Chapter 6: Bones in General

Types and Locations of Skeletal Cartilage

Skeletal cartilage is a resilient, avascular connective tissue found in various parts of the skeleton. There are three main types:

• Hyaline cartilage: Most abundant; found at articular surfaces, costal cartilages, respiratory tract, and embryonic skeleton.

• Elastic cartilage: Contains more elastic fibers; found in the external ear and epiglottis.

• Fibrocartilage: Highly compressible; found in intervertebral discs, pubic symphysis, and menisci of the knee.

Functions of the Skeleton

• Support: Provides structural framework for the body.

• Protection: Shields vital organs (e.g., skull protects brain).

• Movement: Acts as levers for muscles.

• Mineral storage: Reservoir for calcium and phosphate.

• Blood cell formation: Hematopoiesis occurs in red marrow.

• Triglyceride storage: Fat stored in yellow marrow.

Classification of Bones by Shape

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

• Short bones: Cube-shaped (e.g., carpals, tarsals).

• Flat bones: Thin, flattened (e.g., sternum, skull bones).

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

• Sesamoid bones: Form within tendons (e.g., patella).

Anatomy of a Long Bone

• Epiphysis: Ends of the bone; contains spongy bone and red marrow.

• Diaphysis: Shaft; contains compact bone and medullary cavity.

• Epiphyseal plate/line: Growth plate in children; becomes epiphyseal line in adults.

• Medullary cavity: Central cavity containing yellow marrow in adults.

• Articular cartilage: Hyaline cartilage covering joint surfaces.

• Periosteum: Dense connective tissue covering the bone (except at joints).

• Endosteum: Membrane lining the medullary cavity.

• Compact bone: Dense outer layer.

• Spongy bone: Internal network of trabeculae.

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

Bone Marrow: Yellow vs. Red

• Red marrow: Site of hematopoiesis; found in spongy bone of flat bones and epiphyses of long bones.

• Yellow marrow: Stores fat; found in medullary cavity of long bones in adults.

Bone Markings

Bones have various markings for attachment, passage of vessels/nerves, and articulation. Examples include:

• Foramen: Round opening for vessels/nerves.

• Fossa: Shallow depression.

• Process: Projection for muscle/ligament attachment.

• Condyle: Rounded articular projection.

• Spine: Sharp, slender projection.

Bone Tissue and Matrix

• Type: Connective tissue.

• Matrix: Composed of organic (collagen fibers) and inorganic (hydroxyapatite crystals) components.

Bone Cells: Functions and Locations

• Osteocytes: Mature bone cells in lacunae; maintain matrix.

• Osteogenic cells: Stem cells in periosteum/endosteum; differentiate into osteoblasts.

• Osteoblasts: Bone-forming cells; secrete matrix.

• Osteoclasts: Bone-resorbing cells; break down bone matrix.

Structure of Compact Bone

• Osteon (Haversian system): Structural unit; concentric lamellae around a central canal.

• Central canal: Contains blood vessels and nerves.

• Perforating (Volkmann's) canals: Connect central canals transversely.

• Lacunae: Small spaces housing osteocytes.

• Lamellae: Layers of bone matrix.

• Canaliculi: Tiny canals connecting lacunae.

Structure of Spongy Bone

• Trabeculae: Lattice-like network; spaces filled with marrow.

• Spongy bone lacks osteons; nutrients diffuse through canaliculi.

Bone Formation (Ossification)

• Endochondral ossification: Bone replaces hyaline cartilage; forms most bones below the skull.

• Intramembranous ossification: Bone develops from fibrous membrane; forms flat bones of skull and clavicle.

Bone Growth

• Interstitial growth: Lengthening at epiphyseal plate.

• Appositional growth: Increase in bone thickness.

• Epiphyseal plate closure signals end of longitudinal growth.

Bone Remodeling and Repair

• Bone remodeling involves osteoblasts (formation) and osteoclasts (resorption).

• Remodeling occurs throughout life; regulated by hormones and mechanical stress.

• Weight-bearing exercise increases bone mass.

• Vitamins (D, C, A) and minerals (calcium, phosphate) are essential for bone health.

• Parathyroid hormone and calcitonin regulate calcium homeostasis.

Bone Fractures

• Open (compound) fracture: Bone pierces skin.

• Closed (simple) fracture: Bone does not pierce skin.

• Six common types: transverse, oblique, spiral, comminuted, impacted, greenstick.

• Steps of fracture repair: hematoma formation, fibrocartilaginous callus, bony callus, bone remodeling.

