Ch 6: Bone and Skeletal Tissues

Components of Skeletal Tissues

The skeletal system is composed of several key structures that provide support, protection, and movement for the body.

• Cartilage: Flexible connective tissue found in joints, ear, nose, and respiratory tract.

• Bone: Rigid connective tissue forming the skeleton, providing structure and protection.

• Ligaments: Dense connective tissue connecting bones to other bones at joints.

• Joints: Sites where two or more bones meet, allowing for movement and flexibility.

Functions of Skeletal Tissues

Each component of the skeletal system serves specific functions essential for bodily health and activity.

• Support: Framework for the body, maintaining shape and posture.

• Protection: Shields vital organs (e.g., skull protects brain, rib cage protects heart and lungs).

• Movement: Provides attachment points for muscles, enabling locomotion.

• Storage: Reservoir for minerals, especially calcium and phosphorus.

• Blood Cell Production: Hematopoiesis occurs in red bone marrow.

Types of Cartilage

Cartilage is classified based on its structure and location.

• Hyaline Cartilage: Most abundant; found in nose, trachea, larynx, and at the ends of long bones.

• Elastic Cartilage: Flexible; found in ear and epiglottis.

• Fibrocartilage: Tough; found in intervertebral discs and menisci of knee.

Types of Bones

Bones are categorized by their shapes and functions.

• Long Bones: Longer than wide (e.g., femur, humerus).

• Short Bones: Cube-shaped (e.g., carpals, tarsals); sesamoid bones are a subtype found within tendons (e.g., patella).

• Irregular Bones: Complex shapes (e.g., vertebrae, pelvis).

• Flat Bones: Thin and broad (e.g., skull, ribs, sternum).

Parts of a Long Bone

Long bones have distinct anatomical regions.

• Epiphysis: Ends of the bone, often containing spongy bone and red marrow.

• Diaphysis: Shaft of the bone, primarily compact bone.

• Epiphyseal Line: Remnant of growth plate in adults.

• Medullary Cavity: Central cavity containing yellow marrow (fat storage).

• Periosteum: Outer fibrous membrane covering bone.

• Endosteum: Membrane lining the medullary cavity.

• Sharpey's Fibers: Collagen fibers anchoring periosteum to bone.

• Cortical Bone: Dense outer layer (compact bone).

• Medullary Bone: Inner region containing marrow.

Bone Composition

Bones consist of organic and inorganic components.

• Organic Components: Cells (osteoblasts, osteocytes, osteoclasts) and collagen fibers provide flexibility and tensile strength.

• Inorganic Components: Mineral salts (mainly hydroxyapatite) provide hardness and resistance to compression.

Microscopic Structure: Osteon System

The osteon (Haversian system) is the fundamental unit of compact bone.

• Osteon: Cylindrical structure with concentric lamellae surrounding a central canal.

• Central Canal: Contains blood vessels and nerves.

• Lacunae: Small spaces housing osteocytes.

• Canaliculi: Tiny channels connecting lacunae for nutrient exchange.

Bone Formation and Growth

Bones develop through two main processes:

• Intramembranous Ossification: Bone develops directly from mesenchymal tissue (e.g., flat bones of skull).

• Endochondral Ossification: Bone forms by replacing hyaline cartilage (e.g., long bones).

• Bone Remodeling and Repair: Continuous process involving bone resorption and formation to maintain strength and mineral homeostasis.

Ch 7: Axial Skeleton

Landmarks on Bones

Bony landmarks are used for muscle attachment, articulation, and passage of nerves and vessels.

• Raised/Rough Spots: Process, tubercle, tuberosity, trochanter, epicondyle, malleolus, crest, spine, line—sites for muscle or ligament attachment.

• Depressions: Fossa, sulcus, groove, alveolus—hold or support structures.

• Openings: Foramen, meatus, canal, fissure, sinus—allow passage of nerves, blood vessels, or air.

Axial Skeleton Components

• Skull: Cranial and facial bones.

• Hyoid: U-shaped bone in neck supporting tongue.

• Vertebral Column: 7 cervical, 12 thoracic, 5 lumbar, sacrum (5 fused), coccyx (3-5 fused).

• Thoracic Cage: 7 true ribs, 5 false ribs (2 floating), sternum.

