Anatomy Ch. 6

Rickets

-A disorder caused by a lack of vitamin D, calcium, or phosphate. -Causes inadequate calcification of bone matrix. -Leads to softening and weakening of bones.

Osteogenisis Imperfecta

-A genetic disorder in which people are born with defective connective tissue or the inability to make it. -Deficiency in Type-1 collagen -Used to form bone

Spongy Bone

-Does not contain osteons -Consists of trabeculae (little beams) surrounding many red marrow filled spaces. -Forms most of the structure of short, flat, and irregular bones. -Forms the epiphysis of long bones. -Light weight. -Supports and protects the red bone marrow

Ossification (osteogenesis)

-During initial bone development as an embryo and fetus. -Growth during childhood and adolescence. -Remodeling of bone during adulthood -Repair of fractures throughout life.

Nutrient arteries

-Enter through nutrient foramina (foramen = opening). -Supplies compact bone of diaphysis.

Intramembranous ossification (intra = within)

-Forms the flat bones of the skull. -Begins as mesenchymal cells that develop within a membrane. -Many ossification centers grow simultaneously. -Does not go through a cartilage stage

Compact Bone

-Looks like a solid layer of bone. -Contains few spaces -Makes up the diaphysis (shaft) of long bones and the external layer of all bones. -Resists stresses produced by weight and movement. -Contains osteons

Endochondral ossification (chondral = cartilage

-Method used in the formation of most bones, especially long bones. -Bone formation begins with a cartilage model that gets replaced by bone. -Ossification begins in the diaphysis at the primary ossification center. -Secondary ossification centers take place in the epiphyses. -A layer of hyaline cartilage remains between the two ossification centers as the epiphyseal (growth) plate.

Periosteal arteries

-Supply the periosteum. -Accompanied by nerves

Intramembranous ossification (intra = within) Endochondral ossification (chondral = cartilage

2 types of ossification take place:

Mechanical Stress

Bone constantly remodels and redistributes its matrix along lines of

Diaphysis

Bone shaft

Rickets

Bones may also become too soft is called

Osteoporosis

Excessive loss of calcium weakens the bones is called

18-21

Growth plate closes

Thick and heavy (acromegaly)

If too much new tissue is formed, the bones become

Osteoporosis

Older individuals (especially post-menopausal women) experience a decrease in bone mass when resorption outpaces deposition

Metaphyseal and Epiphyseal arteries

Supply the red marrow and bone tissue of the epiphyses.

Collagen Fibers and Hydroxyapatite

The matrix consists of

Parathyroid hormone (PTH)

When blood calcium levels are low, osteoclasts are stimulated to resorb bone. Under control of

Calcitonin (Thyroid gland)

When blood calcium levels are too high, osteoblasts are stimulated to deposit bone. Under control of

Fracture

a break in a bone

Deposition

addition of minerals and collagen fibers to bone by osteoblasts.

Bone formation

begins during 6th week of embryonic development.

Osteoclast

bone crusher

Osteoprogenitor cells

bone stem cells able to differentiate into the other types of cells

Osteoblasts

bone-building cells that secrete matrix

2 Epiphyses

both ends of the bone at the joints

Periosteum

connective tissue surrounding the diaphysis

Medullary Cavity

hollow space within diaphysis

Reparative phase

includes formation of a fibrocartilaginous callus first and a bony callus second.

Reactive phase

is an early inflammatory phase

Compact Bone

is good at providing protection and support.

Spongy Bone

is lightweight and provides tissue support

Bone remodeling phase

is the last step as a bony callus is remodeled

Ossification (osteogenesis)

is the process of bone formation.

Osteocytes

mature bone cells

Calcification

mineral salts are deposited in a framework of collagen fibers.

Calcification

only occurs in the presence of collagen fibers

2 Metaphyses

region between diaphysis and epiphysis

Osteoclasts

remodel bones and cause them to release calcium

Resorption

removal of minerals and collagen fibers from bone by osteoclasts.

Endosteum

thin membrane lining the medulary cavity

Bone (osseous)

tissue consists of widely separated cells surrounded by a hardened extracellular matrix

adulthood

when are production and remodeling rates the same

birth through adolescence

when is more bone is produced than lost during remodeling.