文档介绍：Bones, Joints and Muscles
Bones: 206 in human body
Function:
support (eg) pelvic bowl, legs
protect (eg) skull, vertebrae
mineral storage (eg) calcium, phosphate, ponent
movement (eg) walk, grasp objects
blood-cell formation (eg) red bone marrow
Osteoblasts: anic part of bone matrix = osteoid
Osteocytes: mature bone cells, maintain bone matrix
Some Reminders about Bones
Bone = bone tissue (type of CT)
A Bone = pact vs. Spongy position: Hydroxyapatite, protoplasm, bone collagen, blood vessels, marrow
Skeleton = bones, cartilage (avascular, no nerves, 80% H2O), joints, ligaments
Shapes of Bones
Long, Flat, Irregular, Short
Before 8 weeks, embryo is all cartilage
Structure of Bone
Anatomy of a Long Bone
Diaphysis
Medullary Cavity
Nutrient Art & Vein
2 Epiphyses
Epiphyseal Plates
Epiphyseal Art & Vein
Periosteum
Outer: Dense irregular CT
Inner: Osteoblasts, osteoclasts
Does not cover epiphyses
Attaches to bone matrix via collagen fibers
Endosteum
Osteoblasts, osteoclasts
Covers trabeculae, lines medullary cavity
2 Types of Bone Formation
1) Intramembranous Ossification
Membrane bones: most skull bones and clavicle
Osteoblasts in membrane secrete osteoid that mineralizes
Osteocytes maintain new bone tissue
Trabeculae forms between blood vessels
Grows into thickened plates at periphery = compact bone
Periosteum forms over it
2 Types of Bone Formation :
2) Endochondral Ossification: All other bones
Begins with a cartilaginous model
Perichondrium es replaced by periosteum
Cartilage in diaphysis calcifies
Trabeculae forms from Periosteal bud
Periosteal bud = arteries & veins, cells forming bone marrow, osteoblasts, osteoclasts
Medullary cavity is formed by action of osteoclasts
Epiphyses grow and eventually calcify
Epiphyseal plates remain cartilage for up to 20 years
Bone Growth & Remodeling
GROWTH
Appositional Growth = widening of bone
Bone tissue added on surface by osteoblasts of periosteum
Medullary cavity maintained by osteoclasts
Lengthening of Bone