chapter 6: skeletal system

Main functions of the skeletal system/bone

• Support and protection of soft tissues.

• Attachment site for muscles → movement

• Mineral storage and homeostasis - calcium

• Hemopoiesis- blood cell production in red bone marrow

• Energy (lipid) storage- in yellow bone marrow

The 3 steps for bone fracture and repair

1. Fracture Hematoma: blood gathers in area of fracture

2. Callus formation: osteoblasts lay down matrix in fibrocartilage

3. Remodeling: osteoclasts reabsorb fragments of bone and any excess callus

• Compare and contrast the major features of Intramembranous and endochondral ossification

intramembranous:

• most bones in the body use endochondral ossification, not Intramembranous.

• Does not go thru cartilage stage

Endochondral:

• most bone use this

• Uses a hyaline cartilage model

• Hyaline cartilage on ends of bone remains -> articular cartilage

Factors required for normal bone growth and development (length & diameter)

Bone growth in length

• Occurs at epiphyseal plate

• Thickness of epiphyseal plate remains constant until cartilage cells stop dividing -> epiphyseal line -> no more growth in length

Bone growth in diameter

• Under periosteum, osteoblasts lay down matrix

• Factors required for normal bone growth and development (Medullary Cavity)

Osteoclasts eat away at area under endosteum → larger medullary cavity

Remodeling

• Osteoclasts carve out small tunnels and osteoblasts rebuild

  Osteoporosis

• Decrease bone mass → increase in fractures

• Decrease osteoblast activity so osteoclast activity outpaces osteoblast actvity

Long Bones (regions, linings/coverings and spaces)

Structure (diaphysis, epiphysis, metaphysis, medullary cavity)

Structure

• Diaphysis - (shaft) middle

• Epiphysis - ends of long bones, proximal and distal

  = spongy bone filled with bone marrow

  = hemopoiesis

• Metaphysis - epiphysis and diaphysis meet; contains epiphyseal plate (growth plate) in growing bone, where growth in length occurs, ossifies → epiphyseal line in adult (no more growth in length)

• Medullary Cavity- yellow marrow

  = fat/lipid storage

Long Bones (regions, linings/coverings and spaces)

Coverings and linings (articular cartilage, edosteum, periosteum)

Articulate cartilage

• Hyaline cartilage

• Covers ends of bones/joint surfaces → reduces friction, acts as shock absorber

  Endosteum

• Membrane lining the medullary cavity

• Contains osteoclasts which helps break down bone to make medullary cavity larger

  Periosteum

• Tough membrane covering outer surface of bone (not cartilage)

• Growth in diameter occurs under this

• Osteoclasts = new bone

• Tendons and ligaments attach here

• Does not cover bone ends

Parts of compact bone (osteon, lamelle, canaliculi, lacunae, central canal, perforating canals, interstitial lamelle, etc)

Osteon

• Set of concentric rings= lamellae

• Central canal = center of osteon

  Perforating Canal

• Blood vessels pass thu periosteum & horizontally into bone thru perforating canal

  Lamellae

• Rings

  Lacunae

• Spaces which contains osteocytes, between lamellae

  Canaliculi

• Small canals which radiate out from lacunae - contains osteocytes reaching out to contact other osteocytes

  Interstitial Lamellae

• Fragments of old osteons found between new osteons

Parts of Songy Bone (Trabeculae and red bone marrow)

Location

• Inside epiphysis of long bones

• Inside all other types of bones

Parts of Songy Bone (Trabeculae and red bone marrow)

• Open spaces which contains osteocytes reaching red bone marrow

  Trabeculae

• Thin shelf-like projections of bone

• No true osteons

Compare and contrast 4 major cell types found in bone (osteogenic, osteocyte, osteoclast, osteoblast)

Osteogenic

• Unspecialized/undifferentiated stem cells → osteoblasts

Compare and contrast 4 major cell types found in bone (osteogenic, osteocyte, osteoclast, osteoblast)

Osteoblasts

• Bone forming/building cells → osteocytes

Compare and contrast 4 major cell types found in bone (osteogenic, osteocyte, osteoclast, osteoblast)

Osteocytes

• Mature bone cells contained in lacunae

Compare and contrast 4 major cell types found in bone (osteogenic, osteocyte, osteoclast, osteoblast)

Osteoclasts

• Break down bone (resorption) for remodeling, repair, make medullary cavity larger