SKELETAL SYSTEM

1. SKELETAL SYSTEM

2. SKELETAL SYSTEM FUNCTIONS • Support (Primary function) • Movement (Passive) • Protection of Vital Organs • Mineral Storage • Blood Cell Formation (Hematopoiesis or Hemopoiesis)

3. OSSEOUS TISSUE • Cancellous (spongy) Bone • Compact (dense) Bone • Bone Cells • Osteoblasts – Secrete to form bone • Osteocytes • Mature bone cells • “Trapped” osteoblasts • Osteoclasts – destroy bone • Enzymes digest protein • Acids dissolve minerals • Forms Marrow Cavity; Involved in Remodelling

4. CANCELLOUS OR SPONGY BONE • Open spaces, light weight • Lattice arrangement • Made of microscopic trabeculae subunits • Location of bone marrow • Site of blood cell formation (red marrow) • Within epiphyses of long bones

6. COMPACT OR DENSE BONE • Dense, Ivory-like • Forms the outside layer of bones • Forms Diaphyses of long bones • Made of microscopic osteon (Haversian system) subunits

8. Appendicular skeleton Axial skeleton STRUCTURAL CLASSIFICATION: APPENDICULAR AND AXIAL

9. STRUCTURAL CLASSIFICATION BASED ON BONE SHAPE

10. Short Bones Long Bone Flat Bone Irregular Bone STRUCTURAL CLASSIFICATION BASED ON TYPE OF BONE

11. Epiphysis Spongy bone Compact bone Medullary cavity Diaphysis Epiphyseal line ANATOMY OF A LONG BONE • Periosteum • Epiphysis • Diaphysis • Compact bone • Spongy bone • Medullary cavity • Endosteum • Nutrient foramen • Epiphyseal line

14. BONE DEVELOPMENT • Ossification = replacement of other tissues with bone • Begins about the 6th week of gestation • Size increases until late teens (females) to mid-twenties (males) • Requires Ca2+ • Ossification processes include: • Intramembranous bone formation • Endochondral bone formation

15. GENERAL FEATURES OF INTRA-MEMBRANOUS BONE FORMATION • Occurs in flat bones of skull, clavicles • Begins with collagenous fiber membrane model • Membrane calcifies into compact bone • Fontanels (“Soft spot”, not yet ossified)

17. THE PROCESS OF INTRA-MEMBRANOUS BONE FORMATION • C.T. Cells cluster & centers of ossification appear • Cells differentiate into osteoblasts • Osteoblasts secrete a matrix, forming trabeculae • Calcium salts are deposited

19. THE PROCESS OF INTRA-MEMBRANOUS BONE FORMATION CONTINUED • Trabeculaefuse into spongy bone lattice • Lattice fills with red bone marrow • Eventually, peripheral trabeculae thicken into compact bone (periosteal ossification)

20. GENERAL FEATURES OF ENDOCHONDRAL BONE FORMATION • Occurs in remainder of skeleton • Begins with hyaline cartilage model • Cartilage is replaced by bony tissue

21. THE PROCESS OF ENDOCHONDRAL BONE FORMATION • FORMATION OF BONE COLLAR • Cartilage model is covered by perichondrium • Perichondrium becomes periosteum • A “collar” of bone is produced around the diaphysis

23. THE PROCESS OF ENDOCHONDRAL BONE FORMATION • CALCIFICATION OF DIAPHYSEAL CARTILAGE • Hypertrophy of chondrocytes • Surrounding matrix calcifies • Diffusion disabled, chondrocytes die • Cartilaginous matrix disintegrates

25. THE PROCESS OF ENDOCHONDRAL BONE FORMATION CONTINUED • FORMATION OF PRIMARY OSSIFICATION CENTER • Diaphysis penetrated by blood vessels, osteoblasts, osteoclasts • Marrow cavity formed by osteoclasts • Trabeculae form (Spongy bone) • Cartilage model grows at ends, elongating bone

27. THE PROCESS OF ENDOCHONDRAL BONE FORMATION CONTINUED • FORMATION OF SECONDARY CENTER OF OSSIFICATION • Blood vessels reach epiphyses • Secondary ossification centers develop • Spongy bone is formed • Cartilage is replaced by bone, except at articular surfaces • Cartilage remains at epiphyseal plate (metaphysis) until growth is complete

29. FRACTURES AND THEIR REPAIR • Definition: Any break in a bone • Repair may take months • Types include • Simple (skin not broken) • Compound (bone protrudes through skin) • Greenstick (shaft bent/broken) • Spiral (twisting force, ragged break) • Comminuted (shattered into fragments)

31. STEPS IN FRACTURE REPAIR • Broken blood vessels form a fracture hematoma • C.T. and Capillaries invade site, form fibrocartilage callus • Repair cells (osteoblasts) are activated in about 48 hours • Bony callus replaces fibrocartilage callus • Bony callus is remodeled by osteoclasts

33. BONES AS LEVERS • Lever: A rigid rod that moves about a fixed point • Fulcrum: The fixed point around which a lever moves (joints) • Forces: Act to move levers at two points • Resistance: Force to be overcome • Effort or Work: Force required to overcome resistance; supplied by skeletal muscles

34. CLASSES OF LEVERS • First Class: The fulcrum is between the effort/force and the resistance • Seesaw • Tilting head backward

35. R R R R R R R F E E E E E E E FIRST CLASS LEVER

36. CLASSES OF LEVERS CONTINUED • Second Class: Resistance is between the fulcrum and the effort/force • Wheelbarrow • Rising up on one’s toes

37. R R R R R R R R F E E E E E E E E SECOND CLASS LEVER

38. CLASSES OF LEVERS CONTINUED • Third Class: The effort/force is between the fulcrum and the resistance • Most common type in the human body • Flexing the elbow

39. R R R R R R R R F E E E E E E E E THIRD CLASS LEVER

40. ARTICULATIONS: CLASSIFICATION BY FUNCTION

41. ARTICULATIONS: CLASSIFICATION BY STRUCTURE

42. Pubic symphysis Functional: AmphiarthrosisStructural: Cartilagenous Knee Functional: DiarthrosisStructural: Synovial Sutures Functional: SynarthrosisStructural: Fibrous ARTICULATIONS: EXAMPLES

43. STRUCTURE OF A SYNOVIAL JOINT • Articular cartilage – cover bone ends • Synovial membrane – lines joint capsule • Synovial fluid – lubricates & nourishes cartilage • Synovial cavity • Joint capsule – fibrous C.T. • Ligaments – reinforce joint • Bursae – synovial sacs at other sites of friction

46. TYPES OF SYNOVIAL JOINTS Classified based on shape of articular surfaces • Gliding (plane) • Hinge • Pivot • Ellipsoidal (condyloid) • Saddle • Ball-and-socket