Anatomy and physiology l Bone tissue

Bone is divided into

cortical (hard) bone and trabecular (spongy) bone

Osteoblast

builds bone

Osteocyte

maintain bone

Osteoclast

breaks down bone

Osteoporosis

decrease bone density and health making bone more susceptible to breaks

Paget’s disease

Increased osteoclast activity causing bones to get thick but not strong because of haphazard osteoblast activity

Cortical (compact) bone

organized into osteons, have circular layers of collagen fibers known as lamellae and have blood vessels traveling through center known as the central canal.

Trabecular (spongy) bone

consist of mesh-like framework called trabeculae, found predominantly in end of long bones and contains red bone marrow

Long bones

ex femur

Short bones

ex carpals

flat bones

ex scapula

irregular bones

ex vertebrae

sesamoid bones

ex patella

epiphysis

wider end of long bones containing red bone marrow covered by articular cartilage

metaphysis

junction between epiphysis and diaphysis that contains epiphyseal plate (growth plate)

diaphysis

shaft of long bone containing the medullary cavity

endosteum

inner layer of medullary cavity that is site of bone growth and development

periosteum

outer layer of bone containing blood vessels and nerves, helps bone growth

medullary cavity

inner space within diaphysis that houses yellow bone marrow

Intramembranous formation

flat bones, stem cells differentiate into osteoblasts and secrete matrix then ossification continues to form spongy bone around blood vessels and compact bone forms around outside

Endochondral formation

starts with hyaline cartilage, diaphysis penetrated with blood vessels and osteoblasts, minerals then follow and ossification occurs then the same at tops of bones

Appositional growth

occurs at periosteum (surface), osteoblasts deposit new matrix and osteoclasts on inner surface break down bone, girth increases but weight not much

Interstitial growth

chondrocytes divide in epiphyseal plate, cells secrete matrix and gets pushed toward diaphysis and hypertrophy, chondrocytes calcify and blood vessels bring osteoblasts, full ossification at ~20 years. Bone chases cartilage till growth plate fuses

Wolf’s Law

body adapts to stresses and changes it is put under