Lecture K Notes_The Skeletal System

Lecture Objectives

• Define terms related to the skeletal system.

• Describe the functions of the skeletal system and its role in maintaining homeostasis.

• Describe 5 functions of the skeletal system.

• List the 3 connective tissues found in the skeletal system.

• Explain why bone is considered alive and dynamic.

• List and describe the 3 cells that develop and maintain bone.

• Describe the organization of compact and spongy bone.

• Identify the anatomy of a long bone.

• List and describe the 2 cells that develop and maintain cartilage.

• Distinguish between hyaline, fibrocartilage, and elastic cartilage.

• Describe the function and structure of ligaments.

• Explain the development, maintenance, and repair of bone.

• Describe bone remodeling.

• Describe the stages of fracture repair.

• Explain endochondral ossification.

• Classify bones according to their shape.

• Name bone markings.

• Identify the bones of the axial skeleton.

• Identify the bones of the appendicular skeleton.

• Distinguish three types of joints based on structure and function.

• Identify movements at synovial joints.

• Describe measures to care for the skeletal system.

• Clinical perspectives:

  • Explain the cause and risks of rickets.

  • Explain how forensic science can use the epiphyseal plates of various bones to determine the age of a person.

  • Describe a herniated disc and explain how it can result in pain.

  • Describe the proper way to lift objects to prevent back injury.

  • Describe the development of the curvatures of the vertebral column.

  • Distinguish scoliosis, lordosis, and kyphosis.

  • Distinguish osteoarthritis, rheumatoid arthritis, and gouty arthritis.

Overview of the Skeletal System

• The skeletal system consists of 206 bones, cartilages, and ligaments.

• Provides framework for maintaining posture and points of attachment for muscles.

• Protects internal organs (e.g., skull protects brain; rib cage protects heart and lungs).

• Stores minerals and is the site for blood cell production (red bone marrow).

• Divided into two divisions:

  • Axial Skeleton: bones located along the body's long axis.

  • Appendicular Skeleton: girdles and limbs.

Functions of the Skeletal System

• Support: Rigid framework supports body against gravity.

• Protection: Protects delicate organs and internal structures.

• Movement: Works with skeletal muscles to enable movement.

• Mineral Storage: Stores calcium and phosphate.

• Energy Storage: Yellow bone marrow stores fats for energy.

Bone Characteristics

• Bone is alive and dynamic, requiring oxygen and nutrients.

• It produces waste, responds to hormones, and can repair itself.

Types of Bone Tissue

• Types of Bone Cells:

  • Osteoprogenitor Cells: Stem cells that develop into osteoblasts.

  • Osteoblasts: Build bone matrix through ossification; develop into osteocytes.

  • Osteocytes: Mature bone cells that maintain bone tissue.

  • Osteoclasts: Phagocytic cells that dissolve bone (bone resorption).

Types of Bone Tissue

• Compact Bone:

  • Hard, dense tissue in long bone shafts and outer layers.

  • Organized into osteons (Haversian systems) surrounding central canals (containing blood vessels).

• Spongy Bone:

  • Composed of trabeculae (small bony plates and spaces).

  • Contains red and yellow bone marrow; found at the ends of long bones and centers of others.

Cartilage Types

• Cartilage produced by chondroblasts and maintained by chondrocytes.

• Types of Cartilage:

  • Hyaline Cartilage: Most common, located at ends of long bones, nose, ribs, larynx, trachea.

  • Fibrocartilage: Stronger, found in intervertebral discs and knees.

  • Elastic Cartilage: Flexible, found in ear flaps and epiglottis.

Ligaments

• Tough fibrous bands that connect bones at joints and support internal organs.

• Composed of dense fibrous collagen bundles and cells called fibrocytes.

Bone Maintenance and Repair

• Bone Remodeling: Cycles of new bone deposition and old bone resorption.

• Fracture Repair:

  • Blood clot formation (fracture hematoma) followed by soft callus formation (fibrocartilage).

  • Gradual replacement with hard callus (compact bone matrix) over months.

  • Remodeling by osteoclasts and osteoblasts.

  • Endochondral Ossification: Cartilage replaced with bone during fetal development.

Hormonal Influence on Skeletal System

• Growth Hormone: Stimulates cartilage growth at epiphyseal plates.