Chapter 7: Axial Skeleton

Skull

• Composed of cranial and facial bones.

• Frontal bone: Forehead.

• Other cranial bones: Parietal, temporal, occipital, sphenoid, ethmoid.

• Foramen magnum: Large opening for spinal cord in occipital bone.

• Temporal bone divisions: Squamous, tympanic, mastoid, petrous parts.

• Zygomatic bone: Cheekbone.

• Ossicles: Malleus, incus, stapes (middle ear bones).

• Carotid canal: Passage for carotid artery.

• Sella turcica: Depression in sphenoid for pituitary gland.

• Nasal septum: Formed by vomer and perpendicular plate of ethmoid.

• Paranasal sinuses: Air-filled spaces in skull bones; lighten skull, warm air.

• Hyoid bone: U-shaped bone in neck; not articulated with other bones.

Vertebral Column

• Divided into cervical (7), thoracic (12), lumbar (5), sacral (5 fused), coccygeal (4 fused) regions.

• C1 (Atlas): Supports skull; allows nodding.

• C2 (Axis): Dens (odontoid process) allows rotation.

• Thoracic vertebrae: Articulate with ribs.

• Curvatures: Cervical and lumbar (concave), thoracic and sacral (convex).

• Coccyx: Tailbone; remnant of embryonic tail.

Thoracic Cage

• Composed of sternum, ribs, and thoracic vertebrae.

• True ribs: 1-7, attach directly to sternum.

• False ribs: 8-10, attach indirectly.

• Floating ribs: 11-12, no anterior attachment.

Chapter 8: Appendicular Skeleton

Pectoral Girdle and Upper Limb

• Pectoral girdle: Clavicle and scapula.

• Humerus: Arm bone; articulates with scapula and radius/ulna.

• Radius and ulna: Forearm bones; radius lateral, ulna medial.

• Carpals, metacarpals, phalanges: Bones of wrist, hand, and fingers.

• Annular ligament: Stabilizes head of radius during pronation/supination.

Pelvic Girdle and Lower Limb

• Pelvic girdle: Two coxal (hip) bones.

• Femur: Thigh bone; articulates with pelvis and tibia.

• Tibia and fibula: Leg bones; tibia bears weight, fibula does not.

• Tarsals, metatarsals, phalanges: Bones of ankle, foot, and toes.

• Arches of the foot: Medial, lateral, and transverse; absorb shock and support weight.

Chapter 9: Articulations

Types of Joints

• Articulation: Site where two or more bones meet.

• Fibrous joints: Sutures (skull), syndesmoses (radius/ulna), gomphoses (teeth).

• Cartilaginous joints: Synchondroses (epiphyseal plate), symphyses (pubic symphysis).

• Synovial joints: Freely movable; have joint cavity, articular cartilage, synovial fluid.

Structure of Synovial Joints

• Articular cartilage, joint (synovial) cavity, articular capsule, synovial fluid, reinforcing ligaments, nerves, and blood vessels.

• Bursa: Fluid-filled sac reducing friction.

• Tendon sheath: Elongated bursa around tendons.

Movements at Synovial Joints

• Gliding: Flat surfaces slide past each other.

• Angular: Flexion, extension, hyperextension, abduction, adduction, circumduction.

• Rotation: Turning bone around its axis.

• Special movements: Supination, pronation, inversion, eversion, protraction, retraction, elevation, depression, opposition.

Classification of Synovial Joints by Axis

• Nonaxial: Gliding movements (e.g., intercarpal joints).

• Uniaxial: Movement in one plane (e.g., elbow).

• Biaxial: Movement in two planes (e.g., wrist).

• Multiaxial: Movement in all axes (e.g., shoulder, hip).

Ligaments, Tendons, and Joint Stability

• Knee joint: Reinforced by ligaments (ACL, PCL, MCL, LCL), tendons, and menisci.

• Elbow joint: Stabilized by ulnar and radial collateral ligaments.

• TMJ (temporomandibular joint): Allows jaw movement; prone to dislocation.

• Shoulder joint: Reinforced by coracohumeral and glenohumeral ligaments; rotator cuff muscles provide stability.

• Hip joint: Reinforced by iliofemoral, pubofemoral, and ischiofemoral ligaments.

Common Joint Injuries

• Knee: Ligament tears, meniscus injury, dislocation.

• Elbow: Tendon and ligament injuries (e.g., "tennis elbow").

Table: Comparison of Joint Types

Additional info:

• Some details, such as the specific steps of bone fracture repair and the full list of bone markings, were expanded for completeness.

• Table content inferred and summarized for clarity.