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SKELETAL SYSTEM. SKELETAL SYSTEM FUNCTIONS. Support (Primary function) Movement (Passive) Protection of Vital Organs Mineral Storage Blood Cell Formation (Hematopoiesis or Hemopoiesis). OSSEOUS TISSUE. Cancellous (spongy) Bone Compact (dense) Bone Bone Cells

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skeletal system functions
SKELETAL SYSTEM FUNCTIONS
  • Support (Primary function)
  • Movement (Passive)
  • Protection of Vital Organs
  • Mineral Storage
  • Blood Cell Formation (Hematopoiesis or Hemopoiesis)
osseous tissue
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
cancellous or spongy bone
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
compact or dense bone
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
slide10

Short Bones

Long Bone

Flat Bone

Irregular Bone

STRUCTURAL CLASSIFICATION BASED ON TYPE OF BONE

anatomy of a long bone

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
bone development
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
general features of intra membranous bone formation
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)
the process of intra membranous bone formation
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
the process of intra membranous bone formation continued
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)
general features of endochondral bone formation
GENERAL FEATURES OF ENDOCHONDRAL BONE FORMATION
  • Occurs in remainder of skeleton
  • Begins with hyaline cartilage model
  • Cartilage is replaced by bony tissue
the process of endochondral bone formation
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
the process of endochondral bone formation23
THE PROCESS OF ENDOCHONDRAL BONE FORMATION
  • CALCIFICATION OF DIAPHYSEAL CARTILAGE
    • Hypertrophy of chondrocytes
    • Surrounding matrix calcifies
    • Diffusion disabled, chondrocytes die
    • Cartilaginous matrix disintegrates
the process of endochondral bone formation continued
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
the process of endochondral bone formation continued27
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
fractures and their repair
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)
steps in fracture repair
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
bones as levers
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
classes of levers
CLASSES OF LEVERS
  • First Class: The fulcrum is between the effort/force and the resistance
    • Seesaw
    • Tilting head backward
first class lever

R

R

R

R

R

R

R

F

E

E

E

E

E

E

E

FIRST CLASS LEVER
classes of levers continued
CLASSES OF LEVERS CONTINUED
  • Second Class: Resistance is between the fulcrum and the effort/force
    • Wheelbarrow
    • Rising up on one’s toes
second class lever

R

R

R

R

R

R

R

R

F

E

E

E

E

E

E

E

E

SECOND CLASS LEVER
classes of levers continued38
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
third class lever

R

R

R

R

R

R

R

R

F

E

E

E

E

E

E

E

E

THIRD CLASS LEVER
slide42

Pubic symphysis

Functional: AmphiarthrosisStructural: Cartilagenous

Knee

Functional: DiarthrosisStructural: Synovial

Sutures

Functional: SynarthrosisStructural: Fibrous

ARTICULATIONS: EXAMPLES

structure of a synovial joint
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
types of synovial joints
TYPES OF SYNOVIAL JOINTS

Classified based on shape of articular surfaces

  • Gliding (plane)
  • Hinge
  • Pivot
  • Ellipsoidal (condyloid)
  • Saddle
  • Ball-and-socket