Spinal Curvatures

Normal curvatures include cervical, thoracic, lumbar, and sacral curves. Abnormal curvatures include scoliosis, kyphosis, and lordosis.

Ch 8: Appendicular Skeleton

Pectoral Girdle

• Clavicle: Collarbone connecting sternum and scapula.

• Scapula: Shoulder blade articulating with humerus.

Upper Limb

• Arm: Humerus.

• Forearm: Radius and ulna.

• Hand: 8 carpals, 5 metacarpals, 14 phalanges.

Pelvic Girdle and Lower Limb

• Pelvic Girdle: Hip bones (ilium, ischium, pubis).

• Thigh: Femur.

• Leg: Tibia and fibula.

• Foot: 7 tarsals, 5 metatarsals, 14 phalanges.

Ch 9: Joints

Classification of Joints

Joints are classified structurally and functionally.

• Structural Classification:

  • Fibrous: Sutures, syndesmoses, gomphoses.

  • Cartilaginous: Synchondroses, symphyses.

  • Synovial: Freely movable joints with synovial cavity.

• Functional Classification:

  • Synarthroses: Immovable.

  • Amphiarthroses: Slightly movable.

  • Diarthroses: Freely movable.

Synovial Joints

Synovial joints have unique structural features and allow various movements.

• Basic Features: Articular cartilage, joint cavity, synovial fluid, articular capsule, reinforcing ligaments.

• Types of Movements: Gliding, angular, rotation, special movements (e.g., pronation, supination).

• Types of Synovial Joints:

  • Plane: Intercarpal joints.

  • Hinge: Elbow.

  • Pivot: Proximal radioulnar joint.

  • Wrist.

  • Saddle: Thumb (carpometacarpal joint).

  • Ball and Socket: Shoulder, hip.

Ch 10: Muscle Tissues

Types of Muscle Tissue

Muscle tissue is classified into three types, each with distinct structure and function.

• Skeletal Muscle: Voluntary, striated, attached to bones for movement.

• Cardiac Muscle: Involuntary, striated, found in heart walls.

• Smooth Muscle: Involuntary, non-striated, found in walls of hollow organs.

Functions of Muscle Tissue

• Movement: Locomotion and manipulation of environment.

• Posture: Maintains body position.

• Joint Stabilization: Reinforces joints.

• Heat Generation: Maintains body temperature.

Functional Characteristics of Muscle

• Contractility: Ability to shorten forcibly.

• Excitability: Responsiveness to stimuli.

• Extensibility: Ability to be stretched.

• Elasticity: Ability to recoil to resting length.

Basic Muscle Organ Structure

• Tendon: Connects muscle to bone.

• Muscle Belly: Main body of muscle.

• Epimysium: Outer connective tissue covering muscle.

• Fascicle: Bundle of muscle fibers.

• Perimysium: Surrounds fascicles.

• Fiber: Individual muscle cell.

• Endomysium: Surrounds each muscle fiber.

Microscopic Structure of Muscle Fiber

• Sarcomere: Functional unit of muscle contraction, defined by Z lines.

• Sliding Filament Mechanism: Myosin and actin filaments slide past each other to produce contraction.

• Cross Bridge Cycling: Myosin heads bind to actin, pulling filaments and causing shortening.

• Band and Line Demarcations: A band, I band, H zone, M line, Z disc.

Excitation-Contraction Coupling

• NMJ (Neuromuscular Junction): Site where motor neuron stimulates muscle fiber.

• Synapse: Junction between nerve and muscle.

• Process: Action potential triggers calcium release, leading to contraction.

Skeletal Muscle Fiber Types

• SO (Slow Oxidative): Fatigue-resistant, used for endurance.

• FG (Fast Glycolytic): Rapid, powerful contractions, fatigue quickly.

• FOG (Fast Oxidative-Glycolytic): Intermediate properties.

Motor Units

A motor unit consists of a motor neuron and all the muscle fibers it innervates. It is the basic functional unit for muscle contraction.

Key Equations

• Force of Muscle Contraction: Where F is total force, n is number of cross bridges, f is force per cross bridge.

• Calcium Homeostasis in Bone: Describes exchange of calcium between blood and bone.

Table: Types of Synovial Joints and Examples

Additional info: Academic context and definitions have been expanded for clarity and completeness. Table entries and equations are inferred from standard Anatomy & Physiology curriculum.