Bones and bone tissues

Functions of bone tissue

Provide attachment for skeletal muscles

Assist in movements along with skeletal muscles

Contain red bone marrow (produce RBC)

Contain yellow bone marrow (store triglycerides)

Types of bones

long, short, flat, irregular, sesamoid

long bones

longer than they are wide, bones of the arms and legs

short bones

bones of the wrist and ankles

flat bones

thin, flat, and curved; form the ribs, breastbone, and skull.

sesamoid bones

patella and pisiform

Parts of a long bone

diaphysis, epiphyses, metaphyses, articular cartilage, periosteum (line outside of bone), medullary cavity (yellow bone marrow), endosteum (line medullary cavity)

Bone surface markings

tuberosity, tubercle, trochanter, process, spine, line, crest, head, condyle, epicondyle, fossa, fovea, impression, sulcus, incisura, fissure, foramen, canal, meatus

composition of intercellular matrix of bone tissue

type 1 collagen (organic matrix); inorganic matrix (calcium hydroxyapatite crystal); ground substance (proteoglycans + osteocalcin, osteopontin...)

osteoprogenitor cells

only bone cells that can divide; mesenchyme derived

Osteoblasts

produce bone ECM; become osteocytes after being trapped in their secretions; located on forming bone surface

Osteocytes

maintain bone tissue; located in lacunas; connect with each other through processes (gap junctions)

osteoclasts

breakdown of bone ECM (lysosomal enzymes); large cells with many nuclei; located on interior bone surface (Howship lacunas)

woven bone

high cellular density; low organized ; uneven mineralization; produced when growing fast, fracture healing, forming embryonic bone

lamellar bone

compact and spongy bone; structural units - osteon

primary ossification

undifferentiated mesenchymal cells form osteoblasts directly

secondary ossification

pre-existing supporting tissue is converted into bone; intramembranous and endochondral ossification

intramembranous ossification

initial tissue - connective tissue; flat bones of skull, mandible, clavicles

endochondral ossification

initial tissue - cartilage

epiphyseal plate

hyaline cartilage; allow diaphysis of bone to increase in length; found between epiphysis and metaphysis

appositional growth

thickening of long bone; increase in the diameter of bones by the addition of bony tissue at the surface of bones (under periosteum)

remodeling of bone

Resorption by osteoclasts and replacement by osteoblasts

Bone remodeling units: osteoclast and osteoblast

Triggered by parathyroid hormone (PTH)

Active when young, slow down in old age