Bone Composition and Formation Notes

What do compact and spongy bone both do?

store minerals for strength

Compact Bone; what do they look like?

Osteon (ring-like)

Spongy Bone; what do they look like?

Trabeculae (Rod-like)

Bone Marrow

soft tissue found inside cavities of bones

Red Bone Marrow

Present in children in all bones, produces blood cells, at birth ALL bone marrow is red.

What composes Red Bone Marrow?

Reticular tissue (collagen), adipocytes

Where is red bone marrow found in adults?

Vertebrae, ribs, sternum, pelvis, proximal(end closest to torso) ends of humerus and femur.

When does yellow bone marrow start to appear greatly?

10-20 years, starts at 1-10 years.

Yellow Bone Marrow

replaces red bone marrow in adults, doesn't produce blood, with age (atrophy) of adipose in yellow marrow it may turn to gelatinous marrow.

What is yellow bone marrow composed of?

Adipocytes (stores energy)

What happens with yellow bone marrow in severe cases of anemia?

It may turn back to red blood marrow to help produce more blood.

Gelatinous Bone Marrow

yellow bone turns to this, useless

Ossification (osteogenesis)

process of bone formation

intramembranous ossification

produces bones with spongy bone between two layers of compact bone, produces flat bones of skill and collar bone. starts during fetal development, less common

endochondral ossification

produces vertebrae, pelvic, limb bones, embryonic connective tissue first becomes a cartilage then is reorganized and calcified to form bone, little layer of compact on outside, mainly spongy on inside.

What helps with the reorganizing/remodeling/removal in endochondral ossification?

osteoclasts

Why do bones grow and change?

to accommodate changing forces and needs of the skeleton.

Epiphyseal Plate

line of cartilage inside the end of bone, that means bone is still growing in length. AKA - growth plate.

Epiphyseal Plate - what affects it?

Estrogen and testosterone, promote calcification.

What does estrogen do for the epiphyseal plate?

stimulates osteoblasts

What does testosterone do for the epiphyseal plate?

Stimulates muscle growth = extra strain on bones so osteocytes stimulate osteoblasts.

When do your bones stop growing?

Epiphyseal plates close and are calcified bone.