
Short Bones:
Cube-like, offer stability while allowing some motion.
Examples: Carpals, tarsals.
Sesamoid Bones:
Small and round; found embedded in tendons.
Example: Patella, which protects tendons from compressive forces.
Flat Bones:
Thin and curved; serve as muscle attachment points and protect internal organs.
Examples: Sternum, ribs, scapulae.
Irregular Bones:
Complex shapes; protect internal organs.
Examples: Vertebrae, facial bones.
Detailed Structures of Long Bones
Gross Anatomy of Long Bones:
Composed of a shaft (diaphysis) and ends (epiphyses).
Diaphysis:
Long axis, surrounded by compact bone and containing a central medullary cavity filled with yellow marrow.
Epiphysis:
Outer compact bone covering a spongy interior; articular cartilage cushions joints.
Metaphysis:
Region between diaphysis and epiphysis, containing the growth plate.
Periosteum:
Double-layered membrane covering external surfaces of bones, contains osteogenic cells for bone formation and repair.
Anchors tendons and ligaments through perforating fibers.
Endosteum:
Connective tissue covering internal bone surfaces, including trabecular bone and canals in compact bone.
Bone Structure: Blood Vessels and Hematopoietic Tissue
Vascularization of Bones:
Richly supplied by blood vessels including:
Nutrient artery and vein for diaphysis access via nutrient foramen.
Epiphyseal arteries/veins serve each epiphysis.
Metaphyseal arteries/veins derived from nutrient vessels.
Hematopoietic Tissue (Red Marrow):
Produces red blood cells.
Changes in distribution between infancy (filled medullary cavities and spongy bone) and adulthood (mostly yellow marrow, with red marrow in select flat bones).
Bone Markings
Three Categories of Bone Markings:
Projections: Sites of muscle and ligament attachment (e.g., tuberosity, crest, process).
Joint Surfaces: Features forming joints (e.g., head, facet, condyle).
Openings/Depressions: For blood vessels and nerve passage (e.g., groove, fissure, foramen).
Microscopic Anatomy of Bone Tissue
Essential Cells:
Osteoprogenitor Cells: Stem cells that can differentiate into osteoblasts.
Osteoblasts: Bone-forming cells that secrete osteoid.
Osteocytes: Mature bone cells that maintain the bone matrix.
Bone Lining Cells: Cells on the surface of bones that help regulate the passage of calcium.
Osteoclasts: Bone-resorbing cells that break down bone tissue.
Chemical Composition of Bone
Organic Components:
Provide flexibility and tensile strength, crucial for resisting stretch and torsion; includes:
Osteoprogenitor cells, osteoblasts, osteocytes, bone lining cells, osteoclasts, ground substance, and collagen fibers.
Inorganic Components:
Provide hardness to bone, including:
Hydroxyapatites, predominantly calcium phosphates, tightly packed around collagen fibers in the extracellular matrix.
Bone Tissue Formation
Bone Development Timeline:
Initially only fibrous connective tissue and hyaline cartilage exist pre-eight weeks.
Ossification/Osteogenesis: The bone tissue formation process, which occurs in two main types:
Endochondral Ossification: Replacement of hyaline cartilage with bone below the skull (except clavicles).
Intramembranous Ossification: Development of flat bones (e.g., cranial bones) from fibrous membranes.
Postnatal Bone Growth
Bone Growth:
Length: Involves interstitial growth at the epiphyseal plate with specific zones: resting, proliferation, hypertrophic, calcification, ossification.
Width (Thickness): Appositional growth increases diameter through osteoblast activity in periosteum and osteoclast activity in endosteum.
Hormonal Regulation: Growth hormone for infancy (anterior pituitary) and sex hormones (estrogen, testosterone) during puberty regulate growth.
Bone Remodeling
Continuous Process: Bones undergoing deposition and resorption due to hormonal and mechanical stimuli.
Calculating and Resorbing Mechanism:
Osteoclasts release enzymes and acids to break down bone and transcytose dissolved materials back into the extracellular fluid.
Homeostasis of Calcium Levels: Hormones like PTH control serum calcium, stimulating bone resorption and calcium release when low.
Mechanical Stress Influence: Increased stress leads to greater bone density and development of prominent structures (example: skeletal adaptations to gravity).
