Overview
This lecture covers the tissues and organs of the skeletal system, focusing on cartilage, bone, and ligaments, their structures, functions, types, and anatomical terms relevant to bone markings and composition.
Skeletal System Overview
- The skeletal system includes bones, cartilage, and ligaments.
- Cartilage is the embryonic forerunner of most bones and covers many joint surfaces.
- Ligaments connect bone to bone at joints; tendons connect muscles to bones.
- The human skeleton is initially cartilage and fibrous membranes, mostly replaced by bone except in flexible areas.
Types of Skeletal Cartilage
- Three types: hyaline, elastic, and fibrocartilage.
- Cartilage is mainly water, lacks blood vessels and nerves, and is surrounded by perichondrium.
- Hyaline cartilage: most abundant; provides support, flexibility, and resilience; found at joints (articular), ribs (costal), larynx (respiratory), and nose (nasal).
- Elastic cartilage: more elastic fibers; found in external ear and epiglottis; maintains shape with repeated bending.
- Fibrocartilage: high tensile strength; found in intervertebral discs, knee menisci, and pubic symphysis.
Bone Classification and Function
- Functions: support, protection, movement, mineral storage, blood cell production, fat storage, acid-base balance, and detoxification.
- 206 bones in adult skeleton; divided into axial (skull, vertebral column, rib cage) and appendicular (limbs, girdles) skeletons.
- Bones are classified by shape: long (limb bones), short (wrist/ankle), flat (skull, sternum), and irregular (vertebrae, hip).
Structure of Bones
- Bone is an organ with bone tissue, nerve tissue, cartilage, and connective tissue.
- Three anatomy levels: gross, microscopic, chemical.
- Gross anatomy: outer compact bone, internal spongy bone (trabeculae), bone marrow (red for blood, yellow for fat).
- Bones display projections, depressions, and openings for muscle/ligament attachment and passage of vessels/nerves.
Markings and Bone Anatomy Terms
- Projections for muscles/ligaments: tuberosity, tubercle, crest, line, epicondyle, trochanter, spine, process.
- Projections forming joints: head, condyle, ramus, facet.
- Depressions and openings: fossa, groove, meatus, fissure, foramen, notch, sinus.
Detailed Bone Structure
- Long bones: have diaphysis (shaft) and epiphyses (ends).
- Diaphysis: thick compact bone around medullary (yellow marrow) cavity.
- Epiphyses: compact and spongy bone, joint surface covered by articular cartilage, contains red bone marrow.
- Epiphyseal line (adults): remnant of growth plate (epiphyseal plate in children).
- Membranes: periosteum (outer double layer), endosteum (internal lining).
Microscopic Bone Anatomy
- Bone cells: osteoblasts (form bone), osteocytes (maintain bone), osteoclasts (break down bone), osteogenic cells.
- Compact bone: structural unit is osteon (Haversian system) with concentric lamellae around central (Haversian) canal.
- Perforating (Volkmann's) canals connect periosteum with central canal.
- Lacunae (spaces with osteocytes) are connected by canaliculi.
- Lamellae: interstitial (between osteons), circumferential (around bone surface).
- Spongy bone: trabeculae help resist stress.
Chemical Composition of Bone
- Organic: cells and osteoid (ground substance, collagen fibers).
- Inorganic: hydroxyapatite (calcium phosphate), calcium carbonate, and other minerals for hardness.
Key Terms & Definitions
- Perichondrium — connective tissue sheath around cartilage.
- Osteon — structural unit of compact bone.
- Trabeculae — small struts in spongy bone.
- Diaphysis — shaft of a long bone.
- Epiphysis — end of a long bone.
- Hematopoiesis — blood cell production in bone marrow.
- Periosteum — membrane covering outer bone surface.
- Canaliculi — small canals connecting bone cells.
- Hyaline cartilage — flexible, most common cartilage type.
- Fibrocartilage — tough cartilage with high tensile strength.
Action Items / Next Steps
- Review all bone markings and their definitions.
- Study the types and locations of the three cartilage types.
- Prepare for lab identification of bone structures and features.