• Thyroid Hormones: Stimulate bone growth by increasing metabolic rate of bone cells.

• Sex Hormones: Accelerate bone growth during puberty; stimulate osteoblast activity.

• Calcitonin: Decreases blood calcium levels by promoting deposition into bone.

• Parathyroid Hormone: Increases blood calcium levels by resorbing bone and increasing absorption of calcium in the intestine.

Care of the Skeletal System

• A well-balanced diet for strong bones:

  • Protein: Needed for collagen synthesis (meats, eggs, dairy, beans).

  • Vitamin C: Important for collagen synthesis (fruits and vegetables).

  • Vitamin D: Necessary for calcium absorption (fatty fish).

  • Minerals: Calcium and phosphorus are essential for bone matrix; sources include dairy.

  • Magnesium and Potassium: Both help maintain pH and bone strength (found in beans, potatoes, green vegetables).

• Regular exercise is vital for maintaining skeletal health.

Classification of Bones

• Long Bones: Longer than they are wide (e.g., thigh & arm bones).

• Short Bones: Cube-shaped; consist mostly of spongy bone.

• Flat Bones: Thin and flat; protect organs (e.g., skull, ribs).

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

• Sesamoid Bones: Round bones (e.g., patella); found in tendons.

• Sutural Bones: Small bones between larger flat bones.

Anatomy of a Long Bone

• Diaphysis: Shaft providing weight support.

• Epiphysis: Knobby ends, enlarged for joint strength.

• Articular Cartilage: Reduces friction at joints.

• Periosteum: Covers bone, site of attachment for blood vessels;

• Endosteum: Lines internal surfaces; involved in growth and repair.

• Medullary Cavity: Contains red or yellow marrow (blood or fat storage).

Bone Markings

• All bones have surface markings associated with specific purposes.

• Components such as heads, necks, condyles, processes, spines, and fossae are identified based on their structure and function.

Axial Skeleton

• Composed of approximately 80 bones, providing support and protection.

• Components: Skull, vertebral column, thoracic cage.

Skull Components

• Cranial Bones: 8 in total, including the frontal, parietal, temporal, occipital, ethmoid, and sphenoid.

• Facial Bones: 14 in total, including maxillae, zygomatic bones, mandible, nasal bones, lacrimal bones, inferior nasal concha, vomer, and palatine bones.

Vertebral Column

• Composed of 33 vertebrae (cervical, thoracic, lumbar, sacral, coccygeal).

• Typical vertebrae structure includes body, spinous processes, transverse processes, and intervertebral discs.

Clinical Perspectives

• Rickets: Caused by calcium and vitamin D deficiency; leads to bowing of weight-bearing bones.

• Herniated Disc: Occurs when gelatinous material protrudes through the fibrous layer, pressing on nerves.

• Curvatures: Cervical, thoracic, lumbar, and sacral curvatures provide support and balance.

• Scoliosis, Lordosis, Kyphosis: Abnormal curvatures of the spine.

Appendicular Skeleton

• Pectoral Girdle: Clavicle and scapula attachment of arms to axial skeleton.

• Upper Limb Bones: Humerus, radius, ulna, carpals, metacarpals, phalanges.

• Pelvic Girdle: Composed of os coxa (ilium, pubis, ischium) attaching legs to axial skeleton.

• Lower Limb Bones: Femur, tibia, fibula, patella, tarsals, metatarsals, phalanges.

Joints Classification

• Functional Classification:

  • Synarthroses (immovable).

  • Amphiarthroses (slightly movable).

  • Diarthroses (freely movable).

• Structural Classification:

  • Fibrous (e.g., sutures), Cartilaginous (e.g., ribs to sternum), Synovial (e.g., shoulder joint).

Types of Synovial Joints

• Ball-and-socket, hinge, pivot, saddle, condylar, plane joints—all allowing various degrees of movement.

Clinical Perspectives on Joint Disorders

• Arthritis: Inflammatory or degenerative joint disorders (e.g., osteoarthritis, rheumatoid arthritis, gouty arthritis).

Movements at Synovial Joints

• Abduction, Adduction, Flexion, Extension, Hyperextension, Dorsiflexion, Plantar flexion, Pronation, Supination, Inversion, Eversion, Circumduction, Rotation.