Skull Anatomy
General Anatomical Features
Anterior, Posterior, Lateral, and Midsagittal Views: Key structures noted, including:
Frontal Bone: Forehead region.
Parietal Bones: On the sides of the head.
Temporal Bone: Includes the squamous part and mastoid process.
Occipital Bone: Base of the skull, contains foramen magnum.
Features of Mandible: Contains mental protuberance and angles, contributing to jaw structure.
Key Bone Markings
Occipital Condyle: Articulates with the first cervical vertebra.
Sella Turcica: Holds pituitary gland, located in sphenoid bone.
Various Foramina: Essential for nerve and vascular passage (e.g., mandibular foramen).
Vertebral Column
Regions
Cervical: Lordotic (concave posteriorly)
Thoracic: Kyphotic (convex posteriorly)
Lumbar: Lordotic (concave posteriorly)
Ligaments and Structure
Major ligaments such as anterior longitudinal, posterior longitudinal, ligamentum flavum support the vertebral column.
Intervertebral Discs: Contain nucleus pulposus (gel-like center) and anulus fibrosus (outer ring).
General Vertebrae Structure
Composed of a body, vertebral arch, and numerous processes (spinous, transverse).
Specific Types of Vertebrae
Cervical Vertebrae (C3-C7): Smaller size, bifid spinous processes, significant range of motion including flexion and rotation.
Atlas (C1): No body; involved in nodding motion.
Axis (C2): Contains dens for pivotal movement.
Thoracic Vertebrae (T1-T12): Larger, heart-shaped bodies with facets for rib articulation.
Lumbar Vertebrae (L1-L5): Largest vertebrae, primarily permit flexion and extension.
Sacrum & Coccyx: Fusion of vertebrae; supports pelvic girdle structure.
Thoracic Cage and Upper Extremity Bones
Scapula
Structures: Acromion, coracoid process, glenoid cavity, and various fossa (supra- and infra-).
Clavicle
Anatomical Features: Sternal end, acromial end, superior/inferior surface differentiations.
Humerus
Various anatomical landmarks such as greater tubercle and coronoid fossa.
Ulna and Radius
Descriptions of proximal and distal features like the olecranon and styloid processes.
Lower Extremity Bones
Femur
Key components: Head, neck, greater and lesser trochanters, and epicondyles.
Patella
Structure and articulation for femur; serves in knee joint mechanics.
Tibia and Fibula
Notable features such as medial and lateral condyles, interosseous membrane.
Joints Classification
Structural Categories
Fibrous Joints:
Types: Suture, Syndesmosis, Gomphosis.
Mainly immobile (synarthrosis) or slightly movable (amphiarthrosis).
Cartilaginous Joints:
Types: Synchondroses (hyaline cartilage), Symphyses (fibrocartilage).
Ranges from immobile to slightly movable.
Synovial Joints:
Types: Plane, hinge, pivot, condylar, saddle, ball-and-socket.
Freely movable (diarthrosis).
Functional Categories
Synarthroses: Immovable joints.
Amphiarthroses: Slightly movable joints.
Diarthroses: Freely movable joints.
Pathologies and Conditions
Fractures
Classification: Nondisplaced vs. Displaced, Complete vs. Incomplete, Open (compound) vs. Closed (simple).
Types: Comminuted, Spiral, Depressed, Compression, Epiphyseal, Greenstick.
Fracture Treatment & Repair
Begins with reduction:
Closed Reduction: Manual repositioning of bone ends.
Open Reduction: Surgical stabilization with screws/plates.
Four Stages of Repair:
Hematoma Formation
Fibrocartilaginous Callus Formation
Bony Callus Formation
Bone Remodeling.
Bone Disorders
Osteomalacia: Softening of bones due to vitamin D deficiency.
Rickets: Pediatric version of osteomalacia.
Osteoporosis: Loss of bone density and strength.
Paget’s Disease: Abnormal bone remodeling process.
Joint Disorders
Cartilage Tears, Sprains, Dislocations (luxation).
Bursitis and Tendonitis: Inflammation occurrences in joints and tendons respectively.
Arthritis and Lyme Disease: Conditions affecting joint health and mobility.
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